vrend: fix text in stellarium.

If we are blitting to an emulated alpha we should rewrite inside
the shader, not in the incoming texture swizzle.

src/vrend_blitter.c

@@ -58,6 +58,7 @@ struct vrend_blitter_ctx {
    GLuint vs;
    GLuint vs_pos_only;
    GLuint fs_texfetch_col[PIPE_MAX_TEXTURE_TYPES];
+   GLuint fs_texfetch_col_emu_alpha[PIPE_MAX_TEXTURE_TYPES];
    GLuint fs_texfetch_depth[PIPE_MAX_TEXTURE_TYPES];
    GLuint fs_texfetch_depth_msaa[PIPE_MAX_TEXTURE_TYPES];
    GLuint fb_id;
@@ -154,6 +155,59 @@ static GLuint blit_build_frag_tex_col(struct vrend_blitter_ctx *blit_ctx, int tg
    return fs_id;
 }
 
+static GLuint blit_build_frag_tex_col_emu_alpha(struct vrend_blitter_ctx *blit_ctx, int tgsi_tex_target)
+{
+   GLuint fs_id;
+   char shader_buf[4096];
+   int is_shad;
+   const char *twm;
+   const char *ext_str = "";
+   switch (tgsi_tex_target) {
+   case TGSI_TEXTURE_1D:
+   case TGSI_TEXTURE_BUFFER:
+      twm = ".x";
+      break;
+   case TGSI_TEXTURE_1D_ARRAY:
+   case TGSI_TEXTURE_2D:
+   case TGSI_TEXTURE_RECT:
+   case TGSI_TEXTURE_2D_MSAA:
+   default:
+      twm = ".xy";
+      break;
+   case TGSI_TEXTURE_SHADOW1D:
+   case TGSI_TEXTURE_SHADOW2D:
+   case TGSI_TEXTURE_SHADOW1D_ARRAY:
+   case TGSI_TEXTURE_SHADOWRECT:
+   case TGSI_TEXTURE_3D:
+   case TGSI_TEXTURE_CUBE:
+   case TGSI_TEXTURE_2D_ARRAY:
+   case TGSI_TEXTURE_2D_ARRAY_MSAA:
+      twm = ".xyz";
+      break;
+   case TGSI_TEXTURE_SHADOWCUBE:
+   case TGSI_TEXTURE_SHADOW2D_ARRAY:
+   case TGSI_TEXTURE_SHADOWCUBE_ARRAY:
+   case TGSI_TEXTURE_CUBE_ARRAY:
+      twm = "";
+      break;
+   }
+
+   if (tgsi_tex_target == TGSI_TEXTURE_CUBE_ARRAY ||
+       tgsi_tex_target == TGSI_TEXTURE_SHADOWCUBE_ARRAY)
+      ext_str = "#extension GL_ARB_texture_cube_map_array : require\n";
+
+   snprintf(shader_buf, 4096, FS_TEXFETCH_COL_ALPHA_DEST, ext_str, vrend_shader_samplertypeconv(tgsi_tex_target, &is_shad), twm, "");
+
+   fs_id = glCreateShader(GL_FRAGMENT_SHADER);
+
+   if (!build_and_check(fs_id, shader_buf)) {
+      glDeleteShader(fs_id);
+      return 0;
+   }
+
+   return fs_id;
+}
+
 static GLuint blit_build_frag_tex_writedepth(struct vrend_blitter_ctx *blit_ctx, int tgsi_tex_target)
 {
    GLuint fs_id;
@@ -280,6 +334,24 @@ static GLuint blit_get_frag_tex_col(struct vrend_blitter_ctx *blit_ctx, int pipe
    }
 }
 
+static GLuint blit_get_frag_tex_col_emu_alpha(struct vrend_blitter_ctx *blit_ctx, int pipe_tex_target, unsigned nr_samples)
+{
+   assert(pipe_tex_target < PIPE_MAX_TEXTURE_TYPES);
+
+   if (nr_samples > 1) {
+      return 0;
+   } else {
+      GLuint *shader = &blit_ctx->fs_texfetch_col_emu_alpha[pipe_tex_target];
+
+      if (!*shader) {
+         unsigned tgsi_tex = util_pipe_tex_to_tgsi_tex(pipe_tex_target, 0);
+
+         *shader = blit_build_frag_tex_col_emu_alpha(blit_ctx, tgsi_tex);
+      }
+      return *shader;
+   }
+}
+
 static void vrend_renderer_init_blit_ctx(struct vrend_blitter_ctx *blit_ctx)
 {
    struct virgl_gl_ctx_param ctx_params;
@@ -501,6 +573,8 @@ void vrend_renderer_blit_gl(struct vrend_context *ctx,
 
    if (blit_depth || blit_stencil)
       fs_id = blit_get_frag_tex_writedepth(blit_ctx, src_res->base.target, src_res->base.nr_samples);
+   else if (vrend_format_is_emulated_alpha(info->dst.format))
+      fs_id = blit_get_frag_tex_col_emu_alpha(blit_ctx, src_res->base.target, src_res->base.nr_samples);
    else
       fs_id = blit_get_frag_tex_col(blit_ctx, src_res->base.target, src_res->base.nr_samples);
    glAttachShader(prog_id, fs_id);

src/vrend_blitter.h

@@ -45,6 +45,16 @@
    "   gl_FragColor = texture(samp, tc%s)%s;\n" \
    "}\n"
 
+#define FS_TEXFETCH_COL_ALPHA_DEST              \
+   "#version 130\n"                             \
+   "%s"                                         \
+   "uniform sampler%s samp;\n"                  \
+   "in vec4 tc;\n"                              \
+   "void main() {\n"                            \
+   "   vec4 temp = texture(samp, tc%s)%s;\n"     \
+   "   gl_FragColor = temp.aaaa;\n" \
+   "}\n"
+
 #define FS_TEXFETCH_DS                                  \
    "#version 130\n"                                     \
    "uniform sampler%s samp;\n"                          \

src/vrend_renderer.c

@@ -439,7 +439,7 @@ bool vrend_is_ds_format(enum virgl_formats format)
    return vrend_format_is_ds(format);
 }
 
-static inline bool vrend_format_is_emulated_alpha(enum virgl_formats format)
+bool vrend_format_is_emulated_alpha(enum virgl_formats format)
 {
    if (!vrend_state.use_core_profile)
       return false;
@@ -5498,6 +5498,9 @@ static void vrend_renderer_blit_int(struct vrend_context *ctx,
    if (info->src.box.depth != info->dst.box.depth)
       use_gl = true;
 
+   if (vrend_format_is_emulated_alpha(info->dst.format))
+      use_gl = true;
+
    if (use_gl) {
       vrend_renderer_blit_gl(ctx, src_res, dst_res, info);
       vrend_clicbs->make_current(0, ctx->sub->gl_context);

src/vrend_renderer.h

@@ -365,7 +365,7 @@ void vrend_fb_bind_texture(struct vrend_resource *res,
                            int idx,
                            uint32_t level, uint32_t layer);
 bool vrend_is_ds_format(enum virgl_formats format);
-
+bool vrend_format_is_emulated_alpha(enum virgl_formats format);
 /* blitter interface */
 void vrend_renderer_blit_gl(struct vrend_context *ctx,
                             struct vrend_resource *src_res,