mesa: add explicit enable for EXT_float_blend, and error condition

If EXT_float_blend is not supported, error out on blending of FP32
attachments in an ES2 context.

Signed-off-by: Ilia Mirkin <[email protected]>
Reviewed-by: Tapani Pälli <[email protected]>
Reviewed-by: Jason Ekstrand <[email protected]>

1 files changed, 19 insertions, 0 deletions

diff --git a/src/mesa/main/draw_validate.c b/src/mesa/main/draw_validate.c
index b715a27f8b7..779cd1c12c7 100644
--- a/src/mesa/main/draw_validate.c
+++ b/src/mesa/main/draw_validate.c
@@ -304,6 +304,25 @@ check_valid_to_render(struct gl_context *ctx, const char *function)
                      "%s(tess ctrl shader is missing)", function);
          return false;
       }
+
+      /* From GL_EXT_color_buffer_float:
+       *
+       *     "Blending applies only if the color buffer has a fixed-point or
+       *     or floating-point format. If the color buffer has an integer
+       *     format, proceed to the next operation.  Furthermore, an
+       *     INVALID_OPERATION error is generated by DrawArrays and the other
+       *     drawing commands defined in section 2.8.3 (10.5 in ES 3.1) if
+       *     blending is enabled (see below) and any draw buffer has 32-bit
+       *     floating-point format components."
+       *
+       * However GL_EXT_float_blend removes this text.
+       */
+      if (!ctx->Extensions.EXT_float_blend &&
+          (ctx->DrawBuffer->_FP32Buffers & ctx->Color.BlendEnabled)) {
+         _mesa_error(ctx, GL_INVALID_OPERATION,
+                     "%s(32-bit float output + blending)", function);
+         return false;
+      }
       break;
 
    case API_OPENGL_CORE: