Drag and Drop: BeginDragDropSource(): temporarily removed the optional mouse_button=0 parameter because it is really usable in typical conditions at the moment. (#143, #1637)

imgui.cpp

@@ -250,6 +250,7 @@
  Here is a change-log of API breaking changes, if you are using one of the functions listed, expect to have to fix some code.
  Also read releases logs https://github.com/ocornut/imgui/releases for more details.
 
+ - 2018/02/18 (1.60) - BeginDragDropSource(): temporarily removed the optional mouse_button=0 parameter because it is really usable in typical conditions at the moment. 
  - 2018/02/16 (1.60) - obsoleted the io.RenderDrawListsFn callback, you can call your graphics engine render function after ImGui::Render(). Use ImGui::GetDrawData() to retrieve the ImDrawData* to display.
  - 2018/02/07 (1.60) - reorganized context handling to be more explicit,
                        - YOU NOW NEED TO CALL ImGui::CreateContext() AT THE BEGINNING OF YOUR APP, AND CALL ImGui::DestroyContext() AT THE END.
@@ -12744,7 +12745,7 @@ void ImGui::ClearDragDrop()
 
 // Call when current ID is active. 
 // When this returns true you need to: a) call SetDragDropPayload() exactly once, b) you may render the payload visual/description, c) call EndDragDropSource()
-bool ImGui::BeginDragDropSource(ImGuiDragDropFlags flags, int mouse_button)
+bool ImGui::BeginDragDropSource(ImGuiDragDropFlags flags)
 {
     ImGuiContext& g = *GImGui;
     ImGuiWindow* window = g.CurrentWindow;
@@ -12752,6 +12753,7 @@ bool ImGui::BeginDragDropSource(ImGuiDragDropFlags flags, int mouse_button)
     bool source_drag_active = false;
     ImGuiID source_id = 0;
     ImGuiID source_parent_id = 0;
+    int mouse_button = 0;
     if (!(flags & ImGuiDragDropFlags_SourceExtern))
     {
         source_id = window->DC.LastItemId;

imgui.h

@@ -452,7 +452,7 @@ namespace ImGui
 
     // Drag and Drop
     // [BETA API] Missing Demo code. API may evolve.
-    IMGUI_API bool          BeginDragDropSource(ImGuiDragDropFlags flags = 0, int mouse_button = 0);                // call when the current item is active. If this return true, you can call SetDragDropPayload() + EndDragDropSource()
+    IMGUI_API bool          BeginDragDropSource(ImGuiDragDropFlags flags = 0);                                      // call when the current item is active. If this return true, you can call SetDragDropPayload() + EndDragDropSource()
     IMGUI_API bool          SetDragDropPayload(const char* type, const void* data, size_t size, ImGuiCond cond = 0);// type is a user defined string of maximum 12 characters. Strings starting with '_' are reserved for dear imgui internal types. Data is copied and held by imgui.
     IMGUI_API void          EndDragDropSource();                                                                    // only call EndDragDropSource() if BeginDragDropSource() returns true!
     IMGUI_API bool          BeginDragDropTarget();                                                                  // call after submitting an item that may receive an item. If this returns true, you can call AcceptDragDropPayload() + EndDragDropTarget()