[cogl/fosdem-2012: 8/16] Add a utility to make a GSource out of a CoglContext

[Robert Bragg <rbragg src gnome org>]

commit 88a7afa87ae13e3ad9f7b2290c08eaf60efa3233
Author: Neil Roberts <neil linux intel com>
Date:   Mon Dec 19 14:38:28 2011 +0000

    Add a utility to make a GSource out of a CoglContext
    
    The GSource is created using cogl_gsource_new which takes a pointer to
    a CoglContext. The source calls cogl_context_begin_idle() in its
    prepare function and cogl_context_dispatch() in its dispatch
    function. The poll FDs on the source are updated according to what
    Cogl reports.
    
    The header is only included and the source only compiled if Cogl is
    configured with GLib support.

 cogl/Makefile.am    |    7 ++
 cogl/cogl-gsource.c |  193 +++++++++++++++++++++++++++++++++++++++++++++++++++
 cogl/cogl-gsource.h |   56 +++++++++++++++
 cogl/cogl.h         |    3 +
 4 files changed, 259 insertions(+), 0 deletions(-)
---
diff --git a/cogl/Makefile.am b/cogl/Makefile.am
index 6da9764..db1d978 100644
--- a/cogl/Makefile.am
+++ b/cogl/Makefile.am
@@ -346,6 +346,13 @@ cogl_sources_c = \
 	$(srcdir)/gl-prototypes/cogl-glsl-functions.h	\
 	$(NULL)
 
+if USE_GLIB
+cogl_public_h += \
+	$(srcdir)/cogl-gsource.h
+cogl_sources_c += \
+	$(srcdir)/cogl-gsource.c
+endif
+
 if SUPPORT_XLIB
 cogl_public_h += \
 	$(srcdir)/cogl-clutter-xlib.h \
diff --git a/cogl/cogl-gsource.c b/cogl/cogl-gsource.c
new file mode 100644
index 0000000..4af0aac
--- /dev/null
+++ b/cogl/cogl-gsource.c
@@ -0,0 +1,193 @@
+/*
+ * Cogl
+ *
+ * An object oriented GL/GLES Abstraction/Utility Layer
+ *
+ * Copyright (C) 2011 Intel Corporation.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ *
+ *
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include "cogl-gsource.h"
+
+typedef struct _CoglGSource
+{
+  GSource source;
+
+  CoglContext *context;
+
+  GArray *poll_fds;
+
+  gint64 expiration_time;
+} CoglGSource;
+
+static gboolean
+cogl_gsource_poll_fds_changed (CoglGSource *cogl_source,
+                               const CoglPollFD *poll_fds,
+                               int n_poll_fds)
+{
+  int i;
+
+  if (cogl_source->poll_fds->len != n_poll_fds)
+    return TRUE;
+
+  for (i = 0; i < n_poll_fds; i++)
+    if (g_array_index (cogl_source->poll_fds, CoglPollFD, i).fd !=
+        poll_fds[i].fd)
+      return TRUE;
+
+  return FALSE;
+}
+
+static gboolean
+cogl_gsource_prepare (GSource *source, int *timeout)
+{
+  CoglGSource *cogl_source = (CoglGSource *) source;
+  CoglPollFD *poll_fds;
+  int n_poll_fds;
+  gint64 cogl_timeout;
+  int i;
+
+  cogl_context_begin_idle (cogl_source->context,
+                           &poll_fds,
+                           &n_poll_fds,
+                           &cogl_timeout);
+
+  /* We have to be careful not to call g_source_add/remove_poll unless
+     the FDs have changed because it will cause the main loop to
+     immediately wake up. If we call it every time the source is
+     prepared it will effectively never go idle. */
+  if (cogl_gsource_poll_fds_changed (cogl_source, poll_fds, n_poll_fds))
+    {
+      /* Remove any existing polls before adding the new ones */
+      for (i = 0; i < cogl_source->poll_fds->len; i++)
+        {
+          GPollFD *poll_fd = &g_array_index (cogl_source->poll_fds, GPollFD, i);
+          g_source_remove_poll (source, poll_fd);
+        }
+
+      g_array_set_size (cogl_source->poll_fds, n_poll_fds);
+
+      for (i = 0; i < n_poll_fds; i++)
+        {
+          GPollFD *poll_fd = &g_array_index (cogl_source->poll_fds, GPollFD, i);
+          poll_fd->fd = poll_fds[i].fd;
+          g_source_add_poll (source, poll_fd);
+        }
+    }
+
+  /* Update the events */
+  for (i = 0; i < n_poll_fds; i++)
+    {
+      GPollFD *poll_fd = &g_array_index (cogl_source->poll_fds, GPollFD, i);
+      poll_fd->events = poll_fds[i].events;
+      poll_fd->revents = 0;
+    }
+
+  if (cogl_timeout == -1)
+    {
+      *timeout = -1;
+      cogl_source->expiration_time = -1;
+    }
+  else
+    {
+      /* Round up to ensure that we don't try again too early */
+      *timeout = (cogl_timeout + 999) / 1000;
+      cogl_source->expiration_time = (g_source_get_time (source) +
+                                      cogl_timeout);
+    }
+
+  return *timeout == 0;
+}
+
+static gboolean
+cogl_gsource_check (GSource *source)
+{
+  CoglGSource *cogl_source = (CoglGSource *) source;
+  int i;
+
+  if (cogl_source->expiration_time >= 0 &&
+      g_source_get_time (source) >= cogl_source->expiration_time)
+    return TRUE;
+
+  for (i = 0; i < cogl_source->poll_fds->len; i++)
+    {
+      GPollFD *poll_fd = &g_array_index (cogl_source->poll_fds, GPollFD, i);
+      if (poll_fd->revents != 0)
+        return TRUE;
+    }
+
+  return FALSE;
+}
+
+static gboolean
+cogl_gsource_dispatch (GSource *source,
+                       GSourceFunc callback,
+                       void *user_data)
+{
+  CoglGSource *cogl_source = (CoglGSource *) source;
+  CoglPollFD *poll_fds =
+    (CoglPollFD *) &g_array_index (cogl_source->poll_fds, GPollFD, 0);
+
+  cogl_context_dispatch (cogl_source->context,
+                         poll_fds,
+                         cogl_source->poll_fds->len);
+
+  return TRUE;
+}
+
+static void
+cogl_gsource_finalize (GSource *source)
+{
+  CoglGSource *cogl_source = (CoglGSource *) source;
+
+  cogl_object_unref (cogl_source->context);
+
+  g_array_free (cogl_source->poll_fds, TRUE);
+}
+
+static GSourceFuncs
+cogl_gsource_funcs =
+  {
+    cogl_gsource_prepare,
+    cogl_gsource_check,
+    cogl_gsource_dispatch,
+    cogl_gsource_finalize
+  };
+
+GSource *
+cogl_gsource_new (CoglContext *context,
+                  int priority)
+{
+  GSource *source;
+  CoglGSource *cogl_source;
+
+  source = g_source_new (&cogl_gsource_funcs,
+                         sizeof (CoglGSource));
+  cogl_source = (CoglGSource *) source;
+
+  cogl_source->context = cogl_object_ref (context);
+  cogl_source->poll_fds = g_array_new (FALSE, FALSE, sizeof (GPollFD));
+
+  if (priority != G_PRIORITY_DEFAULT)
+    g_source_set_priority (source, priority);
+
+  return source;
+}
diff --git a/cogl/cogl-gsource.h b/cogl/cogl-gsource.h
new file mode 100644
index 0000000..37879d9
--- /dev/null
+++ b/cogl/cogl-gsource.h
@@ -0,0 +1,56 @@
+/*
+ * Cogl
+ *
+ * An object oriented GL/GLES Abstraction/Utility Layer
+ *
+ * Copyright (C) 2011 Intel Corporation.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ *
+ *
+ */
+
+/**
+ * SECTION:cogl-gsource
+ * @short_description: A convenience utility for GLib to integrate
+ *                     Cogl's main loop
+ *
+ * #CoglGSource provides a convenient way to integrate the mainloop
+ * functions of #CoglContext into the GLib main loop. This provides a
+ * replacement for having to call cogl_context_begin_idle() and
+ * cogl_context_dispatch().
+ *
+ * Stability: unstable
+ * Since: 1.10
+ */
+
+#if !defined(__COGL_H_INSIDE__) && !defined(CLUTTER_COMPILATION)
+#error "Only <cogl/cogl.h> can be included directly."
+#endif
+
+#ifndef __COGL_GSOURCE_H__
+#define __COGL_GSOURCE_H__
+
+#include <glib.h>
+#include <cogl/cogl-context.h>
+
+G_BEGIN_DECLS
+
+GSource *
+cogl_gsource_new (CoglContext *context,
+                  int priority);
+
+G_END_DECLS
+
+#endif /* __COGL_GSOURCE_H__ */
diff --git a/cogl/cogl.h b/cogl/cogl.h
index ec2ccc7..248399e 100644
--- a/cogl/cogl.h
+++ b/cogl/cogl.h
@@ -103,6 +103,9 @@ typedef struct _CoglFramebuffer CoglFramebuffer;
 #if COGL_HAS_WIN32_SUPPORT
 #include <cogl/cogl-win32-renderer.h>
 #endif
+#ifdef COGL_HAS_GLIB_SUPPORT
+#include <cogl/cogl-gsource.h>
+#endif
 /* XXX: This will definitly go away once all the Clutter winsys
  * code has been migrated down into Cogl! */
 #include <cogl/cogl-clutter.h>