macOS: Respect maximum window size when computing zoomed state geometry

AppKit will normally compute this automatically based on the
contentMaxSize property of the NSWindow, which we set correctly
based on the window's maximum size, but since we ignore the
frame proposed by AppKit (due to not working for borderless
windows), we need to take the maximum size into account ourselves.

We follow the lead of QCocoaWindow::propagateSizeHints(), and
interpret the window's maximum size as referring to the client
area size, not including the frame geometry, but AppKit expects
the NSWindow's frame, so we need to manually add the frame.

In addition, AppKit expects the frame in the native coordinate
system, so we need to map to it. This was an existing bug, that
never manifested before taking the maximum size into account.

Task-number: QTBUG-67376
Change-Id: Id4cf6ff5640610f809472e5b1d591b4ec17df602
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>

1 files changed, 17 insertions, 7 deletions

diff --git a/src/plugins/platforms/cocoa/qnswindowdelegate.mm b/src/plugins/platforms/cocoa/qnswindowdelegate.mm
index 6e5623d679..15c141448d 100644
--- a/src/plugins/platforms/cocoa/qnswindowdelegate.mm
+++ b/src/plugins/platforms/cocoa/qnswindowdelegate.mm
@@ -39,6 +39,7 @@
 
 #include "qnswindowdelegate.h"
 #include "qcocoahelpers.h"
+#include "qcocoascreen.h"
 
 #include <QDebug>
 #include <qpa/qplatformscreen.h>
@@ -69,15 +70,24 @@ static QRegExp whitespaceRegex = QRegExp(QStringLiteral("\\s*"));
     Overridden to ensure that the zoomed state always results in a maximized
     window, which would otherwise not be the case for borderless windows.
 */
-- (NSRect)windowWillUseStandardFrame:(NSWindow *)window defaultFrame:(NSRect)newFrame
+- (NSRect)windowWillUseStandardFrame:(NSWindow *)window defaultFrame:(NSRect)proposedFrame
 {
-    Q_UNUSED(newFrame);
-
-    // We explicitly go through the QScreen API here instead of just using
-    // window.screen.visibleFrame directly, as that ensures we have the same
-    // behavior for both use-cases/APIs.
+    Q_UNUSED(proposedFrame);
     Q_ASSERT(window == m_cocoaWindow->nativeWindow());
-    return NSRectFromCGRect(m_cocoaWindow->screen()->availableGeometry().toCGRect());
+
+    // We compute the maximized state based on the maximum size, and
+    // the current position of the window. This may result in the window
+    // geometry falling outside of the current screen's available geometry,
+    // e.g. when there is not maximize size set, but this is okey, AppKit
+    // will then shift and possibly clip the geometry for us.
+    const QWindow *w = m_cocoaWindow->window();
+    QRect maximizedRect = QRect(w->framePosition(), w->maximumSize());
+
+    // QWindow::maximumSize() refers to the client size,
+    // but AppKit expects the full frame size.
+    maximizedRect.adjust(0, 0, 0, w->frameMargins().top());
+
+    return QCocoaScreen::mapToNative(maximizedRect);
 }
 
 - (BOOL)window:(NSWindow *)window shouldPopUpDocumentPathMenu:(NSMenu *)menu