D3D12: Painter node

Only supports QImage backing.

As a bonus add some notes to the Context2D docs too.

Change-Id: I18457a1f766d2f136c6864ec06fe596668d5e726
Reviewed-by: Andy Nichols <andy.nichols@qt.io>

1 files changed, 18 insertions, 9 deletions

diff --git a/src/quick/items/qquickpainteditem.cpp b/src/quick/items/qquickpainteditem.cpp
index e4a20b9787..5813b4b115 100644
--- a/src/quick/items/qquickpainteditem.cpp
+++ b/src/quick/items/qquickpainteditem.cpp
@@ -63,13 +63,14 @@ public:
 
     \inmodule QtQuick
 
-    The QQuickPaintedItem makes it possible to use the QPainter API with the QML Scene Graph.
-    It sets up a textured rectangle in the Scene Graph and uses a QPainter to paint
-    onto the texture. The render target can be either a QImage or a QOpenGLFramebufferObject.
-    When the render target is a QImage, QPainter first renders into the image then
-    the content is uploaded to the texture.
-    When a QOpenGLFramebufferObject is used, QPainter paints directly onto the texture.
-    Call update() to trigger a repaint.
+    The QQuickPaintedItem makes it possible to use the QPainter API with the
+    QML Scene Graph. It sets up a textured rectangle in the Scene Graph and
+    uses a QPainter to paint onto the texture. The render target can be either
+    a QImage or, when OpenGL is in use, a QOpenGLFramebufferObject. When the
+    render target is a QImage, QPainter first renders into the image then the
+    content is uploaded to the texture. When a QOpenGLFramebufferObject is
+    used, QPainter paints directly onto the texture. Call update() to trigger a
+    repaint.
 
     To enable QPainter to do anti-aliased rendering, use setAntialiasing().
 
@@ -78,6 +79,10 @@ public:
     public function: paint(), which implements the actual painting. The
     painting will be inside the rectangle spanning from 0,0 to
     width(),height().
+
+    \note It important to understand the performance implications such items
+    can incur. See QQuickPaintedItem::RenderTarget and
+    QQuickPaintedItem::renderTarget.
 */
 
 /*!
@@ -172,8 +177,6 @@ QQuickPaintedItem::~QQuickPaintedItem()
     is processed by the QML Scene Graph when the next frame is rendered. The item will only be
     redrawn if it is visible.
 
-    Note that calling this function will trigger a repaint of the whole scene.
-
     \sa paint()
 */
 void QQuickPaintedItem::update(const QRect &rect)
@@ -499,6 +502,12 @@ void QQuickPaintedItem::setFillColor(const QColor &c)
     the QQuickPaintedItem::FramebufferObject render target if the item gets resized often.
 
     By default, the render target is QQuickPaintedItem::Image.
+
+    \note Some Qt Quick backends may not support all render target options. For
+    example, it is likely that non-OpenGL backends will lack support for
+    QQuickPaintedItem::FramebufferObject and
+    QQuickPaintedItem::InvertedYFramebufferObject. Requesting these will then
+    be ignored.
 */
 QQuickPaintedItem::RenderTarget QQuickPaintedItem::renderTarget() const
 {