topic Re: i.mx8mp GPU and GTK4 app: GUI/window present delay and blocking Vivante /dev/galcore ioctl in i.MX Graphics

i.mx8mp GPU and GTK4 app: GUI/window present delay and blocking Vivante /dev/galcore ioctl

jim777 — Sun, 06 Sep 2026 22:14:12 GMT

GTK4 Window Startup Delay (~10s) on i.MX8MP with Vivante GPU

When using the default GTK4 GL renderer:

gtk_window_present(window);

takes approximately 9-10 seconds before the window becomes visible.

The evidence (see attached file) strongly suggests that the startup delay is not caused by GTK application code.

The delay appears correlated with a blocking Vivante /dev/galcore ioctl within the GL rendering path. Software rendering (GSK_RENDERER=cairo) avoids the issue.

We are looking for guidance on known issues, debugging methods, configuration changes, or fixes for GTK4/OpenGL startup latency on i.MX8MP with the Vivante GPU stack.

Re: i.mx8mp GPU and GTK4 app: GUI/window present delay and blocking Vivante /dev/galcore ioctl

Zhiming_Liu — Mon, 07 Sep 2026 05:52:30 GMT

Hi @jim777

Thank you for sharing such detailed information. Could you provide a minimal, reproducible GTK4 source code example? I need to conduct further testing in the NXP BSP.

Best Regards,
Zhiming

Re: i.mx8mp GPU and GTK4 app: GUI/window present delay and blocking Vivante /dev/galcore ioctl

jim777 — Mon, 07 Sep 2026 18:52:51 GMT

Hi Zhiming,

Thanks for your quick response!

Attached is a small skeleton but complete source file to test.
and the environment variables set before running:

#!/bin/sh export XDG_RUNTIME_DIR=/run/user/0 export WAYLAND_DISPLAY=wayland-1 export GDK_BACKEND=wayland export GSK_RENDERER=gl

the relevant from weston.ini:

root@nitrogen8mp:~# cat /etc/xdg/weston/weston.ini [core] #gbm-format=argb8888 use-g2d=true repaint-window=16 idle-time=0 xwayland=true #enable-overlay-view=1 [shell] panel-position=none [libinput] touchscreen_calibrator=true #[output] #name=HDMI-A-1 #mode=1920x1080@60 #transform=rotate-90 #[output] #name=HDMI-A-2 #mode=off # WIDTHxHEIGHT Resolution size width and height in pixels # off Disables the output # preferred Uses the preferred mode # current Uses the current crt controller mode #transform=rotate-90 [screen-share] command=/usr/bin/weston --backend=rdp-backend.so --shell=fullscreen-shell.so --no-clients-resize #start-on-startup=true [input-method] path=/usr/libexec/ibus-wayland

the running time for the gtk_window_present on a desktop w/o GPU support takes some hundreds msec (< 1sec); and on the i.mx8mp device takes 9970 ms :

root@nitrogen8mp:~# gtk4-test A: activate: before _present: 47333 ms B: activate: after _present: 57303 ms, takes: 9970 ms C: activate: after idele_add: 57303 ms D: startup_task_cb: 57315 ms ^C root@nitrogen8mp:~#

I have tried render: ngl, which leads to smear image/widgetrs/video, and Vulkan leads to critical errors: Loader Message: vkCreateDevice: Failed to validate extensions in list; Failed to realize renderer of type ‘GskVulkanRenderer’ for surface ‘GdkWaylandToplevel’: Could not find a Vulkan device with the required features.

Since out app need GPU support, and the recommended renderer under wayland/weston is still gl (UG10159 11.3.2.1 GL renderer) , I hope you can help to find a solution.

Best regards,