[virglrenderer-devel] [PATCH v2] vrend: use the row-stride when directly reading back to an IOV

[Nathan Gauër]

Hi,

On 07/18/2018 10:36 AM, Gert Wollny wrote:
> When guest mesa does a glReadPixel call, it expects the data to be placed
> with correct row strides into the readback buffer. While for calls that
> invert or require more then one IOV this is done in write_transfer_data,
> for a read that only uses a small area and offset making it fit into the
> first IOV this was not done. Consequently, in this case configure the
> PACK_ROW_LENGTH accordingly.
> 
> v2: fix whitespace issues
> 
> This fixes a number of piglits:
>    arb_copy_image-targets (for texture_2d source or dest, non-compressed)
>    arb_get_texture_multisample/sample_position
>    arb_texture_rectangle/fbo-blit rect
>    arb_get_texture__sub_image-cubemap
> 
> Signed-off-by: Gert Wollny <gert.wollny at collabora.com>
> ---
>  src/vrend_renderer.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/src/vrend_renderer.c b/src/vrend_renderer.c
> index 9a22214..4f87925 100644
> --- a/src/vrend_renderer.c
> +++ b/src/vrend_renderer.c
> @@ -5709,6 +5709,7 @@ static int vrend_transfer_send_readpixels(struct vrend_context *ctx,
>     uint32_t h = u_minify(res->base.height0, info->level);
>     int elsize = util_format_get_blocksize(res->base.format);
>     float depth_scale;
> +   int row_stride = info->stride;
>  
>     vrend_use_program(ctx, 0);
>  
> @@ -5734,6 +5735,8 @@ static int vrend_transfer_send_readpixels(struct vrend_context *ctx,
>     } else {
>        send_size = iov[0].iov_len - info->offset;
>        data = myptr;
> +      if (!row_stride)
> +         row_stride = util_format_get_nblocksx(res->base.format, u_minify(res->base.width0, info->level));
>     }
>  
>     if (res->readback_fb_id == 0 || (int)res->readback_fb_level != info->level ||
> @@ -5771,8 +5774,8 @@ static int vrend_transfer_send_readpixels(struct vrend_context *ctx,
>        glPixelStorei(GL_PACK_INVERT_MESA, 1);
>     if (!vrend_format_is_ds(res->base.format))
>        glReadBuffer(GL_COLOR_ATTACHMENT0_EXT);
> -   if (!need_temp && info->stride)
> -      glPixelStorei(GL_PACK_ROW_LENGTH, info->stride / elsize);
> +   if (!need_temp && row_stride)
> +      glPixelStorei(GL_PACK_ROW_LENGTH, row_stride);

This addition seams to trigger a blank screen on glxgears.
to reproduce: run vtest server. Run glxgears using vtest backend.
result: the frame-buffer is black

changing this last line to:
	glPixelStorei(GL_PACK_ROW_LENGTH, row_stride / elsize);
seams to fix this issue..

>  
>     switch (elsize) {
>     case 1:
> @@ -5845,7 +5848,7 @@ static int vrend_transfer_send_readpixels(struct vrend_context *ctx,
>     }
>     if (vrend_state.have_mesa_invert && actually_invert)
>        glPixelStorei(GL_PACK_INVERT_MESA, 0);
> -   if (!need_temp && info->stride)
> +   if (!need_temp && row_stride)
>        glPixelStorei(GL_PACK_ROW_LENGTH, 0);
>     glPixelStorei(GL_PACK_ALIGNMENT, 4);
>     if (need_temp) {
> 


-- 
Nathan Gauër