Alpha channel other than "0xFF" in LinuxFB QPA platform

  • I'm using Qt5.1.1 with LinuxFB QPA platform (I'm bound to LinuxFB platform, and can't use another).

    I would like to have Qt write to LinuxFB custom alpha values alongside values of other color components. For example, if I set following style-sheet for QMainWindow "background-color: rgba(20, 20, 20, 0);" - I get following hex value of ARGB in frame-buffer 0xFF141414.

    Can someone instruct me what code should I change to accomplish this. I've tried to add some log-trace statements and I made some progress in isolating where the problem lies, but Qt is overwhelming and I would really appreciate any tip on this matter.

  • I've managed to convince Qt to write alpha value to the framebuffer with setting framebuffer to be of RGB32 type - not ARGB32!

  • Depends on the framebuffer settings. Most likely linuxfb picks a format that does not have alpha. What does fbset print?

  • @agocs: Thank you for your response!

    My framebuffer is of ARGB32 format. I wanted Qt to output alpha values I assigned for particular widgets and suppress:

    1. software blending,
    2. setting alpha channel in 0xFF for whole application.
      These things happened automatically when LinuxFB platform detected ARGB32 type framebuffer.

    I've accomplished what I was looking with the approach described in my previous post.

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