Introduce methods for retrieving individual buffer dimensions

The new methods can be useful when one wants to get the size of the
buffer along some specific dimension, e.g. width or height.

Of course, size() could be used for this purpose, but with the new
helper methods, one has to type less.

src/wayland/server/buffer_interface.cpp

@@ -314,6 +314,16 @@ wl_resource *BufferInterface::resource() const
     return d->buffer;
 }
 
+int BufferInterface::width() const
+{
+    return d->size.width();
+}
+
+int BufferInterface::height() const
+{
+    return d->size.height();
+}
+
 QSize BufferInterface::size() const
 {
     return d->size;

src/wayland/server/buffer_interface.h

@@ -119,6 +119,14 @@ public:
      **/
     QImage data();
 
+    /**
+     * Returns the width of the buffer in device pixels.
+     */
+    int width() const;
+    /**
+     * Returns the height of the buffer in device pixels.
+     */
+    int height() const;
     /**
      * Returns the size of this BufferInterface.
      * Note: only for shared memory buffers (shmBuffer) the size can be derived,