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Diffstat (limited to 'src/quick/doc/src/concepts/visualcanvas/adaptations.qdoc')
| -rw-r--r-- | src/quick/doc/src/concepts/visualcanvas/adaptations.qdoc | 80 |
1 files changed, 80 insertions, 0 deletions
diff --git a/src/quick/doc/src/concepts/visualcanvas/adaptations.qdoc b/src/quick/doc/src/concepts/visualcanvas/adaptations.qdoc index 9ce26e1bb8..3fd92177f9 100644 --- a/src/quick/doc/src/concepts/visualcanvas/adaptations.qdoc +++ b/src/quick/doc/src/concepts/visualcanvas/adaptations.qdoc @@ -58,6 +58,8 @@ The supported backends are the following \li Direct3D 12 - Requested by the string \c{"d3d12"} or the enum value QSGRendererInterface::Direct3D12. +\li OpenVG - Requested by the string \c{"openvg"} or the enum value QSGRendererInterface::OpenVG. + \endlist When in doubt which backend is in use, enable basic scenegraph information @@ -92,6 +94,14 @@ running on Windows 10, both for Win32 and UWP applications. The details for this adaptation are available here: \l{qtquick-visualcanvas-adaptations-d3d12.html}{Direct3D 12 Adaptation} +\section1 OpenVG + +The OpenVG adaptation is an alternative renderer for \l {Qt Quick} 2 that will +renderer the contents of the scene graph using OpenVG commands to provide +hardware-acclerated 2D vector and raster graphics. The details for this +adaptation are available here: +\l{qtquick-visualcanvas-scenegraph-openvg.html}{OpenVG Adaptation} + */ @@ -387,3 +397,73 @@ between the frames). By default blocking present is disabled. \endlist */ + +/*! +\title Qt Quick OpenVG Adaptation +\page qtquick-visualcanvas-adaptations-openvg.html + +The OpenVG adaptation is an alternative renderer for \l {Qt Quick} 2 that will +renderer the contents of the scene graph using OpenVG commands to provide +hardware-acclerated 2D vector and raster graphics. Much like the Software +adaptation, some features and optimizations are no longer available. Most +Qt Quick 2 applications will run without modification though any attempts to +use unsupported features will be ignored. + +\section2 EGL Requirement +Unlike the defualt OpenGL Renderer, there is no built in support for acquiring +an OpenVG context. This means that the renderer has the responsbility of +requesting and managing the the current context. To do this EGL has to be used +directly in the OpenVG renderer. This means that the OpenVG renderer is only +usable with platform plugins that support creating QWindows with support for +QSurfaceFormat::OpenVG. From this window, the renderer can get an EGLSurface +which can be used with an EGLContext to render OpenVG content. + +\section2 Renderer +The OpenVG Renderer works by using the OpenVG API to send commands and data to +a Vector GPU which will render the scenegraph in an accelerated manner, offloading +graphics rendering from the CPU. Many operations like the rendering of rectangles +and fonts glyphs ideal for OpenVG because these can be represented as paths which +are stroked and filled. Rendering scenegraph items that would typically involve +textures are handled in the OpenVG renderer by using VGImage. In addition when +rendering to offscreen surfaces (like when using Layers), the scene subtree is +rendered to a VGImage which can be reused in the scene. + +\section2 Render Loop +The OpenVG Renderer mirrors the behavior of the Basic render loop and will execute +all OpenVG commands in a single thread. + +See the \l{qtquick-visualcanvas-scenegraph.html}{Scene Graph page} for more +information on render loops + +\section2 Shader Effects +ShaderEffect components in QtQuick 2 can not be rendered by the OpenVG adaptation. +While it is possible to user ShaderEffectSource and QML Item Layers (which are both +offscreen surfaces), it is not actually possible to apply shader effects to them +via the ShaderEffect item. This is because OpenVG lacks an API for applying per +vertex and per fragment shader operations. It may be possible however to take +advantage of Image Filter operations in the OpenVG API to get similar effects to +what is provided by ShaderEffects in custom items. To integrate custom OpenVG +rendering, use QSGRenderNode in combination with QSGRendererInterface. + +\section2 Qt Graphical Effects Module +\l {Qt Graphical Effects} uses ShaderEffect items to render effects. If you use +graphical effects from this module, then you should not hide the source +item so that the original item can still be rendered. + +\section2 Particle Effects +It is not possible to render particle effects with the OpenVG adaptation. Whenever +possible, remove particles completely from the scene. Otherwise they will still +require some processing, even though they are not visible. + +\section2 Rendering Text +The text rendering with the OpenVG adaptation is based on rendering the glpyh +paths, and does not use the distance fields technique used by the OpenGL backend. + +\section2 Perspective Transforms +The OpenVG API does not allow paths to be transformed with non-affine transforms, +while it is possible with Qt Quick. This means that rendering components using +paths like Rectangles and Text, when applying perspective transforms the OpenVG +backend will first render to a VGImage before applying transformations. This uses +more memory at runtime and is a slower path so avoid doing this if necessary. + +*/ |