[Development] [QML][EGLFS] Bits depth

[Denis Shienkov]

> Check with QSG_INFO what you get. It may either be 8880 or 8888

Yes, seems this:

{code}
    QQuickView view;
    QSurfaceFormat format;
    format.setAlphaBufferSize(8);
    view.setFormat(format);
{code}

same as QT_QPA_EGLFS_FORCE888, I got:

{quote}
qt.scenegraph.general: texture atlas dimensions: 2048x2048
qt.scenegraph.general: R/G/B/A Buffers:    8 8 8 8
qt.scenegraph.general: Depth Buffer:       0
qt.scenegraph.general: Stencil Buffer:     0
qt.scenegraph.general: Samples:            0
qt.scenegraph.general: GL_VENDOR:          NVIDIA Corporation
qt.scenegraph.general: GL_RENDERER:        NVIDIA Tegra 3
qt.scenegraph.general: GL_VERSION:         OpenGL ES 2.0 14.01002
{quote}

BUT: I faced with randomly flickering (with a random white polygons on a
black background on 1/2 - 1/3 of
height of my display) when an QML animation is running.. sad sad sad... :(

I have tried to setup a different buffer's sizes, intervals, and other
properties to QSurfaceFormat, but it did not help.

It works without flickering only with RGBA=5650, but then I see borders of
gradients of images..  :(



2016-08-04 18:39 GMT+03:00 Laszlo Agocs <laszlo.agocs at qt.io>:

>
> Hi Denis,
>
>
> QSurfaceFormat::setDefaultFormat() with a format of red/blue/green set to
> 8, or alternatively setting QT_QPA_EGLFS_FORCE888 is indeed what you need.
> The default format with unspecified sizes results in choosing 16 over 32
> bit configs when both are offered, that's normal.
>
>
> Check with QSG_INFO what you get. It may either be 8880 or 8888, depending
> on what is offered by the EGL implementation. As for the 24 bit depth,
> regardless of what X or EGL says, under the hood it is quite likely that
> you have 32 bit framebuffers anyway, true packed 24 bit ones are probably
> rare.
>
>
> As for the "other bad issues", the flickering, that is the real issue
> here, but that's likely caused by something else outside of Qt's scope.
>
>
> Best regards,
>
> Laszlo
> ------------------------------
> *From:* Denis Shienkov <denis.shienkov at gmail.com>
> *Sent:* Thursday, August 4, 2016 4:48:40 PM
> *To:* development at qt-project.org; Laszlo Agocs
> *Subject:* [QML][EGLFS] Bits depth
>
> Hi guys,
>
> I have use Qt 5.7 on Linux Embedded board (Toradex Apalis T30) with the
> EGLFS via X11 platform (NVidia drivers).
>
> My QML application uses 24-bit PNG images. But I see that these images is
> looks like 16-bit (I see the gradients borders, and it looks ugly),
> howewer my X11 uses DefaultDepth == 24!!!
>
> Also this command:
>
> {quote}
> root at apalis-t30:~/deploy-apps# xdpyinfo | grep 'depth of root'
>   depth of root window:    24 planes
> {quote}
>
> shows 24-bit mode too.
>
> Next, I have added this debug env variable:
>
> {quote}
>  export QSG_INFO=1
> {quote}
>
> to see what happens when my QML app starts:
>
> {quote}
> ...
> qt.scenegraph.general: threaded render loop
> qt.scenegraph.general: Using sg animation driver
> qt.scenegraph.general: Animation Driver: using vsync: 16.67 ms
> qt.scenegraph.general: Animation Driver: using vsync: 16.67 ms
> qt.scenegraph.general: texture atlas dimensions: 2048x2048
> qt.scenegraph.general: R/G/B/A Buffers:    5 6 5 0
> qt.scenegraph.general: Depth Buffer:       16
> qt.scenegraph.general: Stencil Buffer:     8
> qt.scenegraph.general: Samples:            0
> qt.scenegraph.general: GL_VENDOR:          NVIDIA Corporation
> qt.scenegraph.general: GL_RENDERER:        NVIDIA Tegra 3
> ...
> {quote}
>
> I see that OpenGL (yes?) initializes with the "R/G/B/A Buffers:    5 6 5
> 0" mode,
> that is 16-bit depth!!! O_O
>
> Next, I have tried to change the FB depth via:
>
> {quote}
>   fbset -fb /dev/fb1 -depth 24
> {quote}
>
> I see that FB changes own settings, but nothing changes when my app starts,
> it still shows images ugly, as 16-bit depth.
>
> Also I have tried to use QT_QPA_EGLFS_DEPTH variable (with 16, 24 or 32),
> but nothing changes, not helps.
>
> Helps only the QT_QPA_EGLFS_FORCE888 variable, but it introduces others
> bad issues,
> like the whole/half HDMI display flickering.. So, I can not to use
> QT_QPA_EGLFS_FORCE888..
>
> So, is there are any tricks to use 24-bit depth?
>
> BR,
> Denis
>
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