Drag and Drop: Added ImGuiDragDropFlags_SourceAutoExpirePayload flag …

…to force payload to expire if the source stops being submitted. (#1725, #143).

CHANGELOG.txt

@@ -54,6 +54,7 @@ Other Changes:
  - Drag and Drop: Calling BeginTooltip() between a BeginDragSource()/EndDragSource() or BeginDropTarget()/EndDropTarget() uses adjusted tooltip
    settings matching the one created when calling BeginDragSource() without the ImGuiDragDropFlags_SourceNoPreviewTooltip flag. (#143)
  - Drag and Drop: Payload stays available and under the mouse if the source stops being submitted, however the tooltip is replaced by "...". (#1725)
+ - Drag and Drop: Added ImGuiDragDropFlags_SourceAutoExpirePayload flag to force payload to expire if the source stops being submitted. (#1725, #143).
  - IsItemHovered(): Added ImGuiHoveredFlags_AllowWhenDisabled flag to query hovered status on disabled items. (#1940, #211)
  - Misc: Added ImGuiMouseCursor_Hand cursor enum + corresponding software cursor. (#1913, 1914) [@aiekick, @ocornut] 
  - Misc: Tweaked software mouse cursor offset to match the offset of the corresponding Windows 10 cursors.

imgui.cpp

@@ -4441,10 +4441,11 @@ void ImGui::EndFrame()
     // Show CTRL+TAB list
     if (g.NavWindowingTarget)
         NavUpdateWindowingList();
-
-    // Drag and Drop: Elapse payload at the end of the frame if mouse has been released
-    if (g.DragDropActive && g.DragDropPayload.DataFrameCount + 1 < g.FrameCount && !IsMouseDown(g.DragDropMouseButton))
-        ClearDragDrop();
+
+    // Drag and Drop: Elapse payload (if source stops being submitted)
+    if (g.DragDropActive && g.DragDropPayload.DataFrameCount + 1 < g.FrameCount)
+        if ((g.DragDropSourceFlags & ImGuiDragDropFlags_SourceAutoExpirePayload) || !IsMouseDown(g.DragDropMouseButton))
+            ClearDragDrop();
 
     // Drag and Drop: Fallback for source tooltip. This is not ideal but better than nothing.
     if (g.DragDropActive && g.DragDropSourceFrameCount < g.FrameCount)

imgui.h

@@ -741,6 +741,7 @@ enum ImGuiDragDropFlags_
     ImGuiDragDropFlags_SourceNoHoldToOpenOthers     = 1 << 2,   // Disable the behavior that allows to open tree nodes and collapsing header by holding over them while dragging a source item.
     ImGuiDragDropFlags_SourceAllowNullID            = 1 << 3,   // Allow items such as Text(), Image() that have no unique identifier to be used as drag source, by manufacturing a temporary identifier based on their window-relative position. This is extremely unusual within the dear imgui ecosystem and so we made it explicit.
     ImGuiDragDropFlags_SourceExtern                 = 1 << 4,   // External source (from outside of imgui), won't attempt to read current item/window info. Will always return true. Only one Extern source can be active simultaneously.
+    ImGuiDragDropFlags_SourceAutoExpirePayload      = 1 << 5,   // Automatically expire the payload if the source cease to be submitted (otherwise payloads are persisting while being dragged)
     // AcceptDragDropPayload() flags
     ImGuiDragDropFlags_AcceptBeforeDelivery         = 1 << 10,  // AcceptDragDropPayload() will returns true even before the mouse button is released. You can then call IsDelivery() to test if the payload needs to be delivered.
     ImGuiDragDropFlags_AcceptNoDrawDefaultRect      = 1 << 11,  // Do not draw the default highlight rectangle when hovering over target.