Add screencopy+dmabuf support to libwayshot

[CheerfulPianissimo]

Tracking issue for my Google Summer of Code 2024 project with Waycrate.
More details may be found here:

• https://cheerfulpianissimo.github.io/notes/GSOC/GSOC.html
• Motivation: https://cheerfulpianissimo.github.io/notes/GSOC/Project%20Design.html
• Design: https://cheerfulpianissimo.github.io/notes/GSOC/Project%20Design.html

The GSoC mentor assigned for this project is @zubairmh

[CheerfulPianissimo]

How should the basic API be structured? My present plan:

• Add a method that returns a GBM buffer object containing the screencapture under the WayshotConnection struct
• Add a new constructor for WayshotConnection that initializes the Linux dmabuf main interface and also initializes a GBMDevice to create the backing dmabuf buffer objects on. Both of these will be stored in WayshotConnection inside an Option (as dmabuf functionality may not always present)
  • One issue that arises here is that GBMDevice, being a wrapper to a C library construct, does not implement Sync/Send and cannot be moved across threads. This means that WayshotConnection will lose it's thread safety and cannot be moved across threads as it contains a GBMDevice : this happens at one point in libwayshot where multiple outputs are captured simultaneosly here . One solution is to remove the use of threads here but perhaps there's another way I'm missing.

What are your thoughts on this @zubairmh and @Shinyzenith ?

[CheerfulPianissimo]

For anyone following, a technical log of the present work on this issue can be found at:
https://cheerfulpianissimo.github.io/notes/GSOC/GSOC%20Devlog%20(June).html
and https://cheerfulpianissimo.github.io/notes/GSOC/GSoC%20Devlog%20(July).html