Bug 108977 - Reading back an EGL Pbuffer using the OpenGL API returns garbled output
Summary: Reading back an EGL Pbuffer using the OpenGL API returns garbled output
Status: ASSIGNED
Alias: None
Product: Mesa
Classification: Unclassified
Component: EGL (show other bugs)
Version: 18.2
Hardware: Other All
: medium normal
Assignee: Tapani Pälli
QA Contact: mesa-dev
URL:
Whiteboard:
Keywords:
Depends on:
Blocks:
 
Reported: 2018-12-08 10:05 UTC by Matthieu Bouron
Modified: 2018-12-11 11:41 UTC (History)
0 users

See Also:
i915 platform:
i915 features:


Attachments
EGL pbuffer test (1.84 KB, text/x-csrc)
2018-12-08 10:05 UTC, Matthieu Bouron
Details

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Description Matthieu Bouron 2018-12-08 10:05:17 UTC
Created attachment 142750 [details]
EGL pbuffer test

Hello,

I am currently facing an issue while reading back EGL Pbuffers using glReadPixels() with the OpenGL API as the output is garbled. It properly works with the OpenGL ES API though.

I can reproduce the issue on different machines running Arch Linux with mesa 18.2.5 on X using the following GPU: Intel HD 5500, Intel Iris 580 Pro, AMD RX 580.

I am not able to reproduce the issue on an NVDIA GTX 1070 running the proprietary driver.

I have attached a sample code that reproduces the issue:

On OpenGL:
gcc `pkg-config --libs egl gl` -Wall egl-pbuffer.c -o egl-pbuffer &&./egl-pbuffer
0xff69fc07 0xff69fc07 0xff69fc07 0xff69fc07 
0xff69fc07 0xff11a1e4 0xff000000 0xff000000 
0xff69fc07 0xff000000 0xff7fc700 0xff000000 
0xff69fc07 0xff000000 0xff000000 0xff3a4e3b 

On OpenGLES (adding the -es parameter to ./egl-pbuffer):
gcc `pkg-config --libs egl gl` -Wall egl-pbuffer.c -o egl-pbuffer &&./egl-pbuffer -es
0xff0000ff 0xff0000ff 0xff0000ff 0xff0000ff 
0xff0000ff 0xff0000ff 0xff0000ff 0xff0000ff 
0xff0000ff 0xff0000ff 0xff0000ff 0xff0000ff 
0xff0000ff 0xff0000ff 0xff0000ff 0xff0000ff
Comment 1 Matthieu Bouron 2018-12-08 10:16:04 UTC
Comment on attachment 142750 [details]
EGL pbuffer test

>#include <stdio.h>
>#include <stdint.h>
>#include <stdlib.h>
>#include <string.h>
>#include <EGL/egl.h>
>
>#include <GL/gl.h>
>
>#define WIDTH 4
>#define HEIGHT 4
>
>int main(int argc, char *argv[])
>{
>    int gles = argc > 1 ? !strcmp(argv[1], "-es") : 0;
>
>    EGLDisplay egl_dpy = eglGetDisplay(EGL_DEFAULT_DISPLAY);
>    if (!egl_dpy)
>        return -1;
>
>    EGLint major, minor;
>    int ret = eglInitialize(egl_dpy, &major, &minor);
>    if (!ret)
>        return -1;
>
>    const EGLint attribs[] = {
>        EGL_SURFACE_TYPE, EGL_PBUFFER_BIT,
>        EGL_RENDERABLE_TYPE, gles ? EGL_OPENGL_ES_BIT : EGL_OPENGL_BIT,
>        EGL_BLUE_SIZE, 8,
>        EGL_GREEN_SIZE, 8,
>        EGL_RED_SIZE, 8,
>        EGL_NONE
>    };
>    EGLint nb_configs;
>    EGLConfig egl_cfg;
>    ret = eglChooseConfig(egl_dpy, attribs, &egl_cfg, 1, &nb_configs);
>    if (!ret)
>        return -1;
>
>    eglBindAPI(gles ? EGL_OPENGL_ES_API : EGL_OPENGL_API);
>
>    EGLContext egl_ctx = eglCreateContext(egl_dpy, egl_cfg, EGL_NO_CONTEXT, NULL);
>    if (!egl_ctx)
>        return -1;
>
>    const EGLint pbuffer_attribs[] = {
>        EGL_WIDTH, WIDTH,
>        EGL_HEIGHT, HEIGHT,
>        EGL_NONE,
>    };
>    EGLSurface egl_surface = eglCreatePbufferSurface(egl_dpy, egl_cfg, pbuffer_attribs);
>    if (!egl_surface)
>        return -1;
>
>    ret = eglMakeCurrent(egl_dpy, egl_surface, egl_surface, egl_ctx);
>    if (!ret)
>        return -1;
>
>    uint8_t *data = calloc(1, 4 * WIDTH * HEIGHT);
>    if (!data)
>        return -1;
>
>    glClearColor(1.0, 0.0, 0.0, 1.0);
>    glClear(GL_COLOR_BUFFER_BIT);
>    glReadPixels(0, 0, WIDTH, HEIGHT, GL_RGBA, GL_UNSIGNED_BYTE, data);
>
>    for(int y = 0; y < HEIGHT; y++) {
>        for(int x = 0; x < WIDTH; x++) {
>            int *color = (int *)data + x*y;

Should be int *color = (int *)data + y*WIDTH + x;

>            printf("0x%8x ", *color);
>        }
>        printf("\n");
>    }
>    free(data);
>
>    eglTerminate(egl_dpy);
>    return 0;
>}
Comment 2 Tapani Pälli 2018-12-10 09:05:26 UTC
FWIW I couldn't reproduce this with Haswell or Skylake machines (using mesa 19.0.0-devel).
Comment 3 Matthieu Bouron 2018-12-10 10:00:09 UTC
Using Mesa 18.2.6, the frame is black instead of garbled (0xff000000 instead of 0xff0000ff for all pixels).
Comment 4 Tapani Pälli 2018-12-10 12:41:51 UTC
Hmm yep, I'm able to reproduce this after all.
Comment 5 Tapani Pälli 2018-12-11 11:41:24 UTC
I've checked for possible regressions in dEQP-EGL suite (that has a lot of clear surface related tests), it seems all of those are passing but I assume they all use gles1, gles2 or gles3.x so this is something specific to OpenGL. Will continue investigation.


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