Qt-contributors-summit-2012-Qt-in-Embedded

Qt Device/Embedded board support vision:

• Qt needs to work out of the box for embedded boards without having to patch Qt and mkspecs over and over again
• Provide an optimal build for the device
• Focus is on cross-compilation and not on on-target compilation

Note: Most of the stuff below is already in qtbase. -device is currently marked as ‘experimental’

configure

• -device <device> specifies the device.
• Together with -sysroot and -device-option CROSS_COMPILE to specify the compiler, you will have Qt for your board!
  • For example, for the raspberry-pi, all one needs to do is:
    
    1.       configure -device pi -sysroot  -device-option CROSS_COMPILE=/xgcc/prefix
• There is mechanism to pass arbitrary device specific options (requires for most BSPs)
  • Also allows us to use the same mkspec to support multiple distros (hardfp/softfp)
• Currently supported boards/devices
  • ST7540, ST7108, Trident Shiner (PNX8473), Broadcom 97425, N9, beagleboard, snowball
  • More information here: http://wiki.qt.io/Category:Devices
• passing options to configure like -no-neon
  • https://codereview.qt.io/#change,27782

eglfs:

• No more depends on widgets, uses raster engine to paint widgets instead of opengl engine
• Integrated the build into configure
• hooks for board specific initialization
  • screen depth, format, gl caps
  • does not pollute board specific stuff into eglfs
• even has a xlib hook, so eglfs can be tested on the desktop just like wayland
• input
  • eglfs now depends on evdev. Future task is to make it compile when evdev is absent but we are yet to see such a device (qnx?)
  • can now be without udev, we have a static discovery
  • moved to platformsupport
  • eglfs loads input statically avoiding obscure args like -plugin EvdevKeyboard
  • synchronized position with multiple cursors
• minimalegl is the old eglfs
• cursor support
  • by default, you get a gl “composed” cursor
  • supports hotspots
  • hw accel on the pi, the cursor is a separate layer
  • it’s now CI (compile) tested
• allows creation of multiple windows and supports the surface format requested by the user
  • required for context menus
  • qmlscene —transparent allows one to create a transparent toplevel
  • on the pi, each window is a layer. poor man’s wayland
• Jorgen suggested moving large parts of code to platformsupport and move device stuff to separate repo
  • Will be investigated post 5.0

directfb:

• similar hooks design as eglfs
• integrated into configure
• supports IDirectFBGL and DirectFB+EGL
• holger maintains directfb these days

pkg-config changes:

• no more a second class citizen for embedded targets unlike qt4
• -force-pkg-config was used only for xcompile builds and used to just check for environment variables.
• Checks PKG_CONFIG_LIBDIR instead of PKG_CONFIG_PATH since the latter pulls in host paths. Checks PKG_CONFIG_SYSROOT_DIR
• (no)pkg-config works for all builds, default ‘auto’
• pkg-config env variables are now stored as part of qdevice.pri (“session”)

configure:

• -sysroot now being actively tested and it also documented
• Saves it’s output into config.summary
• Fixed QPA plugin detection
  • -qpa foo sets the default qpa
• Still have the problem of runtime of autodetection
  • Decided that this was unnecessary

What’s coming

• Hardware image decoding for the pi (based on openmax IL – girish)
• Layer based video rendering for the pi (based on openmax IL – johannes)
• qdoc documentation
• passing options to configure like -no-neon
  • https://codereview.qt.io/#change,27782
• Host tools when xcompiling
• Support for host compilation with -device
• Out of the box serial port configuration with QSerialPort

What’s missing from Qt4/Embedded support

• linuxfb needs to be resurrected
• openvg backend
• wayland will be suggested for multiprocess support, eglfs for single process