From c2acc973ee671b7eed5710fd629ae7a8be65ce3b Mon Sep 17 00:00:00 2001
From: David Capello <david@igarastudio.com>
Date: Tue, 29 Oct 2019 16:37:06 -0300
Subject: [PATCH] Add support to show multiple sections in Export Sprite Sheet

---
 data/pref.xml                                 |   1 +
 data/strings/en.ini                           |   5 +
 data/widgets/export_sprite_sheet.xml          |  67 ++++++-----
 src/app/commands/cmd_export_sprite_sheet.cpp  | 104 +++++++++++++++---
 .../filters/filter_target_buttons.cpp         |   3 +-
 src/app/ui/button_set.cpp                     |  49 +++++++--
 src/app/ui/button_set.h                       |  12 +-
 src/app/ui/color_popup.cpp                    |   9 --
 src/app/ui/color_popup.h                      |   1 -
 src/app/ui/context_bar.cpp                    |   2 +-
 src/app/widget_loader.cpp                     |   8 +-
 src/ui/panel.cpp                              |  34 +++++-
 src/ui/panel.h                                |   9 +-
 13 files changed, 228 insertions(+), 76 deletions(-)

diff --git a/data/pref.xml b/data/pref.xml
index 47f9cdcef..2d845e4c5 100644
--- a/data/pref.xml
+++ b/data/pref.xml
@@ -310,6 +310,7 @@
       <option id="show_overwrite_files_alert" type="bool" default="true" />
       <option id="default_extension" type="std::string" default="&quot;png&quot;" />
       <option id="preview" type="bool" default="true" />
+      <option id="sections" type="std::string" />
     </section>
     <section id="gif">
       <option id="show_alert" type="bool" default="true" />
diff --git a/data/strings/en.ini b/data/strings/en.ini
index 4614892ae..d899a9b83 100644
--- a/data/strings/en.ini
+++ b/data/strings/en.ini
@@ -538,6 +538,11 @@ sprite = Sprite
 sprite_tooltip = Source of sprite samples to export in the sprite sheet
 borders = Borders
 borders_tooltip = Add or trim borders from each sprite in the sprite sheet
+expand_all_sections_tooltip = <<<END
+Show all sections
+
+Use Ctrl+click to display multiple sections at the same time
+END
 layout = Layout
 layout_tooltip = Arrangement of sprites in the final result
 output = Output
diff --git a/data/widgets/export_sprite_sheet.xml b/data/widgets/export_sprite_sheet.xml
index d481ff808..1a8ee58cd 100644
--- a/data/widgets/export_sprite_sheet.xml
+++ b/data/widgets/export_sprite_sheet.xml
@@ -9,19 +9,46 @@
 
     <hbox>
       <separator horizontal="true" expansive="true" />
-      <buttonset id="section_tabs" columns="4">
-        <item id="sectin_sprite_tab" text="@.sprite" tooltip="@.sprite_tooltip" tooltip_dir="bottom" selected="true" />
-        <item id="sectin_borders_tab" text="@.borders" tooltip="@.borders_tooltip" tooltip_dir="bottom" />
-        <item id="sectin_layout_tab" text="@.layout" tooltip="@.layout_tooltip" tooltip_dir="bottom" />
-        <item id="sectin_output_tab" text="@.output" tooltip="@.output_tooltip" tooltip_dir="bottom" />
+      <buttonset id="section_tabs" columns="4" oneormore="true">
+        <item id="section_layout_tab" text="@.layout" tooltip="@.layout_tooltip" tooltip_dir="bottom" />
+        <item id="section_sprite_tab" text="@.sprite" tooltip="@.sprite_tooltip" tooltip_dir="bottom" selected="true" />
+        <item id="section_borders_tab" text="@.borders" tooltip="@.borders_tooltip" tooltip_dir="bottom" />
+        <item id="section_output_tab" text="@.output" tooltip="@.output_tooltip" tooltip_dir="bottom" />
       </buttonset>
       <separator horizontal="true" expansive="true" />
+      <button id="expand_sections" icon="window_center_icon"
+              tooltip="@.expand_all_sections_tooltip" tooltip_dir="bottom" />
     </hbox>
 
     <panel id="panel" expansive="true">
 
+    <!-- Layout -->
+
+    <grid id="section_layout" columns="4" expansive="true">
+      <label text="@.sheet_type" />
+      <combobox id="sheet_type" expansive="true" cell_hspan="3" cell_align="horizontal"
+                tooltip="@.sheet_type_tooltip" tooltip_dir="bottom" />
+
+      <label text="@.constraints" />
+      <hbox cell_hspan="3">
+        <combobox id="constraint_type" tooltip="@.constraints_tooltip" />
+        <expr id="width_constraint" />
+        <expr id="height_constraint" />
+      </hbox>
+
+      <hbox />
+      <hbox cell_hspan="3">
+        <check id="merge_dups" text="@.merge_dups" tooltip="@.merge_dups_tooltip" />
+        <check id="ignore_empty" text="@.ignore_empty" tooltip="@.ignore_empty_tooltip" />
+      </hbox>
+    </grid>
+
     <!-- Sprite -->
 
+    <hbox id="section_sprite_separator">
+      <separator horizontal="true" text="@.sprite" expansive="true" />
+      <button id="close_sprite_section" icon="window_close_icon" />
+    </hbox>
     <grid id="section_sprite" columns="4" expansive="true">
       <label text="@.layers" />
       <combobox id="layers" text="" cell_hspan="2" cell_align="horizontal" />
@@ -34,6 +61,10 @@
 
     <!-- Borders -->
 
+    <hbox id="section_borders_separator">
+      <separator horizontal="true" text="@.borders" expansive="true" />
+      <button id="close_borders_section" icon="window_close_icon" />
+    </hbox>
     <grid id="section_borders" columns="4" expansive="true">
 
       <hbox />
@@ -68,29 +99,12 @@
 
     </grid>
 
-    <!-- Layout -->
-
-    <grid id="section_layout" columns="4" expansive="true">
-      <label text="@.sheet_type" />
-      <combobox id="sheet_type" expansive="true" cell_hspan="3" cell_align="horizontal"
-                tooltip="@.sheet_type_tooltip" tooltip_dir="bottom" />
-
-      <label text="@.constraints" />
-      <hbox cell_hspan="3">
-        <combobox id="constraint_type" tooltip="@.constraints_tooltip" />
-        <expr id="width_constraint" />
-        <expr id="height_constraint" />
-      </hbox>
-
-      <hbox />
-      <hbox cell_hspan="3">
-        <check id="merge_dups" text="@.merge_dups" tooltip="@.merge_dups_tooltip" />
-        <check id="ignore_empty" text="@.ignore_empty" tooltip="@.ignore_empty_tooltip" />
-      </hbox>
-    </grid>
-
     <!-- Output -->
 
+    <hbox id="section_output_separator">
+      <separator horizontal="true" text="@.output" expansive="true" />
+      <button id="close_output_section" icon="window_close_icon" />
+    </hbox>
     <grid id="section_output" columns="4" expansive="true">
       <check id="image_enabled" text="@.output_file" />
       <button id="image_filename" cell_hspan="3" cell_align="horizontal" />
@@ -122,7 +136,6 @@
     </panel>
 
     <separator horizontal="true" cell_hspan="4" />
-
     <hbox cell_hspan="4">
       <boxfiller />
       <hbox>
diff --git a/src/app/commands/cmd_export_sprite_sheet.cpp b/src/app/commands/cmd_export_sprite_sheet.cpp
index 6f68466d0..b99ba76a7 100644
--- a/src/app/commands/cmd_export_sprite_sheet.cpp
+++ b/src/app/commands/cmd_export_sprite_sheet.cpp
@@ -21,6 +21,7 @@
 #include "app/i18n/strings.h"
 #include "app/job.h"
 #include "app/modules/editors.h"
+#include "app/modules/gui.h"
 #include "app/pref/preferences.h"
 #include "app/restore_visible_layers.h"
 #include "app/task.h"
@@ -39,6 +40,7 @@
 #include "doc/layer.h"
 #include "doc/tag.h"
 #include "fmt/format.h"
+#include "ui/message.h"
 #include "ui/system.h"
 
 #include "export_sprite_sheet.xml.h"
@@ -86,9 +88,9 @@ struct ExportSpriteSheetParams : public NewParams {
 #ifdef ENABLE_UI
 
 enum Section {
+  kSectionLayout,
   kSectionSprite,
   kSectionBorders,
-  kSectionLayout,
   kSectionOutput,
 };
 
@@ -288,7 +290,8 @@ class ExportSpriteSheetWindow : public app::gen::ExportSpriteSheet {
 public:
   ExportSpriteSheetWindow(DocExporter& exporter,
                           Site& site,
-                          ExportSpriteSheetParams& params)
+                          ExportSpriteSheetParams& params,
+                          Preferences& pref)
     : m_exporter(exporter)
     , m_frontBuffer(std::make_shared<doc::ImageBuffer>())
     , m_backBuffer(std::make_shared<doc::ImageBuffer>())
@@ -302,6 +305,10 @@ public:
     , m_filenameFormat(params.filenameFormat())
   {
     sectionTabs()->ItemChange.connect(base::Bind<void>(&ExportSpriteSheetWindow::onChangeSection, this));
+    expandSections()->Click.connect(base::Bind<void>(&ExportSpriteSheetWindow::onExpandSections, this));
+    closeSpriteSection()->Click.connect(base::Bind<void>(&ExportSpriteSheetWindow::onCloseSection, this, kSectionSprite));
+    closeBordersSection()->Click.connect(base::Bind<void>(&ExportSpriteSheetWindow::onCloseSection, this, kSectionBorders));
+    closeOutputSection()->Click.connect(base::Bind<void>(&ExportSpriteSheetWindow::onCloseSection, this, kSectionOutput));
 
     static_assert(
       (int)app::SpriteSheetType::None == 0 &&
@@ -397,7 +404,7 @@ public:
 
     if (m_filename.empty() ||
         m_filename == kSpecifiedFilename) {
-      std::string defExt = Preferences::instance().spriteSheet.defaultExtension();
+      std::string defExt = pref.spriteSheet.defaultExtension();
 
       if (base::utf8_icmp(base::get_file_extension(site.document()->filename()), defExt) == 0)
         m_filename = base + "-sheet." + defExt;
@@ -436,13 +443,30 @@ public:
     preview()->Click.connect(base::Bind<void>(&ExportSpriteSheetWindow::generatePreview, this));
     m_genTimer.Tick.connect(base::Bind<void>(&ExportSpriteSheetWindow::onGenTimerTick, this));
 
+    // Select tabs
+    {
+      const std::string s = pref.spriteSheet.sections();
+      const bool layout = (s.find("layout") != std::string::npos);
+      const bool sprite = (s.find("sprite") != std::string::npos);
+      const bool borders = (s.find("borders") != std::string::npos);
+      const bool output = (s.find("output") != std::string::npos);
+      sectionTabs()->getItem(kSectionLayout)->setSelected(layout || (!sprite & !borders && !output));
+      sectionTabs()->getItem(kSectionSprite)->setSelected(sprite);
+      sectionTabs()->getItem(kSectionBorders)->setSelected(borders);
+      sectionTabs()->getItem(kSectionOutput)->setSelected(output);
+    }
+
     onChangeSection();
     onSheetTypeChange();
     onFileNamesChange();
     updateExportButton();
 
-    preview()->setSelected(Preferences::instance().spriteSheet.preview());
+    preview()->setSelected(pref.spriteSheet.preview());
     generatePreview();
+
+    remapWindow();
+    centerWindow();
+    load_window_pos(this, "ExportSpriteSheet");
   }
 
   ~ExportSpriteSheetWindow() {
@@ -456,6 +480,19 @@ public:
     }
   }
 
+  std::string selectedSectionsString() const {
+    const bool layout = sectionTabs()->getItem(kSectionLayout)->isSelected();
+    const bool sprite = sectionTabs()->getItem(kSectionSprite)->isSelected();
+    const bool borders = sectionTabs()->getItem(kSectionBorders)->isSelected();
+    const bool output = sectionTabs()->getItem(kSectionOutput)->isSelected();
+    return
+      fmt::format("{} {} {} {}",
+                  (layout ? "layout": ""),
+                  (sprite ? "sprite": ""),
+                  (borders ? "borders": ""),
+                  (output ? "output": ""));
+  }
+
   bool ok() const {
     return closer() == exportButton();
   }
@@ -491,6 +528,15 @@ public:
 
 private:
 
+  bool onProcessMessage(ui::Message* msg) override {
+    switch (msg->type()) {
+      case kCloseMessage:
+        save_window_pos(this, "ExportSpriteSheet");
+        break;
+    }
+    return Window::onProcessMessage(msg);
+  }
+
   void onBroadcastMouseMessage(WidgetsList& targets) override {
     Window::onBroadcastMouseMessage(targets);
 
@@ -500,17 +546,38 @@ private:
   }
 
   void onChangeSection() {
-    Widget* section = nullptr;
-    switch (sectionTabs()->selectedItem()) {
-      case kSectionSprite:  section = sectionSprite();  break;
-      case kSectionBorders: section = sectionBorders(); break;
-      case kSectionLayout:  section = sectionLayout();  break;
-      case kSectionOutput:  section = sectionOutput();  break;
-    }
-    panel()->showChild(section);
+    panel()->showAllChildren();
+
+    const bool layout = sectionTabs()->getItem(kSectionLayout)->isSelected();
+    const bool sprite = sectionTabs()->getItem(kSectionSprite)->isSelected();
+    const bool borders = sectionTabs()->getItem(kSectionBorders)->isSelected();
+    const bool output = sectionTabs()->getItem(kSectionOutput)->isSelected();
+
+    sectionLayout()->setVisible(layout);
+    sectionSpriteSeparator()->setVisible(sprite && layout);
+    sectionSprite()->setVisible(sprite);
+    sectionBordersSeparator()->setVisible(borders && (layout || sprite));
+    sectionBorders()->setVisible(borders);
+    sectionOutputSeparator()->setVisible(output && (layout || sprite || borders));
+    sectionOutput()->setVisible(output);
+
     resize();
   }
 
+  void onExpandSections() {
+    sectionTabs()->getItem(kSectionLayout)->setSelected(true);
+    sectionTabs()->getItem(kSectionSprite)->setSelected(true);
+    sectionTabs()->getItem(kSectionBorders)->setSelected(true);
+    sectionTabs()->getItem(kSectionOutput)->setSelected(true);
+    onChangeSection();
+  }
+
+  void onCloseSection(const Section section) {
+    if (sectionTabs()->countSelectedItems() > 1)
+      sectionTabs()->getItem(section)->setSelected(false);
+    onChangeSection();
+  }
+
   app::SpriteSheetType spriteSheetTypeValue() const {
     return (app::SpriteSheetType)(sheetType()->getSelectedItemIndex()+1);
   }
@@ -1158,14 +1225,19 @@ void ExportSpriteSheetCommand::onExecute(Context* context)
 
   bool askOverwrite = params.askOverwrite();
   if (showUI) {
-    ExportSpriteSheetWindow window(exporter, site, params);
+    auto& pref = Preferences::instance();
+
+    ExportSpriteSheetWindow window(exporter, site, params, pref);
     window.openWindowInForeground();
+
+    // Save global sprite sheet generation settings anyway (even if
+    // the user cancel the dialog, the global settings are stored).
+    pref.spriteSheet.preview(window.preview()->isSelected());
+    pref.spriteSheet.sections(window.selectedSectionsString());
+
     if (!window.ok())
       return;
 
-    // Preview sprite sheet generation
-    Preferences::instance().spriteSheet.preview(window.preview()->isSelected());
-
     window.updateParams(params);
     docPref.spriteSheet.defined(true);
     docPref.spriteSheet.type            (params.type());
diff --git a/src/app/commands/filters/filter_target_buttons.cpp b/src/app/commands/filters/filter_target_buttons.cpp
index 7795be650..1488e63a5 100644
--- a/src/app/commands/filters/filter_target_buttons.cpp
+++ b/src/app/commands/filters/filter_target_buttons.cpp
@@ -1,4 +1,5 @@
 // Aseprite
+// Copyright (C) 2019  Igara Studio S.A.
 // Copyright (C) 2001-2018  David Capello
 //
 // This program is distributed under the terms of
@@ -41,7 +42,7 @@ FilterTargetButtons::FilterTargetButtons(int imgtype, bool withChannels)
   , m_index(nullptr)
   , m_cels(nullptr)
 {
-  setMultipleSelection(true);
+  setMultiMode(MultiMode::Set);
   addChild(&m_tooltips);
 
   if (withChannels) {
diff --git a/src/app/ui/button_set.cpp b/src/app/ui/button_set.cpp
index f0460e8fc..826adf18d 100644
--- a/src/app/ui/button_set.cpp
+++ b/src/app/ui/button_set.cpp
@@ -1,5 +1,5 @@
 // Aseprite
-// Copyright (C) 2018  Igara Studio S.A.
+// Copyright (C) 2018-2019  Igara Studio S.A.
 // Copyright (C) 2001-2017  David Capello
 //
 // This program is distributed under the terms of
@@ -299,7 +299,7 @@ ButtonSet::ButtonSet(int columns)
   : Grid(columns, false)
   , m_offerCapture(true)
   , m_triggerOnMouseUp(false)
-  , m_multipleSelection(false)
+  , m_multiMode(MultiMode::One)
 {
   InitTheme.connect(
     [this]{
@@ -357,6 +357,15 @@ int ButtonSet::selectedItem() const
   return -1;
 }
 
+int ButtonSet::countSelectedItems() const
+{
+  int count = 0;
+  for (auto child : children())
+    if (child->isSelected())
+      ++count;
+  return count;
+}
+
 void ButtonSet::setSelectedItem(int index, bool focusItem)
 {
   if (index >= 0 && index < (int)children().size())
@@ -372,16 +381,38 @@ void ButtonSet::setSelectedItem(Item* item, bool focusItem)
 
 void ButtonSet::onSelectItem(Item* item, bool focusItem, ui::Message* msg)
 {
-  if (!m_multipleSelection) {
-    if (item && item->isSelected())
+  const int count = countSelectedItems();
+
+  if ((m_multiMode == MultiMode::One) ||
+      (m_multiMode == MultiMode::OneOrMore &&
+       msg &&
+       !msg->shiftPressed() &&
+       !msg->altPressed() &&
+       !msg->ctrlPressed() &&
+       !msg->cmdPressed())) {
+    if (item && item->isSelected() &&
+        ((m_multiMode == MultiMode::One) ||
+         (m_multiMode == MultiMode::OneOrMore && count == 1)))
       return;
 
-    Item* sel = findSelectedItem();
-    if (sel)
-      sel->setSelected(false);
+    if (m_multiMode == MultiMode::One) {
+      if (auto sel = findSelectedItem())
+        sel->setSelected(false);
+    }
+    else if (m_multiMode == MultiMode::OneOrMore) {
+      for (auto child : children())
+        child->setSelected(false);
+    }
   }
 
   if (item) {
+    if (m_multiMode == MultiMode::OneOrMore) {
+      // Item already selected
+      if (count == 1 && item == findSelectedItem())
+        return;
+    }
+
+    // Toggle item
     item->setSelected(!item->isSelected());
     if (focusItem)
       item->requestFocus();
@@ -405,9 +436,9 @@ void ButtonSet::setTriggerOnMouseUp(bool state)
   m_triggerOnMouseUp = state;
 }
 
-void ButtonSet::setMultipleSelection(bool state)
+void ButtonSet::setMultiMode(MultiMode mode)
 {
-  m_multipleSelection = state;
+  m_multiMode = mode;
 }
 
 void ButtonSet::onItemChange(Item* item)
diff --git a/src/app/ui/button_set.h b/src/app/ui/button_set.h
index 66789769d..5a15da0aa 100644
--- a/src/app/ui/button_set.h
+++ b/src/app/ui/button_set.h
@@ -1,4 +1,5 @@
 // Aseprite
+// Copyright (C) 2019  Igara Studio S.A.
 // Copyright (C) 2001-2018  David Capello
 //
 // This program is distributed under the terms of
@@ -38,6 +39,12 @@ namespace app {
       gfx::Color m_hotColor;
     };
 
+    enum class MultiMode {
+      One,       // Only one button can be selected (like radio buttons)
+      Set,       // Each button is a checkbox
+      OneOrMore, // One click selects one button, ctrl+click multiple selections
+    };
+
     ButtonSet(int columns);
 
     Item* addItem(const std::string& text, int hspan = 1, int vspan = 1);
@@ -47,6 +54,7 @@ namespace app {
     int getItemIndex(const Item* item) const;
 
     int selectedItem() const;
+    int countSelectedItems() const;
     Item* findSelectedItem() const;
     void setSelectedItem(int index, bool focusItem = true);
     void setSelectedItem(Item* item, bool focusItem = true);
@@ -54,7 +62,7 @@ namespace app {
 
     void setOfferCapture(bool state);
     void setTriggerOnMouseUp(bool state);
-    void setMultipleSelection(bool state);
+    void setMultiMode(MultiMode mode);
 
     obs::signal<void(Item*)> ItemChange;
     obs::signal<void(Item*)> RightClick;
@@ -67,7 +75,7 @@ namespace app {
   private:
     bool m_offerCapture;
     bool m_triggerOnMouseUp;
-    bool m_multipleSelection;
+    MultiMode m_multiMode;
   };
 
 } // namespace app
diff --git a/src/app/ui/color_popup.cpp b/src/app/ui/color_popup.cpp
index 94d14353a..f64e564f1 100644
--- a/src/app/ui/color_popup.cpp
+++ b/src/app/ui/color_popup.cpp
@@ -125,15 +125,6 @@ ColorPopup::CustomButtonSet::CustomButtonSet()
 {
 }
 
-int ColorPopup::CustomButtonSet::countSelectedItems()
-{
-  int count = 0;
-  for (int i=0; i<COLOR_MODES; ++i)
-    if (getItem(i)->isSelected())
-      ++count;
-  return count;
-}
-
 void ColorPopup::CustomButtonSet::onSelectItem(Item* item, bool focusItem, ui::Message* msg)
 {
   int count = countSelectedItems();
diff --git a/src/app/ui/color_popup.h b/src/app/ui/color_popup.h
index c3bca521f..8795afd1d 100644
--- a/src/app/ui/color_popup.h
+++ b/src/app/ui/color_popup.h
@@ -71,7 +71,6 @@ namespace app {
     class CustomButtonSet : public ButtonSet {
     public:
       CustomButtonSet();
-      int countSelectedItems();
     private:
       void onSelectItem(Item* item, bool focusItem, ui::Message* msg) override;
     };
diff --git a/src/app/ui/context_bar.cpp b/src/app/ui/context_bar.cpp
index 6853bcccd..72f7ac1dc 100644
--- a/src/app/ui/context_bar.cpp
+++ b/src/app/ui/context_bar.cpp
@@ -1107,7 +1107,7 @@ protected:
 class ContextBar::SymmetryField : public ButtonSet {
 public:
   SymmetryField() : ButtonSet(2) {
-    setMultipleSelection(true);
+    setMultiMode(MultiMode::Set);
     SkinTheme* theme = SkinTheme::instance();
     addItem(theme->parts.horizontalSymmetry());
     addItem(theme->parts.verticalSymmetry());
diff --git a/src/app/widget_loader.cpp b/src/app/widget_loader.cpp
index ad1aa91d9..b5db9e349 100644
--- a/src/app/widget_loader.cpp
+++ b/src/app/widget_loader.cpp
@@ -1,4 +1,5 @@
 // Aseprite
+// Copyright (C) 2019  Igara Studio S.A.
 // Copyright (C) 2001-2018  David Capello
 //
 // This program is distributed under the terms of
@@ -451,9 +452,10 @@ Widget* WidgetLoader::convertXmlElementToWidget(const TiXmlElement* elem, Widget
       widget = new ButtonSet(strtol(columns, NULL, 10));
 
     if (ButtonSet* buttonset = dynamic_cast<ButtonSet*>(widget)) {
-      bool multiple = bool_attr_is_true(elem, "multiple");
-      if (multiple)
-        buttonset->setMultipleSelection(multiple);
+      if (bool multiple = bool_attr_is_true(elem, "multiple"))
+        buttonset->setMultiMode(ButtonSet::MultiMode::Set);
+      if (bool oneormore = bool_attr_is_true(elem, "oneormore"))
+        buttonset->setMultiMode(ButtonSet::MultiMode::OneOrMore);
     }
   }
   else if (elem_name == "item") {
diff --git a/src/ui/panel.cpp b/src/ui/panel.cpp
index 616c69c61..b523ecfe4 100644
--- a/src/ui/panel.cpp
+++ b/src/ui/panel.cpp
@@ -1,5 +1,6 @@
 // Aseprite UI Library
-// Copyright (C) 2001-2013, 2015  David Capello
+// 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.
@@ -13,15 +14,18 @@
 #include "ui/resize_event.h"
 #include "ui/size_hint_event.h"
 
+#include <algorithm>
+
 namespace ui {
 
 Panel::Panel()
-  : Widget(kPanelWidget)
+  : m_multiple(false)
 {
 }
 
 void Panel::showChild(Widget* widget)
 {
+  m_multiple = false;
   for (auto child : children()) {
     if (!child->isDecorative())
       child->setVisible(child == widget);
@@ -29,8 +33,23 @@ void Panel::showChild(Widget* widget)
   layout();
 }
 
+void Panel::showAllChildren()
+{
+  m_multiple = true;
+  for (auto child : children()) {
+    if (!child->isDecorative())
+      child->setVisible(true);
+  }
+  layout();
+}
+
 void Panel::onResize(ResizeEvent& ev)
 {
+  if (m_multiple) {
+    VBox::onResize(ev);
+    return;
+  }
+
   // Copy the new position rectangle
   setBoundsQuietly(ev.bounds());
 
@@ -44,6 +63,11 @@ void Panel::onResize(ResizeEvent& ev)
 
 void Panel::onSizeHint(SizeHintEvent& ev)
 {
+  if (m_multiple) {
+    VBox::onSizeHint(ev);
+    return;
+  }
+
   gfx::Size maxSize(0, 0);
   gfx::Size reqSize;
 
@@ -51,13 +75,13 @@ void Panel::onSizeHint(SizeHintEvent& ev)
     if (!child->isDecorative()) {
       reqSize = child->sizeHint();
 
-      maxSize.w = MAX(maxSize.w, reqSize.w);
-      maxSize.h = MAX(maxSize.h, reqSize.h);
+      maxSize.w = std::max(maxSize.w, reqSize.w);
+      maxSize.h = std::max(maxSize.h, reqSize.h);
     }
   }
 
   if (hasText())
-    maxSize.w = MAX(maxSize.w, textWidth());
+    maxSize.w = std::max(maxSize.w, textWidth());
 
   ev.setSizeHint(
     maxSize.w + border().width(),
diff --git a/src/ui/panel.h b/src/ui/panel.h
index eec9d011f..64717435c 100644
--- a/src/ui/panel.h
+++ b/src/ui/panel.h
@@ -1,4 +1,5 @@
 // Aseprite UI Library
+// Copyright (C) 2019  Igara Studio S.A.
 // Copyright (C) 2001-2014  David Capello
 //
 // This file is released under the terms of the MIT license.
@@ -8,19 +9,23 @@
 #define UI_PANEL_H_INCLUDED
 #pragma once
 
-#include "ui/widget.h"
+#include "ui/box.h"
 
 namespace ui {
 
-  class Panel : public Widget {
+  class Panel : public VBox {
   public:
     Panel();
 
     void showChild(Widget* widget);
+    void showAllChildren();
 
   protected:
     virtual void onResize(ResizeEvent& ev) override;
     virtual void onSizeHint(SizeHintEvent& ev) override;
+
+  private:
+    bool m_multiple;
   };
 
 } // namespace ui