meta: Respect the driver's maximum number of draw buffers

Commit c1c1cf5f9 added infrastructure for saving and restoring draw
buffer state.  However, it universially used MAX_DRAW_BUFFERS, but many
drivers support far fewer than that at limit.  For example, the radeon
and i915 drivers only support 1.  Using MAX_DRAW_BUFFERS causes meta to
generate GL errors.

Signed-off-by: Ian Romanick <[email protected]>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=80115
Reviewed-by: Kenneth Graunke <[email protected]>
Tested-by: Kenneth Graunke <[email protected]> [on Broadwell]
Tested-by: [email protected]
Cc: "10.2" <[email protected]>

1 files changed, 2 insertions, 2 deletions

diff --git a/src/mesa/drivers/common/meta.c b/src/mesa/drivers/common/meta.c
index dc9cce5cf23..1a2e4532058 100644
--- a/src/mesa/drivers/common/meta.c
+++ b/src/mesa/drivers/common/meta.c
@@ -801,7 +801,7 @@ _mesa_meta_begin(struct gl_context *ctx, GLbitfield state)
       int buf, real_color_buffers = 0;
       memset(save->ColorDrawBuffers, 0, sizeof(save->ColorDrawBuffers));
 
-      for (buf = 0; buf < MAX_DRAW_BUFFERS; buf++) {
+      for (buf = 0; buf < ctx->Const.MaxDrawBuffers; buf++) {
          int buf_index = ctx->DrawBuffer->_ColorDrawBufferIndexes[buf];
          if (buf_index == -1)
             continue;
@@ -1213,7 +1213,7 @@ _mesa_meta_end(struct gl_context *ctx)
       _mesa_BindRenderbuffer(GL_RENDERBUFFER, save->RenderbufferName);
 
    if (state & MESA_META_DRAW_BUFFERS) {
-      _mesa_DrawBuffers(MAX_DRAW_BUFFERS, save->ColorDrawBuffers);
+      _mesa_DrawBuffers(ctx->Const.MaxDrawBuffers, save->ColorDrawBuffers);
    }
 
    ctx->Meta->SaveStackDepth--;