tor-browser

commit 433cc8224790300fdabe76bd225b644c1812da34
parent 72c331806e9eb09df4f757bd32410681306a75ea
Author: Emilio Cobos Álvarez <emilio@crisal.io>
Date:   Thu, 27 Nov 2025 15:28:12 +0000

Bug 1993474 - Ensure our WNDPROC has precedence over WinAppSDK's. r=gstoll,win-reviewers

See the comment for reasoning. WM_NCCALCSIZE wasn't getting called, and
we rely on that to get the right client area on things like maximized
windows.

Differential Revision: https://phabricator.services.mozilla.com/D274281

Diffstat:
M
widget/windows/nsWindow.cpp
 | 
32
++++++++++++++++++++++----------
M
widget/windows/nsWindow.h
 | 
2
++

2 files changed, 24 insertions(+), 10 deletions(-)
diff --git a/widget/windows/nsWindow.cpp b/widget/windows/nsWindow.cpp
@@ -1081,7 +1081,7 @@ nsresult nsWindow::Create(nsIWidget* aParent, const LayoutDeviceIntRect& aRect,
       mBounds = mLastPaintBounds = GetBounds();
 
       // Reset the WNDPROC for this window and its whole class, as we had
-      // to use our own WNDPROC when creating the the skeleton UI window.
+      // to use our own WNDPROC when creating the skeleton UI window.
       ::SetWindowLongPtrW(mWnd, GWLP_WNDPROC,
                           reinterpret_cast<LONG_PTR>(
                               WinUtils::NonClientDpiScalingDefWindowProcW));
@@ -1520,12 +1520,31 @@ DWORD nsWindow::WindowExStyle() {
  *
  **************************************************************/
 
+bool nsWindow::ShouldAssociateWithWinAppSDK() const {
+  // We currently don't need any SDK functionality for for PiP windows,
+  // and using the SDK on these windows causes them to go under the
+  // taskbar (bug 1995838).
+  //
+  // TODO(emilio): That might not be true anymore after bug 1993474,
+  // consider re-testing and removing that special-case.
+  return IsTopLevelWidget() && !mIsPIPWindow;
+}
+
 bool nsWindow::AssociateWithNativeWindow() {
   if (!mWnd || !IsWindow(mWnd)) {
     NS_ERROR("Invalid window handle");
     return false;
   }
 
+  if (ShouldAssociateWithWinAppSDK()) {
+    // Make sure to call this here to associate our window with the
+    // Windows App SDK _before_ setting our WNDPROC, if needed.
+    // This is important because the SDKs WNDPROC might handle messages like
+    // WM_NCCALCSIZE without calling into us, and that can cause sizing issues,
+    // see bug 1993474.
+    WindowsUIUtils::SetIsTitlebarCollapsed(mWnd, mCustomNonClient);
+  }
+
   // Connect the this pointer to the native window handle.
   // This should be done before SetWindowLongPtrW, because nsWindow::WindowProc
   // uses WinUtils::GetNSWindowPtr internally.
@@ -1552,12 +1571,7 @@ void nsWindow::DissociateFromNativeWindow() {
   DebugOnly<WNDPROC> wndProcBeforeDissociate =
       reinterpret_cast<WNDPROC>(::SetWindowLongPtrW(
           mWnd, GWLP_WNDPROC, reinterpret_cast<LONG_PTR>(*mPrevWndProc)));
-  // If we've used the Windows App SDK to remove the minimize/maximize/close
-  // entries from the titlebar, then the Windows App SDK sets its own WNDPROC
-  // own the window, so this assertion would fail. But we only do this if
-  // Mica is available.
-  NS_ASSERTION(WinUtils::MicaAvailable() ||
-                   wndProcBeforeDissociate == nsWindow::WindowProc,
+  NS_ASSERTION(wndProcBeforeDissociate == nsWindow::WindowProc,
                "Unstacked an unexpected native window procedure");
 
   WinUtils::SetNSWindowPtr(mWnd, nullptr);
@@ -2835,9 +2849,7 @@ void nsWindow::SetCustomTitlebar(bool aCustomTitlebar) {
     mCustomNonClientMetrics = {};
     ResetLayout();
   }
-  // Not needed for PiP windows, and using the Windows App SDK on
-  // these windows causes them to go under the taskbar (bug 1995838)
-  if (!mPIPWindow) {
+  if (ShouldAssociateWithWinAppSDK()) {
     WindowsUIUtils::SetIsTitlebarCollapsed(mWnd, mCustomNonClient);
   }
 }
diff --git a/widget/windows/nsWindow.h b/widget/windows/nsWindow.h
@@ -335,6 +335,8 @@ class nsWindow final : public nsIWidget {
 
   bool IsRTL() const { return mIsRTL; }
 
+  bool ShouldAssociateWithWinAppSDK() const;
+
   /**
    * AssociateDefaultIMC() associates or disassociates the default IMC for
    * the window.