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render/gles2: use byte-aligned rows for glReadPixels

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Setting the GLESv2 parameter GL_PACK_ALIGNMENT to 1 ensures that the
stride of the glReadPixels output matches the value computed in
`pack_stride`. Since the default value of GL_PACK_ALIGNMENT is 4, this
does not make a difference under normal use; but without this patch
the stride can be incorrect; for example, with RGB565 buffers and
screenshots of regions with odd width.
This commit is contained in:
Manuel Stoeckl 2023-01-14 16:55:02 -05:00 committed by Simon Ser
parent 9affcaa93c
commit 40dde59475
1 changed files with 2 additions and 1 deletions
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render/gles2/renderer.c
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@ -473,6 +473,7 @@ static bool gles2_read_pixels(struct wlr_renderer *wlr_renderer,
glGetError(); // Clear the error flag
unsigned char *p = (unsigned char *)data + dst_y * stride;
glPixelStorei(GL_PACK_ALIGNMENT, 1);
uint32_t pack_stride = width * drm_fmt->bpp / 8;
if (pack_stride == stride && dst_x == 0) {
// Under these particular conditions, we can read the pixels with only
@ -480,7 +481,7 @@ static bool gles2_read_pixels(struct wlr_renderer *wlr_renderer,
glReadPixels(src_x, src_y, width, height, fmt->gl_format, fmt->gl_type, p);
} else {
// Unfortunately GLES2 doesn't support GL_PACK_*, so we have to read
// Unfortunately GLES2 doesn't support GL_PACK_ROW_LENGTH, so we have to read
// the lines out row by row
for (size_t i = 0; i < height; ++i) {
uint32_t y = src_y + i;