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Denis 'GNUtoo' Carikli, 01/24/2020 01:23 PM
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Replicant doesn't reply on the GPU for accelerated graphics rendering. Instead it uses the CPU with a technique known as software rendering. At the begining of Replicant, using the dedicated graphics processor (GPU) required non-free software on all of the supported devices. As of today free-software replacements exist but they are not ready yet for Replicant. They also implemnet a subset of the OpenGL/OpenGL-ES API and don't support Vulkan yet. The free GPU drivers would also need to be integrated in Replicant. There are more details on the various options in the GraphicsResearch wiki page. Software rendering is the reason why Replicant devices appear slow at times and is responsible for a lot of crashes that can happen during usage.

Until version 6.0 0003, Replicant used the Android software renderer, also known as libagl. libagl is fast, but caused several issues due to lack of OpenGL ES (GLES) 2.0 support.

As of Replicant 6.0 0004 rc1, llvmpipe is used as the default software renderer. llvmpipe has a more complete GLES implementation than libagl (see #705), so more apps work with it, like Firefox-based browsers or more recent WebViews (see #1780). Unfortunately, llvmpipe is too slow for certain system components, which may also be true for some apps. Furthermore, certain apps still crash with llvmpipe, although less frequently. Usually the screen stays black if an app does not work with llvmpipe.

To cater for these issues, Replicant 6.0 0004 includes a mechanism to choose between llvmpipe and ligagl, on a per process basis. Such mechanism is actually used on the Replicant 6.0 0004 images to force some system components (bootanimation, SurfaceFlinger and system_server) to use libagl.

Methods to choose the software renderer

For all the methods bellow you must have ADB installed on your computer. Make sure that it can access the device's root shell and that the system partition is mounted as writable.

Choosing the default software renderer

The following command switches between llvmpipe and libagl:

adb shell "grep -q "ro.libagl=1" /system/build.prop && sed "s/ro.libagl=1/ro.libagl=0/" -i /system/build.prop || sed "s/ro.libagl=0/ro.libagl=1/" -i /system/build.prop" 

Then reboot the device. To switch back to previous renderer, run the above command again and reboot the device.

This method works on both Replicant 6.0 0003 and 0004. Do note that: on 0003 you will start with libagl by default, whereas on 0004 the default is llvmpipe.

Choosing the software renderer for a specific app

  1. Find out the app ID. Example: org.gnu.icecat
  2. Force the app to always use libagl by creating empty file named libGLES_android on it's data directory (e.g. /data/data/org.gnu.icecat/). Example command:
    adb shell touch /data/data/org.gnu.icecat/libGLES_android

    To force llvmpipe instead, use a file named libGLES_mesa.
  3. Restart the app. For instance: kill it and open again.
  4. Get back to the default renderer by removing the file. Example command:
    adb shell rm /data/data/org.gnu.icecat/libGLES_android

This method only works for Replicant 6.0 0004.

Choosing the software renderer for a system component

System components usually lack a directory in the data partition. Thus, another method must be used to switch their software renderer.

  1. Find out the full path of the executable. You can use which for that:
    root@i9300:/ # which surfaceflinger
  2. Force the component to always use libagl by creating an empty file at /system/etc/libGLES_android/<executable_full_path>. Example commands:
    adb shell mkdir -p /system/etc/libGLES_android/system/bin
    adb shell touch /system/etc/libGLES_android/system/bin/surfaceflinger

    To force llvmpipe instead, create the file under /system/etc/libGLES_mesa/.
  3. Reboot your device, or restart the specific system component individualy (if possible).
  4. Get back to the default renderer by removing the file. Example command:
    adb shell rm /system/etc/libGLES_android/system/bin/surfaceflinger

This method only works for Replicant 6.0 0004.

Known issues with libagl

  • Selecting the third option besides photo and video (Panorama mode) will crash the Camera app.
  • Video playback in the browser does not work. (issue #1533)
  • Screenshots do not work. (see Screenshots for a workaround)
  • Selecting wallpapers from storage does not work.
  • Screen content is sometimes shortly visible before unlocking. (issue #1275, happens with llvmpipe as well)
  • Previews of the windows in the tasks switcher are missing.
  • Switching between apps, apps and the launcher or different views inside an app is sometimes slow and the device may seem unresponsive.
  • There are issues with using folders with the Trebuchet launcher. (issue #1790, happens with llvmpipe as well)

Popular apps from F-Droid that do not work with libagl

Known issues with llvmpipe

  • Too slow to use in SurfaceFlinger (screen compositor).
  • If SurfaceFlinger uses llvmpipe, Gallery and Orbot render some GUI elements are visible while the main screen is black. The GUI of Simple File Manager works as long as no image is viewed in fullscreen.

See also

There is a page about GraphicsResearch that gathers information to improve graphics support.

Updated by Denis 'GNUtoo' Carikli 6 months ago · 25 revisions