Drag and Drop: extracted a RenderDragDropTargetRect() function (#1603)

imgui.cpp

@@ -11618,7 +11618,6 @@ const ImGuiPayload* ImGui::AcceptDragDropPayload(const char* type, ImGuiDragDrop
     }
 
     // Render default drop visuals
-    // FIXME-DRAGDROP: Settle on a proper default visuals for drop target.
     payload.Preview = was_accepted_previously;
     flags |= (g.DragDropSourceFlags & ImGuiDragDropFlags_AcceptNoDrawDefaultRect); // Source can also inhibit the preview (useful for external sources that live for 1 frame)
     if (!(flags & ImGuiDragDropFlags_AcceptNoDrawDefaultRect) && payload.Preview)
@@ -11632,6 +11631,12 @@ const ImGuiPayload* ImGui::AcceptDragDropPayload(const char* type, ImGuiDragDrop
     return &payload;
 }
 
+// FIXME-DRAGDROP: Settle on a proper default visuals for drop target.
+void ImGui::RenderDragDropTargetRect(const ImRect& bb)
+{
+    GetWindowDrawList()->AddRect(bb.Min - ImVec2(3.5f, 3.5f), bb.Max + ImVec2(3.5f, 3.5f), GetColorU32(ImGuiCol_DragDropTarget), 0.0f, 0, 2.0f);
+}
+
 const ImGuiPayload* ImGui::GetDragDropPayload()
 {
     ImGuiContext& g = *GImGui;

imgui_internal.h

@@ -2772,6 +2772,7 @@ namespace ImGui
     IMGUI_API bool          BeginDragDropTargetCustom(const ImRect& bb, ImGuiID id);
     IMGUI_API void          ClearDragDrop();
     IMGUI_API bool          IsDragDropPayloadBeingAccepted();
+    IMGUI_API void          RenderDragDropTargetRect(const ImRect& bb);
 
     // Internal Columns API (this is not exposed because we will encourage transitioning to the Tables API)
     IMGUI_API void          SetWindowClipRectBeforeSetChannel(ImGuiWindow* window, const ImRect& clip_rect);