[PATCH] dri3: Don't enable the DRI3 extension unless some screen supports it

[Keith Packard]

There's no reason to advertise this extension unless one of the
hardware drivers actually supports it. Not listing it means it's
slightly easier for users to tell what's going on.

On the other hand, not listing it means we may have applications that
only check for the extension and not for appropriate per-screen
support. I don't think that's a real risk as DRI3 is only useful for
systems with deep knowledge of the hardware.

Signed-off-by: Keith Packard <keithp at keithp.com>
---
 dri3/dri3.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/dri3/dri3.c b/dri3/dri3.c
index 76e07b4..385862a 100644
--- a/dri3/dri3.c
+++ b/dri3/dri3.c
@@ -30,6 +30,8 @@ int dri3_request;
 DevPrivateKeyRec dri3_screen_private_key;
 DevPrivateKeyRec dri3_window_private_key;
 
+static int dri3_screen_generation;
+
 static Bool
 dri3_close_screen(ScreenPtr screen)
 {
@@ -44,6 +46,8 @@ dri3_close_screen(ScreenPtr screen)
 Bool
 dri3_screen_init(ScreenPtr screen, dri3_screen_info_ptr info)
 {
+    dri3_screen_generation = serverGeneration;
+
     if (!dixRegisterPrivateKey(&dri3_screen_private_key, PRIVATE_SCREEN, 0))
         return FALSE;
 
@@ -68,6 +72,12 @@ dri3_extension_init(void)
     ExtensionEntry *extension;
     int i;
 
+    /* If no screens support DRI3, there's no point offering the
+     * extension at all
+     */
+    if (dri3_screen_generation != serverGeneration)
+        return;
+
 #ifdef PANORAMIX
     if (!noPanoramiXExtension)
         return;
-- 
1.8.5.3