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>

5 files changed, 44 insertions, 71 deletions

diff --git a/src/compositor/compositor_api/qwaylandoutput.cpp b/src/compositor/compositor_api/qwaylandoutput.cpp
index 545ef713e..b1ee9bbe0 100644
--- a/src/compositor/compositor_api/qwaylandoutput.cpp
+++ b/src/compositor/compositor_api/qwaylandoutput.cpp
@@ -165,6 +165,33 @@ void QWaylandOutputPrivate::sendModesInfo()
     }
 }
 
+void QWaylandOutputPrivate::handleWindowPixelSizeChanged()
+{
+    Q_Q(QWaylandOutput);
+    Q_ASSERT(window);
+    if (sizeFollowsWindow && currentMode <= modes.size() - 1) {
+        if (currentMode >= 0) {
+            QWaylandOutputMode mode = modes.at(currentMode);
+            mode.setSize(windowPixelSize);
+            modes.replace(currentMode, mode);
+            emit q->geometryChanged();
+            if (!availableGeometry.isValid())
+                emit q->availableGeometryChanged();
+            sendModesInfo();
+        } else {
+            // We didn't add a mode during the initialization because the window
+            // size was invalid, let's add it now
+            int mHzRefreshRate = qFloor(window->screen()->refreshRate() * 1000);
+            QWaylandOutputMode mode(windowPixelSize, mHzRefreshRate);
+            if (mode.isValid()) {
+                modes.clear();
+                q->addMode(mode, true);
+                q->setCurrentMode(mode);
+            }
+        }
+    }
+}
+
 void QWaylandOutputPrivate::addView(QWaylandView *view, QWaylandSurface *surface)
 {
     for (int i = 0; i < surfaceViews.size(); i++) {
@@ -286,8 +313,9 @@ void QWaylandOutput::initialize()
     QWaylandCompositorPrivate::get(d->compositor)->addOutput(this);
 
     if (d->window) {
-        QObject::connect(d->window, &QWindow::widthChanged, this, &QWaylandOutput::handleSetWidth);
-        QObject::connect(d->window, &QWindow::heightChanged, this, &QWaylandOutput::handleSetHeight);
+        QObject::connect(d->window, &QWindow::widthChanged, this, &QWaylandOutput::handleMaybeWindowPixelSizeChanged);
+        QObject::connect(d->window, &QWindow::heightChanged, this, &QWaylandOutput::handleMaybeWindowPixelSizeChanged);
+        QObject::connect(d->window, &QWindow::screenChanged, this, &QWaylandOutput::handleMaybeWindowPixelSizeChanged);
         QObject::connect(d->window, &QObject::destroyed, this, &QWaylandOutput::handleWindowDestroyed);
     }
 
@@ -920,66 +948,18 @@ void QWaylandOutput::surfaceLeave(QWaylandSurface *surface)
 /*!
  * \internal
  */
-void QWaylandOutput::handleSetWidth(int newWidth)
+void QWaylandOutput::handleMaybeWindowPixelSizeChanged()
 {
     Q_D(QWaylandOutput);
 
-    if (!d->window || !d->sizeFollowsWindow)
+    if (!d->window)
         return;
 
-    if (d->currentMode <= d->modes.size() - 1) {
-        if (d->currentMode >= 0) {
-            QWaylandOutputMode mode = d->modes.at(d->currentMode);
-            mode.setWidth(newWidth * d->window->devicePixelRatio());
-            d->modes.replace(d->currentMode, mode);
-            emit geometryChanged();
-            if (!d->availableGeometry.isValid())
-                emit availableGeometryChanged();
-            d->sendModesInfo();
-        } else {
-            // We didn't add a mode during the initialization because the window
-            // size was invalid, let's add it now
-            QWaylandOutputMode mode(d->window->size() * d->window->devicePixelRatio(),
-                                    qFloor(d->window->screen()->refreshRate() * 1000));
-            if (mode.isValid()) {
-                d->modes.clear();
-                addMode(mode, true);
-                setCurrentMode(mode);
-            }
-        }
-    }
-}
-
-/*!
- * \internal
- */
-void QWaylandOutput::handleSetHeight(int newHeight)
-{
-    Q_D(QWaylandOutput);
+    const QSize pixelSize = d->window->size() * d->window->devicePixelRatio();
 
-    if (!d->window || !d->sizeFollowsWindow)
-        return;
-
-    if (d->currentMode <= d->modes.size() - 1) {
-        if (d->currentMode >= 0) {
-            QWaylandOutputMode mode = d->modes.at(d->currentMode);
-            mode.setHeight(newHeight * d->window->devicePixelRatio());
-            d->modes.replace(d->currentMode, mode);
-            emit geometryChanged();
-            if (!d->availableGeometry.isValid())
-                emit availableGeometryChanged();
-            d->sendModesInfo();
-        } else {
-            // We didn't add a mode during the initialization because the window
-            // size was invalid, let's add it now
-            QWaylandOutputMode mode(d->window->size() * d->window->devicePixelRatio(),
-                                    qFloor(d->window->screen()->refreshRate() * 1000));
-            if (mode.isValid()) {
-                d->modes.clear();
-                addMode(mode, true);
-                setCurrentMode(mode);
-            }
-        }
+    if (pixelSize != d->windowPixelSize) {
+        d->windowPixelSize = pixelSize;
+        d->handleWindowPixelSizeChanged();
     }
 }
 
diff --git a/src/compositor/compositor_api/qwaylandoutput.h b/src/compositor/compositor_api/qwaylandoutput.h
index f0bea809e..c7f2973b6 100644
--- a/src/compositor/compositor_api/qwaylandoutput.h
+++ b/src/compositor/compositor_api/qwaylandoutput.h
@@ -181,8 +181,7 @@ Q_SIGNALS:
     void windowDestroyed();
 
 private Q_SLOTS:
-    void handleSetWidth(int newWidth);
-    void handleSetHeight(int newHeight);
+    void handleMaybeWindowPixelSizeChanged();
     void handleWindowDestroyed();
 
 protected:
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)
diff --git a/src/compositor/compositor_api/qwaylandoutputmode.cpp b/src/compositor/compositor_api/qwaylandoutputmode.cpp
index 9ae285fd5..545871175 100644
--- a/src/compositor/compositor_api/qwaylandoutputmode.cpp
+++ b/src/compositor/compositor_api/qwaylandoutputmode.cpp
@@ -128,15 +128,7 @@ int QWaylandOutputMode::refreshRate() const
 /*!
  * \internal
  */
-void QWaylandOutputMode::setWidth(int width)
+void QWaylandOutputMode::setSize(const QSize &size)
 {
-    d->size.setWidth(width);
-}
-
-/*!
- * \internal
- */
-void QWaylandOutputMode::setHeight(int height)
-{
-    d->size.setHeight(height);
+    d->size = size;
 }
diff --git a/src/compositor/compositor_api/qwaylandoutputmode.h b/src/compositor/compositor_api/qwaylandoutputmode.h
index 7adb920e5..b03457929 100644
--- a/src/compositor/compositor_api/qwaylandoutputmode.h
+++ b/src/compositor/compositor_api/qwaylandoutputmode.h
@@ -64,10 +64,9 @@ public:
 
 private:
     class QWaylandOutputModePrivate *const d;
-    friend class QWaylandOutput;
+    friend class QWaylandOutputPrivate;
 
-    void setWidth(int width);
-    void setHeight(int height);
+    void setSize(const QSize &size);
 };
 Q_DECLARE_TYPEINFO(QWaylandOutputMode, Q_MOVABLE_TYPE);