[PATCH] glamor: Use GL_ARB_debug_output to log GL errors.

[Eric Anholt]

This should help people debugging when glamor does something stupid on
their driver.

Signed-off-by: Eric Anholt <eric at anholt.net>
---
 glamor/glamor.c | 41 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/glamor/glamor.c b/glamor/glamor.c
index 295f415..317f451 100644
--- a/glamor/glamor.c
+++ b/glamor/glamor.c
@@ -322,6 +322,45 @@ glamor_check_instruction_count(int gl_version)
     return TRUE;
 }
 
+static void GLAPIENTRY
+glamor_debug_output_callback(GLenum source,
+                             GLenum type,
+                             GLuint id,
+                             GLenum severity,
+                             GLsizei length,
+                             const GLchar *message,
+                             const void *userParam)
+{
+    ScreenPtr screen = (void *)userParam;
+    LogMessageVerb(X_ERROR, 0, "glamor%d: GL error: %*s\n",
+               screen->myNum, length, message);
+}
+
+/**
+ * Configures GL_ARB_debug_output to give us immediate callbacks when
+ * GL errors occur, so that we can log them.
+ */
+static void
+glamor_setup_debug_output(ScreenPtr screen)
+{
+    if (!epoxy_has_gl_extension("GL_ARB_debug_output"))
+        return;
+
+    glEnable(GL_DEBUG_OUTPUT_SYNCHRONOUS);
+    glDebugMessageControl(GL_DEBUG_SOURCE_API,
+                          GL_DEBUG_TYPE_ERROR,
+                          GL_DONT_CARE,
+                          0, NULL, GL_TRUE);
+    glDebugMessageCallback(glamor_debug_output_callback,
+                           screen);
+
+    /* If KHR_debug is present, all debug output is disabled by
+     * default on non-debug contexts.
+     */
+    if (epoxy_has_gl_extension("GL_KHR_debug"))
+        glEnable(GL_DEBUG_OUTPUT);
+}
+
 /** Set up glamor for an already-configured GL context. */
 Bool
 glamor_init(ScreenPtr screen, unsigned int flags)
@@ -468,6 +507,8 @@ glamor_init(ScreenPtr screen, unsigned int flags)
         epoxy_gl_version() >= 30 ||
         epoxy_has_gl_extension("GL_NV_pack_subimage");
 
+    glamor_setup_debug_output(screen);
+
     glGetIntegerv(GL_MAX_RENDERBUFFER_SIZE, &glamor_priv->max_fbo_size);
     glGetIntegerv(GL_MAX_TEXTURE_SIZE, &glamor_priv->max_fbo_size);
     glGetIntegerv(GL_MAX_VIEWPORT_DIMS, max_viewport_size);
-- 
2.1.4