blitter: Make fbo sRGB state always act like on GLES

On an GL host set the sRGB blit framebuffer state explicitly to make virgl
behave like on a GLES host.

This does not correct the handing of sRGB completely, because the state
GL_FRAMEBUFFER_SRGB is not properly transmitted to the host. As a result
the piglits  "blit texture linear_to_srgb * * *" flip.
Tests thatset "enable" failed before and pass now, and tests that set "disable"
now fail.

v2: - Move setting the fbo state out of the loop (Robert Tarasov)
    - Use the blitter context to set and store the state, since it is only,
      and currently we don't pass the state from the guest
      relevant when the dst texture is SRGB, there is no need to disable it
    - Just enforce that a source SRGB texture is always decoded when this could
      be disabled

Fixes on GL host:
  dEQP-GLES3.functional.fbo.blit.conversion.rgb8_to_srgb8_alpha8
  dEQP-GLES3.functional.fbo.blit.default_framebuffer.srgb8_alpha8

Reviewed-by: Robert Tarasov <tutankhamen@chromium.org>
Tested-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Tested-by: Jakob Bornecrantz <jakob@collabora.com>
Signed-off-by: Gert Wollny <gert.wollny@collabora.com>
Signed-off-by: Jakob Bornecrantz <jakob@collabora.com>

src/vrend_blitter.c

@@ -55,6 +55,7 @@ struct vrend_blitter_ctx {
    virgl_gl_context gl_context;
    bool initialised;
    bool use_gles;
+   int framebuffer_srgb_enabled;
 
    GLuint vaoid;
 
@@ -460,6 +461,10 @@ static void vrend_renderer_init_blit_ctx(struct vrend_blitter_ctx *blit_ctx)
       blit_ctx->vertices[i][0][3] = 1; /*v.w*/
    glBindVertexArray(blit_ctx->vaoid);
    glBindBuffer(GL_ARRAY_BUFFER, blit_ctx->vbo_id);
+
+   if (!blit_ctx->use_gles)
+      glEnable(GL_FRAMEBUFFER_SRGB);
+   blit_ctx->framebuffer_srgb_enabled = true;
 }
 
 static inline GLenum convert_mag_filter(unsigned int filter)
@@ -686,7 +691,8 @@ static void calc_dst_deltas_from_src(const struct pipe_blit_info *info,
 void vrend_renderer_blit_gl(UNUSED struct vrend_context *ctx,
                             struct vrend_resource *src_res,
                             struct vrend_resource *dst_res,
-                            const struct pipe_blit_info *info)
+                            const struct pipe_blit_info *info,
+                            bool has_texture_srgb_decode)
 {
    struct vrend_blitter_ctx *blit_ctx = &vrend_blit_ctx;
    GLuint buffers;
@@ -787,6 +793,9 @@ void vrend_renderer_blit_gl(UNUSED struct vrend_context *ctx,
                       to_gl_swizzle(src_entry->swizzle[3]));
    }
 
+   /* Just make sure that no stale state disabled decoding */
+   if (has_texture_srgb_decode && util_format_is_srgb(src_res->base.format))
+         glTexParameteri(src_res->target, GL_TEXTURE_SRGB_DECODE_EXT, GL_DECODE_EXT);
 
    glTexParameteri(src_res->target, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(src_res->target, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
@@ -833,4 +842,4 @@ void vrend_renderer_blit_gl(UNUSED struct vrend_context *ctx,
                              GL_TEXTURE_2D, 0, 0);
    glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0,
                              GL_TEXTURE_2D, 0, 0);
-}
+}

src/vrend_renderer.c

@@ -7129,7 +7129,8 @@ static void vrend_renderer_blit_int(struct vrend_context *ctx,
       use_gl = true;
 
    if (use_gl) {
-      vrend_renderer_blit_gl(ctx, src_res, dst_res, info);
+      vrend_renderer_blit_gl(ctx, src_res, dst_res, info,
+                             has_feature(feat_texture_srgb_decode));
       vrend_clicbs->make_current(0, ctx->sub->gl_context);
       return;
    }
@@ -7248,6 +7249,13 @@ static void vrend_renderer_blit_int(struct vrend_context *ctx,
       vrend_fb_bind_texture(dst_res, 0, info->dst.level, info->dst.box.z + i);
       glBindFramebuffer(GL_DRAW_FRAMEBUFFER, ctx->sub->blit_fb_ids[1]);
 
+      if (!vrend_state.use_gles) {
+         if (util_format_is_srgb(dst_res->base.format))
+            glEnable(GL_FRAMEBUFFER_SRGB);
+         else
+            glDisable(GL_FRAMEBUFFER_SRGB);
+      }
+
       glBindFramebuffer(GL_READ_FRAMEBUFFER, intermediate_fbo);
 
       glBlitFramebuffer(info->src.box.x,

src/vrend_renderer.h

@@ -391,7 +391,8 @@ boolean format_is_copy_compatible(enum pipe_format src, enum pipe_format dst);
 void vrend_renderer_blit_gl(struct vrend_context *ctx,
                             struct vrend_resource *src_res,
                             struct vrend_resource *dst_res,
-                            const struct pipe_blit_info *info);
+                            const struct pipe_blit_info *info,
+                            bool has_texture_srgb_decode);
 
 void vrend_renderer_reset(void);
 int vrend_renderer_get_poll_fd(void);