[mutter/wip/carlosg/drop-caps: 1/7] cogl: Defer EGLContext creation to a separate thread

[Carlos Garnacho <carlosg src gnome org>]

commit 0bab932c4e2ba8f41d98dc04be2d8391e58ebae2
Author: Carlos Garnacho <carlosg gnome org>
Date:   Fri Nov 8 14:33:52 2019 +0100

    cogl: Defer EGLContext creation to a separate thread
    
    This is rather pointless and complex at the moment, but will pay
    off as we can then spawn this thread early enough that it keeps
    capabilities to create high priority contexts.
    
    https://gitlab.gnome.org/GNOME/mutter/merge_requests/923

 cogl/cogl/cogl-egl.h               |   9 ++
 cogl/cogl/winsys/cogl-winsys-egl.c | 228 ++++++++++++++++++++++++++++++++++++-
 2 files changed, 233 insertions(+), 4 deletions(-)
---
diff --git a/cogl/cogl/cogl-egl.h b/cogl/cogl/cogl-egl.h
index b9c163126..85e33e959 100644
--- a/cogl/cogl/cogl-egl.h
+++ b/cogl/cogl/cogl-egl.h
@@ -79,6 +79,15 @@ G_BEGIN_DECLS
 EGLDisplay
 cogl_egl_context_get_egl_display (CoglContext *context);
 
+gboolean cogl_egl_init_thread (void);
+
+EGLContext
+cogl_egl_create_context (EGLDisplay     display,
+                         EGLConfig      config,
+                         EGLContext     shared_context,
+                         const EGLint  *attrib_list,
+                         GError       **error);
+
 G_END_DECLS
 
 /* The gobject introspection scanner seems to parse public headers in
diff --git a/cogl/cogl/winsys/cogl-winsys-egl.c b/cogl/cogl/winsys/cogl-winsys-egl.c
index 5dd106d1b..9c591055f 100644
--- a/cogl/cogl/winsys/cogl-winsys-egl.c
+++ b/cogl/cogl/winsys/cogl-winsys-egl.c
@@ -110,6 +110,21 @@ static const CoglFeatureData winsys_feature_data[] =
 #include "winsys/cogl-winsys-egl-feature-functions.h"
   };
 
+static GMainContext *egl_thread_context = NULL;
+
+typedef struct _CreateEGLContextData
+{
+  EGLDisplay display;
+  EGLConfig config;
+  EGLContext shared_context;
+  const EGLint *attrib_list;
+  EGLContext context;
+  GError *error;
+  GMutex mutex;
+  GCond cond;
+  gboolean finished;
+} CreateEGLContextData;
+
 static GCallback
 _cogl_winsys_renderer_get_proc_address (CoglRenderer *renderer,
                                         const char *name,
@@ -386,10 +401,11 @@ try_create_context (CoglDisplay *display,
 
   attribs[i++] = EGL_NONE;
 
-  egl_display->egl_context = eglCreateContext (edpy,
-                                               config,
-                                               EGL_NO_CONTEXT,
-                                               attribs);
+  egl_display->egl_context = cogl_egl_create_context (edpy,
+                                                      config,
+                                                      EGL_NO_CONTEXT,
+                                                      attribs,
+                                                      NULL);
 
   if (egl_display->egl_context == EGL_NO_CONTEXT)
     {
@@ -965,3 +981,207 @@ cogl_egl_context_get_egl_display (CoglContext *context)
 
   return egl_renderer->edpy;
 }
+
+static gpointer
+init_egl_context_thread (gpointer data)
+{
+  GMainContext *main_context = data;
+  GMainLoop *main_loop = g_main_loop_new (main_context, FALSE);
+
+  g_main_loop_run (main_loop);
+  return NULL;
+}
+
+gboolean
+cogl_egl_init_thread (void)
+{
+  g_autoptr (GMainContext) main_context = NULL;
+  g_autoptr (GThread) thread = NULL;
+  g_autoptr (GError) error = NULL;
+
+  if (egl_thread_context != NULL)
+    return TRUE;
+
+  main_context = g_main_context_new ();
+  thread = g_thread_try_new ("EGL context generator thread",
+                             init_egl_context_thread,
+                             main_context, &error);
+  if (!thread)
+    {
+      g_main_context_unref (main_context);
+      g_warning ("Failed to create EGL Context generator thread: %s",
+                 error->message);
+
+      return FALSE;
+    }
+
+  egl_thread_context = g_steal_pointer (&main_context);
+
+  return TRUE;
+}
+
+static CreateEGLContextData *
+create_egl_context_data_new (EGLDisplay    display,
+                             EGLConfig     config,
+                             EGLContext    shared_context,
+                             const EGLint *attrib_list)
+{
+  CreateEGLContextData *data;
+
+  data = g_new0 (CreateEGLContextData, 1);
+  data->display = display;
+  data->config = config;
+  data->shared_context = shared_context;
+  data->attrib_list = attrib_list;
+  data->context = EGL_NO_CONTEXT;
+  g_mutex_init (&data->mutex);
+  g_cond_init (&data->cond);
+
+  return data;
+}
+
+static const char *
+get_egl_error_str (EGLint error_number)
+{
+  switch (error_number)
+    {
+    case EGL_SUCCESS:
+      return "The last function succeeded without error.";
+      break;
+    case EGL_NOT_INITIALIZED:
+      return "EGL is not initialized, or could not be initialized, for the specified EGL display 
connection.";
+      break;
+    case EGL_BAD_ACCESS:
+      return "EGL cannot access a requested resource (for example a context is bound in another thread).";
+      break;
+    case EGL_BAD_ALLOC:
+      return "EGL failed to allocate resources for the requested operation.";
+      break;
+    case EGL_BAD_ATTRIBUTE:
+      return "An unrecognized attribute or attribute value was passed in the attribute list.";
+      break;
+    case EGL_BAD_CONTEXT:
+      return "An EGLContext argument does not name a valid EGL rendering context.";
+      break;
+    case EGL_BAD_CONFIG:
+      return "An EGLConfig argument does not name a valid EGL frame buffer configuration.";
+      break;
+    case EGL_BAD_CURRENT_SURFACE:
+      return "The current surface of the calling thread is a window, pixel buffer or pixmap that is no 
longer valid.";
+      break;
+    case EGL_BAD_DISPLAY:
+      return "An EGLDisplay argument does not name a valid EGL display connection.";
+      break;
+    case EGL_BAD_SURFACE:
+      return "An EGLSurface argument does not name a valid surface (window, pixel buffer or pixmap) 
configured for GL rendering.";
+      break;
+    case EGL_BAD_MATCH:
+      return "Arguments are inconsistent (for example, a valid context requires buffers not supplied by a 
valid surface).";
+      break;
+    case EGL_BAD_PARAMETER:
+      return "One or more argument values are invalid.";
+      break;
+    case EGL_BAD_NATIVE_PIXMAP:
+      return "A NativePixmapType argument does not refer to a valid native pixmap.";
+      break;
+    case EGL_BAD_NATIVE_WINDOW:
+      return "A NativeWindowType argument does not refer to a valid native window.";
+      break;
+    case EGL_CONTEXT_LOST:
+      return "A power management event has occurred. The application must destroy all contexts and 
reinitialise OpenGL ES state and objects to continue rendering. ";
+      break;
+    case EGL_BAD_STREAM_KHR:
+      return "An EGLStreamKHR argument does not name a valid EGL stream.";
+      break;
+    case EGL_BAD_STATE_KHR:
+      return "An EGLStreamKHR argument is not in a valid state";
+      break;
+    case EGL_BAD_DEVICE_EXT:
+      return "An EGLDeviceEXT argument does not name a valid EGL device.";
+      break;
+    case EGL_BAD_OUTPUT_LAYER_EXT:
+      return "An EGLOutputLayerEXT argument does not name a valid EGL output layer.";
+    default:
+      return "Unknown error";
+      break;
+    }
+}
+
+static void
+set_egl_error (GError **error)
+{
+  EGLint error_number;
+  const char *error_str;
+
+  if (!error)
+    return;
+
+  error_number = eglGetError ();
+  error_str = get_egl_error_str (error_number);
+  g_set_error_literal (error, COGL_WINSYS_ERROR,
+                       COGL_WINSYS_ERROR_CREATE_CONTEXT,
+                       error_str);
+}
+
+/* Executed in the EGL context generator thread */
+static gboolean
+create_context_in_thread (gpointer user_data)
+{
+  CreateEGLContextData *data = user_data;
+
+  g_mutex_lock (&data->mutex);
+  data->context = eglCreateContext (data->display,
+                                    data->config,
+                                    data->shared_context,
+                                    data->attrib_list);
+  if (data->context == EGL_NO_CONTEXT)
+    set_egl_error (&data->error);
+  data->finished = TRUE;
+  g_cond_signal (&data->cond);
+  g_mutex_unlock (&data->mutex);
+
+  return G_SOURCE_REMOVE;
+}
+
+EGLContext
+cogl_egl_create_context (EGLDisplay     display,
+                         EGLConfig      config,
+                         EGLContext     shared_context,
+                         const EGLint  *attrib_list,
+                         GError       **error)
+{
+  CreateEGLContextData *data;
+  EGLContext context;
+  GSource *source;
+
+  if (!cogl_egl_init_thread ())
+    {
+      g_set_error_literal (error, COGL_WINSYS_ERROR,
+                           COGL_WINSYS_ERROR_CREATE_CONTEXT,
+                           "EGL thread initialization failed");
+      return EGL_NO_CONTEXT;
+    }
+
+  data = create_egl_context_data_new (display, config,
+                                      shared_context, attrib_list);
+  g_mutex_lock (&data->mutex);
+
+  source = g_idle_source_new ();
+  g_source_set_callback (source, create_context_in_thread,
+                         data, NULL);
+  g_source_attach (source, egl_thread_context);
+  g_source_unref (source);
+
+  while (!data->finished)
+    g_cond_wait (&data->cond, &data->mutex);
+
+  context = data->context;
+  if (data->error)
+    g_propagate_error (error, data->error);
+
+  g_mutex_unlock (&data->mutex);
+  g_clear_error (&data->error);
+  g_free (data);
+
+  return context;
+}