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=<span class="caps">FAQ</span> on How to implement Qt Hardware Support=


==What is the difference between Qt 4.8.x and Qt 5?==
* 4.8: QtQuick1, Javascript core, <span class="caps">QWS</span> (good) and <span class="caps">QPA</span> (not good)
* 5.0: QtQuick2, v8, <span class="caps">QPA</span>, no <span class="caps">QWS</span>, <span class="caps">QPA</span> only supporting OpenGL and DirectFB backends
==What is the difference between <span class="caps">QPA</span> and <span class="caps">QWS</span> and when should I use which?==
* In general use <span class="caps">QWS</span> on 4.8 and <span class="caps">QPA</span> on 5.0
* Depending on the use-case <span class="caps">QPA</span> on 4.8 is a valid choice as well. Some important limitations and requirements are necessary to consider:
** <span class="caps">QPA</span> on Qt4.8 only makes sense on OpenGL Hardware! If you don’t have OpenGL HW there is absolutely no point in choosing Qt4.8-<span class="caps">QPA</span> over Qt4.8-<span class="caps">QWS</span>
** If you have OpenGL HW, there are two distinct use-cases to consider:
*** single-process: The features and limits of <span class="caps">QWS</span> and <span class="caps">QPA</span> are similar. <span class="caps">QWS</span> is older, is therefor considered more stable. Arguments for <span class="caps">QPA</span> could be:
**** you have to work on the graphcis/platform-plugin because your OpenGL implementation need special threadment, and(!):
**** you’re thinking about moving to Qt5
*** multi-process: There is currently no officially supported embedded(!) OpenGL-multi-process offering in Qt4.8. Implementing a platform-plugin for <span class="caps">QPA</span> is considered to be way simpler then writing <span class="caps">QWS</span>-graphics-plugins. Therefor Qt 4.8 <span class="caps">QPA</span> is the primary choice if you start your own platform-plugin or work on an existing platform plugin (e.g. the wayland-platform-plugin)
==What are the technical differences between QtQuick 1 and QtQuick 2?==
* QtQuick 1 is the only choice for Qt4.7 and Qt4.8
* QtQuick 2 comes with and is the primary choice for Qt5.x
* QtQuick 2 is based on a complete new and tailor made graphics stack called scenegraph.
** This leads to rendering performance of QtQuick2 which is a multiple of the rendering performance of QtQuick1
* Both use the same language (<span class="caps">QML</span>) to declare a user interface
* Although the language is the same, QtQuick2 comes with more and improved UI-elements (e.g. a complete new particle-engine)
==When should I use OpenGL, OpenVG, DirectFB versus software rendering?==
* Use OpenGL and DirectFB for hardware acceleration in 4.8 or 5.0. OpenVG only works on 4.8 (it’s a graphics system only tested on Symbian). Be aware of the hardware acceleration capabilities of your device: if you do something it can’t accelerate you will end up with software rendering (not great performance).
==What is the difference between Webkit 1 and Webkit 2 and how are they supported on Qt 4 and Qt 5?==
* Webkit 1 runs on both 4.8 and 5.0, Webkit2 only runs on 5.0. Qt Webkit2 is staying up to date with HTML5 features in webkit.org (Qt Webkit 1 is not).
==What are the options for implementing multimedia playback in Qt 4 and Qt 5?==
* The options are in-process and out-of-process. Most demos are using out-of-process today but if you implement in-process you can apply QtQuick effects to your media. (more from Bhooshan).
==When should I use DirectFB versus Wayland?==
* In general this questions shouldn’t be answered by “Qt” but by the silicon-vender (which should also be the one providing the <span class="caps">BSP</span>)
* The questions is only valid if you want to use OpenGL-HW-acceleration (and you need multi-process)
* Qt has wayland-platform-plugins for Qt4.8 and Qt5
* The Qt5-wayland-plugin get more attention (then the one for Qt4.8) and should be on a par with wayland-development
* [for holder: please comment the directfb-opengl state in Qt4/Qt5]
==How do I implement <span class="caps">QML</span> 1 or <span class="caps">QML</span> 2 in a single process? In multiple processes? Can I implement QML1 and QML2 in the same process?==
* foo
==What is the difference between in-process multimedia play back versus out-of-process multimedia playback?==
* foo
==What do I implement differently using <span class="caps">QML</span> in full screen versus windowed user interfaces?==
* foo
==What is the list of issues and their sequence in which I should check them when encountering less than satisfactory performance on my hardware?==
* foo
==Is OpenVG supported in Qt5?==
* No (at least not unless you contribute it).
==Where does <span class="caps">JIT</span> work in Webkit? (e.g <span class="caps">MIPS</span>, <span class="caps">ARM</span>, IA)==
* foo
* (Holger)
==From what and in what sequence should I build my Qt software stack?==
* foo
* (e.g. always pull from Webkit trunk because it is moving so fast)
* How do I get Qt running on my board? (Also a session at <span class="caps">QCS</span>)
* X86, <span class="caps">ARM</span>, <span class="caps">MIPS</span>,
* GL/notGL (<span class="caps">DFB</span>, OpenVG, Direct3D)
==How much time is a Qt port to new hardware going to take?==
* foo
* How can I make it faster/easier?
* What thinks are '''critical'''? What things are “nice to have”?
* What do I need to do first? Can I do things in stages?
* When doing a Qt port, what technical issues are critical to watch out for?
==What tools can I use when and where across Qt4 and Qt5?==
* Foo
* QtCreator does not yet work on Qt5.
* How do I get the Tools ready?
* How do I deal with version changes?
* What license issues do I need to consider?
* Do I need to do anything to work well with 3rd party (and/or system) tools?
==Performance: How do I identify and resolve driver performance issues?==
* foo
==Performance: How do I identify code that should be running on the <span class="caps">GPU</span> and isn’t?==
* foo
==Performance: How do I identify and resolve multimedia performance issues?==
* foo
==Performance: What issues can I safely ignore?==
* foo
* Features? Modules? Qt Add Ons?
==How do I package and document a fix to upstream it? How do I upstream it?==
* foo
* How should I package my work?
* How should I document my work?
* Where / how should I upstream?
* What do I do if a fix cannot be up streamed?
* What testing should I do?
* How should I test?
* Should I do unit tests?
* What are the pros/cons of unit testing?
==What is the status of Qt Components for embedded? For Desktop?==
* foo
===There is only one article in "hardware faq":===
===D===
* [[:Category:Devices|Category:Devices]]

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