Use of GTK on embedded Linux systems

[HarryMichal (Harry Míchal)]

Hi! I’ve encountered recently a question about which toolkit to use on embedded Linux. Being a GNOME person, I suggested GTK without knowing anything about the embedded use-case. The other party mentioned they’d like to draw directly to framebuffer and have it hardware accelerated. Qt seems to offer well-documented features for this use case: Qt for Embedded Linux | Qt 5.15.

Is GTK a good choice for embedded Linux or is it more convenient to stick with Qt or under solutions? And GTK is a good choice what should one use to properly utilize it?

[ebassi (Emmanuele Bassi)]

@HarryMichal

The other party mentioned they’d like to draw directly to framebuffer and have it hardware accelerated.

No, GTK does not have a direct framebuffer backend. You still need to provide a windowing system, like X11 or Wayland.

[zbrown (Zander Brown)]

@ebassi

You still need to provide a windowing system, like X11 or Wayland.

…such as a minimal copy of Weston (which does provide a framebuffer backend), which is already used “in the wild” for embedded projects. You’ll probably want to look at “kiosk shell” — rather than the default desktop-shell — which autostarts a given fullscreen app

[alatiera (Jordan Petridis)]

Weston also has a kiosk mode, which you can trivially activate with --shell=kiosk-shell.so or appending the following in the weston.ini config file

[core]
shell=kiosk-shell.so

[HarryMichal (Harry Míchal)]

So, the recommend approach would be to set up a Wayland compositor (either Shell, Weston or anything similar) and then use GTK in an application the “classic” way?

Given a more concrete example, let’s say I have a RaspberryPi 3B with a touchscreen display. If I were to use the simplified approach above, would I get hardware acceleration for the created GUI?

[ebassi (Emmanuele Bassi)]

@HarryMichal

So, the recommend approach would be to set up a Wayland compositor (either Shell, Weston or anything similar) and then use GTK in an application the “classic” way?

Yes, that’s how GTK works.

@HarryMichal

Given a more concrete example, let’s say I have a RaspberryPi 3B with a touchscreen display. If I were to use the simplified approach above, would I get hardware acceleration for the created GUI?

Define “hardware acceleration”. RPi3 has a GPU on its SoC that can use GLES, so you can have a Wayland display server that uses hardware acceleration to move buffers and present them on the screen. Additionally, GTK4 supports GLES as a rendering API, so it can use hardware acceleration to draw the contents of an application.

Of course, I would recommend using an RPi4, because anything older than that is kind of low spec’ed for complex rendering, especially if you end up on websites.

But I would also be hard pressed to classify a Raspberry Pi as an “embedded” Linux system. Just because it’s an Arm SoC, it doesn’t mean it’s “embedded”; otherwise, an Apple Arm MacBook would classify as an “embedded” system.

[HarryMichal (Harry Míchal)]

@ebassi

Define “hardware acceleration”. RPi3 has a GPU on its SoC that can use GLES, so you can have a Wayland display server that uses hardware acceleration to move buffers and present them on the screen. Additionally, GTK4 supports GLES as a rendering API, so it can use hardware acceleration to draw the contents of an application.

Sounds like exactly what I’m looking for.

@ebassi

Of course, I would recommend using an RPi4, because anything older than that is kind of low spec’ed for complex rendering, especially if you end up on websites.

Definitely but personally I believe even a RPi3 should be enough for a single running app on the system.But of course a beefier machine is always better.

@ebassi

But I would also be hard pressed to classify a Raspberry Pi as an “embedded” Linux system. Just because it’s an Arm SoC, it doesn’t mean it’s “embedded”; otherwise, an Apple Arm MacBook would classify as an “embedded” system.

You’re probably right. A RPi is the closest I’ve ever gotten to “embedded” myself, so I’m using it as an example. Don’t really know anything else.

Thank you for your insight!