Viewport: Tweaked selection of g.MouseRefViewport, in particular aime…

…d at fixing browsing child-menus while holding mouse buttons with menus in multiple viewports. (#1542)

imgui.cpp

@@ -3513,12 +3513,13 @@ static void ImGui::UpdateViewports()
  g.MouseRefViewport = viewport_ref;
  g.MouseRefViewport->LastFrameAsRefViewport = g.FrameCount;
 
- // When dragging something, always refer to the last hovered viewport (so when we are between viewport, our dragged preview will tend to show in the last viewport)
+ // When dragging something, always refer to the last hovered viewport. 
+ // (So when we are between viewports, our dragged preview will tend to show in the last viewport even if we don't have tooltips in viewports)
+ // Also consider the case of holding on a menu item to browse child menus: even thought a mouse button is held, there's no active id because menu items only react on mouse release.
  const bool is_mouse_dragging_with_an_expected_destination = g.DragDropActive || (g.MovingWindow != NULL);
- const bool is_mouse_all_released = !ImGui::IsAnyMouseDown();
- if (is_mouse_dragging_with_an_expected_destination || is_mouse_all_released)
+ if (is_mouse_dragging_with_an_expected_destination || g.ActiveId == 0 || !ImGui::IsAnyMouseDown())
  {
- if (is_mouse_dragging_with_an_expected_destination)
+ if (is_mouse_dragging_with_an_expected_destination && viewport_hovered == NULL)
  viewport_hovered = g.MouseHoveredLastViewport;
  if (viewport_hovered != NULL && viewport_hovered != g.MouseRefViewport && !(viewport_hovered->Flags & ImGuiViewportFlags_NoInputs))
  {