Selectable: With ImGuiSelectableFlags_AllowDoubleClick doesn't return true on the mouse button releas efollowing the double-click. Only first mouse release + second mouse down (double-click) returns true. Likewise for internal ButtonBehavior() with both _PressedOnClickRelease | _PressedOnDoubleClick. (#2503)

imgui.h

@@ -1435,7 +1435,8 @@ struct ImGuiIO
     bool        MouseClicked[5];                // Mouse button went from !Down to Down
     bool        MouseDoubleClicked[5];          // Has mouse button been double-clicked?
     bool        MouseReleased[5];               // Mouse button went from Down to !Down
-    bool        MouseDownOwned[5];              // Track if button was clicked inside a window. We don't request mouse capture from the application if click started outside ImGui bounds.
+    bool        MouseDownOwned[5];              // Track if button was clicked inside an imgui window. We don't request mouse capture from the application if click started outside ImGui bounds.
+    bool        MouseDownWasDoubleClick[5];     // Track if button down was a double-click
     float       MouseDownDuration[5];           // Duration the mouse button has been down (0.0f == just clicked)
     float       MouseDownDurationPrev[5];       // Previous time the mouse button has been down
     ImVec2      MouseDragMaxDistanceAbs[5];     // Maximum distance, absolute, on each axis, of how much mouse has traveled from the clicking point