doc: More documentation of the graphics effect framework.

1 files changed, 33 insertions, 0 deletions

diff --git a/doc/src/snippets/code/src_gui_effects_qgraphicseffect.cpp b/doc/src/snippets/code/src_gui_effects_qgraphicseffect.cpp
new file mode 100644
index 000000000..6265c806b
--- /dev/null
+++ b/doc/src/snippets/code/src_gui_effects_qgraphicseffect.cpp
@@ -0,0 +1,33 @@
+//! [0]
+MyGraphicsOpacityEffect::draw(QPainter *painter, QGraphicsEffectSource *source)
+{
+    // Fully opaque; draw directly without going through a pixmap.
+    if (qFuzzyCompare(m_opacity, 1)) {
+        source->draw(painter);
+        return;
+    }
+    ...
+}
+//! [0]
+
+//! [1]
+MyGraphicsEffect::draw(QPainter *painter, QGraphicsEffectSource *source)
+{
+    ...
+    QPoint offset;
+    if (source->isPixmap()) {
+        // No point in drawing in device coordinates (pixmap will be scaled anyways).
+        const QPixmap pixmap = source->pixmap(Qt::LogicalCoordinates, &offset);
+        ...
+        painter->drawPixmap(offset, pixmap);
+    } else {
+        // Draw pixmap in device coordinates to avoid pixmap scaling;
+        const QPixmap pixmap = source->pixmap(Qt::DeviceCoordinates, &offset);
+        painter->setWorldTransform(QTransform());
+        ...
+        painter->drawPixmap(offset, pixmap);
+    }
+    ...
+}
+//! [1]
+