mesa: Add draw time validation for advanced blending modes.

[mesa.git] / src / mesa / main / buffers.c

diff --git a/src/mesa/main/buffers.c b/src/mesa/main/buffers.c
index e8aedde877752540b669590cc2d1cbbb8d454b7c..86696b80c8799ec7b0fe1ea52341f8eb5d32907f 100644 (file)
--- a/src/mesa/main/buffers.c
+++ b/src/mesa/main/buffers.c
@@ -173,12 +173,22 @@ draw_buffer_enum_to_bitmask(const struct gl_context *ctx, GLenum buffer)
  * return -1 for an invalid buffer.
  */
 static gl_buffer_index
-read_buffer_enum_to_index(GLenum buffer)
+read_buffer_enum_to_index(const struct gl_context *ctx, GLenum buffer)
 {
    switch (buffer) {
       case GL_FRONT:
          return BUFFER_FRONT_LEFT;
       case GL_BACK:
+         if (_mesa_is_gles(ctx)) {
+            /* In draw_buffer_enum_to_bitmask, when GLES contexts draw to
+             * GL_BACK with a single-buffered configuration, we actually end
+             * up drawing to the sole front buffer in our internal
+             * representation.  For consistency, we must read from that
+             * front left buffer too.
+             */
+            if (!ctx->DrawBuffer->Visual.doubleBufferMode)
+               return BUFFER_FRONT_LEFT;
+         }
          return BUFFER_BACK_LEFT;
       case GL_RIGHT:
          return BUFFER_FRONT_RIGHT;
@@ -724,7 +734,7 @@ read_buffer(struct gl_context *ctx, struct gl_framebuffer *fb,
       if (_mesa_is_gles3(ctx) && !is_legal_es3_readbuffer_enum(buffer))
          srcBuffer = -1;
       else
-         srcBuffer = read_buffer_enum_to_index(buffer);
+         srcBuffer = read_buffer_enum_to_index(ctx, buffer);
 
       if (srcBuffer == -1) {
          _mesa_error(ctx, GL_INVALID_ENUM,