+ if (!st->prefer_blit_based_texture_transfer) {
+ goto fallback;
+ }
+
+ /* This must be done after state validation. */
+ src = strb->texture;
+
+ /* XXX Fallback for depth-stencil formats due to an incomplete
+ * stencil blit implementation in some drivers. */
+ if (format == GL_DEPTH_STENCIL) {
+ goto fallback;
+ }
+
+ /* We are creating a texture of the size of the region being read back.
+ * Need to check for NPOT texture support. */
+ if (!screen->get_param(screen, PIPE_CAP_NPOT_TEXTURES) &&
+ (!util_is_power_of_two(width) ||
+ !util_is_power_of_two(height))) {
+ goto fallback;
+ }
+
+ /* If the base internal format and the texture format don't match, we have
+ * to use the slow path. */
+ if (rb->_BaseFormat !=
+ _mesa_get_format_base_format(rb->Format)) {
+ goto fallback;
+ }
+
+ /* See if the texture format already matches the format and type,
+ * in which case the memcpy-based fast path will likely be used and
+ * we don't have to blit. */
+ if (_mesa_format_matches_format_and_type(rb->Format, format,
+ type, pack->SwapBytes)) {
+ goto fallback;
+ }
+
+ if (_mesa_readpixels_needs_slow_path(ctx, format, type, GL_TRUE)) {
+ goto fallback;
+ }
+
+ if (needs_integer_signed_unsigned_conversion(ctx, format, type)) {
+ goto fallback;
+ }
+
+ /* Convert the source format to what is expected by ReadPixels
+ * and see if it's supported. */
+ src_format = util_format_linear(src->format);
+ src_format = util_format_luminance_to_red(src_format);
+ src_format = util_format_intensity_to_red(src_format);
+
+ if (!src_format ||
+ !screen->is_format_supported(screen, src_format, src->target,
+ src->nr_samples,
+ PIPE_BIND_SAMPLER_VIEW)) {
+ goto fallback;
+ }
+
+ if (format == GL_DEPTH_COMPONENT || format == GL_DEPTH_STENCIL)
+ bind |= PIPE_BIND_DEPTH_STENCIL;
+ else
+ bind |= PIPE_BIND_RENDER_TARGET;
+
+ /* Choose the destination format by finding the best match
+ * for the format+type combo. */
+ dst_format = st_choose_matching_format(st, bind, format, type,
+ pack->SwapBytes);
+ if (dst_format == PIPE_FORMAT_NONE) {
+ goto fallback;
+ }
+
+ /* create the destination texture */
+ memset(&dst_templ, 0, sizeof(dst_templ));
+ dst_templ.target = PIPE_TEXTURE_2D;
+ dst_templ.format = dst_format;
+ dst_templ.bind = bind;
+ dst_templ.usage = PIPE_USAGE_STAGING;
+
+ st_gl_texture_dims_to_pipe_dims(GL_TEXTURE_2D, width, height, 1,
+ &dst_templ.width0, &dst_templ.height0,
+ &dst_templ.depth0, &dst_templ.array_size);
+
+ dst = screen->resource_create(screen, &dst_templ);
+ if (!dst) {
+ goto fallback;
+ }
+
+ memset(&blit, 0, sizeof(blit));
+ blit.src.resource = src;
+ blit.src.level = strb->surface->u.tex.level;
+ blit.src.format = src_format;
+ blit.dst.resource = dst;
+ blit.dst.level = 0;
+ blit.dst.format = dst->format;
+ blit.src.box.x = x;
+ blit.dst.box.x = 0;
+ blit.src.box.y = y;
+ blit.dst.box.y = 0;
+ blit.src.box.z = strb->surface->u.tex.first_layer;
+ blit.dst.box.z = 0;
+ blit.src.box.width = blit.dst.box.width = width;
+ blit.src.box.height = blit.dst.box.height = height;
+ blit.src.box.depth = blit.dst.box.depth = 1;
+ blit.mask = st_get_blit_mask(rb->_BaseFormat, format);
+ blit.filter = PIPE_TEX_FILTER_NEAREST;
+ blit.scissor_enable = FALSE;
+
+ if (st_fb_orientation(ctx->ReadBuffer) == Y_0_TOP) {
+ blit.src.box.y = rb->Height - blit.src.box.y;
+ blit.src.box.height = -blit.src.box.height;
+ }
+
+ /* blit */
+ st->pipe->blit(st->pipe, &blit);
+
+ /* map resources */
+ pixels = _mesa_map_pbo_dest(ctx, pack, pixels);
+
+ map = pipe_transfer_map_3d(pipe, dst, 0, PIPE_TRANSFER_READ,
+ 0, 0, 0, width, height, 1, &tex_xfer);
+ if (!map) {
+ _mesa_unmap_pbo_dest(ctx, pack);
+ pipe_resource_reference(&dst, NULL);
+ goto fallback;
+ }
+
+ /* memcpy data into a user buffer */
+ {
+ const uint bytesPerRow = width * util_format_get_blocksize(dst_format);
+ GLuint row;
+
+ for (row = 0; row < (unsigned) height; row++) {
+ GLvoid *dest = _mesa_image_address3d(pack, pixels,
+ width, height, format,
+ type, 0, row, 0);
+ memcpy(dest, map, bytesPerRow);
+ map += tex_xfer->stride;
+ }
+ }
+
+ pipe_transfer_unmap(pipe, tex_xfer);
+ _mesa_unmap_pbo_dest(ctx, pack);
+ pipe_resource_reference(&dst, NULL);
+ return;
+
+fallback:
+ _mesa_readpixels(ctx, x, y, width, height, format, type, pack, pixels);
+}