Backends: Win32: fixed direct calls to platform_io.Platform_SetWindowPos()/Platform_SetWindowSize() on windows created by application (typically main viewport).

backends/imgui_impl_win32.cpp

@@ -1158,11 +1158,20 @@ static ImVec2 ImGui_ImplWin32_GetWindowPos(ImGuiViewport* viewport)
     return ImVec2((float)pos.x, (float)pos.y);
 }
 
+static void ImGui_ImplWin32_UpdateWin32StyleFromWindow(ImGuiViewport* viewport)
+{
+    ImGui_ImplWin32_ViewportData* vd = (ImGui_ImplWin32_ViewportData*)viewport->PlatformUserData;
+    vd->DwStyle = ::GetWindowLongW(vd->Hwnd, GWL_STYLE);
+    vd->DwExStyle = ::GetWindowLongW(vd->Hwnd, GWL_EXSTYLE);
+}
+
 static void ImGui_ImplWin32_SetWindowPos(ImGuiViewport* viewport, ImVec2 pos)
 {
     ImGui_ImplWin32_ViewportData* vd = (ImGui_ImplWin32_ViewportData*)viewport->PlatformUserData;
     IM_ASSERT(vd->Hwnd != 0);
     RECT rect = { (LONG)pos.x, (LONG)pos.y, (LONG)pos.x, (LONG)pos.y };
+    if (viewport->Flags & ImGuiViewportFlags_OwnedByApp)
+        ImGui_ImplWin32_UpdateWin32StyleFromWindow(viewport); // Not our window, poll style before using
     ::AdjustWindowRectEx(&rect, vd->DwStyle, FALSE, vd->DwExStyle);
     ::SetWindowPos(vd->Hwnd, nullptr, rect.left, rect.top, 0, 0, SWP_NOZORDER | SWP_NOSIZE | SWP_NOACTIVATE);
 }
@@ -1181,6 +1190,8 @@ static void ImGui_ImplWin32_SetWindowSize(ImGuiViewport* viewport, ImVec2 size)
     ImGui_ImplWin32_ViewportData* vd = (ImGui_ImplWin32_ViewportData*)viewport->PlatformUserData;
     IM_ASSERT(vd->Hwnd != 0);
     RECT rect = { 0, 0, (LONG)size.x, (LONG)size.y };
+    if (viewport->Flags & ImGuiViewportFlags_OwnedByApp)
+        ImGui_ImplWin32_UpdateWin32StyleFromWindow(viewport); // Not our window, poll style before using
     ::AdjustWindowRectEx(&rect, vd->DwStyle, FALSE, vd->DwExStyle); // Client to Screen
     ::SetWindowPos(vd->Hwnd, nullptr, 0, 0, rect.right - rect.left, rect.bottom - rect.top, SWP_NOZORDER | SWP_NOMOVE | SWP_NOACTIVATE);
 }
@@ -1227,14 +1238,14 @@ static void ImGui_ImplWin32_SetWindowAlpha(ImGuiViewport* viewport, float alpha)
     IM_ASSERT(alpha >= 0.0f && alpha <= 1.0f);
     if (alpha < 1.0f)
     {
-        DWORD style = ::GetWindowLongW(vd->Hwnd, GWL_EXSTYLE) | WS_EX_LAYERED;
-        ::SetWindowLongW(vd->Hwnd, GWL_EXSTYLE, style);
+        DWORD ex_style = ::GetWindowLongW(vd->Hwnd, GWL_EXSTYLE) | WS_EX_LAYERED;
+        ::SetWindowLongW(vd->Hwnd, GWL_EXSTYLE, ex_style);
         ::SetLayeredWindowAttributes(vd->Hwnd, 0, (BYTE)(255 * alpha), LWA_ALPHA);
     }
     else
     {
-        DWORD style = ::GetWindowLongW(vd->Hwnd, GWL_EXSTYLE) & ~WS_EX_LAYERED;
-        ::SetWindowLongW(vd->Hwnd, GWL_EXSTYLE, style);
+        DWORD ex_style = ::GetWindowLongW(vd->Hwnd, GWL_EXSTYLE) & ~WS_EX_LAYERED;
+        ::SetWindowLongW(vd->Hwnd, GWL_EXSTYLE, ex_style);
     }
 }
 

docs/CHANGELOG.txt

@@ -80,6 +80,8 @@ Docking+Viewports Branch:
 
 - Viewports: fixed an issue where a window manually constrained to the main viewport while crossing
   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: SDL3: added support for viewport->ParentViewportId field to support parenting
   windows at OS level. (#7973) [@RT2code]