[Mesa-dev] [Bug 108977] Reading back an EGL Pbuffer using the OpenGL API returns garbled output

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=108977

--- Comment #1 from Matthieu Bouron <matthieu.bouron at gmail.com> ---
Comment on attachment 142750
  --> https://bugs.freedesktop.org/attachment.cgi?id=142750
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;
>}

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