scene: Make top left corner of CursorItem match the hotspot

It's more convenient if one wants to paint cursor at the specified
location. For example, when drawing the cursor on your own.

src/scene/cursoritem.cpp

@@ -31,13 +31,13 @@ void CursorItem::refresh()
 {
     const CursorSource *source = Cursors::self()->currentCursor()->source();
     if (auto surfaceSource = qobject_cast<const SurfaceCursorSource *>(source)) {
-        setSurface(surfaceSource->surface());
+        setSurface(surfaceSource->surface(), surfaceSource->hotspot());
     } else if (auto shapeSource = qobject_cast<const ShapeCursorSource *>(source)) {
-        setImage(shapeSource->image());
+        setImage(shapeSource->image(), shapeSource->hotspot());
     }
 }
 
-void CursorItem::setSurface(SurfaceInterface *surface)
+void CursorItem::setSurface(SurfaceInterface *surface, const QPointF &hotspot)
 {
     m_imageItem.reset();
 
@@ -48,9 +48,12 @@ void CursorItem::setSurface(SurfaceInterface *surface)
             m_surfaceItem.reset();
         }
     }
+    if (m_surfaceItem) {
+        m_surfaceItem->setPosition(-hotspot);
+    }
 }
 
-void CursorItem::setImage(const QImage &image)
+void CursorItem::setImage(const QImage &image, const QPointF &hotspot)
 {
     m_surfaceItem.reset();
 
@@ -58,6 +61,7 @@ void CursorItem::setImage(const QImage &image)
         m_imageItem = scene()->renderer()->createImageItem(scene(), this);
     }
     m_imageItem->setImage(image);
+    m_imageItem->setPosition(-hotspot);
     m_imageItem->setSize(image.size() / image.devicePixelRatio());
 }
 

src/scene/cursoritem.h

@@ -25,8 +25,8 @@ public:
 
 private:
     void refresh();
-    void setSurface(SurfaceInterface *surface);
-    void setImage(const QImage &image);
+    void setSurface(SurfaceInterface *surface, const QPointF &hotspot);
+    void setImage(const QImage &image, const QPointF &hotspot);
 
     std::unique_ptr<ImageItem> m_imageItem;
     std::unique_ptr<SurfaceItemWayland> m_surfaceItem;

src/scene/cursorscene.cpp

@@ -55,7 +55,7 @@ void CursorScene::postPaint()
 
 void CursorScene::paint(const RenderTarget &renderTarget, const QRegion &region)
 {
-    RenderViewport viewport(QRectF(QPointF(), QSizeF(renderTarget.size()) / m_paintedOutput->scale()), m_paintedOutput->scale(), renderTarget);
+    RenderViewport viewport(QRectF(geometry().topLeft(), QSizeF(renderTarget.size()) / m_paintedOutput->scale()), m_paintedOutput->scale(), renderTarget);
     m_renderer->beginFrame(renderTarget, viewport);
     m_renderer->renderBackground(renderTarget, viewport, region);
     m_renderer->renderItem(renderTarget, viewport, m_rootItem.get(), 0, region, WindowPaintData{});