Add conf vars to trick Cogl to think extensions are disabled

This adds two new configuration environment variables:

COGL_DISABLE_GL_EXTENSIONS and
COGL_OVERRIDE_GL_VERSION

The variables can also be set in the cogl.conf file using the same
names.

The first one is a list of GL extension names separated by commas.
When set Cogl will assume any extension listed here is not available
by removing it from the string returned from
glGetString(GL_EXTENSIONS). If the string is set in both the config
file and the environment variable then the union of the two lists will
be used.

The second overrides the value returned from glGetString(GL_VERSION).
If the string is set in both places the version from the environment
variable will take priority.

These are sometimes useful for debugging Cogl to test the various
combinations of extensions. It could also be useful to work around
driver bugs where an extension is badly supported and it would be
better not to use it.

The variables in cogl-config that just set a global char * variable
have been put together in an array instead of having a separate blob
of code for each one in order to make it simpler to add new variables.

Reviewed-by: Robert Bragg <robert@linux.intel.com>

(cherry picked from commit ec69c2dc576c78664e0b73879365cb7414ecf441)

cogl/cogl-config-private.h

@@ -33,5 +33,7 @@ _cogl_config_read (void);
 
 extern char *_cogl_config_driver;
 extern char *_cogl_config_renderer;
+extern char *_cogl_config_disable_gl_extensions;
+extern char *_cogl_config_override_gl_version;
 
 #endif /* __COGL_CONFIG_PRIVATE_H */

cogl/cogl-config.c

@@ -35,11 +35,27 @@
 
 char *_cogl_config_driver;
 char *_cogl_config_renderer;
+char *_cogl_config_disable_gl_extensions;
+char *_cogl_config_override_gl_version;
+
+/* Array of config options that just set a global string */
+static const struct
+{
+  const char *conf_name;
+  char **variable;
+} cogl_config_string_options[] =
+  {
+    { "COGL_DRIVER", &_cogl_config_driver },
+    { "COGL_RENDERER", &_cogl_config_renderer },
+    { "COGL_DISABLE_GL_EXTENSIONS", &_cogl_config_disable_gl_extensions },
+    { "COGL_OVERRIDE_GL_VERSION", &_cogl_config_override_gl_version }
+  };
 
 static void
 _cogl_config_process (GKeyFile *key_file)
 {
   char *value;
+  int i;
 
   value = g_key_file_get_string (key_file, "global", "COGL_DEBUG", NULL);
   if (value)
@@ -59,22 +75,17 @@ _cogl_config_process (GKeyFile *key_file)
       g_free (value);
     }
 
-  value = g_key_file_get_string (key_file, "global", "COGL_DRIVER", NULL);
+  for (i = 0; i < G_N_ELEMENTS (cogl_config_string_options); i++)
+    {
+      const char *conf_name = cogl_config_string_options[i].conf_name;
+      char **variable = cogl_config_string_options[i].variable;
+
+      value = g_key_file_get_string (key_file, "global", conf_name, NULL);
       if (value)
         {
-      if (_cogl_config_driver)
+          g_free (*variable);
-        g_free (_cogl_config_driver);
+          *variable = value;
-
-      _cogl_config_driver = value;
         }
-
-  value = g_key_file_get_string (key_file, "global", "COGL_RENDERER", NULL);
-  if (value)
-    {
-      if (_cogl_config_renderer)
-        g_free (_cogl_config_renderer);
-
-      _cogl_config_renderer = value;
     }
 }
 

cogl/cogl-context-private.h

@@ -353,4 +353,10 @@ void
 _cogl_context_set_current_modelview_entry (CoglContext *context,
                                            CoglMatrixEntry *entry);
 
+const char *
+_cogl_context_get_gl_extensions (CoglContext *context);
+
+const char *
+_cogl_context_get_gl_version (CoglContext *context);
+
 #endif /* __COGL_CONTEXT_PRIVATE_H */

cogl/cogl-context.c

@@ -48,6 +48,7 @@
 #include "cogl-attribute-private.h"
 #include "cogl1-context.h"
 #include "cogl-gpu-info-private.h"
+#include "cogl-config-private.h"
 
 #include <string.h>
 
@@ -617,3 +618,107 @@ _cogl_context_set_current_modelview_entry (CoglContext *context,
     _cogl_matrix_entry_unref (context->current_modelview_entry);
   context->current_modelview_entry = entry;
 }
+
+const char *
+_cogl_context_get_gl_extensions (CoglContext *context)
+{
+  const char *env_disabled_extensions;
+
+  if ((env_disabled_extensions = g_getenv ("COGL_DISABLE_GL_EXTENSIONS"))
+      || _cogl_config_disable_gl_extensions)
+    {
+      static CoglUserDataKey extensions_key;
+      const char *enabled_extensions;
+      char **split_enabled_extensions;
+      char **split_env_disabled_extensions;
+      char **split_conf_disabled_extensions;
+      char **e;
+      GString *result;
+
+      /* We need to return a const string so we'll attach the results
+       * to the CoglContext to avoid leaking the generated string.
+       * This string is only used rarely so we are using
+       * cogl_object_set_user_data instead of adding an explicit
+       * member to CoglContext to avoid making the struct bigger */
+
+      enabled_extensions =
+        cogl_object_get_user_data (COGL_OBJECT (context), &extensions_key);
+      if (enabled_extensions)
+        return enabled_extensions;
+
+      enabled_extensions = (const char *) context->glGetString (GL_EXTENSIONS);
+
+      split_enabled_extensions = g_strsplit (enabled_extensions,
+                                             " ",
+                                             0 /* no max tokens */);
+
+      if (env_disabled_extensions)
+        split_env_disabled_extensions =
+          g_strsplit (env_disabled_extensions,
+                      ",",
+                      0 /* no max tokens */);
+      else
+        split_env_disabled_extensions = NULL;
+
+      if (_cogl_config_disable_gl_extensions)
+        split_conf_disabled_extensions =
+          g_strsplit (_cogl_config_disable_gl_extensions,
+                      ",",
+                      0 /* no max tokens */);
+      else
+        split_conf_disabled_extensions = NULL;
+
+      result = g_string_new (NULL);
+
+      for (e = split_enabled_extensions; *e; e++)
+        {
+          char **d;
+
+          if (split_env_disabled_extensions)
+            for (d = split_env_disabled_extensions; *d; d++)
+              if (!strcmp (*e, *d))
+                goto disabled;
+          if (split_conf_disabled_extensions)
+            for (d = split_conf_disabled_extensions; *d; d++)
+              if (!strcmp (*e, *d))
+                goto disabled;
+
+          if (result->len > 0)
+            g_string_append_c (result, ' ');
+          g_string_append (result, *e);
+
+        disabled:
+          continue;
+        }
+
+      enabled_extensions = g_string_free (result, FALSE);
+
+      g_strfreev (split_enabled_extensions);
+      if (split_env_disabled_extensions)
+        g_strfreev (split_env_disabled_extensions);
+      if (split_conf_disabled_extensions)
+        g_strfreev (split_conf_disabled_extensions);
+
+      cogl_object_set_user_data (COGL_OBJECT (context),
+                                 &extensions_key,
+                                 (void *) enabled_extensions,
+                                 (CoglUserDataDestroyCallback) g_free);
+
+      return enabled_extensions;
+    }
+  else
+    return (const char *) context->glGetString (GL_EXTENSIONS);
+}
+
+const char *
+_cogl_context_get_gl_version (CoglContext *context)
+{
+  const char *version_override;
+
+  if ((version_override = g_getenv ("COGL_OVERRIDE_GL_VERSION")))
+    return version_override;
+  else if (_cogl_config_override_gl_version)
+    return _cogl_config_override_gl_version;
+  else
+    return (const char *) context->glGetString (GL_VERSION);
+}

cogl/cogl-debug.c

@@ -182,6 +182,16 @@ _cogl_parse_debug_string (const char *value,
       OPT (IGNORED, "ignored", "verbose", "ignored", \
            N_("Enables all non-behavioural debug options"));
 #undef OPT
+
+      g_printerr ("\n"
+                  "%28s\n"
+                  " COGL_DISABLE_GL_EXTENSIONS: %s\n"
+                  "   COGL_OVERRIDE_GL_VERSION: %s\n",
+                  _("Additional environment variables:"),
+                  _("Comma-separated list of GL extensions to pretend are "
+                    "disabled"),
+                  _("Override the GL version that Cogl will assume the driver "
+                    "supports"));
       exit (1);
     }
   else

cogl/cogl-gpu-info.c

@@ -482,7 +482,7 @@ _cogl_gpu_info_init (CoglContext *ctx,
   int i;
 
   strings.renderer_string = (const char *) ctx->glGetString (GL_RENDERER);
-  strings.version_string = (const char *) ctx->glGetString (GL_VERSION);
+  strings.version_string = _cogl_context_get_gl_version (ctx);
   strings.vendor_string = (const char *) ctx->glGetString (GL_VENDOR);
 
   /* Determine the driver package */

cogl/driver/gl/cogl-gl.c

@@ -228,7 +228,7 @@ _cogl_get_gl_version (CoglContext *ctx,
   int major = 0, minor = 0;
 
   /* Get the OpenGL version number */
-  if ((version_string = (const char *) ctx->glGetString (GL_VERSION)) == NULL)
+  if ((version_string = _cogl_context_get_gl_version (ctx)) == NULL)
     return FALSE;
 
   /* Extract the major number */
@@ -276,7 +276,7 @@ check_gl_version (CoglContext *ctx,
   if (COGL_CHECK_GL_VERSION (major, minor, 1, 3))
     return TRUE;
 
-  gl_extensions = (const char*) ctx->glGetString (GL_EXTENSIONS);
+  gl_extensions = _cogl_context_get_gl_extensions (ctx);
 
   /* OpenGL 1.2 is only supported if we have the multitexturing
      extension */
@@ -335,8 +335,8 @@ _cogl_driver_update_features (CoglContext *ctx,
              "  GL_EXTENSIONS: %s",
              ctx->glGetString (GL_VENDOR),
              ctx->glGetString (GL_RENDERER),
-             ctx->glGetString (GL_VERSION),
+             _cogl_context_get_gl_version (ctx),
-             ctx->glGetString (GL_EXTENSIONS));
+             _cogl_context_get_gl_extensions (ctx));
 
   _cogl_get_gl_version (ctx, &gl_major, &gl_minor);
 
@@ -352,7 +352,7 @@ _cogl_driver_update_features (CoglContext *ctx,
   if (COGL_CHECK_GL_VERSION (gl_major, gl_minor, 1, 4))
     COGL_FLAGS_SET (ctx->features, COGL_FEATURE_ID_MIRRORED_REPEAT, TRUE);
 
-  gl_extensions = (const char *)ctx->glGetString (GL_EXTENSIONS);
+  gl_extensions = _cogl_context_get_gl_extensions (ctx);
 
   _cogl_feature_check_ext_functions (ctx,
                                      gl_major,

cogl/driver/gles/cogl-gles.c

@@ -182,12 +182,12 @@ _cogl_driver_update_features (CoglContext *context,
              "  GL_EXTENSIONS: %s",
              context->glGetString (GL_VENDOR),
              context->glGetString (GL_RENDERER),
-             context->glGetString (GL_VERSION),
+             _cogl_context_get_gl_version (context),
-             context->glGetString (GL_EXTENSIONS));
+             _cogl_context_get_gl_extensions (context));
 
   _cogl_gpu_info_init (context, &context->gpu);
 
-  gl_extensions = (const char*) context->glGetString (GL_EXTENSIONS);
+  gl_extensions = _cogl_context_get_gl_extensions (context);
 
   _cogl_feature_check_ext_functions (context,
                                      -1 /* GL major version */,

cogl/winsys/cogl-winsys-wgl.c

@@ -580,7 +580,7 @@ get_wgl_extensions_string (HDC dc)
      extensions isn't supported then we can at least fake it to
      support the swap control extension */
   if (_cogl_check_extension ("WGL_EXT_swap_control",
-                             (char *) ctx->glGetString (GL_EXTENSIONS)))
+                             _cogl_context_get_gl_extensions (ctx)))
     return "WGL_EXT_swap_control";
 
   return NULL;