Fixed a bug where multiple itemDropped() callbacks were being triggered when using drag and drop

modules/juce_gui_basics/mouse/juce_DragAndDropContainer.cpp

@@ -393,6 +393,15 @@ void DragAndDropContainer::startDragging (const var& sourceDescription,
                                           const Point<int>* imageOffsetFromMouse,
                                           const MouseInputSource* inputSourceCausingDrag)
 {
+    if (isAlreadyDragging (sourceComponent))
+        return;
+
+    if (inputSourceCausingDrag == nullptr || ! inputSourceCausingDrag->isDragging())
+    {
+        jassertfalse;   // You must call startDragging() from within a mouseDown or mouseDrag callback!
+        return;
+    }
+
     auto* draggingSource = getMouseInputSourceForDrag (sourceComponent, inputSourceCausingDrag);
     auto lastMouseDown = draggingSource->getLastMouseDownPosition().roundToInt();
     Point<int> imageOffset;
@@ -571,6 +580,17 @@ const MouseInputSource* DragAndDropContainer::getMouseInputSourceForDrag (Compon
     return inputSourceCausingDrag;
 }
 
+bool DragAndDropContainer::isAlreadyDragging (Component* component) const noexcept
+{
+    for (auto* dragImageComp : dragImageComponents)
+    {
+        if (dragImageComp->sourceDetails.sourceComponent == component)
+            return true;
+    }
+
+    return false;
+}
+
 //==============================================================================
 DragAndDropTarget::SourceDetails::SourceDetails (const var& desc, Component* comp, Point<int> pos) noexcept
     : description (desc),

modules/juce_gui_basics/mouse/juce_DragAndDropContainer.h

@@ -233,6 +233,7 @@ private:
     OwnedArray<DragImageComponent> dragImageComponents;
 
     const MouseInputSource* getMouseInputSourceForDrag (Component* sourceComponent, const MouseInputSource* inputSourceCausingDrag);
+    bool isAlreadyDragging (Component* sourceComponent) const noexcept;
 
    #if JUCE_CATCH_DEPRECATED_CODE_MISUSE
     // This is just here to cause a compile error in old code that hasn't been changed to use the new