diff options
Diffstat (limited to 'src/quick/items/context2d')
| -rw-r--r-- | src/quick/items/context2d/qquickcanvasitem.cpp | 26 |
1 files changed, 17 insertions, 9 deletions
diff --git a/src/quick/items/context2d/qquickcanvasitem.cpp b/src/quick/items/context2d/qquickcanvasitem.cpp index 6603d8158d..f654261cb2 100644 --- a/src/quick/items/context2d/qquickcanvasitem.cpp +++ b/src/quick/items/context2d/qquickcanvasitem.cpp @@ -255,17 +255,18 @@ QQuickCanvasItemPrivate::~QQuickCanvasItemPrivate() The Canvas item supports two render targets: \c Canvas.Image and \c Canvas.FramebufferObject. - The \c Canvas.Image render target is a \a QImage object. This render - target supports background thread rendering, allowing complex or long - running painting to be executed without blocking the UI. + The \c Canvas.Image render target is a \a QImage object. This render target + supports background thread rendering, allowing complex or long running + painting to be executed without blocking the UI. This is the only render + target that is supported by all Qt Quick backends. The Canvas.FramebufferObject render target utilizes OpenGL hardware acceleration rather than rendering into system memory, which in many cases - results in faster rendering. Canvas.FramebufferObject relies on the - OpenGL extensions \c GL_EXT_framebuffer_multisample and - \c GL_EXT_framebuffer_blit for antialiasing. It will also use more - graphics memory when rendering strategy is anything other than - Canvas.Cooperative. + results in faster rendering. Canvas.FramebufferObject relies on the OpenGL + extensions \c GL_EXT_framebuffer_multisample and \c GL_EXT_framebuffer_blit + for antialiasing. It will also use more graphics memory when rendering + strategy is anything other than Canvas.Cooperative. Framebuffer objects may + not be available with Qt Quick backends other than OpenGL. The default render target is Canvas.Image and the default renderStrategy is Canvas.Immediate. @@ -300,7 +301,14 @@ QQuickCanvasItemPrivate::~QQuickCanvasItemPrivate() and can be used directly in \l {ShaderEffect}{ShaderEffects} and other classes that consume texture providers. - \sa Context2D + \note In general large canvases, frequent updates, and animation should be + avoided with the Canvas.Image render target. This is because with + accelerated graphics APIs each update will lead to a texture upload. Also, + if possible, prefer QQuickPaintedItem and implement drawing in C++ via + QPainter instead of the more expensive and likely less performing + JavaScript and Context2D approach. + + \sa Context2D QQuickPaintedItem */ QQuickCanvasItem::QQuickCanvasItem(QQuickItem *parent) |