- const GLenum srcFormat = _mesa_get_format_base_format(src->Format);
- const GLenum dstLogicalFormat = _mesa_get_format_base_format(dst->TexFormat);
+ /* Get logical base formats for the src and dest.
+ * That is, use the user-requested formats and not the actual, device-
+ * chosen formats.
+ * For example, the user may have requested an A8 texture but the
+ * driver may actually be using an RGBA texture format. When we
+ * copy/blit to that texture, we only want to copy the Alpha channel
+ * and not the RGB channels.
+ *
+ * Similarly, when the src FBO was created an RGB format may have been
+ * requested but the driver actually chose an RGBA format. In that case,
+ * we don't want to copy the undefined Alpha channel to the dest texture
+ * (it should be 1.0).
+ */
+ const GLenum srcFormat = _mesa_base_fbo_format(ctx, src->InternalFormat);
+ const GLenum dstFormat = _mesa_base_tex_format(ctx, dst->InternalFormat);