Drag and Drop: Fixes an issue when elapsing payload would be based on last payload frame instead of last drag source frame.

docs/CHANGELOG.txt

@@ -62,6 +62,9 @@ Other changes:
   Added corresponding ImGuiCol_TabSelectedOverline and ImGuiCol_TabDimmedSelectedOverline colors.
 - Drag and Drop: BeginDragDropSource() with ImGuiDragDropFlags_SourceExtern sets
   active id so a multi-frame extern source doesn't interfere with hovered widgets. (#143)
+- Drag and Drop: Fixes an issue when elapsing payload would be based on last payload
+  frame instead of last drag source frame, which makes a difference if not resubmitting
+  payload every frame.
 - Examples: GLFW+Vulkan, SDL+Vulkan: handle swap chain resize even without Vulkan
   returning VK_SUBOPTIMAL_KHR, which doesn't seem to happen on Wayland. (#7671)
   [@AndreiNego, @ocornut]

imgui.cpp

@@ -5136,7 +5136,7 @@ void ImGui::EndFrame()
     if (g.DragDropActive)
     {
         bool is_delivered = g.DragDropPayload.Delivery;
-        bool is_elapsed = (g.DragDropPayload.DataFrameCount + 1 < g.FrameCount) && ((g.DragDropSourceFlags & ImGuiDragDropFlags_SourceAutoExpirePayload) || !IsMouseDown(g.DragDropMouseButton));
+        bool is_elapsed = (g.DragDropSourceFrameCount + 1 < g.FrameCount) && ((g.DragDropSourceFlags & ImGuiDragDropFlags_SourceAutoExpirePayload) || !IsMouseDown(g.DragDropMouseButton));
         if (is_delivered || is_elapsed)
             ClearDragDrop();
     }
@@ -13306,7 +13306,7 @@ bool ImGui::SetDragDropPayload(const char* type, const void* data, size_t data_s
     IM_ASSERT(strlen(type) < IM_ARRAYSIZE(payload.DataType) && "Payload type can be at most 32 characters long");
     IM_ASSERT((data != NULL && data_size > 0) || (data == NULL && data_size == 0));
     IM_ASSERT(cond == ImGuiCond_Always || cond == ImGuiCond_Once);
-    IM_ASSERT(payload.SourceId != 0);                               // Not called between BeginDragDropSource() and EndDragDropSource()
+    IM_ASSERT(payload.SourceId != 0); // Not called between BeginDragDropSource() and EndDragDropSource()
 
     if (cond == ImGuiCond_Always || payload.DataFrameCount == -1)
     {