glx: Implement GLX_EXT_no_config_context (v2)

Only enabled for the DRI backends at the moment. In principle WGL/CGL
could support this - it's sort of implied by GL 3.0 support - but in
practice their implementations back GLX drawables with native drawables
(and not anonymous FBOs), so they would need either a corresponding
window system binding extension or significant implementation work.

v2: Require that the two screen numbers match, per v4 of spec.

Khronos: https://github.com/KhronosGroup/OpenGL-Registry/pull/102
Signed-off-by: Adam Jackson <ajax@redhat.com>
Reviewed-by: Eric Anholt <eric@anholt.net>

6 files changed, 35 insertions, 14 deletions

diff --git a/glx/createcontext.c b/glx/createcontext.c
index 1216f9412..76316db67 100644
--- a/glx/createcontext.c
+++ b/glx/createcontext.c
@@ -93,7 +93,7 @@ __glXDisp_CreateContextAttribsARB(__GLXclientState * cl, GLbyte * pc)
     __GLXcontext *ctx = NULL;
     __GLXcontext *shareCtx = NULL;
     __GLXscreen *glxScreen;
-    __GLXconfig *config;
+    __GLXconfig *config = NULL;
     int err;
 
     /* The GLX_ARB_create_context_robustness spec says:
@@ -136,8 +136,10 @@ __glXDisp_CreateContextAttribsARB(__GLXclientState * cl, GLbyte * pc)
     if (!validGlxScreen(client, req->screen, &glxScreen, &err))
         return __glXError(GLXBadFBConfig);
 
-    if (!validGlxFBConfig(client, glxScreen, req->fbconfig, &config, &err))
-        return __glXError(GLXBadFBConfig);
+    if (req->fbconfig) {
+        if (!validGlxFBConfig(client, glxScreen, req->fbconfig, &config, &err))
+            return __glXError(GLXBadFBConfig);
+    }
 
     /* Validate the context with which the new context should share resources.
      */
@@ -182,6 +184,9 @@ __glXDisp_CreateContextAttribsARB(__GLXclientState * cl, GLbyte * pc)
             break;
 
         case GLX_RENDER_TYPE:
+            /* Not valid for GLX_EXT_no_config_context */
+            if (!req->fbconfig)
+                return BadValue;
             render_type = attribs[2 * i + 1];
             break;
 
@@ -206,6 +211,15 @@ __glXDisp_CreateContextAttribsARB(__GLXclientState * cl, GLbyte * pc)
             break;
 #endif
 
+        case GLX_SCREEN:
+            /* Only valid for GLX_EXT_no_config_context */
+            if (req->fbconfig)
+                return BadValue;
+            /* Must match the value in the request header */
+            if (attribs[2 * i + 1] != req->screen)
+                return BadValue;
+            break;
+
         default:
             if (!req->isDirect)
                 return BadValue;
diff --git a/glx/extension_string.c b/glx/extension_string.c
index d1da4815c..102f9dd42 100644
--- a/glx/extension_string.c
+++ b/glx/extension_string.c
@@ -86,6 +86,7 @@ static const struct extension_info known_glx_extensions[] = {
     { GLX(EXT_framebuffer_sRGB),        VER(0,0), N, },
     { GLX(EXT_import_context),          VER(0,0), Y, },
     { GLX(EXT_libglvnd),                VER(0,0), N, },
+    { GLX(EXT_no_config_context),       VER(0,0), N, },
     { GLX(EXT_stereo_tree),             VER(0,0), N, },
     { GLX(EXT_texture_from_pixmap),     VER(0,0), N, },
     { GLX(EXT_visual_info),             VER(0,0), Y, },
diff --git a/glx/extension_string.h b/glx/extension_string.h
index a10d7108a..f049f5840 100644
--- a/glx/extension_string.h
+++ b/glx/extension_string.h
@@ -48,6 +48,7 @@ enum {
     EXT_fbconfig_packed_float_bit,
     EXT_import_context_bit,
     EXT_libglvnd_bit,
+    EXT_no_config_context_bit,
     EXT_stereo_tree_bit,
     EXT_texture_from_pixmap_bit,
     EXT_visual_info_bit,
diff --git a/glx/glxcmds.c b/glx/glxcmds.c
index 9c005c717..2ebf4a350 100644
--- a/glx/glxcmds.c
+++ b/glx/glxcmds.c
@@ -1770,13 +1770,13 @@ DoQueryContext(__GLXclientState * cl, GLXContextID gcId)
     sendBuf[0] = GLX_SHARE_CONTEXT_EXT;
     sendBuf[1] = (int) (ctx->share_id);
     sendBuf[2] = GLX_VISUAL_ID_EXT;
-    sendBuf[3] = (int) (ctx->config->visualID);
+    sendBuf[3] = (int) (ctx->config ? ctx->config->visualID : 0);
     sendBuf[4] = GLX_SCREEN_EXT;
     sendBuf[5] = (int) (ctx->pGlxScreen->pScreen->myNum);
     sendBuf[6] = GLX_FBCONFIG_ID;
-    sendBuf[7] = (int) (ctx->config->fbconfigID);
+    sendBuf[7] = (int) (ctx->config ? ctx->config->fbconfigID : 0);
     sendBuf[8] = GLX_RENDER_TYPE;
-    sendBuf[9] = (int) (ctx->config->renderType);
+    sendBuf[9] = (int) (ctx->config ? ctx->config->renderType : GLX_DONT_CARE);
 
     if (client->swapped) {
         int length = reply.length;
diff --git a/glx/glxdri2.c b/glx/glxdri2.c
index 2c542bfdf..2e24b56e6 100644
--- a/glx/glxdri2.c
+++ b/glx/glxdri2.c
@@ -441,6 +441,7 @@ create_driver_context(__GLXDRIcontext * context,
                       int *error)
 {
     context->driContext = NULL;
+    const __DRIconfig *driConfig = config ? config->driConfig : NULL;
 
     if (screen->dri2->base.version >= 3) {
         uint32_t ctx_attribs[4 * 2];
@@ -483,10 +484,8 @@ create_driver_context(__GLXDRIcontext * context,
         }
 
         context->driContext =
-            (*screen->dri2->createContextAttribs)(screen->driScreen,
-                                                  api,
-                                                  config->driConfig,
-                                                  driShare,
+            (*screen->dri2->createContextAttribs)(screen->driScreen, api,
+                                                  driConfig, driShare,
                                                   num_ctx_attribs / 2,
                                                   ctx_attribs,
                                                   &dri_err,
@@ -522,8 +521,7 @@ create_driver_context(__GLXDRIcontext * context,
     }
 
     context->driContext =
-        (*screen->dri2->createNewContext) (screen->driScreen,
-                                           config->driConfig,
+        (*screen->dri2->createNewContext) (screen->driScreen, driConfig,
                                            driShare, context);
 }
 
@@ -831,6 +829,9 @@ initializeExtensions(__GLXscreen * screen)
     __glXEnableExtension(screen->glx_enable_bits, "GLX_MESA_copy_sub_buffer");
     LogMessage(X_INFO, "AIGLX: enabled GLX_MESA_copy_sub_buffer\n");
 
+    __glXEnableExtension(screen->glx_enable_bits, "GLX_EXT_no_config_context");
+    LogMessage(X_INFO, "AIGLX: enabled GLX_EXT_no_config_context\n");
+
     if (dri->dri2->base.version >= 3) {
         __glXEnableExtension(screen->glx_enable_bits,
                              "GLX_ARB_create_context");
diff --git a/glx/glxdriswrast.c b/glx/glxdriswrast.c
index c000d6cfb..adc97df93 100644
--- a/glx/glxdriswrast.c
+++ b/glx/glxdriswrast.c
@@ -211,6 +211,7 @@ __glXDRIscreenCreateContext(__GLXscreen * baseScreen,
     __GLXDRIscreen *screen = (__GLXDRIscreen *) baseScreen;
     __GLXDRIcontext *context, *shareContext;
     __GLXDRIconfig *config = (__GLXDRIconfig *) glxConfig;
+    const __DRIconfig *driConfig = config ? config->driConfig : NULL;
     const __DRIcoreExtension *core = screen->core;
     __DRIcontext *driShare;
 
@@ -240,8 +241,8 @@ __glXDRIscreenCreateContext(__GLXscreen * baseScreen,
     context->base.releaseTexImage = __glXDRIreleaseTexImage;
 
     context->driContext =
-        (*core->createNewContext) (screen->driScreen,
-                                   config->driConfig, driShare, context);
+        (*core->createNewContext) (screen->driScreen, driConfig, driShare,
+                                   context);
 
     return &context->base;
 }
@@ -352,6 +353,9 @@ initializeExtensions(__GLXscreen * screen)
     __glXEnableExtension(screen->glx_enable_bits, "GLX_MESA_copy_sub_buffer");
     LogMessage(X_INFO, "IGLX: enabled GLX_MESA_copy_sub_buffer\n");
 
+    __glXEnableExtension(screen->glx_enable_bits, "GLX_EXT_no_config_context");
+    LogMessage(X_INFO, "IGLX: enabled GLX_EXT_no_config_context\n");
+
     if (dri->swrast->base.version >= 3) {
         __glXEnableExtension(screen->glx_enable_bits,
                              "GLX_ARB_create_context");