[RFC PATCH] glx: Try to reduce the number of GLX visuals

[Thomas Hellstrom]

Don't create GLX visuals that would be viewed as identical as an already
existing GLX visual by glXChooseVisual. Multiple fbconfigs may point to
the same GLX visual.

Signed-off-by: Thomas Hellstrom <thellstrom at vmware.com>
---
 glx/glxscreens.c | 67 +++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 66 insertions(+), 1 deletion(-)

diff --git a/glx/glxscreens.c b/glx/glxscreens.c
index 99bf6dd..f07850d 100644
--- a/glx/glxscreens.c
+++ b/glx/glxscreens.c
@@ -158,6 +158,55 @@ static const char GLServerExtensions[] =
     "GL_SGIX_shadow_ambient "
     "GL_SUN_slice_accum ";
 
+/**
+ * Are visuals equal in terms of glXChooseVisual?
+ *
+ * Some fields of the __GLXconfig structure are, according to the
+ * GLX spec not part of the visual structure meaning that their
+ * corresponding attribute can not be used in glXChooseVisual, nor
+ * using glXGetConfig. Eliminating those fields, check whether
+ * two __GLXconfigs would be considered equal.
+ */
+static Bool
+glxVisualsEqual(const __GLXconfig *c1, const __GLXconfig *c2) {
+    /* GLX 1.4 spec */
+    return c1->rgbBits == c2->rgbBits &&
+	c1->indexBits == c2->indexBits &&
+	c1->level == c2->level &&
+	(c1->renderType & GLX_RGBA_BIT) ==
+	(c2->renderType & GLX_RGBA_BIT) &&
+	c1->doubleBufferMode == c2->doubleBufferMode &&
+	c1->stereoMode == c2->stereoMode &&
+	c1->numAuxBuffers == c2->numAuxBuffers &&
+	c1->redBits == c2->redBits &&
+	c1->greenBits == c2->greenBits &&
+	c1->blueBits == c2->blueBits &&
+	c1->alphaBits == c2->alphaBits &&
+	c1->depthBits == c2->depthBits &&
+	c1->stencilBits == c2->stencilBits &&
+	c1->accumRedBits == c2->accumRedBits &&
+	c1->accumGreenBits == c2->accumGreenBits &&
+	c1->accumBlueBits == c2->accumBlueBits &&
+	c1->accumAlphaBits == c2->accumAlphaBits &&
+	c1->sampleBuffers == c2->sampleBuffers &&
+	c1->samples == c2->samples &&
+	c1->visualType == c2->visualType &&
+	/* EXT_visual_rating, but NOT GLX 1.4 */
+	c1->visualRating == c2->visualRating &&
+	/* EXT_visual_info, but NOT GLX 1.4 */
+	c1->transparentPixel == c2->transparentPixel &&
+	c1->transparentRed == c2->transparentRed &&
+	c1->transparentGreen == c2->transparentGreen &&
+	c1->transparentBlue == c2->transparentBlue &&
+	c1->transparentAlpha == c2->transparentAlpha &&
+	c1->transparentIndex == c2->transparentIndex &&
+	/* SGIX_visual_select_group */
+	c1->visualSelectGroup == c2->visualSelectGroup &&
+	/* ARB_framebuffer_sRGB */
+	c1->sRGBCapable == c2->sRGBCapable;
+}
+
+
 static Bool
 glxCloseScreen(ScreenPtr pScreen)
 {
@@ -358,9 +407,10 @@ __glXScreenInit(__GLXscreen * pGlxScreen, ScreenPtr pScreen)
      * an existing, appropriate visual.
      */
     for (config = pGlxScreen->fbconfigs; config != NULL; config = config->next) {
-        int depth;
+        int depth, vis;
 
         VisualPtr visual;
+        const __GLXconfig *config2;
 
         if (config->visualID != 0)
             continue;
@@ -393,6 +443,21 @@ __glXScreenInit(__GLXscreen * pGlxScreen, ScreenPtr pScreen)
             continue;
         }
 
+        /* We don't need to create a new visual if we already have an
+         * identical visual. Instead we will have multiple fbconfigs
+         * pointing to the same GLX visual.
+         */
+        for (vis = 0; vis < pGlxScreen->numVisuals; ++vis) {
+            config2 = pGlxScreen->visuals[vis];
+            if (glxVisualsEqual(config, config2)) {
+                config->visualID = config2->visualID;
+                break;
+            }
+        }
+
+        if (config->visualID != 0)
+            continue;
+
         /* Create a new X visual for our FBconfig. */
         visual = AddScreenVisuals(pScreen, 1, depth);
         if (visual == NULL)
-- 
2.9.5