Fix WaylandOutput.sizeFollowsWindow when window changes screen

If a QWaylandOutput's QWindow is moved from one screen to another and that
causes the devicePixelRatio to change, it may result in a new pixel size,
but QWindow::width and height may stay unchanged (because they're not in pixel
coordinates). This is a problem because the sizeFollowsWindow functionality of
QWaylandOutput relied on the widthChanged and heightChanged signals, which are
then not fired, although the pixel size did change.

There's no QWindow::devicePixelRatioChanged signal we can attach to, so to fix
this, we attach to screenChanged instead and then compute the new pixelSize
using QWindow::devicePixelRatio() and call the handler if it changed.

This also removes some duplication between the old width and height handlers.

Change-Id: Ibcbf10489b83498b4a0fee2b520f528f94cb9ce3
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>
Reviewed-by: Paul Olav Tvete <paul.tvete@qt.io>

1 files changed, 3 insertions, 0 deletions

diff --git a/src/compositor/compositor_api/qwaylandoutput_p.h b/src/compositor/compositor_api/qwaylandoutput_p.h
index 38bb1ec6e..d8b2c9dfa 100644
--- a/src/compositor/compositor_api/qwaylandoutput_p.h
+++ b/src/compositor/compositor_api/qwaylandoutput_p.h
@@ -108,6 +108,8 @@ public:
     void sendMode(const Resource *resource, const QWaylandOutputMode &mode);
     void sendModesInfo();
 
+    void handleWindowPixelSizeChanged();
+
 protected:
     void output_bind_resource(Resource *resource) override;
 
@@ -128,6 +130,7 @@ private:
     int scaleFactor = 1;
     bool sizeFollowsWindow = false;
     bool initialized = false;
+    QSize windowPixelSize;
 
     Q_DECLARE_PUBLIC(QWaylandOutput)
     Q_DISABLE_COPY(QWaylandOutputPrivate)