Add UI feedback when dragging over the timeline

src/app/ui/timeline/timeline.cpp

@@ -54,6 +54,8 @@
 #include "fmt/format.h"
 #include "gfx/point.h"
 #include "gfx/rect.h"
+#include "os/event.h"
+#include "os/event_queue.h"
 #include "os/surface.h"
 #include "os/system.h"
 #include "text/font.h"
@@ -257,7 +259,7 @@ Timeline::Timeline(TooltipManager* tooltipManager)
   , m_fromTimeline(false)
   , m_aniControls(tooltipManager)
 {
-  enableFlags(CTRL_RIGHT_CLICK);
+  enableFlags(CTRL_RIGHT_CLICK | ALLOW_DROP);
 
   m_ctxConn1 = m_context->BeforeCommandExecution.connect(
     &Timeline::onBeforeCommandExecution, this);
@@ -3538,7 +3540,7 @@ Timeline::Hit Timeline::hitTest(ui::Message* msg, const gfx::Point& mousePos)
     else
       hit.part = PART_NOTHING;
 
-    if (!hasCapture()) {
+    if (!hasCapture() && msg) {
       gfx::Rect outline = getPartBounds(Hit(PART_RANGE_OUTLINE));
       if (outline.contains(mousePos)) {
         auto mouseMsg = dynamic_cast<MouseMessage*>(msg);
@@ -4460,6 +4462,60 @@ void Timeline::onCancel(Context* ctx)
   invalidate();
 }
 
+void Timeline::onDragEnter(ui::DragEvent& e)
+{
+  m_state = STATE_MOVING_RANGE;
+}
+
+void Timeline::onDragLeave(ui::DragEvent& e)
+{
+  m_state = STATE_STANDBY;
+  m_range.clearRange();
+  invalidate();
+  flushRedraw();
+  os::Event ev;
+  os::System::instance()->eventQueue()->queueEvent(ev);
+}
+
+void Timeline::onDrag(ui::DragEvent& e)
+{
+  Widget::onDrag(e);
+  setHot(hitTest(nullptr, e.position()));
+  switch (m_hot.part) {
+    case PART_ROW:
+    case PART_ROW_EYE_ICON:
+    case PART_ROW_CONTINUOUS_ICON:
+    case PART_ROW_PADLOCK_ICON:
+    case PART_ROW_TEXT: {
+      m_range.startRange(nullptr, m_frame, Range::kLayers);
+      break;
+    }
+    case PART_CEL:
+    case PART_HEADER_FRAME:
+      m_range.startRange(nullptr, m_frame, Range::kFrames);
+      break;
+  }
+
+  updateDropRange(e.position());
+
+  flushRedraw();
+  os::Event ev;
+  os::System::instance()->eventQueue()->queueEvent(ev);
+}
+
+void Timeline::onDrop(ui::DragEvent& e)
+{
+  Widget::onDrop(e);
+
+  e.handled(true);
+  m_state = STATE_STANDBY;
+  m_range.clearRange();
+  invalidate();
+  flushRedraw();
+  os::Event ev;
+  os::System::instance()->eventQueue()->queueEvent(ev);
+}
+
 int Timeline::tagFramesDuration(const Tag* tag) const
 {
   ASSERT(m_sprite);

src/app/ui/timeline/timeline.h

@@ -46,6 +46,7 @@ namespace doc {
 namespace ui {
   class Graphics;
   class TooltipManager;
+  class DragEvent;
 }
 
 namespace app {
@@ -195,6 +196,11 @@ namespace app {
     bool onClear(Context* ctx) override;
     void onCancel(Context* ctx) override;
 
+    void onDragEnter(ui::DragEvent& e) override;
+    void onDragLeave(ui::DragEvent& e) override;
+    void onDrag(ui::DragEvent& e) override;
+    void onDrop(ui::DragEvent& e) override;
+
   private:
     struct DrawCelData;
 

src/ui/drag_event.h

@@ -8,7 +8,9 @@
 #define UI_DRAG_EVENT_H_INCLUDED
 #pragma once
 
+#include "base/paths.h"
 #include "os/dnd.h"
+#include "os/surface.h"
 #include "ui/event.h"
 #include "ui/widget.h"
 
@@ -37,6 +39,22 @@ namespace ui {
 
     const gfx::Point& position() const { return m_position; }
 
+    bool hasPaths() const {
+      return m_ev.dataProvider()->contains(os::DragDataItemType::Paths);
+    }
+
+    bool hasImage() const {
+      return m_ev.dataProvider()->contains(os::DragDataItemType::Image);
+    }
+
+    base::paths getPaths() const {
+      return m_ev.dataProvider()->getPaths();
+    }
+
+    os::SurfaceRef getImage() const {
+      return m_ev.dataProvider()->getImage();
+    }
+
   private:
     bool m_handled = false;
     gfx::Point m_position;