Docking: Fix misuse of PushClipRect in UpdateWindowManualResize(). (#3311)

imgui.cpp

@@ -5502,9 +5502,10 @@ static bool ImGui::UpdateWindowManualResize(ImGuiWindow* window, const ImVec2& s
     //   This is however not the case with current back-ends under Win32, but a custom borderless window implementation would benefit from it.
     // - When decoration are enabled we typically benefit from that distance, but then our resize elements would be conflicting with OS resize elements, so we also narrow.
     // - Note that we are unable to tell if the platform setup allows hovering with a distance threshold (on Win32, decorated window have such threshold).
+    // We only clip interaction so we overwrite window->ClipRect, cannot call PushClipRect() yet as DrawList is not yet setup.
     const bool clip_with_viewport_rect = !(g.IO.BackendFlags & ImGuiBackendFlags_HasMouseHoveredViewport) || (g.IO.MouseHoveredViewport != window->ViewportId) || !(window->Viewport->Flags & ImGuiViewportFlags_NoDecoration);
     if (clip_with_viewport_rect)
-        PushClipRect(window->Viewport->Pos, window->Viewport->Pos + window->Viewport->Size, true); // Won't incur a draw command as we are not drawing here.
+        window->ClipRect = window->Viewport->GetMainRect();
 
     // Resize grips and borders are on layer 1
     window->DC.NavLayerCurrent = ImGuiNavLayer_Menu;
@@ -5568,8 +5569,6 @@ static bool ImGui::UpdateWindowManualResize(ImGuiWindow* window, const ImVec2& s
         }
     }
     PopID();
-    if (clip_with_viewport_rect)
-        PopClipRect();
 
     // Restore nav layer
     window->DC.NavLayerCurrent = ImGuiNavLayer_Main;

imgui.h

@@ -1697,7 +1697,7 @@ struct ImGuiSizeCallbackData
 // Important: the content of this class is still highly WIP and likely to change and be refactored
 // before we stabilize Docking features. Please be mindful if using this.
 // Provide hints:
-// - To the platform back-end via altered viewport flags (enable/disable OS decoration, OS task bar icons, etc.) 
+// - To the platform back-end via altered viewport flags (enable/disable OS decoration, OS task bar icons, etc.)
 // - To the platform back-end for OS level parent/child relationships of viewport.
 // - To the docking system for various options and filtering.
 struct ImGuiWindowClass
@@ -1707,7 +1707,7 @@ struct ImGuiWindowClass
     ImGuiViewportFlags  ViewportFlagsOverrideSet;   // Viewport flags to set when a window of this class owns a viewport. This allows you to enforce OS decoration or task bar icon, override the defaults on a per-window basis.
     ImGuiViewportFlags  ViewportFlagsOverrideClear; // Viewport flags to clear when a window of this class owns a viewport. This allows you to enforce OS decoration or task bar icon, override the defaults on a per-window basis.
     ImGuiDockNodeFlags  DockNodeFlagsOverrideSet;   // [EXPERIMENTAL] Dock node flags to set when a window of this class is hosted by a dock node (it doesn't have to be selected!)
-    ImGuiDockNodeFlags  DockNodeFlagsOverrideClear; // [EXPERIMENTAL] 
+    ImGuiDockNodeFlags  DockNodeFlagsOverrideClear; // [EXPERIMENTAL]
     bool                DockingAlwaysTabBar;        // Set to true to enforce single floating windows of this class always having their own docking node (equivalent of setting the global io.ConfigDockingAlwaysTabBar)
     bool                DockingAllowUnclassed;      // Set to true to allow windows of this class to be docked/merged with an unclassed window.