Windows QPA: don't override user-removed margins

When calculating margins, added a check to see if the window rect and
the client rect are the same size. If they are, we return early, to
avoid overwriting user-defined specific margins.

Fixes: QTBUG-117704
Change-Id: I9947feab4cb900293fb6be6cf09c56268f38d64a
Reviewed-by: Oliver Wolff <[email protected]>
(cherry picked from commit 03a4164206d64151da7e0b0f850063e501bdea57)
Reviewed-by: Qt Cherry-pick Bot <[email protected]>
(cherry picked from commit d2881ae09b0a5e06b9c223e51a61a99655b4036f)
(cherry picked from commit 0056998ba8def608c00e544765484407b186b3ff)

1 files changed, 14 insertions, 5 deletions

diff --git a/src/plugins/platforms/windows/qwindowswindow.cpp b/src/plugins/platforms/windows/qwindowswindow.cpp
index b21ef874f88..b53eb9cf6e1 100644
--- a/src/plugins/platforms/windows/qwindowswindow.cpp
+++ b/src/plugins/platforms/windows/qwindowswindow.cpp
@@ -2780,11 +2780,6 @@ void QWindowsWindow::calculateFullFrameMargins()
 {
     if (shouldOmitFrameAdjustment(m_data.flags, m_data.hwnd))
         return;
-    // Normally obtained from WM_NCCALCSIZE. This calculation only works
-    // when no native menu is present.
-    const auto systemMargins = testFlag(DisableNonClientScaling)
-        ? QWindowsGeometryHint::frameOnPrimaryScreen(window(), m_data.hwnd)
-        : frameMargins_sys();
 
     // QTBUG-113736: systemMargins depends on AdjustWindowRectExForDpi. This doesn't take into
     // account possible external modifications to the titlebar, as with ExtendsContentIntoTitleBar()
@@ -2798,6 +2793,20 @@ void QWindowsWindow::calculateFullFrameMargins()
     RECT clientRect{};
     GetWindowRect(handle(), &windowRect);
     GetClientRect(handle(), &clientRect);
+
+    // QTBUG-117704 It is also possible that the user has manually removed the frame (for example
+    // by handling WM_NCCALCSIZE). If that is the case, i.e., the client area and the window area
+    // have identical sizes, we don't want to override the user-defined margins.
+
+    if (qrectFromRECT(windowRect).size() == qrectFromRECT(clientRect).size())
+        return;
+
+    // Normally obtained from WM_NCCALCSIZE. This calculation only works
+    // when no native menu is present.
+    const auto systemMargins = testFlag(DisableNonClientScaling)
+        ? QWindowsGeometryHint::frameOnPrimaryScreen(window(), m_data.hwnd)
+        : frameMargins_sys();
+
     const int yDiff = (windowRect.bottom - windowRect.top) - (clientRect.bottom - clientRect.top);
     const bool typicalFrame = (systemMargins.left() == systemMargins.right())
             && (systemMargins.right() == systemMargins.bottom());