Make QWindow's windowState a QFlags of the WindowState

This reflects QWidget API, and restores some behavior from Qt4.
Some WM can have several state at the same time. On Plasma for example,
when a window is both maximized and minimized, the "maximized" checkbox
is checked from the taskbar entry.

The API of QPlatformWindow was changed to take a QFlag and the platform
plugins were adapted.

 - On XCB: Always send the full state to the WM. And read the full state.

 - On Windows: The code was originally written with '&' in Qt4, and was changed
   to == when porting. Some adaptation had to be made so the states would be
   preserved.

 - On macOS: Only a single state can be set and is reported back for now,
   with the possibly to expand this in the future.

 - Other platforms: Just do as before with the effective state.

Task-number: QTBUG-57882
Task-number: QTBUG-52616
Task-number: QTBUG-52555
Change-Id: I7a1f7cac64236bbd4c591f796374315639233dad
Reviewed-by: Gunnar Sletta <gunnar@crimson.no>
Reviewed-by: Robin Burchell <robin.burchell@crimson.no>

2 files changed, 10 insertions, 2 deletions

diff --git a/src/plugins/platforms/mirclient/qmirclientwindow.cpp b/src/plugins/platforms/mirclient/qmirclientwindow.cpp
index adc8ae652a..369073a70e 100644
--- a/src/plugins/platforms/mirclient/qmirclientwindow.cpp
+++ b/src/plugins/platforms/mirclient/qmirclientwindow.cpp
@@ -785,8 +785,16 @@ void QMirClientWindow::handleSurfaceStateChanged(Qt::WindowState state)
     QWindowSystemInterface::handleWindowStateChanged(window(), state);
 }
 
-void QMirClientWindow::setWindowState(Qt::WindowState state)
+void QMirClientWindow::setWindowState(Qt::WindowStates states)
 {
+    Qt::WindowState state = Qt::WindowNoState;
+    if (states & Qt::WindowMinimized)
+        state = Qt::WindowMinimized;
+    else if (states & Qt::WindowFullScreen)
+        state = Qt::WindowFullScreen;
+    else if (states & Qt::WindowMaximized)
+        state = Qt::WindowMaximized;
+
     QMutexLocker lock(&mMutex);
     qCDebug(mirclient, "setWindowState(window=%p, %s)", this, qtWindowStateToStr(state));
 
diff --git a/src/plugins/platforms/mirclient/qmirclientwindow.h b/src/plugins/platforms/mirclient/qmirclientwindow.h
index 324e7691ff..6c5695d62f 100644
--- a/src/plugins/platforms/mirclient/qmirclientwindow.h
+++ b/src/plugins/platforms/mirclient/qmirclientwindow.h
@@ -73,7 +73,7 @@ public:
     WId winId() const override;
     QRect geometry() const override;
     void setGeometry(const QRect&) override;
-    void setWindowState(Qt::WindowState state) override;
+    void setWindowState(Qt::WindowStates state) override;
     void setWindowFlags(Qt::WindowFlags flags) override;
     void setVisible(bool visible) override;
     void setWindowTitle(const QString &title) override;