From 4f96d37b1f9f91d7b2dc73e5d5fcf6e03b291823 Mon Sep 17 00:00:00 2001
From: David Capello <david@igara.com>
Date: Wed, 19 Oct 2022 12:09:27 -0300
Subject: [PATCH] Add repeat field to animation tags (#1275, #1740)

---
 data/strings/en.ini                           |   2 +
 data/widgets/tag_properties.xml               |   5 +
 docs/ase-file-specs.md                        |  10 +-
 src/app/CMakeLists.txt                        |   1 +
 src/app/cmd/set_tag_repeat.cpp                |  38 ++
 src/app/cmd/set_tag_repeat.h                  |  38 ++
 src/app/commands/cmd_frame_tag_properties.cpp |   5 +
 src/app/commands/cmd_new_frame_tag.cpp        |   3 +-
 src/app/commands/cmd_save_file.cpp            |   4 +
 src/app/doc_diff.cpp                          |   5 +-
 src/app/doc_exporter.cpp                      |   3 +
 src/app/file/ase_format.cpp                   |   3 +-
 src/app/script/engine.cpp                     |   1 +
 src/app/ui/editor/play_state.cpp              |  47 +-
 src/app/ui/editor/play_state.h                |   4 +-
 src/app/ui/layer_frame_comboboxes.cpp         |   4 +-
 src/app/ui/tag_window.cpp                     |  69 ++-
 src/app/ui/tag_window.h                       |  24 +-
 src/app/ui/timeline/timeline.cpp              |   2 +-
 src/dio/aseprite_decoder.cpp                  |   7 +-
 src/doc/CMakeLists.txt                        |   2 +-
 src/doc/anidir.cpp                            |   3 +
 src/doc/anidir.h                              |   4 +-
 src/doc/handle_anidir.cpp                     | 101 ----
 src/doc/handle_anidir.h                       |  28 -
 src/doc/playback.cpp                          | 500 ++++++++++++++++
 src/doc/playback.h                            | 136 +++++
 src/doc/playback_tests.cpp                    | 540 ++++++++++++++++++
 src/doc/tag.cpp                               |  14 +-
 src/doc/tag.h                                 |  14 +-
 src/doc/tag_io.cpp                            |  14 +-
 src/doc/tags.h                                |  14 +-
 src/render/render.cpp                         |  21 +-
 33 files changed, 1455 insertions(+), 211 deletions(-)
 create mode 100644 src/app/cmd/set_tag_repeat.cpp
 create mode 100644 src/app/cmd/set_tag_repeat.h
 delete mode 100644 src/doc/handle_anidir.cpp
 delete mode 100644 src/doc/handle_anidir.h
 create mode 100644 src/doc/playback.cpp
 create mode 100644 src/doc/playback.h
 create mode 100644 src/doc/playback_tests.cpp

diff --git a/data/strings/en.ini b/data/strings/en.ini
index fcbdd6361..18d4039eb 100644
--- a/data/strings/en.ini
+++ b/data/strings/en.ini
@@ -14,6 +14,7 @@ right_click = Right-click: Show playback options
 forward = Forward
 reverse = Reverse
 ping_pong = Ping-pong
+ping_pong_reverse = Ping-pong Reverse
 
 [ask_for_color_profile]
 title = Color Profile
@@ -1941,6 +1942,7 @@ from = From:
 to = To:
 color = Color:
 ani_dir = Animation Direction:
+repeat = Repeat:
 
 [tga_options]
 title = TGA Options
diff --git a/data/widgets/tag_properties.xml b/data/widgets/tag_properties.xml
index 13cf6136d..4d0f2303c 100644
--- a/data/widgets/tag_properties.xml
+++ b/data/widgets/tag_properties.xml
@@ -6,17 +6,22 @@
 <window id="tag_properties" text="@.title">
   <vbox>
     <grid id="properties_grid" columns="3">
+
       <label text="@.name" />
       <entry maxsize="256" id="name" magnet="true" cell_align="horizontal" expansive="true" />
       <button id="user_data" icon="icon_user_data" maxsize="32" tooltip="@general.user_data" />
+
       <label text="@.from" />
       <expr id="from" cell_hspan="2" />
 
       <label text="@.to" />
       <expr id="to" cell_hspan="2" />
+
       <label text="@.ani_dir" />
       <combobox id="anidir" cell_hspan="2" />
 
+      <check text="@.repeat" id="limit_repeat" />
+      <vbox id="repeat_placeholder" cell_hspan="2" />
     </grid>
     <grid columns="2">
       <separator horizontal="true" cell_hspan="2" minwidth="180" />
diff --git a/docs/ase-file-specs.md b/docs/ase-file-specs.md
index 98d8c95f1..80e858115 100644
--- a/docs/ase-file-specs.md
+++ b/docs/ase-file-specs.md
@@ -292,7 +292,15 @@ for each tag.
                   0 = Forward
                   1 = Reverse
                   2 = Ping-pong
-      BYTE[8]   For future (set to zero)
+                  3 = Ping-pong Reverse
+      WORD      Repeat N times. Play this animation section N times:
+                  0 = Doesn't specify (plays infinite in UI, once on export,
+                      for ping-pong it plays once in each direction)
+                  1 = Plays once (for ping-pong, it plays just in one direction)
+                  2 = Plays twice (for ping-pong, it plays once in one direction,
+                      and once in reverse)
+                  n = Plays N times
+      BYTE[6]   For future (set to zero)
       BYTE[3]   RGB values of the tag color
                   Deprecated, used only for backward compatibility with Aseprite v1.2.x
                   The color of the tag is the one in the user data field following
diff --git a/src/app/CMakeLists.txt b/src/app/CMakeLists.txt
index 64eb35ce4..c91c8fab9 100644
--- a/src/app/CMakeLists.txt
+++ b/src/app/CMakeLists.txt
@@ -521,6 +521,7 @@ add_library(app-lib
   cmd/set_tag_color.cpp
   cmd/set_tag_name.cpp
   cmd/set_tag_range.cpp
+  cmd/set_tag_repeat.cpp
   cmd/set_tileset_base_index.cpp
   cmd/set_tileset_name.cpp
   cmd/set_total_frames.cpp
diff --git a/src/app/cmd/set_tag_repeat.cpp b/src/app/cmd/set_tag_repeat.cpp
new file mode 100644
index 000000000..fd0d14b23
--- /dev/null
+++ b/src/app/cmd/set_tag_repeat.cpp
@@ -0,0 +1,38 @@
+// Aseprite
+// Copyright (C) 2021  Igara Studio S.A.
+//
+// This program is distributed under the terms of
+// the End-User License Agreement for Aseprite.
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include "app/cmd/set_tag_repeat.h"
+
+#include "doc/tag.h"
+
+namespace app {
+namespace cmd {
+
+SetTagRepeat::SetTagRepeat(Tag* tag, int repeat)
+  : WithTag(tag)
+  , m_oldRepeat(tag->repeat())
+  , m_newRepeat(repeat)
+{
+}
+
+void SetTagRepeat::onExecute()
+{
+  tag()->setRepeat(m_newRepeat);
+  tag()->incrementVersion();
+}
+
+void SetTagRepeat::onUndo()
+{
+  tag()->setRepeat(m_oldRepeat);
+  tag()->incrementVersion();
+}
+
+} // namespace cmd
+} // namespace app
diff --git a/src/app/cmd/set_tag_repeat.h b/src/app/cmd/set_tag_repeat.h
new file mode 100644
index 000000000..be139bb43
--- /dev/null
+++ b/src/app/cmd/set_tag_repeat.h
@@ -0,0 +1,38 @@
+// Aseprite
+// Copyright (C) 2021  Igara Studio S.A.
+//
+// This program is distributed under the terms of
+// the End-User License Agreement for Aseprite.
+
+#ifndef APP_CMD_SET_TAG_REPEAT_H_INCLUDED
+#define APP_CMD_SET_TAG_REPEAT_H_INCLUDED
+#pragma once
+
+#include "app/cmd.h"
+#include "app/cmd/with_tag.h"
+
+namespace app {
+namespace cmd {
+  using namespace doc;
+
+  class SetTagRepeat : public Cmd
+                      , public WithTag {
+  public:
+    SetTagRepeat(Tag* tag, int repeat);
+
+  protected:
+    void onExecute() override;
+    void onUndo() override;
+    size_t onMemSize() const override {
+      return sizeof(*this);
+    }
+
+  private:
+    int m_oldRepeat;
+    int m_newRepeat;
+  };
+
+} // namespace cmd
+} // namespace app
+
+#endif
diff --git a/src/app/commands/cmd_frame_tag_properties.cpp b/src/app/commands/cmd_frame_tag_properties.cpp
index 95427d5df..a06afc74f 100644
--- a/src/app/commands/cmd_frame_tag_properties.cpp
+++ b/src/app/commands/cmd_frame_tag_properties.cpp
@@ -13,6 +13,7 @@
 #include "app/cmd/set_tag_color.h"
 #include "app/cmd/set_tag_name.h"
 #include "app/cmd/set_tag_range.h"
+#include "app/cmd/set_tag_repeat.h"
 #include "app/cmd/set_user_data.h"
 #include "app/color.h"
 #include "app/commands/command.h"
@@ -108,6 +109,10 @@ void FrameTagPropertiesCommand::onExecute(Context* context)
   if (tag->aniDir() != anidir)
     tx(new cmd::SetTagAniDir(tag, anidir));
 
+  const int repeat = window.repeatValue();
+  if (tag->repeat() != repeat)
+    tx(new cmd::SetTagRepeat(tag, repeat));
+
   // Change user data
   doc::UserData userData = window.userDataValue();
   if (tag->userData() != userData) {
diff --git a/src/app/commands/cmd_new_frame_tag.cpp b/src/app/commands/cmd_new_frame_tag.cpp
index da48f7de1..bc72eb07b 100644
--- a/src/app/commands/cmd_new_frame_tag.cpp
+++ b/src/app/commands/cmd_new_frame_tag.cpp
@@ -1,5 +1,5 @@
 // Aseprite
-// Copyright (C) 2019-2020  Igara Studio S.A.
+// Copyright (C) 2019-2022  Igara Studio S.A.
 // Copyright (C) 2001-2018  David Capello
 //
 // This program is distributed under the terms of
@@ -69,6 +69,7 @@ void NewFrameTagCommand::onExecute(Context* context)
   tag->setFrameRange(from, to);
   tag->setName(window.nameValue());
   tag->setAniDir(window.aniDirValue());
+  tag->setRepeat(window.repeatValue());
   tag->setUserData(window.userDataValue());
 
   {
diff --git a/src/app/commands/cmd_save_file.cpp b/src/app/commands/cmd_save_file.cpp
index 7e30f1a88..08c53788b 100644
--- a/src/app/commands/cmd_save_file.cpp
+++ b/src/app/commands/cmd_save_file.cpp
@@ -202,6 +202,10 @@ void SaveFileBaseCommand::saveDocumentInBackground(
       case AniDir::PING_PONG:
         m_selFrames = m_selFrames.makePingPong();
         break;
+      case AniDir::PING_PONG_REVERSE:
+        m_selFrames = m_selFrames.makePingPong();
+        m_selFrames = m_selFrames.makeReverse();
+        break;
     }
   }
 
diff --git a/src/app/doc_diff.cpp b/src/app/doc_diff.cpp
index 4f915dcee..105ab0dd6 100644
--- a/src/app/doc_diff.cpp
+++ b/src/app/doc_diff.cpp
@@ -1,5 +1,5 @@
 // Aseprite
-// Copyright (C) 2019-2020  Igara Studio S.A.
+// Copyright (C) 2019-2022  Igara Studio S.A.
 // Copyright (C) 2018  David Capello
 //
 // This program is distributed under the terms of
@@ -67,7 +67,8 @@ DocDiff compare_docs(const Doc* a,
           aTag->toFrame()   != bTag->toFrame()   ||
           aTag->name()      != bTag->name()      ||
           aTag->color()     != bTag->color()     ||
-          aTag->aniDir()    != bTag->aniDir()) {
+          aTag->aniDir()    != bTag->aniDir() ||
+          aTag->repeat()    != bTag->repeat()) {
         diff.anything = diff.tags = true;
       }
     }
diff --git a/src/app/doc_exporter.cpp b/src/app/doc_exporter.cpp
index 3927d60da..1da404385 100644
--- a/src/app/doc_exporter.cpp
+++ b/src/app/doc_exporter.cpp
@@ -1435,6 +1435,9 @@ void DocExporter::createDataFile(const Samples& samples,
            << " \"from\": " << (tag->fromFrame()) << ","
            << " \"to\": " << (tag->toFrame()) << ","
            " \"direction\": \"" << escape_for_json(convert_anidir_to_string(tag->aniDir())) << "\"";
+        if (tag->repeat() > 0) {
+          os << ", \"repeat\": \"" << tag->repeat() << "\"";
+        }
         os << tag->userData() << " }";
       }
     }
diff --git a/src/app/file/ase_format.cpp b/src/app/file/ase_format.cpp
index ddd3b8b96..2a7549fdc 100644
--- a/src/app/file/ase_format.cpp
+++ b/src/app/file/ase_format.cpp
@@ -1109,7 +1109,8 @@ static void ase_file_write_tags_chunk(FILE* f,
     fputw(to, f);
     fputc((int)tag->aniDir(), f);
 
-    fputl(0, f);  // 8 reserved bytes
+    fputw(std::clamp(tag->repeat(), 0, Tag::kMaxRepeat), f);  // repeat
+    fputw(0, f);  // 6 reserved bytes
     fputl(0, f);
 
     fputc(doc::rgba_getr(tag->color()), f);
diff --git a/src/app/script/engine.cpp b/src/app/script/engine.cpp
index e9d757959..b917d8abe 100644
--- a/src/app/script/engine.cpp
+++ b/src/app/script/engine.cpp
@@ -275,6 +275,7 @@ Engine::Engine()
   setfield_integer(L, "FORWARD", doc::AniDir::FORWARD);
   setfield_integer(L, "REVERSE", doc::AniDir::REVERSE);
   setfield_integer(L, "PING_PONG", doc::AniDir::PING_PONG);
+  setfield_integer(L, "PING_PONG_REVERSE", doc::AniDir::PING_PONG_REVERSE);
   lua_pop(L, 1);
 
   lua_newtable(L);
diff --git a/src/app/ui/editor/play_state.cpp b/src/app/ui/editor/play_state.cpp
index ff2aa82bf..b363236fa 100644
--- a/src/app/ui/editor/play_state.cpp
+++ b/src/app/ui/editor/play_state.cpp
@@ -21,7 +21,6 @@
 #include "app/ui/editor/scrolling_state.h"
 #include "app/ui/skin/skin_theme.h"
 #include "app/ui_context.h"
-#include "doc/handle_anidir.h"
 #include "doc/tag.h"
 #include "ui/manager.h"
 #include "ui/message.h"
@@ -39,7 +38,6 @@ PlayState::PlayState(const bool playOnce,
   , m_toScroll(false)
   , m_playTimer(10)
   , m_nextFrameTime(-1)
-  , m_pingPongForward(true)
   , m_refFrame(0)
   , m_tag(nullptr)
 {
@@ -85,10 +83,17 @@ void PlayState::onEnterState(Editor* editor)
     m_editor->setFrame(frame);
   }
 
+  m_playback = doc::Playback(m_editor->sprite(),
+                             TagsList(), // TODO add support to follow subtags
+                             m_editor->frame(),
+                             m_playOnce ? doc::Playback::PlayOnce:
+                             m_playAll ? doc::Playback::PlayWithoutTagsInLoop:
+                                         doc::Playback::PlayInLoop,
+                             m_tag);
+
   m_toScroll = false;
   m_nextFrameTime = getNextFrameTime();
   m_curFrameTick = base::current_tick();
-  m_pingPongForward = true;
 
   // Maybe we came from ScrollingState and the timer is already
   // running.
@@ -195,40 +200,12 @@ void PlayState::onPlaybackTick()
 
   m_nextFrameTime -= (base::current_tick() - m_curFrameTick);
 
-  doc::Sprite* sprite = m_editor->sprite();
-
   while (m_nextFrameTime <= 0) {
-    doc::frame_t frame = m_editor->frame();
-
-    if (m_playOnce) {
-      bool atEnd = false;
-      if (m_tag) {
-        switch (m_tag->aniDir()) {
-          case AniDir::FORWARD:
-            atEnd = (frame == m_tag->toFrame());
-            break;
-          case AniDir::REVERSE:
-            atEnd = (frame == m_tag->fromFrame());
-            break;
-          case AniDir::PING_PONG:
-            atEnd = (!m_pingPongForward &&
-                     frame == m_tag->fromFrame());
-            break;
-        }
-      }
-      else {
-        atEnd = (frame == sprite->lastFrame());
-      }
-      if (atEnd) {
-        m_editor->stop();
-        break;
-      }
+    doc::frame_t frame = m_playback.nextFrame();
+    if (m_playback.isStopped()) {
+      m_editor->stop();
+      break;
     }
-
-    frame = calculate_next_frame(
-      sprite, frame, frame_t(1), m_tag,
-      m_pingPongForward);
-
     m_editor->setFrame(frame);
     m_nextFrameTime += getNextFrameTime();
   }
diff --git a/src/app/ui/editor/play_state.h b/src/app/ui/editor/play_state.h
index cf1751a60..6f7bce273 100644
--- a/src/app/ui/editor/play_state.h
+++ b/src/app/ui/editor/play_state.h
@@ -1,5 +1,5 @@
 // Aseprite
-// Copyright (C) 2020-2021  Igara Studio S.A.
+// Copyright (C) 2020-2022  Igara Studio S.A.
 // Copyright (C) 2001-2017  David Capello
 //
 // This program is distributed under the terms of
@@ -12,6 +12,7 @@
 #include "app/ui/editor/state_with_wheel_behavior.h"
 #include "base/time.h"
 #include "doc/frame.h"
+#include "doc/playback.h"
 #include "obs/connection.h"
 #include "ui/timer.h"
 
@@ -50,6 +51,7 @@ namespace app {
     double getNextFrameTime();
 
     Editor* m_editor;
+    doc::Playback m_playback;
     bool m_playOnce;
     bool m_playAll;
     bool m_toScroll;
diff --git a/src/app/ui/layer_frame_comboboxes.cpp b/src/app/ui/layer_frame_comboboxes.cpp
index 495e8c08f..e93af3474 100644
--- a/src/app/ui/layer_frame_comboboxes.cpp
+++ b/src/app/ui/layer_frame_comboboxes.cpp
@@ -141,11 +141,13 @@ void fill_anidir_combobox(ui::ComboBox* anidir, doc::AniDir defAnidir)
   static_assert(
     int(doc::AniDir::FORWARD) == 0 &&
     int(doc::AniDir::REVERSE) == 1 &&
-    int(doc::AniDir::PING_PONG) == 2, "doc::AniDir has changed");
+    int(doc::AniDir::PING_PONG) == 2 &&
+    int(doc::AniDir::PING_PONG_REVERSE) == 3, "doc::AniDir has changed");
 
   anidir->addItem(Strings::anidir_combo_forward());
   anidir->addItem(Strings::anidir_combo_reverse());
   anidir->addItem(Strings::anidir_combo_ping_pong());
+  anidir->addItem(Strings::anidir_combo_ping_pong_reverse());
   anidir->setSelectedItemIndex(int(defAnidir));
 }
 
diff --git a/src/app/ui/tag_window.cpp b/src/app/ui/tag_window.cpp
index 5126af33e..215c8570c 100644
--- a/src/app/ui/tag_window.cpp
+++ b/src/app/ui/tag_window.cpp
@@ -15,14 +15,41 @@
 #include "app/pref/preferences.h"
 #include "app/ui/layer_frame_comboboxes.h"
 #include "app/ui/user_data_view.h"
+#include "base/convert_to.h"
 #include "doc/sprite.h"
 #include "doc/tag.h"
 #include "ui/manager.h"
+#include "ui/message.h"
 
 #include <algorithm>
 
 namespace app {
 
+const char* kInfiniteSymbol = "\xE2\x88\x9E"; // Infinite symbol (UTF-8)
+
+TagWindow::Repeat::Repeat()
+{
+}
+
+bool TagWindow::Repeat::onProcessMessage(ui::Message* msg)
+{
+  switch (msg->type()) {
+    case ui::kFocusEnterMessage: {
+      if (text() == kInfiniteSymbol)
+        setText("");
+      break;
+    }
+  }
+  return ExprEntry::onProcessMessage(msg);
+}
+
+void TagWindow::Repeat::onFormatExprFocusLeave(std::string& buf)
+{
+  ExprEntry::onFormatExprFocusLeave(buf);
+  if (buf.empty() || base::convert_to<int>(buf) == 0)
+    buf = kInfiniteSymbol;
+}
+
 TagWindow::TagWindow(const doc::Sprite* sprite, const doc::Tag* tag)
   : m_sprite(sprite)
   , m_base(Preferences::instance().document(
@@ -32,11 +59,25 @@ TagWindow::TagWindow(const doc::Sprite* sprite, const doc::Tag* tag)
 {
   m_userDataView.configureAndSet(m_userData, propertiesGrid());
 
+  repeatPlaceholder()->addChild(&m_repeat);
+
   name()->setText(tag->name());
   from()->setTextf("%d", tag->fromFrame()+m_base);
   to()->setTextf("%d", tag->toFrame()+m_base);
 
+  if (tag->repeat() > 0) {
+    limitRepeat()->setSelected(true);
+    repeat()->setTextf("%d", tag->repeat());
+  }
+  else {
+    limitRepeat()->setSelected(false);
+    repeat()->setText(kInfiniteSymbol);
+  }
+
   fill_anidir_combobox(anidir(), tag->aniDir());
+
+  limitRepeat()->Click.connect([this]{ onLimitRepeat(); });
+  repeat()->Change.connect([this]{ onRepeatChange(); });
   userData()->Click.connect([this]{ onToggleUserData(); });
 }
 
@@ -46,12 +87,12 @@ bool TagWindow::show()
   return (closer() == ok());
 }
 
-std::string TagWindow::nameValue()
+std::string TagWindow::nameValue() const
 {
   return name()->text();
 }
 
-void TagWindow::rangeValue(doc::frame_t& from, doc::frame_t& to)
+void TagWindow::rangeValue(doc::frame_t& from, doc::frame_t& to) const
 {
   doc::frame_t first = 0;
   doc::frame_t last = m_sprite->lastFrame();
@@ -62,11 +103,33 @@ void TagWindow::rangeValue(doc::frame_t& from, doc::frame_t& to)
   to   = std::clamp(to, from, last);
 }
 
-doc::AniDir TagWindow::aniDirValue()
+doc::AniDir TagWindow::aniDirValue() const
 {
   return (doc::AniDir)anidir()->getSelectedItemIndex();
 }
 
+int TagWindow::repeatValue() const
+{
+  return repeat()->textInt();
+}
+
+void TagWindow::onLimitRepeat()
+{
+  if (limitRepeat()->isSelected())
+    repeat()->setText("1");
+  else
+    repeat()->setText(kInfiniteSymbol);
+}
+
+void TagWindow::onRepeatChange()
+{
+  if (repeat()->text().empty() ||
+      repeat()->textInt() == 0)
+    limitRepeat()->setSelected(false);
+  else
+    limitRepeat()->setSelected(true);
+}
+
 void TagWindow::onToggleUserData()
 {
   m_userDataView.toggleVisibility();
diff --git a/src/app/ui/tag_window.h b/src/app/ui/tag_window.h
index 92601680e..ef41e144e 100644
--- a/src/app/ui/tag_window.h
+++ b/src/app/ui/tag_window.h
@@ -1,5 +1,5 @@
 // Aseprite
-// Copyright (C) 2019-2020  Igara Studio S.A.
+// Copyright (C) 2019-2022  Igara Studio S.A.
 // Copyright (C) 2001-2017  David Capello
 //
 // This program is distributed under the terms of
@@ -10,6 +10,7 @@
 #pragma once
 
 #include "app/ui/color_button.h"
+#include "app/ui/expr_entry.h"
 #include "app/ui/user_data_view.h"
 #include "doc/anidir.h"
 #include "doc/frame.h"
@@ -30,18 +31,33 @@ namespace app {
 
     bool show();
 
-    std::string nameValue();
-    void rangeValue(doc::frame_t& from, doc::frame_t& to);
-    doc::AniDir aniDirValue();
+    std::string nameValue() const;
+    void rangeValue(doc::frame_t& from, doc::frame_t& to) const;
+    doc::AniDir aniDirValue() const;
+    int repeatValue() const;
     const doc::UserData& userDataValue() const { return m_userDataView.userData(); }
 
   private:
+    class Repeat : public ExprEntry {
+    public:
+      Repeat();
+    private:
+      bool onProcessMessage(ui::Message* msg) override;
+      void onFormatExprFocusLeave(std::string& buf) override;
+    };
+
+    const Repeat* repeat() const { return &m_repeat; }
+    Repeat* repeat() { return &m_repeat; }
+
+    void onLimitRepeat();
+    void onRepeatChange();
     void onToggleUserData();
 
     const doc::Sprite* m_sprite;
     int m_base;
     doc::UserData m_userData;
     UserDataView m_userDataView;
+    Repeat m_repeat;
   };
 
 }
diff --git a/src/app/ui/timeline/timeline.cpp b/src/app/ui/timeline/timeline.cpp
index 6b1c28199..919c43a35 100644
--- a/src/app/ui/timeline/timeline.cpp
+++ b/src/app/ui/timeline/timeline.cpp
@@ -584,7 +584,7 @@ void Timeline::activateClipboardRange()
 }
 
 Tag* Timeline::getTagByFrame(const frame_t frame,
-                                       const bool getLoopTagIfNone)
+                             const bool getLoopTagIfNone)
 {
   if (!m_sprite)
     return nullptr;
diff --git a/src/dio/aseprite_decoder.cpp b/src/dio/aseprite_decoder.cpp
index e132604af..1ba1a2e7a 100644
--- a/src/dio/aseprite_decoder.cpp
+++ b/src/dio/aseprite_decoder.cpp
@@ -986,11 +986,13 @@ void AsepriteDecoder::readTagsChunk(doc::Tags* tags)
     int aniDir = read8();
     if (aniDir != int(doc::AniDir::FORWARD) &&
         aniDir != int(doc::AniDir::REVERSE) &&
-        aniDir != int(doc::AniDir::PING_PONG)) {
+        aniDir != int(doc::AniDir::PING_PONG) &&
+        aniDir != int(doc::AniDir::PING_PONG_REVERSE)) {
       aniDir = int(doc::AniDir::FORWARD);
     }
 
-    read32();                     // 8 reserved bytes
+    int repeat = read16();      // Number of times we repeat this tag
+    read16();                   // 6 reserved bytes
     read32();
 
     int r = read8();
@@ -1009,6 +1011,7 @@ void AsepriteDecoder::readTagsChunk(doc::Tags* tags)
 
     tag->setName(name);
     tag->setAniDir((doc::AniDir)aniDir);
+    tag->setRepeat(repeat);
     tags->add(tag);
   }
 }
diff --git a/src/doc/CMakeLists.txt b/src/doc/CMakeLists.txt
index 391c06a39..63a32b10d 100644
--- a/src/doc/CMakeLists.txt
+++ b/src/doc/CMakeLists.txt
@@ -39,7 +39,6 @@ add_library(doc-lib
   file/pal_file.cpp
   grid.cpp
   grid_io.cpp
-  handle_anidir.cpp
   image.cpp
   image_impl.cpp
   image_io.cpp
@@ -55,6 +54,7 @@ add_library(doc-lib
   octree_map.cpp
   palette.cpp
   palette_io.cpp
+  playback.cpp
   primitives.cpp
   remap.cpp
   rgbmap_rgb5a3.cpp
diff --git a/src/doc/anidir.cpp b/src/doc/anidir.cpp
index 5c99ceb1e..16be076f0 100644
--- a/src/doc/anidir.cpp
+++ b/src/doc/anidir.cpp
@@ -1,4 +1,5 @@
 // Aseprite Document Library
+// Copyright (c) 2021 Igara Studio S.A.
 // Copyright (c) 2001-2018 David Capello
 //
 // This file is released under the terms of the MIT license.
@@ -18,6 +19,7 @@ std::string convert_anidir_to_string(AniDir anidir)
     case AniDir::FORWARD: return "forward";
     case AniDir::REVERSE: return "reverse";
     case AniDir::PING_PONG: return "pingpong";
+    case AniDir::PING_PONG_REVERSE: return "pingpong_reverse";
   }
   return "";
 }
@@ -27,6 +29,7 @@ doc::AniDir convert_string_to_anidir(const std::string& s)
   if (s == "forward") return AniDir::FORWARD;
   if (s == "reverse") return AniDir::REVERSE;
   if (s == "pingpong") return AniDir::PING_PONG;
+  if (s == "pingpong_reverse") return AniDir::PING_PONG_REVERSE;
   return AniDir::FORWARD;
 }
 
diff --git a/src/doc/anidir.h b/src/doc/anidir.h
index 6859ee2ff..63809133f 100644
--- a/src/doc/anidir.h
+++ b/src/doc/anidir.h
@@ -1,4 +1,5 @@
 // Aseprite Document Library
+// Copyright (c) 2021 Igara Studio S.A.
 // Copyright (c) 2001-2018 David Capello
 //
 // This file is released under the terms of the MIT license.
@@ -15,7 +16,8 @@ namespace doc {
   enum class AniDir {
     FORWARD = 0,
     REVERSE = 1,
-    PING_PONG = 2,
+    PING_PONG = 2,              // First playback is in forward
+    PING_PONG_REVERSE = 3,      // First playback is in reverse
   };
 
   std::string convert_anidir_to_string(AniDir anidir);
diff --git a/src/doc/handle_anidir.cpp b/src/doc/handle_anidir.cpp
deleted file mode 100644
index a8c37fbad..000000000
--- a/src/doc/handle_anidir.cpp
+++ /dev/null
@@ -1,101 +0,0 @@
-// Aseprite Document Library
-// Copyright (C) 2019-2022  Igara Studio S.A.
-// Copyright (C) 2001-2016  David Capello
-//
-// This file is released under the terms of the MIT license.
-// Read LICENSE.txt for more information.
-
-#ifdef HAVE_CONFIG_H
-#include "config.h"
-#endif
-
-#include "doc/handle_anidir.h"
-
-#include "doc/frame.h"
-#include "doc/sprite.h"
-#include "doc/tag.h"
-
-namespace doc {
-
-frame_t calculate_next_frame(
-  const Sprite* sprite,
-  frame_t frame,
-  frame_t frameDelta,
-  const Tag* tag,
-  bool& pingPongForward)
-{
-  if (frameDelta == 0)
-    return frame;
-
-  frame_t first = frame_t(0);
-  frame_t last = sprite->lastFrame();
-  AniDir aniDir = AniDir::FORWARD;
-
-  if (tag) {
-    frame_t loopFrom, loopTo;
-
-    loopFrom = tag->fromFrame();
-    loopTo   = tag->toFrame();
-    loopFrom = std::clamp(loopFrom, first, last);
-    loopTo   = std::clamp(loopTo, first, last);
-
-    first  = loopFrom;
-    last   = loopTo;
-    aniDir = tag->aniDir();
-  }
-
-  frame_t frameRange = (last - first + 1);
-
-  switch (aniDir) {
-
-    case AniDir::REVERSE:
-      frameDelta = -frameDelta;
-      [[fallthrough]];
-
-    case AniDir::FORWARD:
-      frame += frameDelta;
-      while (frame > last) frame -= frameRange;
-      while (frame < first) frame += frameRange;
-      break;
-
-    case AniDir::PING_PONG: {
-      bool invertPingPong;
-      if (frameDelta < 0) {
-        frameDelta = -frameDelta;
-        pingPongForward = !pingPongForward;
-        invertPingPong = true;
-      }
-      else
-       invertPingPong = false;
-
-      while (--frameDelta >= 0) {
-        if (pingPongForward) {
-          ++frame;
-          if (frame > last) {
-            frame = last-1;
-            if (frame < first)
-              frame = first;
-            pingPongForward = false;
-          }
-        }
-        else {
-          --frame;
-          if (frame < first) {
-            frame = first+1;
-            if (frame > last)
-              frame = last;
-            pingPongForward = true;
-          }
-        }
-      }
-
-      if (invertPingPong)
-        pingPongForward = !pingPongForward;
-      break;
-    }
-  }
-
-  return frame;
-}
-
-} // namespace doc
diff --git a/src/doc/handle_anidir.h b/src/doc/handle_anidir.h
deleted file mode 100644
index 033782a06..000000000
--- a/src/doc/handle_anidir.h
+++ /dev/null
@@ -1,28 +0,0 @@
-// Aseprite Document Library
-// Copyright (C) 2019  Igara Studio S.A.
-// Copyright (C) 2001-2015  David Capello
-//
-// This file is released under the terms of the MIT license.
-// Read LICENSE.txt for more information.
-
-#ifndef DOC_HANDLE_ANIDIR_H_INCLUDED
-#define DOC_HANDLE_ANIDIR_H_INCLUDED
-#pragma once
-
-#include "doc/frame.h"
-
-namespace doc {
-
-  class Sprite;
-  class Tag;
-
-  frame_t calculate_next_frame(
-    const Sprite* sprite,
-    frame_t frame,
-    frame_t frameDelta,
-    const Tag* tag,
-    bool& pingPongForward);
-
-} // namespace doc
-
-#endif
diff --git a/src/doc/playback.cpp b/src/doc/playback.cpp
new file mode 100644
index 000000000..7b8cb5cd3
--- /dev/null
+++ b/src/doc/playback.cpp
@@ -0,0 +1,500 @@
+// Aseprite Document Library
+// Copyright (C) 2021-2022  Igara Studio S.A.
+//
+// This file is released under the terms of the MIT license.
+// Read LICENSE.txt for more information.
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include "doc/playback.h"
+
+#include "doc/frame.h"
+#include "doc/sprite.h"
+#include "doc/tag.h"
+
+#include <limits>
+
+#define PLAY_TRACE(...) // TRACEARGS
+
+namespace doc {
+
+[[maybe_unused]]
+static const char* mode_to_string(Playback::Mode mode)
+{
+  switch (mode) {
+    case Playback::PlayAll: return "PlayAll";
+    case Playback::PlayInLoop: return "PlayInLoop";
+    case Playback::PlayWithoutTagsInLoop: return "PlayWithoutTagsInLoop";
+    case Playback::PlayOnce: return "PlayOnce";
+    case Playback::Stopped: return "Stopped";
+  }
+  return "";
+}
+
+Playback::PlayTag::PlayTag(const Tag* tag, int parentForward)
+  : tag(tag)
+  , forward(parentForward * (tag->aniDir() == AniDir::FORWARD ||
+                             tag->aniDir() == AniDir::PING_PONG ? 1: -1))
+{
+  if (tag->repeat() > 0) {
+    repeat = tag->repeat();
+  }
+  // Repeat=0 is a "infinite repeat", but we'll play the tag just
+  // once.
+  else {
+    if (tag->aniDir() == AniDir::PING_PONG ||
+        tag->aniDir() == AniDir::PING_PONG_REVERSE) {
+      repeat = 2;
+    }
+    else {
+      repeat = 1;
+    }
+  }
+}
+
+Playback::Playback(const Sprite* sprite,
+                   const TagsList& tags,
+                   const frame_t frame,
+                   const Mode playMode,
+                   const Tag* tag)
+  : m_sprite(sprite)
+  , m_tags(tags)
+  , m_initialFrame(frame)
+  , m_frame(frame)
+  , m_playMode(playMode)
+{
+  PLAY_TRACE("--Playback-- tag=", (tag ? tag->name(): ""), "mode=", mode_to_string(m_playMode));
+
+  // Go to the first frame of the animation or active frame tag
+  if (playMode == Mode::PlayOnce) {
+    if (tag) {
+      m_frame = (tag->aniDir() == AniDir::REVERSE ||
+                 tag->aniDir() == AniDir::PING_PONG_REVERSE ?
+                 tag->toFrame():
+                 tag->fromFrame());
+
+      addTag(tag, false, 1);
+    }
+    else {
+      m_frame = 0;
+    }
+  }
+  else if (playMode == Mode::PlayInLoop) {
+    if (tag) {
+      addTag(tag, false, 1);
+
+      // Loop the given tag in the constructor infite times
+      m_playing.back()->repeat = std::numeric_limits<int>::max();
+    }
+  }
+
+  if (m_sprite)
+    handleEnterFrame(frame, true);
+}
+
+Playback::Playback(const Sprite* sprite,
+                   const frame_t frame,
+                   const Mode playMode,
+                   const Tag* tag)
+  : Playback(sprite,
+             (sprite ? sprite->tags().getInternalList(): TagsList()),
+             frame,
+             playMode,
+             tag)
+{
+}
+
+frame_t Playback::nextFrame(frame_t frameDelta)
+{
+  PLAY_TRACE("  Playback::nextFrame { frame=", m_frame, "+", frameDelta);
+
+  int step = (frameDelta > 0 ? +1: -1);
+
+  while (frameDelta != 0 && m_playMode != Stopped) {
+    bool move = handleExitFrame(step);
+    if (move)
+      handleMoveFrame(step);
+    handleEnterFrame(step, false);
+
+    if (frameDelta > 0)
+      --frameDelta;
+    else if (frameDelta < 0)
+      ++frameDelta;
+  }
+
+  PLAY_TRACE("  } =", m_frame,
+             "(tag=", (tag() ? tag()->name(): "nullptr"),
+             ", repeat=", (!m_playing.empty() ? m_playing.back()->repeat: -1), ")");
+  return m_frame;
+}
+
+void Playback::stop()
+{
+  if (m_playMode == Mode::PlayAll ||
+      m_playMode == Mode::PlayOnce) {
+    m_frame = m_initialFrame;
+  }
+  m_playMode = Mode::Stopped;
+}
+
+Tag* Playback::tag() const
+{
+  return (!m_playing.empty() ? const_cast<Tag*>(m_playing.back()->tag): nullptr);
+}
+
+void Playback::handleEnterFrame(const frame_t frameDelta, const bool firstTime)
+{
+  PLAY_TRACE("    handleEnterFrame", m_frame, "+", frameDelta);
+
+  switch (m_playMode) {
+
+    case PlayAll:
+    case PlayInLoop: {
+      const Tag* tag = this->tag();
+      const frame_t frame = m_frame;
+      const int forward = getParentForward();
+
+      for (const Tag* t : m_tags) {
+        if (t->contains(frame)) {
+          // Ignored tags that were played
+          if (m_played.find(t) != m_played.end()) {
+            continue;
+          }
+
+          if (tag &&
+              (tag->toFrame() < t->toFrame() ||
+               tag->fromFrame() > t->fromFrame())) {
+            // Cascade
+            addTag(t, true, 1);
+          }
+          else {
+            addTag(t, false, forward);
+            if (!firstTime)
+              goToFirstTagFrame(t, frameDelta);
+          }
+        }
+      }
+      break;
+    }
+
+    case PlayWithoutTagsInLoop:
+    case PlayOnce:
+      // Do nothing
+      break;
+
+  }
+}
+
+bool Playback::handleExitFrame(const frame_t frameDelta)
+{
+  PLAY_TRACE("    handleExitFrame", m_frame, "+", frameDelta);
+
+  switch (m_playMode) {
+
+    case PlayAll:
+    case PlayInLoop: {
+      if (auto tag = this->tag()) {
+        ASSERT(!m_playing.empty());
+        int forward = m_playing.back()->forward;
+
+        PLAY_TRACE("tag aniDir=", (int)tag->aniDir(),
+                   "range=", (int)tag->fromFrame(), (int)tag->toFrame(),
+                   "forward=", forward);
+
+        if ((tag->aniDir() == AniDir::FORWARD ||
+             tag->aniDir() == AniDir::REVERSE)
+            && ((forward > 0 && m_frame == tag->toFrame())
+                ||
+                (forward < 0 && m_frame == tag->fromFrame()))) {
+          decrementRepeat(frameDelta);
+          return false;
+        }
+        // Change ping-pong direction
+        else if ((tag->aniDir() == AniDir::PING_PONG ||
+                  tag->aniDir() == AniDir::PING_PONG_REVERSE)
+                 && ((m_frame == tag->fromFrame() && forward < 0)
+                     || (m_frame == tag->toFrame() && forward > 0))) {
+          PLAY_TRACE("    Changing direction frame=", m_frame,
+                     " forward=", forward, "->", -forward);
+
+          // Changing the direction of the ping-pong animation
+          m_playing.back()->invertForward();
+          return decrementRepeat(frameDelta);
+        }
+      }
+
+      if (frameDelta > 0 && m_frame == m_sprite->lastFrame()) {
+        if (m_playMode == PlayInLoop) {
+          PLAY_TRACE("    Going back to frame=0 (PlayInLoop)", m_frame,
+                     m_sprite->lastFrame());
+          m_frame = 0;
+          return false;
+        }
+        else {
+          PLAY_TRACE("    Stop animation (PlayAll)");
+          stop();
+          return false;
+        }
+      }
+      else if (frameDelta < 0 && m_frame == 0) {
+        if (m_playMode == PlayInLoop) {
+          PLAY_TRACE("    Going back to frame=last frame (PlayInLoop)");
+          m_frame = m_sprite->lastFrame();
+          return false;
+        }
+        else {
+          PLAY_TRACE("    Stop animation in first frame (PlayAll)");
+          stop();
+          return false;
+        }
+      }
+      break;
+    }
+
+    case PlayWithoutTagsInLoop:
+      // Do nothing
+      break;
+
+    case PlayOnce: {
+      if (auto tag = this->tag()) {
+        ASSERT(m_playing.size() == 1);
+        int forward = m_playing.back()->forward;
+
+        if ((tag->aniDir() == AniDir::FORWARD && m_frame == tag->toFrame()) ||
+            (tag->aniDir() == AniDir::REVERSE && m_frame == tag->fromFrame()) ||
+            (tag->aniDir() == AniDir::PING_PONG && m_frame == tag->fromFrame() && forward < 0) ||
+            (tag->aniDir() == AniDir::PING_PONG_REVERSE && m_frame == tag->toFrame() && forward > 0)) {
+          stop();
+          return false;
+        }
+        else if ((tag->aniDir() == AniDir::PING_PONG &&
+                  m_frame == tag->toFrame() && forward > 0)
+                 || (tag->aniDir() == AniDir::PING_PONG_REVERSE &&
+                     m_frame == tag->fromFrame() && forward < 0)) {
+          PLAY_TRACE("    Changing direction frame=", m_frame,
+                     " forward=", forward, "->", -forward);
+
+          // Changing the direction of the ping-pong animation
+          m_playing.back()->invertForward();
+        }
+      }
+      else if ((frameDelta > 0 && m_frame == m_sprite->lastFrame()) ||
+               (frameDelta < 0 && m_frame == 0)) {
+        stop();
+        return false;
+      }
+      break;
+    }
+
+  }
+
+  return true;
+}
+
+void Playback::handleMoveFrame(const frame_t frameDelta)
+{
+  PLAY_TRACE("    handleMoveFrame", m_frame, "+", frameDelta);
+
+  switch (m_playMode) {
+
+    case PlayWithoutTagsInLoop: {
+      ASSERT(m_playing.empty());
+
+      frame_t first = 0;
+      frame_t last = m_sprite->lastFrame();
+      m_frame += frameDelta;
+      if (m_frame < 0) m_frame = last;
+      if (m_frame > last) m_frame = first;
+      break;
+    }
+
+    case PlayAll:
+    case PlayInLoop:
+    case PlayOnce: {
+      m_frame += frameDelta * getParentForward();
+      break;
+    }
+
+  }
+}
+
+void Playback::addTag(const Tag* tag,
+                      const bool rewind,
+                      const int forward)
+{
+  auto playTag = std::make_unique<PlayTag>(tag, forward);
+
+  PLAY_TRACE("    addTag", tag->name(),
+             "rewind", rewind,
+             "new playTag forward", playTag->forward);
+
+  if (rewind) {
+    playTag->rewind = true;
+
+    // Delay the deletion of currentPlayTag to this new tag
+    PlayTag* currentPlayTag = m_playing.back().get();
+    PlayTag* delayed = currentPlayTag;
+
+    while (delayed->delayedDelete)
+      delayed = delayed->delayedDelete;
+    delayed->delayedDelete = playTag.get();
+    for (const Tag* otherTag : delayed->removeThese)
+      playTag->removeThese.push_back(otherTag);
+    playTag->removeThese.push_back(delayed->tag);
+    delayed->removeThese.clear();
+
+    auto it = m_playing.end(),
+      begin = m_playing.begin();
+    --it;
+    ASSERT(it->get() == currentPlayTag);
+    while (it != begin) {
+      if ((*it)->tag == delayed->tag)
+        break;
+      --it;
+    }
+
+    m_playing.insert(it, std::move(playTag));
+  }
+  else {
+    m_playing.push_back(std::move(playTag));
+  }
+  m_played.insert(tag);
+}
+
+void Playback::removeLastTagFromPlayed()
+{
+  PlayTag* playTag = m_playing.back().get();
+
+  for (auto otherTag : playTag->removeThese) {
+    auto it = m_played.find(otherTag);
+    ASSERT(it != m_played.end());
+    if (it != m_played.end())
+      m_played.erase(it);
+  }
+
+  auto it = m_played.find(playTag->tag);
+  ASSERT(it != m_played.end());
+  if (it != m_played.end())
+    m_played.erase(it);
+}
+
+bool Playback::decrementRepeat(const frame_t frameDelta)
+{
+  while (true) {
+    Tag* tag = this->tag();
+    PLAY_TRACE("    Decrement tag", tag->name(),
+               "repeat", m_playing.back()->repeat, "-1");
+
+    if (m_playing.back()->repeat > 1) {
+      --m_playing.back()->repeat;
+      goToFirstTagFrame(tag, frameDelta);
+
+      PLAY_TRACE("    Repeat tag", tag->name(), " frame=", m_frame,
+                 "repeat=", m_playing.back()->repeat,
+                 "forward=", m_playing.back()->forward);
+      return true;
+    }
+    else {
+      // Remove tag from played
+      if (!m_playing.back()->delayedDelete) {
+        PLAY_TRACE("    Removing played tag", tag->name());
+        removeLastTagFromPlayed();
+      }
+      else {
+        PLAY_TRACE("    Delaying the removal of played tag", tag->name());
+      }
+
+      // Delete and remove PlayTag
+      m_playing.pop_back();
+
+      // Forward direction of the parent tag
+      int forward = (m_playing.empty() ? +1: m_playing.back()->forward);
+      bool rewind = (m_playing.empty() ? false: m_playing.back()->rewind);
+
+      // New frame outside the tag
+      frame_t newFrame;
+      if (rewind) {
+        newFrame = firstTagFrame(m_playing.back()->tag, frameDelta);
+      }
+      else {
+        newFrame = (frameDelta * forward < 0 ? tag->fromFrame()-1: tag->toFrame()+1);
+      }
+
+      PLAY_TRACE("    After tag", tag->name(),
+                 "possible new frame=", newFrame,
+                 "forward", forward);
+
+      if (newFrame < 0 || newFrame > m_sprite->lastFrame()) {
+        if (m_playMode == PlayAll) {
+          stop();
+          return false;
+        }
+        if (newFrame < 0)
+          newFrame = m_sprite->lastFrame();
+        else if (newFrame > m_sprite->lastFrame())
+          newFrame = 0;
+      }
+
+      m_frame = newFrame;
+
+      if (auto newTag = this->tag()) {
+        if (newTag->contains(m_frame)) {
+          PLAY_TRACE("    Back to tag", newTag->name(), "frame=", m_frame);
+          return false;
+        }
+        else {
+          // Now we try to decrement this tag repeat counter...
+        }
+      }
+      else {
+        // Special case where a ping-pong animation ends in the 1st
+        // frame and we are playing in loop mode, so starting the
+        // animation again should continue in the 2nd frame
+        if (m_playing.empty() &&
+            m_playMode == PlayInLoop &&
+            (tag->aniDir() == AniDir::PING_PONG ||
+             tag->aniDir() == AniDir::PING_PONG_REVERSE) &&
+            tag->fromFrame() == 0 &&
+            tag->toFrame() == m_sprite->lastFrame()) {
+          PLAY_TRACE("    Re-adding ping-pong tag", tag->name(), "frame=", m_frame);
+          addTag(tag, false, getParentForward());
+          return false;
+        }
+        else {
+          PLAY_TRACE("    Going outside the tag", tag->name(), "frame=", m_frame);
+          return false;
+        }
+      }
+    }
+  }
+}
+
+frame_t Playback::firstTagFrame(const Tag* tag,
+                                const frame_t frameDelta)
+{
+  ASSERT(tag);
+  ASSERT(!m_playing.empty());
+  int forward = m_playing.back()->forward;
+  return (frameDelta * forward < 0 ? tag->toFrame():
+                                     tag->fromFrame());
+}
+
+void Playback::goToFirstTagFrame(const Tag* tag,
+                                 const frame_t frameDelta)
+{
+  ASSERT(tag);
+  m_frame = firstTagFrame(tag, frameDelta);
+  PLAY_TRACE("    Go to first frame of tag", tag->name(), "frame=", m_frame);
+}
+
+int Playback::getParentForward() const
+{
+  if (m_playing.empty())
+    return 1;
+  else
+    return m_playing.back()->forward;
+}
+
+} // namespace doc
diff --git a/src/doc/playback.h b/src/doc/playback.h
new file mode 100644
index 000000000..fd0b7f24e
--- /dev/null
+++ b/src/doc/playback.h
@@ -0,0 +1,136 @@
+// Aseprite Document Library
+// Copyright (C) 2021-2022  Igara Studio S.A.
+//
+// This file is released under the terms of the MIT license.
+// Read LICENSE.txt for more information.
+
+#ifndef DOC_PLAYBACK_H_INCLUDED
+#define DOC_PLAYBACK_H_INCLUDED
+#pragma once
+
+#include "doc/frame.h"
+#include "doc/tag.h"
+#include "doc/tags.h"
+
+#include <memory>
+#include <set>
+#include <vector>
+
+namespace doc {
+
+  class Sprite;
+  class Tag;
+
+  class Playback {
+  public:
+    enum Mode {
+      // Play all the animation until it ends (infinite loops just
+      // played once). Useful to export GIF files with tags+loops.
+      PlayAll,
+      // Regular playback mode for a sprite editor when we start
+      // playing in no tag (infinite loops are just played once, tags
+      // with repeat are respected). We start from the given frame on
+      // Playback() ctor.
+      PlayInLoop,
+      // Play all frames ignoring tags in loop from the first frame to
+      // the last one.
+      PlayWithoutTagsInLoop,
+      // Play once the full sprite or the given tag from beginning to
+      // end (ignoring starting frame, but we back to the starting
+      // frame when the animation stops). Useful to play the full
+      // sprite/current tag in one snapshot.
+      PlayOnce,
+      // We reached the end of the playback (generally we reach this
+      // state after a full PlayAll or PlayOnce, and never in a
+      // PlayInLoop).
+      Stopped,
+    };
+
+    Playback(const Sprite* sprite,
+             const TagsList& tagsList,
+             const frame_t frame,
+             const Mode playMode,
+             const Tag* tag);
+
+    Playback(const Sprite* sprite = nullptr,
+             const frame_t frame = 0,
+             const Mode playMode = PlayAll,
+             const Tag* tag = nullptr);
+
+    frame_t initialFrame() const { return m_initialFrame; }
+    frame_t frame() const { return m_frame; }
+
+    bool isStopped() const { return m_playMode == Mode::Stopped; }
+    void stop();
+
+    // Sets the list of possible tags to iterate/enter when we are
+    // playing. By default are all the available sprite tags.
+    void setTags(const TagsList& tags) {
+      m_tags = tags;
+    }
+
+    // If "delta" is +1, it's the next frame, if it's -1, it's the
+    // previous frame, etc.
+    frame_t nextFrame(frame_t frameDelta = frame_t(+1));
+
+    // The tag that is being played right now (can be nullptr).
+    Tag* tag() const;
+
+  private:
+    // Information about playing tags (and inner tags)
+    struct PlayTag {
+      const Tag* tag = nullptr;
+      int forward = 1;
+      int repeat = 0;
+      // True if we have to go to the first tag frame when we enter to
+      // this PlayTag. Used for overlapped tags, e.g.
+      //  A
+      // ---> B
+      //   ---->
+      // 0 1 2 3
+      //
+      // The tag "B" will have rewind=true, because when we finish
+      // "A", we should start from the beginning of "B".
+      bool rewind = false;
+
+      // Indicates what PlayTag deletes this PlayTag.
+      PlayTag* delayedDelete = nullptr;
+
+      // This PlayTag will remove the following tags from m_played.
+      std::vector<const Tag*> removeThese;
+
+      PlayTag(const Tag* tag, int parentForward);
+      void invertForward() { forward = -forward; }
+    };
+
+    void handleEnterFrame(const frame_t frameDelta, const bool firstTime);
+    bool handleExitFrame(const frame_t frameDelta);
+    void handleMoveFrame(const frame_t frameDelta);
+    void addTag(const Tag* tag,
+                const bool rewind,
+                const int forward);
+    void removeLastTagFromPlayed();
+    bool decrementRepeat(const frame_t frameDelta);
+    frame_t firstTagFrame(const Tag* tag,
+                          const frame_t frameDelta);
+    void goToFirstTagFrame(const Tag* tag,
+                           const frame_t frameDelta);
+    int getParentForward() const;
+
+    const Sprite* m_sprite;
+
+    // List of possible tags that can be played/iterated.
+    TagsList m_tags;
+
+    frame_t m_initialFrame;
+    frame_t m_frame;
+    Mode m_playMode;
+
+    // Queue of tags to play and tags that are being played
+    std::vector<std::unique_ptr<PlayTag>> m_playing;
+    std::set<const Tag*> m_played;
+  };
+
+} // namespace doc
+
+#endif
diff --git a/src/doc/playback_tests.cpp b/src/doc/playback_tests.cpp
new file mode 100644
index 000000000..46500f45b
--- /dev/null
+++ b/src/doc/playback_tests.cpp
@@ -0,0 +1,540 @@
+// Aseprite Document Library
+// Copyright (c) 2021-2022 Igara Studio S.A.
+//
+// This file is released under the terms of the MIT license.
+// Read LICENSE.txt for more information.
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <gtest/gtest.h>
+
+#include "doc/playback.h"
+#include "doc/sprite.h"
+#include "doc/tag.h"
+#include "doc/tags.h"
+
+#include <iostream>
+#include <memory>
+
+#define PLAY_TRACE(...) // TRACEARGS
+
+using namespace doc;
+
+namespace std {
+
+std::ostream& operator<<(std::ostream& os,
+                         const std::vector<doc::frame_t>& frames)
+{
+  os << "{ ";
+  for (int i=0; i<int(frames.size()); ++i)
+    os << "[" << i << "]=" << frames[i] << (i < frames.size()-1 ? ", ": " ");
+  os << "} ";
+  return os;
+}
+
+}
+
+static std::unique_ptr<Sprite> make_sprite(frame_t nframes,
+                                           std::vector<Tag*> tags = {})
+{
+  std::unique_ptr<Sprite> sprite(Sprite::MakeStdSprite(ImageSpec(ColorMode::RGB, 4, 4)));
+  sprite->setTotalFrames(nframes);
+  for (auto tag : tags)
+    sprite->tags().add(tag);
+  return sprite;
+}
+
+static Tag* make_tag(const char* name, frame_t from, frame_t to, AniDir aniDir, int repeat = 0)
+{
+  Tag* tag = new Tag(from, to);
+  tag->setName(name);
+  tag->setAniDir(aniDir);
+  tag->setRepeat(repeat);
+  return tag;
+}
+
+static void expect_frames(Playback& play,
+                          const std::vector<frame_t>& expected)
+{
+  std::vector<frame_t> result;
+  result.push_back(play.frame());
+  for (int i=1; i<expected.size(); ++i) {
+    PLAY_TRACE("[", i, "]");
+    result.push_back(play.nextFrame());
+  }
+
+  for (int i=0; i<expected.size(); ++i) {
+    ASSERT_EQ(expected[i], result[i])
+      << "[ " << i << " ]"
+      << "\n  expected=" << expected
+      << "\n  result  =" << result;
+  }
+}
+
+TEST(Playback, OnceFullSprite)
+{
+  auto sprite = make_sprite(5);
+  Playback play(sprite.get(), 2, Playback::Mode::PlayOnce);
+  expect_frames(play, {0,1,2,3,4,2,2,2,2,2});
+  EXPECT_TRUE(play.isStopped());
+}
+
+TEST(Playback, OnceTag)
+{
+  //     A
+  //   ---->
+  // 0 1 2 3 4
+
+  Tag* a = make_tag("A", 1, 3, AniDir::FORWARD);
+  auto sprite = make_sprite(5, { a });
+  Playback play(sprite.get(), 2, Playback::Mode::PlayOnce, a);
+  expect_frames(play, {1,2,3,2,2,2,2,2});
+  EXPECT_TRUE(play.isStopped());
+
+  a->setAniDir(AniDir::REVERSE);
+  play = Playback(sprite.get(), 2, Playback::Mode::PlayOnce, a);
+  expect_frames(play, {3,2,1,2,2,2,2,2});
+
+  a->setAniDir(AniDir::PING_PONG);
+  play = Playback(sprite.get(), 0, Playback::Mode::PlayOnce, a);
+  expect_frames(play, {1,2,3,2,1,0,0,0,0});
+
+  a->setAniDir(AniDir::PING_PONG_REVERSE);
+  play = Playback(sprite.get(), 0, Playback::Mode::PlayOnce, a);
+  expect_frames(play, {3,2,1,2,3,0,0,0,0});
+
+  // Just check playing the full sprite when there is a tag (the tag must be ignored)
+  play = Playback(sprite.get(), 2, Playback::Mode::PlayOnce);
+  expect_frames(play, {0,1,2,3,4,2,2,2,2});
+  EXPECT_TRUE(play.isStopped());
+
+  play = Playback(sprite.get(), 2, Playback::Mode::PlayWithoutTagsInLoop);
+  expect_frames(play, {2,3,4,0,1,2,3,4,0,1,2,3,4,0});
+  EXPECT_FALSE(play.isStopped());
+}
+
+TEST(Playback, LoopSprite)
+{
+  auto sprite = make_sprite(4);
+  Playback play(sprite.get(), 0, Playback::Mode::PlayInLoop);
+  expect_frames(play, {0,1,2,3,0,1,2,3,0,1,2,3,0});
+  EXPECT_FALSE(play.isStopped());
+}
+
+TEST(Playback, LoopSpriteStartFromFrame2)
+{
+  auto sprite = make_sprite(4);
+  Playback play(sprite.get(), 2, Playback::Mode::PlayInLoop);
+  expect_frames(play, {2,3,0,1,2,3,0,1,2,3,0});
+  EXPECT_FALSE(play.isStopped());
+}
+
+TEST(Playback, WithTagRepetitions)
+{
+  Tag* a = make_tag("A", 1, 2, AniDir::FORWARD, 2);
+  auto sprite = make_sprite(4, { a });
+
+  Playback play(sprite.get(), 0, Playback::Mode::PlayInLoop);
+  expect_frames(play, {0,1,2,1,2,3,0,1,2,1,2,3,0});
+  EXPECT_FALSE(play.isStopped());
+
+  play = Playback(sprite.get(), 0, Playback::Mode::PlayAll);
+  expect_frames(play, {0,1,2,1,2,3,0,0,0});
+  EXPECT_TRUE(play.isStopped());
+}
+
+TEST(Playback, LoopTagInfinite)
+{
+  Tag* a = make_tag("A", 1, 2, AniDir::FORWARD, 0);
+  auto sprite = make_sprite(4, { a });
+  Playback play(sprite.get(), 0, Playback::Mode::PlayInLoop, a);
+  expect_frames(play, {0,1,2,1,2,1,2,1,2});
+  EXPECT_FALSE(play.isStopped());
+}
+
+TEST(Playback, LoopTagInfiniteAndFinite)
+{
+  //   A
+  //   -->
+  // 0 1 2 3
+
+  Tag* a = make_tag("A", 1, 2, AniDir::FORWARD, 2);
+  auto sprite = make_sprite(4, { a });
+  Playback play(sprite.get(), 2, Playback::Mode::PlayInLoop, a);
+  expect_frames(play, {2,1,2,1,2,1,2});
+  EXPECT_FALSE(play.isStopped());
+
+  // This is not infinite because the tag is not specified in the
+  // Playback() ctor.
+  play = Playback(sprite.get(), 2, Playback::Mode::PlayInLoop);
+  expect_frames(play, {2,1,2,3,0,1,2,1,2,3,0});
+  EXPECT_FALSE(play.isStopped());
+}
+
+TEST(Playback, SimpleForward)
+{
+  //  A
+  // -->
+  // 0 1
+
+  Tag* a = make_tag("A", 0, 1, AniDir::FORWARD, 2);
+  auto sprite = make_sprite(2, { a });
+
+  Playback play(sprite.get(), 0, Playback::Mode::PlayInLoop);
+  expect_frames(play, {0,1,0,1,0,1,0,1,0,1});
+  EXPECT_FALSE(play.isStopped());
+}
+
+TEST(Playback, SimpleLoopBug)
+{
+  //   Loop
+  //   -->
+  // 0 1 2 3
+
+  Tag* loop = make_tag("Loop", 1, 2, AniDir::FORWARD, 0);
+  auto sprite = make_sprite(4, { loop });
+
+  Playback play(sprite.get(), 0, Playback::Mode::PlayInLoop);
+  expect_frames(play, {0,1,2,3,0,1,2,3,0});
+  EXPECT_FALSE(play.isStopped());
+
+  play = Playback(sprite.get(), 0, Playback::Mode::PlayInLoop, loop);
+  expect_frames(play, {0,1,2,1,2,1,2,1,2});
+  EXPECT_FALSE(play.isStopped());
+
+  // Here we detected a bug where the playback kept playing 3,4,5,6,etc.
+  play = Playback(sprite.get(), 3, Playback::Mode::PlayInLoop, loop);
+  expect_frames(play, {3,0,1,2,1,2,1,2,1,2});
+  EXPECT_FALSE(play.isStopped());
+}
+
+TEST(Playback, TwoSimpleForwards)
+{
+  //  A
+  // -->
+  //  B
+  // -->
+  // 0 1
+
+  Tag* a = make_tag("A", 0, 1, AniDir::FORWARD, 2);
+  Tag* b = make_tag("B", 0, 1, AniDir::FORWARD, 2);
+  auto sprite = make_sprite(2, { a, b });
+
+  Playback play(sprite.get(), 0, Playback::Mode::PlayInLoop);
+  expect_frames(play, {0,1,0,1,0,1,0,1,0,1});
+  EXPECT_FALSE(play.isStopped());
+}
+
+TEST(Playback, SimplePingPong2)
+{
+  //  A
+  // <->
+  // 0 1
+
+  Tag* a = make_tag("A", 0, 1, AniDir::PING_PONG, 2);
+  auto sprite = make_sprite(2, { a });
+
+  Playback play(sprite.get(), 0, Playback::Mode::PlayInLoop);
+  expect_frames(play, {0,1,0, 0,1,0, 0,1,0, 0,1,0});
+  EXPECT_FALSE(play.isStopped());
+}
+
+TEST(Playback, SimplePingPong3)
+{
+  //  A
+  // <->
+  // 0 1
+
+  Tag* a = make_tag("A", 0, 1, AniDir::PING_PONG, 3);
+  auto sprite = make_sprite(2, { a });
+
+  Playback play(sprite.get(), 0, Playback::Mode::PlayInLoop);
+  expect_frames(play, {0,1,0,1,0,1,0,1,0,1,0,1,0,1});
+  EXPECT_FALSE(play.isStopped());
+}
+
+TEST(Playback, SimplePingPong3Repeats)
+{
+  //   A
+  // <--->
+  // 0 1 2
+
+  Tag* a = make_tag("A", 0, 2, AniDir::PING_PONG, 3);
+  auto sprite = make_sprite(3, { a });
+
+  Playback play(sprite.get(), 0, Playback::Mode::PlayInLoop);
+  expect_frames(play, {0,1,2,1,0,1,2,
+                       0,1,2,1,0,1,2});
+  EXPECT_FALSE(play.isStopped());
+}
+
+TEST(Playback, TagOneFrame)
+{
+  // A
+  // ->
+  // 0  1
+
+  Tag* tagA = make_tag("A", 0, 0, AniDir::FORWARD, 2);
+  auto sprite = make_sprite(2, { tagA });
+
+  Playback play(sprite.get(), 1, Playback::Mode::PlayInLoop);
+  expect_frames(play, {1,0,0,1,0,0,1,0,0,1});
+  EXPECT_FALSE(play.isStopped());
+}
+
+TEST(Playback, FourTags)
+{
+  //    A    B     C        D
+  //   --> <---- <--->   >------<
+  // 0 1 2 3 4 5 6 7 8 9 10 11 12 13
+
+  Tag* a = make_tag("A", 1, 2, AniDir::FORWARD, 1);
+  Tag* b = make_tag("B", 3, 5, AniDir::REVERSE, 2);
+  Tag* c = make_tag("C", 6, 8, AniDir::PING_PONG, 3);
+  Tag* d = make_tag("D", 10, 12, AniDir::PING_PONG_REVERSE, 2);
+  auto sprite = make_sprite(14, { a, b, c, d });
+
+  Playback play(sprite.get(), 0, Playback::Mode::PlayWithoutTagsInLoop);
+  expect_frames(play, {0,1,2,3,4,5,6,7,8,9,10,11,12,13,0,1,2,3,4,5,6,7,8,9,10,11,12,13,0});
+  EXPECT_FALSE(play.isStopped());
+
+  play = Playback(sprite.get(), 0, Playback::Mode::PlayAll);
+  expect_frames(play, {0, 1,2, 5,4,3,5,4,3, 6,7,8,7,6,7,8, 9, 12,11,10,11,12, 13,0,0,0,0});
+  EXPECT_TRUE(play.isStopped());
+}
+
+TEST(Playback, ForwardTagWithInnerPingPong)
+{
+  //    A
+  //   -------->
+  //       B
+  //     <--->
+  // 0 1 2 3 4 5 6
+
+  Tag* tagA = make_tag("A", 1, 5, AniDir::FORWARD, 2);
+  Tag* tagB = make_tag("B", 2, 4, AniDir::PING_PONG, 3);
+  auto sprite = make_sprite(7, { tagA, tagB });
+
+  Playback play(sprite.get(), 0, Playback::Mode::PlayInLoop);
+  expect_frames(play, {0, 1,2,3,4,3,2,3,4,5, 1,2,3,4,3,2,3,4,5, 6,
+                       0, 1,2,3,4,3,2,3,4,5, 1,2,3,4,3,2,3,4,5, 6 });
+  EXPECT_FALSE(play.isStopped());
+}
+
+TEST(Playback, ForwardTagWithInnerForwardEndSameFrame)
+{
+  //    A
+  //   ------>
+  //       B
+  //     ---->
+  // 0 1 2 3 4
+
+  Tag* tagA = make_tag("A", 1, 4, AniDir::FORWARD, 2);
+  Tag* tagB = make_tag("B", 2, 4, AniDir::FORWARD, 2);
+  auto sprite = make_sprite(5, { tagA, tagB });
+
+  Playback play(sprite.get(), 0, Playback::Mode::PlayInLoop);
+  expect_frames(play, {0, 1,2,3,4,2,3,4, 1,2,3,4,2,3,4,
+                       0, 1,2,3,4,2,3,4, 1,2,3,4,2,3,4, 0 });
+  EXPECT_FALSE(play.isStopped());
+}
+
+TEST(Playback, ForwardTagWithInnerPingPongEndSameFrame)
+{
+  //    A
+  //   ---->
+  //      B
+  //   <--->
+  // 0 1 2 3
+
+  Tag* tagA = make_tag("A", 1, 3, AniDir::FORWARD, 2);
+  Tag* tagB = make_tag("B", 1, 3, AniDir::PING_PONG, 4);
+  auto sprite = make_sprite(4, { tagA, tagB });
+
+  Playback play(sprite.get(), 0, Playback::Mode::PlayInLoop);
+  expect_frames(play, {0, 1,2,3,2,1,2,3,2,1, 1,2,3,2,1,2,3,2,1,
+                       0, 1,2,3,2,1,2,3,2,1, 1,2,3,2,1,2,3,2,1, 0 });
+  EXPECT_FALSE(play.isStopped());
+}
+
+TEST(Playback, ForwardTagWithInnerReverse)
+{
+  //    A
+  //   ------>
+  //      B
+  //   <----
+  // 0 1 2 3 4
+
+  Tag* tagA = make_tag("A", 1, 4, AniDir::FORWARD, 2);
+  Tag* tagB = make_tag("B", 1, 3, AniDir::REVERSE, 2);
+  auto sprite = make_sprite(5, { tagA, tagB });
+
+  Playback play(sprite.get(), 0, Playback::Mode::PlayInLoop);
+  expect_frames(play, {0, 3,2,1,3,2,1, 4, 3,2,1,3,2,1, 4,
+                       0, 3,2,1,3,2,1, 4, 3,2,1,3,2,1, 4, 0 });
+  EXPECT_FALSE(play.isStopped());
+}
+
+TEST(Playback, PingPongWithInnerReverse)
+{
+  //     A
+  // <------->
+  //     B
+  //   <----
+  // 0 1 2 3 4
+
+  Tag* tagA = make_tag("A", 0, 4, AniDir::PING_PONG, 2);
+  Tag* tagB = make_tag("B", 1, 3, AniDir::REVERSE, 3);
+  auto sprite = make_sprite(5, { tagA, tagB });
+
+  Playback play(sprite.get(), 0, Playback::Mode::PlayInLoop);
+  expect_frames(play, {0, 3,2,1,3,2,1,3,2,1, 4, 1,2,3,1,2,3,1,2,3, 0 });
+  EXPECT_FALSE(play.isStopped());
+}
+
+TEST(Playback, OnePingPongInsideOther)
+{
+  //     A
+  // <------->
+  //     B
+  //   >---<
+  // 0 1 2 3 4
+
+  Tag* tagA = make_tag("A", 0, 4, AniDir::PING_PONG, 2);
+  Tag* tagB = make_tag("B", 1, 3, AniDir::PING_PONG_REVERSE, 3);
+  auto sprite = make_sprite(5, { tagA, tagB });
+
+  Playback play(sprite.get(), 0, Playback::Mode::PlayInLoop);
+  expect_frames(play, {0, 3,2,1,2,3,2,1, 4, 1,2,3,2,1,2,3, 0,
+                       0, 3,2,1,2,3,2,1, 4, 1,2,3,2,1,2,3, 0, });
+  EXPECT_FALSE(play.isStopped());
+}
+
+TEST(Playback, OnePingPongInsideOther3)
+{
+  //     A
+  // <------->
+  //     B
+  //   >---<
+  // 0 1 2 3 4
+
+  Tag* tagA = make_tag("A", 0, 4, AniDir::PING_PONG, 3);
+  Tag* tagB = make_tag("B", 1, 3, AniDir::PING_PONG_REVERSE, 2);
+  auto sprite = make_sprite(5, { tagA, tagB });
+
+  Playback play(sprite.get(), 0, Playback::Mode::PlayInLoop);
+  expect_frames(play, {0, 3,2,1,2,3, 4, 1,2,3,2,1, 0, 3,2,1,2,3, 4,
+                       0, 3,2,1,2,3, 4, 1,2,3,2,1, 0, 3,2,1,2,3, 4, 0 });
+  EXPECT_FALSE(play.isStopped());
+}
+
+TEST(Playback, TwoLoopsInCascade)
+{
+  //    A
+  //   ---->
+  //       B
+  //     ---->
+  // 0 1 2 3 4
+
+  Tag* tagA = make_tag("A", 1, 3, AniDir::FORWARD, 2);
+  Tag* tagB = make_tag("B", 2, 4, AniDir::FORWARD, 2);
+  auto sprite = make_sprite(5, { tagA, tagB });
+
+  Playback play(sprite.get(), 0, Playback::Mode::PlayInLoop);
+  expect_frames(play, {0, 1,2,3,1,2,3, 2,3,4,2,3,4,
+                       0, 1,2,3,1,2,3, 2,3,4,2,3,4, 0 });
+  EXPECT_FALSE(play.isStopped());
+}
+
+TEST(Playback, TwoLoopsInCascadeReverse)
+{
+  GTEST_SKIP() << "TODO not yet ready";
+
+  //    A
+  //   <----
+  //       B
+  //     <----
+  // 0 1 2 3 4
+
+  Tag* a = make_tag("A", 1, 3, AniDir::REVERSE, 2);
+  Tag* b = make_tag("B", 2, 4, AniDir::REVERSE, 2);
+  auto sprite = make_sprite(5, { a, b });
+
+  Playback play(sprite.get(), 0, Playback::Mode::PlayInLoop);
+  expect_frames(play, {0, 3,2,1,3,2,1, 4,3,2,4,3,2,
+                       0, 3,2,1,3,2,1, 4,3,2,4,3,2, 0 });
+  EXPECT_FALSE(play.isStopped());
+}
+
+TEST(Playback, ThreeLoopsInCascade)
+{
+  //    A
+  //   ---->
+  //       B
+  //     ---->
+  //         C
+  //       ---->
+  // 0 1 2 3 4 5
+
+  Tag* a = make_tag("A", 1, 3, AniDir::FORWARD, 2);
+  Tag* b = make_tag("B", 2, 4, AniDir::FORWARD, 2);
+  Tag* c = make_tag("C", 3, 5, AniDir::FORWARD, 2);
+  auto sprite = make_sprite(6, { a, b, c });
+
+  Playback play(sprite.get(), 0, Playback::Mode::PlayInLoop);
+  expect_frames(play, {0, 1,2,3,1,2,3, 2,3,4,2,3,4, 3,4,5,3,4,5,
+                       0, 1,2,3,1,2,3, 2,3,4,2,3,4, 3,4,5,3,4,5, 0});
+  EXPECT_FALSE(play.isStopped());
+}
+
+TEST(Playback, ThreeLoopsInCascadeDiffAniDirs)
+{
+  //    A
+  //   ---->
+  //       B
+  //     <----
+  //         C
+  //       <--->
+  // 0 1 2 3 4 5 6
+
+  Tag* tagA = make_tag("A", 1, 3, AniDir::FORWARD, 2);
+  Tag* tagB = make_tag("B", 2, 4, AniDir::REVERSE, 2);
+  Tag* tagC = make_tag("C", 3, 5, AniDir::PING_PONG, 2);
+  auto sprite = make_sprite(7, { tagA, tagB, tagC });
+
+  Playback play(sprite.get(), 0, Playback::Mode::PlayInLoop);
+  expect_frames(play, {0, 1,2,3,1,2,3, 4,3,2,4,3,2, 3,4,5,4,3, 6,
+                       0, 1,2,3,1,2,3, 4,3,2,4,3,2, 3,4,5,4,3, 6, 0});
+  EXPECT_FALSE(play.isStopped());
+}
+
+TEST(Playback, InnerCascades)
+{
+  GTEST_SKIP() << "TODO not yet ready";
+
+  //      A
+  //   <--------->
+  //       B
+  //     <----
+  //         C
+  //       <--->
+  // 0 1 2 3 4 5 6
+
+  Tag* a = make_tag("A", 1, 6, AniDir::PING_PONG, 2);
+  Tag* b = make_tag("B", 2, 4, AniDir::REVERSE, 2);
+  Tag* c = make_tag("C", 3, 5, AniDir::PING_PONG, 2);
+  auto sprite = make_sprite(7, { a, b, c });
+
+  Playback play(sprite.get(), 0, Playback::Mode::PlayInLoop);
+  expect_frames(play, {0, 1, 4,3,2,4,3,2, 3,4,5,4,3, 6, 5,4,3,4,5, 2,3,4,2,3,4, 1,
+                       0, 1, 4,3,2,4,3,2, 3,4,5,4,3, 6, 5,4,3,4,5, 2,3,4,2,3,4, 1, 0});
+  EXPECT_FALSE(play.isStopped());
+}
+
+int main(int argc, char** argv)
+{
+  ::testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}
diff --git a/src/doc/tag.cpp b/src/doc/tag.cpp
index cd3c69a82..a8cf9261d 100644
--- a/src/doc/tag.cpp
+++ b/src/doc/tag.cpp
@@ -1,5 +1,5 @@
 // Aseprite Document Library
-// Copyright (C) 2019-2020  Igara Studio S.A.
+// Copyright (C) 2019-2022  Igara Studio S.A.
 // Copyright (C) 2001-2016  David Capello
 //
 // This file is released under the terms of the MIT license.
@@ -14,6 +14,8 @@
 #include "base/debug.h"
 #include "doc/tags.h"
 
+#include <algorithm>
+
 namespace doc {
 
 Tag::Tag(frame_t from, frame_t to)
@@ -22,7 +24,6 @@ Tag::Tag(frame_t from, frame_t to)
   , m_from(from)
   , m_to(to)
   , m_name("Tag")
-  , m_aniDir(AniDir::FORWARD)
 {
   color_t defaultColor = rgba_a_mask;// black color with full opacity.
   userData().setColor(defaultColor);
@@ -35,6 +36,7 @@ Tag::Tag(const Tag& other)
   , m_to(other.m_to)
   , m_name(other.m_name)
   , m_aniDir(other.m_aniDir)
+  , m_repeat(other.m_repeat)
 {
 }
 
@@ -83,9 +85,15 @@ void Tag::setAniDir(AniDir aniDir)
 {
   ASSERT(m_aniDir == AniDir::FORWARD ||
          m_aniDir == AniDir::REVERSE ||
-         m_aniDir == AniDir::PING_PONG);
+         m_aniDir == AniDir::PING_PONG ||
+         m_aniDir == AniDir::PING_PONG_REVERSE);
 
   m_aniDir = aniDir;
 }
 
+void Tag::setRepeat(int repeat)
+{
+  m_repeat = std::clamp(repeat, 0, kMaxRepeat);
+}
+
 } // namespace doc
diff --git a/src/doc/tag.h b/src/doc/tag.h
index 1fac5ba6d..43f56e688 100644
--- a/src/doc/tag.h
+++ b/src/doc/tag.h
@@ -1,5 +1,5 @@
 // Aseprite Document Library
-// Copyright (C) 2019-2020  Igara Studio S.A.
+// Copyright (C) 2019-2022  Igara Studio S.A.
 // Copyright (C) 2001-2016  David Capello
 //
 // This file is released under the terms of the MIT license.
@@ -23,6 +23,8 @@ namespace doc {
 
   class Tag : public WithUserData {
   public:
+    static constexpr int kMaxRepeat = 65535;
+
     Tag(frame_t from, frame_t to);
     Tag(const Tag& other);
     ~Tag();
@@ -35,19 +37,27 @@ namespace doc {
     const std::string& name() const { return m_name; }
     color_t color() const { return userData().color(); }
     AniDir aniDir() const { return m_aniDir; }
+    int repeat() const { return m_repeat; }
 
     void setFrameRange(frame_t from, frame_t to);
     void setName(const std::string& name);
     void setColor(color_t color);
     void setAniDir(AniDir aniDir);
+    void setRepeat(int repeat);
 
     void setOwner(Tags* owner);
 
+    bool contains(const frame_t frame) const {
+      return (frame >= m_from &&
+              frame <= m_to);
+    }
+
   public:
     Tags* m_owner;
     frame_t m_from, m_to;
     std::string m_name;
-    AniDir m_aniDir;
+    AniDir m_aniDir = AniDir::FORWARD;
+    int m_repeat = 0;
 
     // Disable operator=
     Tag& operator=(Tag&);
diff --git a/src/doc/tag_io.cpp b/src/doc/tag_io.cpp
index 0271e55ea..2818be344 100644
--- a/src/doc/tag_io.cpp
+++ b/src/doc/tag_io.cpp
@@ -1,5 +1,5 @@
 // Aseprite Document Library
-// Copyright (C) 2019-2020  Igara Studio S.A.
+// Copyright (C) 2019-2022  Igara Studio S.A.
 // Copyright (C) 2001-2018  David Capello
 //
 // This file is released under the terms of the MIT license.
@@ -34,6 +34,7 @@ void write_tag(std::ostream& os, const Tag* tag)
   write8(os, (int)tag->aniDir());
   write_string(os, tag->name());
   write_user_data(os, tag->userData());
+  write32(os, tag->repeat());
 }
 
 Tag* read_tag(std::istream& is,
@@ -54,16 +55,21 @@ Tag* read_tag(std::istream& is,
   UserData userData;
 
   // If we are reading the new v1.3.x version, there is a user data with the color + text
-  if (!oldVersion)
+  int repeat = 0;
+  if (!oldVersion) {
     userData = read_user_data(is);
+    repeat = read32(is);
+  }
 
-  std::unique_ptr<Tag> tag(new Tag(from, to));
+  auto tag = std::make_unique<Tag>(from, to);
   tag->setAniDir(aniDir);
   tag->setName(name);
   if (oldVersion)
     tag->setColor(color);
-  else
+  else {
     tag->setUserData(userData);
+    tag->setRepeat(repeat);
+  }
   if (setId)
     tag->setId(id);
   return tag.release();
diff --git a/src/doc/tags.h b/src/doc/tags.h
index b3ac40d39..3864acf4a 100644
--- a/src/doc/tags.h
+++ b/src/doc/tags.h
@@ -1,5 +1,5 @@
 // Aseprite Document Library
-// Copyright (C) 2019  Igara Studio S.A.
+// Copyright (C) 2019-2022  Igara Studio S.A.
 // Copyright (C) 2001-2015  David Capello
 //
 // This file is released under the terms of the MIT license.
@@ -21,12 +21,12 @@ namespace doc {
   class Tag;
   class Sprite;
 
-  class Tags {
-    typedef std::vector<Tag*> List;
+  using TagsList = std::vector<Tag*>;
 
+  class Tags {
   public:
-    typedef List::iterator iterator;
-    typedef List::const_iterator const_iterator;
+    using iterator = TagsList::iterator;
+    using const_iterator = TagsList::const_iterator;
 
     Tags(Sprite* sprite);
     ~Tags();
@@ -50,9 +50,11 @@ namespace doc {
     Tag* innerTag(const frame_t frame) const;
     Tag* outerTag(const frame_t frame) const;
 
+    const TagsList& getInternalList() const { return m_tags; }
+
   private:
     Sprite* m_sprite;
-    List m_tags;
+    TagsList m_tags;
 
     DISABLE_COPYING(Tags);
   };
diff --git a/src/render/render.cpp b/src/render/render.cpp
index 44b8306d8..5c290ae53 100644
--- a/src/render/render.cpp
+++ b/src/render/render.cpp
@@ -14,9 +14,9 @@
 #include "doc/blend_internals.h"
 #include "doc/blend_mode.h"
 #include "doc/doc.h"
-#include "doc/handle_anidir.h"
 #include "doc/image_impl.h"
 #include "doc/layer_tilemap.h"
+#include "doc/playback.h"
 #include "doc/tileset.h"
 #include "doc/tilesets.h"
 #include "gfx/clip.h"
@@ -854,21 +854,16 @@ void Render::renderOnionskin(
     Tag* loop = m_onionskin.loopTag();
     Layer* onionLayer = (m_onionskin.layer() ? m_onionskin.layer():
                                                m_sprite->root());
-    frame_t frameIn;
+    Playback play(m_sprite, frame,
+                  loop ? Playback::PlayInLoop:
+                         Playback::PlayOnce,
+                  loop);
+    play.nextFrame(-m_onionskin.prevFrames());
 
     for (frame_t frameOut = frame - m_onionskin.prevFrames();
          frameOut <= frame + m_onionskin.nextFrames();
-         ++frameOut) {
-      if (loop) {
-        bool pingPongForward = true;
-        frameIn =
-          calculate_next_frame(m_sprite,
-                               frame, frameOut - frame,
-                               loop, pingPongForward);
-      }
-      else {
-        frameIn = frameOut;
-      }
+         ++frameOut, play.nextFrame()) {
+      const frame_t frameIn = play.frame();
 
       if (frameIn == frame ||
           frameIn < 0 ||