Viewports: fix/amend dcb6335 to (1) avoid refocusing when focus action was actionned from a click within imgui boundaries and (2) restore a null focus as well. (#6299)

imgui.cpp

@@ -13916,13 +13916,21 @@ static void ImGui::UpdateViewportsNewFrame()
                 focused_viewport->LastFocusedStampCount = ++g.ViewportFocusedStampCount;
             g.PlatformLastFocusedViewportId = focused_viewport->ID;
 
-            // Focus associated dear imgui window (#6299)
+            // Focus associated dear imgui window if focus didn't happen with a click within imgui boundaries (#6299)
-            // FIXME: perhaps 'FocusTopMostWindowUnderOne()' can handle both cases?
+            // e.g. Clicking platform title bar.
+            // FIXME: perhaps 'FocusTopMostWindowUnderOne()' can handle the 'focused_window->Window != NULL' case as well.
+            if (!IsAnyMouseDown())
+            {
                 if (focused_viewport->Window != NULL)
                     FocusWindow(NavRestoreLastChildNavWindow(focused_viewport->Window));
-            else
+                else if (focused_viewport->LastFocusedHadNavWindow)
                     FocusTopMostWindowUnderOne(NULL, NULL, focused_viewport);
+                else
+                    FocusWindow(NULL);
+            }
         }
+        if (focused_viewport)
+            focused_viewport->LastFocusedHadNavWindow = (g.NavWindow != NULL) && (g.NavWindow->Viewport == focused_viewport);
     }
 
     // Create/update main viewport with current platform position.

imgui_internal.h

@@ -1738,6 +1738,7 @@ struct ImGuiViewportP : public ImGuiViewport
     ImVec2              LastPos;
     float               Alpha;                  // Window opacity (when dragging dockable windows/viewports we make them transparent)
     float               LastAlpha;
+    bool                LastFocusedHadNavWindow;// Instead of maintaining a LastFocusedWindow (which may harder to correctly maintain), we merely store weither NavWindow != NULL last time the viewport was focused.
     short               PlatformMonitor;
     int                 DrawListsLastFrame[2];  // Last frame number the background (0) and foreground (1) draw lists were used
     ImDrawList*         DrawLists[2];           // Convenience background (0) and foreground (1) draw lists. We use them to draw software mouser cursor when io.MouseDrawCursor is set and to draw most debug overlays.
@@ -1751,7 +1752,7 @@ struct ImGuiViewportP : public ImGuiViewport
     ImVec2              BuildWorkOffsetMin;     // Work Area: Offset being built during current frame. Generally >= 0.0f.
     ImVec2              BuildWorkOffsetMax;     // Work Area: Offset being built during current frame. Generally <= 0.0f.
 
-    ImGuiViewportP()                    { Window = NULL; Idx = -1; LastFrameActive = DrawListsLastFrame[0] = DrawListsLastFrame[1] = LastFocusedStampCount = -1; LastNameHash = 0; Alpha = LastAlpha = 1.0f; PlatformMonitor = -1; Window = NULL; DrawLists[0] = DrawLists[1] = NULL; LastPlatformPos = LastPlatformSize = LastRendererSize = ImVec2(FLT_MAX, FLT_MAX); }
+    ImGuiViewportP()                    { Window = NULL; Idx = -1; LastFrameActive = DrawListsLastFrame[0] = DrawListsLastFrame[1] = LastFocusedStampCount = -1; LastNameHash = 0; Alpha = LastAlpha = 1.0f; LastFocusedHadNavWindow = false; PlatformMonitor = -1; Window = NULL; DrawLists[0] = DrawLists[1] = NULL; LastPlatformPos = LastPlatformSize = LastRendererSize = ImVec2(FLT_MAX, FLT_MAX); }
     ~ImGuiViewportP()                   { if (DrawLists[0]) IM_DELETE(DrawLists[0]); if (DrawLists[1]) IM_DELETE(DrawLists[1]); }
     void    ClearRequestFlags()         { PlatformRequestClose = PlatformRequestMove = PlatformRequestResize = false; }