Process os::Event::MouseEnter/Leave in correct order

When we received a MouseEnter/Leave, we were processing those laf-os
events immediately without taking care of all the MouseMove/Down/Up
events in the middle. Now we enqueue all the events as
messages (MouseEnter -> MouseMove/Down/Up -> MouseLeave).

This is important because when we process MouseLeave we are calling
setMouse(nullptr), which resets the mouse widget HAS_MOUSE flag, and
some widgets needs to know if they have the mouse above before the
MouseUp event. With this change we can remove the
Widget::hasMouseOver() function (that was checking the global
ui::get_mouse_position() instead of the HAS_MOUSE flag directly).

Another change was introduced to keep the old behavior now that
hasMouseOver() is not available: the ui::Manager doesn't assign the
HAS_MOUSE flag if the mouse is captured (it only assign the HAS_MOUSE
to the widget with the mouse captured, or to no widget, at least until
the capture is released).

src/app/ui/color_button.cpp

@@ -277,7 +277,7 @@ void ColorButton::onPaint(PaintEvent& ev)
   draw_color_button(g, rc,
                     color,
                     (doc::ColorMode)m_pixelFormat,
-                    hasMouseOver(), false);
+                    hasMouse(), false);
 
   // Draw text
   std::string str = m_color.toHumanReadableString(m_pixelFormat,

src/app/ui/icon_button.cpp

@@ -1,5 +1,5 @@
 // Aseprite
-// Copyright (C) 2022  Igara Studio S.A.
+// Copyright (C) 2022-2023  Igara Studio S.A.
 // Copyright (C) 2001-2017  David Capello
 //
 // This program is distributed under the terms of
@@ -56,7 +56,7 @@ void IconButton::onPaint(PaintEvent& ev)
     fg = theme->colors.menuitemHighlightText();
     bg = theme->colors.menuitemHighlightFace();
   }
-  else if (isEnabled() && hasMouseOver()) {
+  else if (isEnabled() && hasMouse()) {
     fg = theme->colors.menuitemHotText();
     bg = theme->colors.menuitemHotFace();
   }

src/app/ui/notifications.cpp

@@ -62,7 +62,7 @@ void Notifications::onPaint(PaintEvent& ev)
   Graphics* g = ev.graphics();
 
   PaintWidgetPartInfo info;
-  if (hasMouseOver()) info.styleFlags |= ui::Style::Layer::kMouse;
+  if (hasMouse()) info.styleFlags |= ui::Style::Layer::kMouse;
   if (m_red) info.styleFlags |= ui::Style::Layer::kFocus;
   if (isSelected()) info.styleFlags |= ui::Style::Layer::kSelected;
 

src/app/ui/skin/skin_theme.cpp

@@ -1489,16 +1489,16 @@ void SkinTheme::paintSlider(PaintEvent& ev)
     SkinPartPtr empty_part;
 
     if (isMiniLook) {
-      full_part = widget->hasMouseOver() ? parts.miniSliderFullFocused():
+      full_part = (widget->hasMouse() ? parts.miniSliderFullFocused():
-                                           parts.miniSliderFull();
+                                        parts.miniSliderFull());
-      empty_part = widget->hasMouseOver() ? parts.miniSliderEmptyFocused():
+      empty_part = (widget->hasMouse() ? parts.miniSliderEmptyFocused():
-                                            parts.miniSliderEmpty();
+                                         parts.miniSliderEmpty());
     }
     else {
-      full_part = widget->hasFocus() ? parts.sliderFullFocused():
+      full_part = (widget->hasFocus() ? parts.sliderFullFocused():
-                                       parts.sliderFull();
+                                        parts.sliderFull());
-      empty_part = widget->hasFocus() ? parts.sliderEmptyFocused():
+      empty_part = (widget->hasFocus() ? parts.sliderEmptyFocused():
-                                        parts.sliderEmpty();
+                                         parts.sliderEmpty());
     }
 
     if (value == min)

src/app/ui/tabs.cpp

@@ -1,5 +1,5 @@
 // Aseprite
-// Copyright (C) 2018-2022  Igara Studio S.A.
+// Copyright (C) 2018-2023  Igara Studio S.A.
 // Copyright (C) 2001-2017  David Capello
 //
 // This program is distributed under the terms of
@@ -1042,7 +1042,7 @@ void Tabs::updateDragTabIndexes(int mouseX, bool startAni)
         startAni = true;
       }
     }
-    else if (hasMouseOver()) {
+    else if (hasMouse()) {
       i = std::clamp(i, 0, int(m_list.size())-1);
       if (i != m_dragTabIndex) {
         m_list.erase(m_list.begin()+m_dragTabIndex);

src/app/ui/tile_button.cpp

@@ -1,5 +1,5 @@
 // Aseprite
-// Copyright (c) 2020-2022  Igara Studio S.A.
+// Copyright (c) 2020-2023  Igara Studio S.A.
 //
 // This program is distributed under the terms of
 // the End-User License Agreement for Aseprite.
@@ -164,7 +164,7 @@ void TileButton::onPaint(PaintEvent& ev)
   Site site = UIContext::instance()->activeSite();
   draw_tile_button(g, rc,
                    site, m_tile,
-                   hasMouseOver(), false);
+                   hasMouse(), false);
 
   // Draw text
   if (m_tile != doc::notile) {

src/app/ui/timeline/timeline.cpp

@@ -3241,7 +3241,7 @@ void Timeline::updateScrollBars()
 void Timeline::updateByMousePos(ui::Message* msg, const gfx::Point& mousePos)
 {
   Hit hit = hitTest(msg, mousePos);
-  if (hasMouseOver())
+  if (hasMouse())
     setCursor(msg, hit);
   setHot(hit);
 }

src/ui/button.cpp

@@ -204,7 +204,7 @@ bool ButtonBase::onProcessMessage(Message* msg)
       if (hasCapture()) {
         releaseMouse();
 
-        if (hasMouseOver()) {
+        if (hasMouse()) {
           switch (m_behaviorType) {
 
             case kButtonWidget:
@@ -270,7 +270,7 @@ void ButtonBase::onStartDrag()
 
 void ButtonBase::onSelectWhenDragging()
 {
-  bool hasMouse = hasMouseOver();
+  const bool hasMouse = this->hasMouse();
 
   // Switch state when the mouse go out
   if ((hasMouse && isSelected() != m_pressedStatus) ||

src/ui/link_label.cpp

@@ -1,5 +1,5 @@
 // Aseprite UI Library
-// Copyright (C) 2018  Igara Studio S.A.
+// Copyright (C) 2018-2023  Igara Studio S.A.
 // Copyright (C) 2001-2017  David Capello
 //
 // This file is released under the terms of the MIT license.
@@ -48,7 +48,7 @@ bool LinkLabel::onProcessMessage(Message* msg)
 
     case kSetCursorMessage:
       // TODO theme stuff
-      if (isEnabled() && hasMouseOver()) {
+      if (isEnabled() && hasMouse()) {
         set_mouse_cursor(kHandCursor);
         return true;
       }
@@ -66,7 +66,7 @@ bool LinkLabel::onProcessMessage(Message* msg)
 
     case kMouseMoveMessage:
       if (isEnabled() && hasCapture())
-        setSelected(hasMouseOver());
+        setSelected(hasMouse());
       break;
 
     case kMouseDownMessage:
@@ -83,7 +83,7 @@ bool LinkLabel::onProcessMessage(Message* msg)
         setSelected(false);
         invalidate();           // TODO theme specific
 
-        if (hasMouseOver())
+        if (hasMouse())
           onClick();
       }
       break;

src/ui/manager.cpp

@@ -496,30 +496,37 @@ void Manager::generateMessagesFromOSEvents()
       }
 
       case os::Event::MouseEnter: {
-        if (get_multiple_displays()) {
+        auto msg = new CallbackMessage([osEvent, display]{
-          if (osEvent.window()) {
+          if (get_multiple_displays()) {
-            ASSERT(display != nullptr);
+            if (osEvent.window()) {
-            _internal_set_mouse_display(display);
+              ASSERT(display != nullptr);
+              _internal_set_mouse_display(display);
+            }
           }
-        }
+          set_mouse_cursor(kArrowCursor);
-        set_mouse_cursor(kArrowCursor);
+          mouse_display = display;
+        });
+        enqueueMessage(msg);
         lastMouseMoveEvent = osEvent;
-        mouse_display = display;
         break;
       }
 
       case os::Event::MouseLeave: {
-        if (mouse_display == display) {
+        auto msg = new CallbackMessage([this, display]{
-          set_mouse_cursor(kOutsideDisplay);
+          if (mouse_display == display) {
-          setMouse(nullptr);
+            set_mouse_cursor(kOutsideDisplay);
+            setMouse(nullptr);
 
-          _internal_no_mouse_position();
+            _internal_no_mouse_position();
-          mouse_display = nullptr;
+            mouse_display = nullptr;
+          }
+        });
 
-          // To avoid calling kSetCursorMessage when the mouse leaves
+        enqueueMessage(msg);
-          // the window.
+
-          lastMouseMoveEvent = os::Event();
+        // To avoid calling kSetCursorMessage when the mouse leaves
-        }
+        // the window.
+        lastMouseMoveEvent = os::Event();
         break;
       }
 
@@ -1000,54 +1007,61 @@ void Manager::setMouse(Widget* widget)
             (widget ? widget->id(): ""));
 #endif
 
-  if ((mouse_widget != widget) && (!capture_widget)) {
+  if (mouse_widget == widget)
-    Widget* commonAncestor = findLowestCommonAncestor(mouse_widget, widget);
+    return;
 
-    // Fetch the mouse
+  Widget* commonAncestor = findLowestCommonAncestor(mouse_widget, widget);
-    if (mouse_widget && mouse_widget != commonAncestor) {
-      auto msg = new Message(kMouseLeaveMessage);
-      msg->setRecipient(mouse_widget);
-      msg->setPropagateToParent(true);
-      msg->setCommonAncestor(commonAncestor);
-      enqueueMessage(msg);
 
-      // Remove HAS_MOUSE from all the hierarchy
+  // Fetch the mouse
-      auto a = mouse_widget;
+  if (mouse_widget && mouse_widget != commonAncestor) {
-      while (a && a != commonAncestor) {
+    auto msg = new Message(kMouseLeaveMessage);
-        a->disableFlags(HAS_MOUSE);
+    msg->setRecipient(mouse_widget);
-        a = a->parent();
+    msg->setPropagateToParent(true);
-      }
+    msg->setCommonAncestor(commonAncestor);
+    enqueueMessage(msg);
+
+    // Remove HAS_MOUSE from all the hierarchy
+    auto a = mouse_widget;
+    while (a && a != commonAncestor) {
+      a->disableFlags(HAS_MOUSE);
+      a = a->parent();
     }
+  }
 
-    // Put the mouse
+  // If the mouse is captured, we can just put the HAS_MOUSE flag in
-    mouse_widget = widget;
+  // the captured widget (or in none).
-    if (widget) {
+  if (capture_widget && capture_widget != widget) {
-      Display* display = mouse_widget->display();
+    widget = nullptr;
-      gfx::Point mousePos = display->nativeWindow()->pointFromScreen(get_mouse_position());
+  }
 
-      auto msg = newMouseMessage(
+  // Put the mouse
-        kMouseEnterMessage,
+  mouse_widget = widget;
-        display, nullptr,
+  if (widget) {
-        mousePos,
+    Display* display = mouse_widget->display();
-        PointerType::Unknown,
+    gfx::Point mousePos = display->nativeWindow()->pointFromScreen(get_mouse_position());
-        m_mouseButton,
-        kKeyUninitializedModifier);
 
-      msg->setRecipient(widget);
+    auto msg = newMouseMessage(
-      msg->setPropagateToParent(true);
+      kMouseEnterMessage,
-      msg->setCommonAncestor(commonAncestor);
+      display, nullptr,
-      enqueueMessage(msg);
+      mousePos,
-      generateSetCursorMessage(display,
+      PointerType::Unknown,
-                               mousePos,
+      m_mouseButton,
-                               kKeyUninitializedModifier,
+      kKeyUninitializedModifier);
-                               PointerType::Unknown);
 
-      // Add HAS_MOUSE to all the hierarchy
+    msg->setRecipient(widget);
-      auto a = mouse_widget;
+    msg->setPropagateToParent(true);
-      while (a && a != commonAncestor) {
+    msg->setCommonAncestor(commonAncestor);
-        a->enableFlags(HAS_MOUSE);
+    enqueueMessage(msg);
-        a = a->parent();
+    generateSetCursorMessage(display,
-      }
+                             mousePos,
+                             kKeyUninitializedModifier,
+                             PointerType::Unknown);
+
+    // Add HAS_MOUSE to all the hierarchy
+    auto a = mouse_widget;
+    while (a && a != commonAncestor) {
+      a->enableFlags(HAS_MOUSE);
+      a = a->parent();
     }
   }
 }
@@ -1929,9 +1943,10 @@ bool Manager::sendMessageToWidget(Message* msg, Widget* widget)
       "kSetCursorMessage",
       "kMouseWheelMessage",
       "kTouchMagnifyMessage",
+      "kCallbackMessage",
     };
     static_assert(kOpenMessage == 0 &&
-                  kTouchMagnifyMessage == sizeof(msg_name)/sizeof(const char*)-1,
+                  kCallbackMessage == sizeof(msg_name)/sizeof(const char*)-1,
                   "MessageType enum has changed");
     const char* string =
       (msg->type() >= 0 &&

src/ui/message.h

@@ -1,5 +1,5 @@
 // Aseprite UI Library
-// Copyright (C) 2018-2022  Igara Studio S.A.
+// Copyright (C) 2018-2023  Igara Studio S.A.
 // Copyright (C) 2001-2018  David Capello
 //
 // This file is released under the terms of the MIT license.
@@ -18,6 +18,8 @@
 #include "ui/mouse_button.h"
 #include "ui/pointer_type.h"
 
+#include <functional>
+
 namespace ui {
 
   class Display;
@@ -81,6 +83,18 @@ namespace ui {
     KeyModifiers m_modifiers; // Key modifiers pressed when message was created
   };
 
+  class CallbackMessage : public Message {
+  public:
+    CallbackMessage(std::function<void()>&& callback)
+      : Message(kCallbackMessage)
+      , m_callback(std::move(callback)) { }
+    void call() {
+      m_callback();
+    }
+  private:
+    std::function<void()> m_callback;
+  };
+
   class KeyMessage : public Message {
   public:
     KeyMessage(MessageType type,

src/ui/message_type.h

@@ -1,5 +1,5 @@
 // Aseprite UI Library
-// Copyright (C) 2019  Igara Studio S.A.
+// Copyright (C) 2019-2023  Igara Studio S.A.
 // Copyright (C) 2001-2018  David Capello
 //
 // This file is released under the terms of the MIT license.
@@ -45,6 +45,11 @@ namespace ui {
     // TODO Drag'n'drop messages...
     // k...DndMessage
 
+    // Call a generic function when we are processing the queue of
+    // messages. Used to process an laf-os event in the same order
+    // they were received in some cases (e.g. mouse leave/enter).
+    kCallbackMessage,
+
     // User widgets.
     kFirstRegisteredMessage,
     kLastRegisteredMessage = 0x7fffffff

src/ui/widget.cpp

@@ -1496,11 +1496,6 @@ bool Widget::offerCapture(ui::MouseMessage* mouseMsg, int widget_type)
   return false;
 }
 
-bool Widget::hasMouseOver() const
-{
-  return (this == pickFromScreenPos(get_mouse_position()));
-}
-
 gfx::Point Widget::mousePosInDisplay() const
 {
   return display()->nativeWindow()->pointFromScreen(get_mouse_position());

src/ui/widget.h

@@ -349,12 +349,29 @@ namespace ui {
     void captureMouse();
     void releaseMouse();
 
+    // True when the widget has the keyboard focus (only widgets with
+    // FOCUS_STOP flag will receive the HAS_FOCUS flag/receive the
+    // focus when the user press the tab key to navigate widgets).
     bool hasFocus() const { return hasFlags(HAS_FOCUS); }
-    bool hasMouse() const { return hasFlags(HAS_MOUSE); }
-    bool hasCapture() const { return hasFlags(HAS_CAPTURE); }
 
-    // Checking if the mouse is currently above the widget.
+    // True when the widget has the mouse above. If the mouse leaves
-    bool hasMouseOver() const;
+    // the widget, the widget will lose the HAS_MOUSE flag. If some
+    // widget captures the mouse, no other widget will have this flag,
+    // so in this case there are just two options:
+    //
+    // 1) The widget with the capture (hasCapture()) will has the
+    //    mouse flag too.
+    // 2) Or no other widget will have the mouse flag until the widget
+    //    releases the capture (releaseCapture())
+    bool hasMouse() const { return hasFlags(HAS_MOUSE); }
+
+    // True when the widget has captured the mouse, e.g. generally
+    // when the user press a mouse button above a clickeable widget
+    // (e.g. ui::Button), the widget will capture the mouse
+    // temporarily until the mouse button is released. If a widget
+    // captures the mouse, it will receive all mouse events until it
+    // release (even if the mouse moves outside the widget).
+    bool hasCapture() const { return hasFlags(HAS_CAPTURE); }
 
     // Returns the mouse position relative to the top-left corner of
     // the ui::Display's client area/content rect.