shader: get maximum number of render targets dynamically

[airlied: pushed the get up a bit higher to make it cleaner]
Reviewed-by: Jakob Bornecrantz <jakob@collabora.com>
Reviewed-by: Dave Airlie <airlied@redhat.com>

src/vrend_renderer.c

@@ -122,6 +122,7 @@ struct global_renderer_state {
    /* these appeared broken on at least one driver */
    bool use_explicit_locations;
    uint32_t max_uniform_blocks;
+   uint32_t max_draw_buffers;
    struct list_head active_ctx_list;
 
    /* threaded sync */
@@ -4378,6 +4379,8 @@ int vrend_renderer_init(struct vrend_if_cbs *cbs, uint32_t flags)
       fprintf(stderr, "gl_version %d - compat profile\n", gl_ver);
    }
 
+   glGetIntegerv(GL_MAX_DRAW_BUFFERS, (GLint *) &vrend_state.max_draw_buffers);
+
    if (epoxy_has_gl_extension("GL_ARB_robustness")) {
       vrend_state.have_arb_robustness = true;
    } else if (gles && epoxy_has_gl_extension("GL_KHR_robustness")) {
@@ -4634,6 +4637,7 @@ struct vrend_context *vrend_create_context(int id, uint32_t nlen, const char *de
    grctx->shader_cfg.use_gles = vrend_state.use_gles;
    grctx->shader_cfg.use_core_profile = vrend_state.use_core_profile;
    grctx->shader_cfg.use_explicit_locations = vrend_state.use_explicit_locations;
+   grctx->shader_cfg.max_draw_buffers = vrend_state.max_draw_buffers;
    vrend_renderer_create_sub_ctx(grctx, 0);
    vrend_renderer_set_sub_ctx(grctx, 0);
 
@@ -7012,8 +7016,7 @@ static bool vrend_renderer_fill_caps_common(uint32_t set, UNUSED uint32_t versio
 
 
    /* Common limits for all backends. */
-   glGetIntegerv(GL_MAX_DRAW_BUFFERS, &max);
-   caps->v1.max_render_targets = max;
+   caps->v1.max_render_targets = vrend_state.max_draw_buffers;
 
    glGetIntegerv(GL_MAX_SAMPLES, &max);
    caps->v1.max_samples = max;

src/vrend_shader.c

@@ -1208,7 +1208,7 @@ static int emit_cbuf_writes(struct dump_ctx *ctx)
    int i;
    char *sret;
 
-   for (i = ctx->num_outputs; i < 8; i++) {
+   for (i = ctx->num_outputs; i < ctx->cfg->max_draw_buffers; i++) {
       snprintf(buf, 255, "fsout_c%d = fsout_c0;\n", i);
       sret = add_str_to_glsl_main(ctx, buf);
       if (!sret)
@@ -3494,7 +3494,7 @@ static char *emit_ios(struct dump_ctx *ctx, char *glsl_hdr)
    }
 
    if (ctx->write_all_cbufs) {
-      for (i = 0; i < 8; i++) {
+      for (i = 0; i < ctx->cfg->max_draw_buffers; i++) {
          if (ctx->cfg->use_gles)
             snprintf(buf, 255, "layout (location=%d) out vec4 fsout_c%d;\n", i, i);
          else

src/vrend_shader.h

@@ -102,6 +102,7 @@ struct vrend_shader_key {
 
 struct vrend_shader_cfg {
    int glsl_version;
+   int max_draw_buffers;
    bool use_gles;
    bool use_core_profile;
    bool use_explicit_locations;