[server] Add a size property to SurfaceInterface

Basically just wraps the size of the attached buffer. Convenience to
not have to go down to the Buffer to read the size.

TODO: apply buffer scale and transform.

src/wayland/surface_interface.cpp

@@ -182,13 +182,20 @@ void SurfaceInterface::Private::commit()
     const bool inputRegionChanged = pending.inputIsSet;
     const bool scaleFactorChanged = current.scale != pending.scale;
     const bool transformFactorChanged = current.transform != pending.transform;
+    bool sizeChanged = false;
     auto buffer = current.buffer;
     if (bufferChanged) {
+        QSize oldSize;
         if (current.buffer) {
+            oldSize = current.buffer->size();
             current.buffer->unref();
+            QObject::disconnect(current.buffer, &BufferInterface::sizeChanged, q, &SurfaceInterface::sizeChanged);
         }
         if (pending.buffer) {
             pending.buffer->ref();
+            QObject::connect(pending.buffer, &BufferInterface::sizeChanged, q, &SurfaceInterface::sizeChanged);
+            const QSize newSize = pending.buffer->size();
+            sizeChanged = newSize.isValid() && newSize != oldSize;
         }
         buffer = pending.buffer;
     }
@@ -226,6 +233,9 @@ void SurfaceInterface::Private::commit()
             emit q->unmapped();
         }
     }
+    if (sizeChanged) {
+        emit q->sizeChanged();
+    }
 }
 
 void SurfaceInterface::Private::damage(const QRect &rect)
@@ -436,6 +446,16 @@ QPointer< SubSurfaceInterface > SurfaceInterface::subSurface() const
     return d->subSurface;
 }
 
+QSize SurfaceInterface::size() const
+{
+    Q_D();
+    // TODO: apply transform and scale to the buffer size
+    if (d->current.buffer) {
+        return d->current.buffer->size();
+    }
+    return QSize();
+}
+
 SurfaceInterface::Private *SurfaceInterface::d_func() const
 {
     return reinterpret_cast<Private*>(d.data());

src/wayland/surface_interface.h

@@ -45,6 +45,7 @@ class KWAYLANDSERVER_EXPORT SurfaceInterface : public Resource
     Q_PROPERTY(QRegion input READ input NOTIFY inputChanged)
     Q_PROPERTY(qint32 scale READ scale NOTIFY scaleChanged)
     Q_PROPERTY(KWayland::Server::OutputInterface::Transform transform READ transform NOTIFY transformChanged)
+    Q_PROPERTY(QSize size READ size NOTIFY sizeChanged)
 public:
     virtual ~SurfaceInterface();
 
@@ -58,6 +59,11 @@ public:
     OutputInterface::Transform transform() const;
     BufferInterface *buffer();
     QPoint offset() const;
+    /**
+     * The size of the Surface.
+     * @since 5.3
+     **/
+    QSize size() const;
 
     /**
      * @returns The SubSurface for this Surface in case there is one.
@@ -85,6 +91,10 @@ Q_SIGNALS:
      * Emitted when the Surface removes its content
      **/
     void unmapped();
+    /**
+     * @since 5.3
+     **/
+    void sizeChanged();
 
 private:
     friend class CompositorInterface;