main: Allow for the possibility of GL 3.2 without ARB_geometry_shader4.

Previously, we assumed that the only way Mesa would expose geometry
shader support was via the ARB_geometry_shader4 extension.  But this
extension has some extra complications over GL 3.2 (interactions with
compatibility-only features, and link-time initialization of the
constant gl_VerticesIn).  So we want to allow for the possibility of
supporting GL 3.2 (with GLSL 1.50 style geometry shaders) even if
ctx->Extensions.ARB_geometry_shader4 is false.

This patch adds a new function, _mesa_has_geometry_shaders(), which
returns true if either ARB_geometry_shader4 is supported or the GL
version is at least 3.2 desktop.  Since compute_version() only enables
GL 3.2 functionality when GLSL 1.50 support is present, a sufficient
way for a back-end to advertise geometry shader support is to set
ctx->Const.GLSLVersion >= 150.

v2: Remove unnecessary ctx->Const.GeometryShaders150 constant.

Reviewed-by: Ian Romanick <[email protected]>
Reviewed-by: Kenneth Graunke <[email protected]>

6 files changed, 16 insertions, 7 deletions

diff --git a/src/mesa/main/api_validate.c b/src/mesa/main/api_validate.c
index 7ab8e305ddd..8a2ec7b293a 100644
--- a/src/mesa/main/api_validate.c
+++ b/src/mesa/main/api_validate.c
@@ -222,7 +222,7 @@ _mesa_is_valid_prim_mode(struct gl_context *ctx, GLenum mode)
    case GL_LINE_STRIP_ADJACENCY:
    case GL_TRIANGLES_ADJACENCY:
    case GL_TRIANGLE_STRIP_ADJACENCY:
-      return _mesa_is_desktop_gl(ctx) && ctx->Extensions.ARB_geometry_shader4;
+      return _mesa_has_geometry_shaders(ctx);
    default:
       return false;
    }
diff --git a/src/mesa/main/context.h b/src/mesa/main/context.h
index 8872be1f4f5..792ab4cd55e 100644
--- a/src/mesa/main/context.h
+++ b/src/mesa/main/context.h
@@ -312,6 +312,17 @@ _mesa_is_gles3(const struct gl_context *ctx)
 }
 
 
+/**
+ * Checks if the context supports geometry shaders.
+ */
+static inline GLboolean
+_mesa_has_geometry_shaders(const struct gl_context *ctx)
+{
+   return _mesa_is_desktop_gl(ctx) &&
+      (ctx->Version >= 32 || ctx->Extensions.ARB_geometry_shader4);
+}
+
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/src/mesa/main/fbobject.c b/src/mesa/main/fbobject.c
index bf7e85c8826..c6e6dd5c553 100644
--- a/src/mesa/main/fbobject.c
+++ b/src/mesa/main/fbobject.c
@@ -2476,7 +2476,7 @@ _mesa_FramebufferTexture(GLenum target, GLenum attachment,
 {
    GET_CURRENT_CONTEXT(ctx);
 
-   if (ctx->Version >= 32 || ctx->Extensions.ARB_geometry_shader4) {
+   if (_mesa_has_geometry_shaders(ctx)) {
       framebuffer_texture(ctx, "Layer", target, attachment, 0, texture,
                           level, 0, GL_TRUE);
    } else {
diff --git a/src/mesa/main/get.c b/src/mesa/main/get.c
index 0b33fa49b5a..09b008a072e 100644
--- a/src/mesa/main/get.c
+++ b/src/mesa/main/get.c
@@ -989,7 +989,7 @@ check_extra(struct gl_context *ctx, const char *func, const struct value_desc *d
       case EXTRA_EXT_UBO_GS4:
          api_check = GL_TRUE;
          api_found = (ctx->Extensions.ARB_uniform_buffer_object &&
-                      ctx->Extensions.ARB_geometry_shader4);
+                      _mesa_has_geometry_shaders(ctx));
          break;
       case EXTRA_END:
 	 break;
diff --git a/src/mesa/main/shaderapi.c b/src/mesa/main/shaderapi.c
index c3011f58f0e..3f9402c598c 100644
--- a/src/mesa/main/shaderapi.c
+++ b/src/mesa/main/shaderapi.c
@@ -179,7 +179,7 @@ validate_shader_target(const struct gl_context *ctx, GLenum type)
    case GL_VERTEX_SHADER:
       return ctx->Extensions.ARB_vertex_shader;
    case GL_GEOMETRY_SHADER_ARB:
-      return _mesa_is_desktop_gl(ctx) && ctx->Extensions.ARB_geometry_shader4;
+      return _mesa_has_geometry_shaders(ctx);
    default:
       return false;
    }
@@ -478,8 +478,7 @@ get_programiv(struct gl_context *ctx, GLuint program, GLenum pname, GLint *param
 
    /* Are geometry shaders available in this context?
     */
-   const bool has_gs =
-      _mesa_is_desktop_gl(ctx) && ctx->Extensions.ARB_geometry_shader4;
+   const bool has_gs = _mesa_has_geometry_shaders(ctx);
 
    /* Are uniform buffer objects available in this context?
     */
diff --git a/src/mesa/main/version.c b/src/mesa/main/version.c
index ab9b14c026e..55411faf8c5 100644
--- a/src/mesa/main/version.c
+++ b/src/mesa/main/version.c
@@ -262,7 +262,6 @@ compute_version(struct gl_context *ctx)
                               ctx->Extensions.ARB_depth_clamp &&
                               ctx->Extensions.ARB_draw_elements_base_vertex &&
                               ctx->Extensions.ARB_fragment_coord_conventions &&
-                              ctx->Extensions.ARB_geometry_shader4 &&
                               ctx->Extensions.EXT_provoking_vertex &&
                               ctx->Extensions.ARB_seamless_cube_map &&
                               ctx->Extensions.ARB_sync &&