Add ability to disable scaling

[manio]

Currently wayland displays can have some scalling applied (it is widely used with HiDPI displays).
It is then handled via a viewporter or fractional-scale protocols.
However it is sometimes desirable to explicitly disable scaling for some GLFW application to have a clear and perfect 1:1 pixel window content (ie. no scaling applied).

This PR adds such a possiblity.
To use it one can eg. set/export a variable like this:
export GLFW_SCALE_TO_MONITOR=1
and then start the application.

[elmindreda]

With a9cc7c7 there is now the GLFW_SCALE_FRAMEBUFFER window hint that lets you control this scaling per-window on Wayland. Is that sufficient for your needs?

[manio]

I'll try to test this ASAP...

[manio]

@elmindreda
Please tell me if I did the change properly:
manio/SDRPlusPlus@599b3d6

I built master branch of glfw and the above application with the above change included but unfortunately it is still ugly/upscaled, while with this PR it is working fine (without scaling).

[elmindreda]

However it is sometimes desirable to explicitly disable scaling for some GLFW application to have a clear and perfect 1:1 pixel window content (ie. no scaling applied).

I think this is the issue.

You seem to be referring to the scaling the compositor performs on the window, over which we have no control.

The GLFW_SCALE_FRAMEBUFFER hint refers to GLFW scaling the framebuffer relative to the window size, so that the window contents (typically) maps 1:1 to output pixels again even if window sizes no longer do.

I think you want to set the hint to true.

[manio]

I tested with GLFW_SCALE_FRAMEBUFFER set to true and false now:
true: https://skyboo.net/temp/glfw/SCALE_FRAMEBUFFER_TRUE.png
false: https://skyboo.net/temp/glfw/SCALE_FRAMEBUFFER_FALSE.png

But this PR is doing something different, which I'd like to have. Disable UI scaling completely. Please take a look how it looks: https://skyboo.net/temp/glfw/SCALE_TO_MONITOR.png
This way the whole UI is not scaled (I can see more details on the screen), and this is done with the changes in this PR.

In fact this scaling is applied only when this env variable is set, so it doesn't affect any user, only those who are aware of this feature... so maybe you're willing to merge this?

[elmindreda]

This PR essentially adds an option that switches the behaviors of glfwGetWindowSize and glfwGetFramebufferSize. It's not changing the actual size of the window or framebuffer, just what values are retrieved via these functions.

If the changes in this PR makes your program draw correctly, then it is likely using the wrong one of these functions somewhere.

[manio]

@AlexandreRouma
Could you please comment on this? Are you able to adjust sdrpp scalling in the app itself instead of glfw ?

Setting the scale to 200% doesn't help to get the result as in my screenshot.

[AlexandreRouma]

SDR++ bases the scaling on glfwGetWindowSize()