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Windows: Don't rely on top level QWindow to scale children on DPI change

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The native size of a QWindow on Windows is the logical size of the window
times the window's device pixel ratio. We manage this relationship
for top level windows via the WM_GETDPISCALEDSIZE message, and during
WM_DPICHANGED we then applied the same scale to child windows.

This is problematic in the case where a child window does not have
a QWindow parent, so instead of scaling all children when the parent
gets a WM_DPICHANGED message, we scale each individual child in the
child's WM_DPICHANGED_AFTERPARENT message.

Task-number: QTBUG-103383
Pick-to: 6.4
Change-Id: Ia0845aa19a3bb97b7bc9e7d9554ac02b95ca65a5
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
This commit is contained in:
Tor Arne Vestbø 2022-06-16 14:55:14 +02:00
parent 54f328f0e8
commit 97665c9615
1 changed files with 9 additions and 13 deletions
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22
src/plugins/platforms/windows/qwindowswindow.cpp
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@ -1966,7 +1966,6 @@ void QWindowsWindow::handleDpiScaledSize(WPARAM wParam, LPARAM lParam, LRESULT *
void QWindowsWindow::handleDpiChanged(HWND hwnd, WPARAM wParam, LPARAM lParam)
{
const UINT dpi = HIWORD(wParam);
const qreal scale = qreal(dpi) / qreal(savedDpi());
setSavedDpi(dpi);
// Send screen change first, so that the new screen is set during any following resize
@ -1995,24 +1994,21 @@ void QWindowsWindow::handleDpiChanged(HWND hwnd, WPARAM wParam, LPARAM lParam)
prcNewWindow->right - prcNewWindow->left,
prcNewWindow->bottom - prcNewWindow->top, SWP_NOZORDER | SWP_NOACTIVATE);
}
// Scale child QPlatformWindow size. Windows sends WM_DPICHANGE to top-level windows only.
for (QWindow *childWindow : window()->findChildren<QWindow *>()) {
QWindowsWindow *platformChildWindow = static_cast<QWindowsWindow *>(childWindow->handle());
if (!platformChildWindow)
continue;
QRect currentGeometry = platformChildWindow->geometry();
QRect scaledGeometry = QRect(currentGeometry.topLeft() * scale, currentGeometry.size() * scale);
platformChildWindow->setGeometry(scaledGeometry);
}
}
void QWindowsWindow::handleDpiChangedAfterParent(HWND hwnd)
{
// FIXME: refactor, do we really need this?
setSavedDpi(GetDpiForWindow(hwnd));
const UINT dpi = GetDpiForWindow(hwnd);
const qreal scale = qreal(dpi) / qreal(savedDpi());
setSavedDpi(dpi);
checkForScreenChanged(QWindowsWindow::FromDpiChange);
// Child windows do not get WM_GETDPISCALEDSIZE messages to inform
// Windows about the new size, so we need to manually scale them.
QRect currentGeometry = geometry();
QRect scaledGeometry = QRect(currentGeometry.topLeft() * scale, currentGeometry.size() * scale);
setGeometry(scaledGeometry);
}
static QRect normalFrameGeometry(HWND hwnd)