Backends: Win32: fixed an issue where a viewport destroyed while clicking would hog mouse tracking and temporary lead to incorrect update of HoveredWindow. (#7971)

Author: ocornut

backends/imgui_impl_win32.cpp

@@ -23,6 +23,7 @@
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
 //  2024-XX-XX: Platform: Added support for multiple windows via the ImGuiPlatformIO interface.
+//  2024-09-16: [Docking] Inputs: fixed an issue where a viewport destroyed while clicking would hog mouse tracking and temporary lead to incorrect update of HoveredWindow. (#7971)
 //  2024-07-08: Inputs: Fixed ImGuiMod_Super being mapped to VK_APPS instead of VK_LWIN||VK_RWIN. (#7768)
 //  2023-10-05: Inputs: Added support for extra ImGuiKey values: F13 to F24 function keys, app back/forward keys.
 //  2023-09-25: Inputs: Synthesize key-down event on key-up for VK_SNAPSHOT / ImGuiKey_PrintScreen as Windows doesn't emit it (same behavior as GLFW/SDL).
@@ -114,7 +115,7 @@ struct ImGui_ImplWin32_Data
 {
     HWND                        hWnd;
     HWND                        MouseHwnd;
-    int                         MouseTrackedArea;   // 0: not tracked, 1: client are, 2: non-client area
+    int                         MouseTrackedArea;   // 0: not tracked, 1: client area, 2: non-client area
     int                         MouseButtonsDown;
     INT64                       Time;
     INT64                       TicksPerSecond;
@@ -705,6 +706,16 @@ IMGUI_IMPL_API LRESULT ImGui_ImplWin32_WndProcHandler(HWND hwnd, UINT msg, WPARA
         }
         return 0;
     }
+    case WM_DESTROY:
+        if (bd->MouseHwnd == hwnd && bd->MouseTrackedArea != 0)
+        {
+            TRACKMOUSEEVENT tme_cancel = { sizeof(tme_cancel), TME_CANCEL, hwnd, 0 };
+            ::TrackMouseEvent(&tme_cancel);
+            bd->MouseHwnd = nullptr;
+            bd->MouseTrackedArea = 0;
+            io.AddMousePosEvent(-FLT_MAX, -FLT_MAX);
+        }
+        return 0;
     case WM_LBUTTONDOWN: case WM_LBUTTONDBLCLK:
     case WM_RBUTTONDOWN: case WM_RBUTTONDBLCLK:
     case WM_MBUTTONDOWN: case WM_MBUTTONDBLCLK:

docs/CHANGELOG.txt

@@ -82,6 +82,8 @@ Docking+Viewports Branch:
   over main viewport bounds isn't translated properly. (#7985)
 - Backends: Win32: fixed direct calls to platform_io.Platform_SetWindowPos()/Platform_SetWindowSize()
   on windows created by application (typically main viewport).
+- Backends: Win32: fixed an issue where a viewport destroyed while clicking would hog
+  mouse tracking and temporary lead to incorrect update of HoveredWindow. (#7971)
 - Backends: SDL3: added support for viewport->ParentViewportId field to support parenting
   windows at OS level. (#7973) [@RT2code]