gstreamer/ext/gtk/gtkgstglwidget.c

/*
 * GStreamer
 * Copyright (C) 2015 Matthew Waters <matthew@centricular.com>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library 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
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
 * Boston, MA 02110-1301, USA.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <stdio.h>

#include "gtkgstglwidget.h"
#include <gst/video/video.h>

#if GST_GL_HAVE_WINDOW_X11 && defined (GDK_WINDOWING_X11)
#include <gdk/gdkx.h>
#include <gst/gl/x11/gstgldisplay_x11.h>
#include <gst/gl/x11/gstglcontext_glx.h>
#endif

#if GST_GL_HAVE_WINDOW_WAYLAND && defined (GDK_WINDOWING_WAYLAND)
#include <gdk/gdkwayland.h>
#include <gst/gl/wayland/gstgldisplay_wayland.h>
#endif

/**
 * SECTION:gtkgstglwidget
 * @short_description: a #GtkGLArea that renders GStreamer video #GstBuffers
 * @see_also: #GtkGLArea, #GstBuffer
 *
 * #GtkGstGLWidget is an #GtkWidget that renders GStreamer video buffers.
 */

#define GST_CAT_DEFAULT gtk_gst_gl_widget_debug
GST_DEBUG_CATEGORY_STATIC (GST_CAT_DEFAULT);

G_DEFINE_TYPE_WITH_CODE (GtkGstGLWidget, gtk_gst_gl_widget, GTK_TYPE_GL_AREA,
    GST_DEBUG_CATEGORY_INIT (GST_CAT_DEFAULT, "gtkgstglwidget", 0,
        "Gtk Gst GL Widget"););

#define GTK_GST_GL_WIDGET_GET_PRIVATE(obj) (G_TYPE_INSTANCE_GET_PRIVATE ((obj), \
    GTK_TYPE_GST_GL_WIDGET, GtkGstGLWidgetPrivate))

#define DEFAULT_FORCE_ASPECT_RATIO  TRUE
#define DEFAULT_PAR_N               0
#define DEFAULT_PAR_D               1
#define DEFAULT_IGNORE_ALPHA        TRUE

enum
{
  PROP_0,
  PROP_FORCE_ASPECT_RATIO,
  PROP_PIXEL_ASPECT_RATIO,
  PROP_IGNORE_ALPHA,
};

struct _GtkGstGLWidgetPrivate
{
  GMutex lock;

  /* properties */
  gboolean force_aspect_ratio;
  gint par_n, par_d;
  gboolean ignore_alpha;

  gint display_width;
  gint display_height;

  gboolean negotiated;
  GstBuffer *buffer;
  GstCaps *gl_caps;
  GstCaps *caps;
  GstVideoInfo v_info;
  gboolean new_buffer;

  gboolean initted;
  GstGLDisplay *display;
  GdkGLContext *gdk_context;
  GstGLContext *other_context;
  GstGLContext *context;
  GstGLUpload *upload;
  GstGLShader *shader;
  GLuint vao;
  GLuint vertex_buffer;
  GLint attr_position;
  GLint attr_texture;
  GLuint current_tex;
};

static void
gtk_gst_gl_widget_get_preferred_width (GtkWidget * widget, gint * min,
    gint * natural)
{
  GtkGstGLWidget *gst_widget = (GtkGstGLWidget *) widget;
  gint video_width = GST_VIDEO_INFO_WIDTH (&gst_widget->priv->v_info);

  if (!gst_widget->priv->negotiated)
    video_width = 10;

  if (min)
    *min = 1;
  if (natural)
    *natural = video_width;
}

static void
gtk_gst_gl_widget_get_preferred_height (GtkWidget * widget, gint * min,
    gint * natural)
{
  GtkGstGLWidget *gst_widget = (GtkGstGLWidget *) widget;
  gint video_height = GST_VIDEO_INFO_HEIGHT (&gst_widget->priv->v_info);

  if (!gst_widget->priv->negotiated)
    video_height = 10;

  if (min)
    *min = 1;
  if (natural)
    *natural = video_height;
}

static const GLfloat vertices[] = {
  1.0f, 1.0f, 0.0f, 1.0f, 0.0f,
  -1.0f, 1.0f, 0.0f, 0.0f, 0.0f,
  -1.0f, -1.0f, 0.0f, 0.0f, 1.0f,
  1.0f, -1.0f, 0.0f, 1.0f, 1.0f
};

static void
gtk_gst_gl_widget_bind_buffer (GtkGstGLWidget * gst_widget)
{
  const GstGLFuncs *gl = gst_widget->priv->context->gl_vtable;

  gl->BindBuffer (GL_ARRAY_BUFFER, gst_widget->priv->vertex_buffer);

  /* Load the vertex position */
  gl->VertexAttribPointer (gst_widget->priv->attr_position, 3, GL_FLOAT,
      GL_FALSE, 5 * sizeof (GLfloat), (void *) 0);

  /* Load the texture coordinate */
  gl->VertexAttribPointer (gst_widget->priv->attr_texture, 2, GL_FLOAT,
      GL_FALSE, 5 * sizeof (GLfloat), (void *) (3 * sizeof (GLfloat)));

  gl->EnableVertexAttribArray (gst_widget->priv->attr_position);
  gl->EnableVertexAttribArray (gst_widget->priv->attr_texture);
}

static void
gtk_gst_gl_widget_unbind_buffer (GtkGstGLWidget * gst_widget)
{
  const GstGLFuncs *gl = gst_widget->priv->context->gl_vtable;

  gl->BindBuffer (GL_ARRAY_BUFFER, 0);

  gl->DisableVertexAttribArray (gst_widget->priv->attr_position);
  gl->DisableVertexAttribArray (gst_widget->priv->attr_texture);
}

static void
gtk_gst_gl_widget_init_redisplay (GtkGstGLWidget * gst_widget)
{
  const GstGLFuncs *gl = gst_widget->priv->context->gl_vtable;

  gst_widget->priv->shader = gst_gl_shader_new (gst_widget->priv->context);

  gst_gl_shader_compile_with_default_vf_and_check
      (gst_widget->priv->shader, &gst_widget->priv->attr_position,
      &gst_widget->priv->attr_texture);

  if (gl->GenVertexArrays) {
    gl->GenVertexArrays (1, &gst_widget->priv->vao);
    gl->BindVertexArray (gst_widget->priv->vao);
  }

  gl->GenBuffers (1, &gst_widget->priv->vertex_buffer);
  gl->BindBuffer (GL_ARRAY_BUFFER, gst_widget->priv->vertex_buffer);
  gl->BufferData (GL_ARRAY_BUFFER, 4 * 5 * sizeof (GLfloat), vertices,
      GL_STATIC_DRAW);

  if (gl->GenVertexArrays) {
    gtk_gst_gl_widget_bind_buffer (gst_widget);
    gl->BindVertexArray (0);
  }

  gl->BindBuffer (GL_ARRAY_BUFFER, 0);

  gst_widget->priv->initted = TRUE;
}

static void
_redraw_texture (GtkGstGLWidget * gst_widget, guint tex)
{
  const GstGLFuncs *gl = gst_widget->priv->context->gl_vtable;
  GLushort indices[] = { 0, 1, 2, 0, 2, 3 };

  if (gst_widget->priv->force_aspect_ratio) {
    GstVideoRectangle src, dst, result;
    gint gtk_viewport[4];

    gl->ClearColor (0.0, 0.0, 0.0, 0.0);
    gl->Clear (GL_COLOR_BUFFER_BIT);

    gl->GetIntegerv (GL_VIEWPORT, gtk_viewport);

    src.x = 0;
    src.y = 0;
    src.w = gst_widget->priv->display_width;
    src.h = gst_widget->priv->display_height;

    dst.x = gtk_viewport[0];
    dst.y = gtk_viewport[1];
    dst.w = gtk_viewport[2];
    dst.h = gtk_viewport[3];

    gst_video_sink_center_rect (src, dst, &result, TRUE);

    gl->Viewport (result.x, result.y, result.w, result.h);
  }

  gst_gl_shader_use (gst_widget->priv->shader);

  if (gl->BindVertexArray)
    gl->BindVertexArray (gst_widget->priv->vao);
  else
    gtk_gst_gl_widget_bind_buffer (gst_widget);

  gl->ActiveTexture (GL_TEXTURE0);
  gl->BindTexture (GL_TEXTURE_2D, tex);
  gst_gl_shader_set_uniform_1i (gst_widget->priv->shader, "tex", 0);

  gl->DrawElements (GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, indices);

  if (gl->BindVertexArray)
    gl->BindVertexArray (0);
  else
    gtk_gst_gl_widget_unbind_buffer (gst_widget);

  gl->BindTexture (GL_TEXTURE_2D, 0);
}

static gboolean
gtk_gst_gl_widget_render (GtkGLArea * widget, GdkGLContext * context)
{
  GtkGstGLWidget *gst_widget = (GtkGstGLWidget *) widget;

  g_mutex_lock (&gst_widget->priv->lock);

  if (!gst_widget->priv->initted && gst_widget->priv->context)
    gtk_gst_gl_widget_init_redisplay (gst_widget);

  if (gst_widget->priv->initted && gst_widget->priv->negotiated
      && gst_widget->priv->buffer) {
    GST_DEBUG ("rendering buffer %p with gdk context %p",
        gst_widget->priv->buffer, context);

    gst_gl_context_activate (gst_widget->priv->other_context, TRUE);

    if (gst_widget->priv->new_buffer || gst_widget->priv->current_tex == 0) {
      GstVideoFrame gl_frame;
      GstGLSyncMeta *sync_meta;

      if (!gst_video_frame_map (&gl_frame, &gst_widget->priv->v_info,
              gst_widget->priv->buffer, GST_MAP_READ | GST_MAP_GL)) {
        goto error;
      }

      sync_meta = gst_buffer_get_gl_sync_meta (gst_widget->priv->buffer);
      if (sync_meta) {
        gst_gl_sync_meta_set_sync_point (sync_meta, gst_widget->priv->context);
        gst_gl_sync_meta_wait (sync_meta, gst_widget->priv->other_context);
      }

      gst_widget->priv->current_tex = *(guint *) gl_frame.data[0];

      gst_video_frame_unmap (&gl_frame);
    }

    _redraw_texture (gst_widget, gst_widget->priv->current_tex);
    gst_widget->priv->new_buffer = FALSE;
  } else {
  error:
    /* FIXME: nothing to display */
    glClearColor (0.0, 0.0, 0.0, 0.0);
    glClear (GL_COLOR_BUFFER_BIT);
  }

  if (gst_widget->priv->other_context)
    gst_gl_context_activate (gst_widget->priv->other_context, FALSE);

  g_mutex_unlock (&gst_widget->priv->lock);
  return FALSE;
}

typedef void (*ThreadFunc) (gpointer data);

struct invoke_context
{
  ThreadFunc func;
  gpointer data;
  GMutex lock;
  GCond cond;
  gboolean fired;
};

static gboolean
_invoke_func (struct invoke_context *info)
{
  g_mutex_lock (&info->lock);
  info->func (info->data);
  info->fired = TRUE;
  g_cond_signal (&info->cond);
  g_mutex_unlock (&info->lock);

  return G_SOURCE_REMOVE;
}

static void
_invoke_on_main (ThreadFunc func, gpointer data)
{
  GMainContext *main_context = g_main_context_default ();
  struct invoke_context info;

  g_mutex_init (&info.lock);
  g_cond_init (&info.cond);
  info.fired = FALSE;
  info.func = func;
  info.data = data;

  g_main_context_invoke (main_context, (GSourceFunc) _invoke_func, &info);

  g_mutex_lock (&info.lock);
  while (!info.fired)
    g_cond_wait (&info.cond, &info.lock);
  g_mutex_unlock (&info.lock);

  g_mutex_clear (&info.lock);
  g_cond_clear (&info.cond);
}

static void
_reset_gl (GtkGstGLWidget * gst_widget)
{
  const GstGLFuncs *gl = gst_widget->priv->other_context->gl_vtable;

  if (!gst_widget->priv->gdk_context)
    gst_widget->priv->gdk_context =
        gtk_gl_area_get_context (GTK_GL_AREA (gst_widget));
  if (gst_widget->priv->gdk_context == NULL)
    return;

  gdk_gl_context_make_current (gst_widget->priv->gdk_context);
  gst_gl_context_activate (gst_widget->priv->other_context, TRUE);

  if (gst_widget->priv->vao) {
    gl->DeleteVertexArrays (1, &gst_widget->priv->vao);
    gst_widget->priv->vao = 0;
  }

  if (gst_widget->priv->vertex_buffer) {
    gl->DeleteBuffers (1, &gst_widget->priv->vertex_buffer);
    gst_widget->priv->vertex_buffer = 0;
  }

  if (gst_widget->priv->upload) {
    gst_object_unref (gst_widget->priv->upload);
    gst_widget->priv->upload = NULL;
  }

  if (gst_widget->priv->shader) {
    gst_object_unref (gst_widget->priv->shader);
    gst_widget->priv->shader = NULL;
  }

  gst_gl_context_activate (gst_widget->priv->other_context, FALSE);

  gst_object_unref (gst_widget->priv->other_context);
  gst_widget->priv->other_context = NULL;

  gdk_gl_context_clear_current ();

  g_object_unref (gst_widget->priv->gdk_context);
  gst_widget->priv->gdk_context = NULL;
}

static void
_reset (GtkGstGLWidget * gst_widget)
{
  gst_buffer_replace (&gst_widget->priv->buffer, NULL);

  gst_caps_replace (&gst_widget->priv->caps, NULL);
  gst_caps_replace (&gst_widget->priv->gl_caps, NULL);

  gst_widget->priv->negotiated = FALSE;
  gst_widget->priv->initted = FALSE;
  gst_widget->priv->vao = 0;
  gst_widget->priv->vertex_buffer = 0;
  gst_widget->priv->attr_position = 0;
  gst_widget->priv->attr_texture = 0;
  gst_widget->priv->current_tex = 0;
  gst_widget->priv->new_buffer = TRUE;
}

static void
gtk_gst_gl_widget_finalize (GObject * object)
{
  GtkGstGLWidget *widget = GTK_GST_GL_WIDGET_CAST (object);

  g_mutex_clear (&widget->priv->lock);

  _reset (widget);

  if (widget->priv->other_context) {
    _invoke_on_main ((ThreadFunc) _reset_gl, widget);
  }

  if (widget->priv->context) {
    gst_object_unref (widget->priv->context);
    widget->priv->context = NULL;
  }

  if (widget->priv->display) {
    gst_object_unref (widget->priv->display);
    widget->priv->display = NULL;
  }

  G_OBJECT_CLASS (gtk_gst_gl_widget_parent_class)->finalize (object);
}

static void
gtk_gst_gl_widget_set_property (GObject * object, guint prop_id,
    const GValue * value, GParamSpec * pspec)
{
  GtkGstGLWidget *gtk_widget = GTK_GST_GL_WIDGET (object);

  switch (prop_id) {
    case PROP_FORCE_ASPECT_RATIO:
      gtk_widget->priv->force_aspect_ratio = g_value_get_boolean (value);
      break;
    case PROP_PIXEL_ASPECT_RATIO:
      gtk_widget->priv->par_n = gst_value_get_fraction_numerator (value);
      gtk_widget->priv->par_d = gst_value_get_fraction_denominator (value);
      break;
    case PROP_IGNORE_ALPHA:
      gtk_widget->priv->ignore_alpha = g_value_get_boolean (value);
      gtk_gl_area_set_has_alpha ((GtkGLArea *) gtk_widget,
          !gtk_widget->priv->ignore_alpha);
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
  }
}

static void
gtk_gst_gl_widget_get_property (GObject * object, guint prop_id, GValue * value,
    GParamSpec * pspec)
{
  GtkGstGLWidget *gtk_widget = GTK_GST_GL_WIDGET (object);

  switch (prop_id) {
    case PROP_FORCE_ASPECT_RATIO:
      g_value_set_boolean (value, gtk_widget->priv->force_aspect_ratio);
      break;
    case PROP_PIXEL_ASPECT_RATIO:
      gst_value_set_fraction (value, gtk_widget->priv->par_n,
          gtk_widget->priv->par_d);
      break;
    case PROP_IGNORE_ALPHA:
      g_value_set_boolean (value, gtk_widget->priv->ignore_alpha);
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
  }
}

static void
gtk_gst_gl_widget_class_init (GtkGstGLWidgetClass * klass)
{
  GObjectClass *gobject_klass = (GObjectClass *) klass;
  GtkWidgetClass *widget_klass = (GtkWidgetClass *) klass;
  GtkGLAreaClass *gl_widget_klass = (GtkGLAreaClass *) klass;

  g_type_class_add_private (klass, sizeof (GtkGstGLWidgetPrivate));

  gobject_klass->set_property = gtk_gst_gl_widget_set_property;
  gobject_klass->get_property = gtk_gst_gl_widget_get_property;
  gobject_klass->finalize = gtk_gst_gl_widget_finalize;

  g_object_class_install_property (gobject_klass, PROP_FORCE_ASPECT_RATIO,
      g_param_spec_boolean ("force-aspect-ratio",
          "Force aspect ratio",
          "When enabled, scaling will respect original aspect ratio",
          DEFAULT_FORCE_ASPECT_RATIO,
          G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));

  g_object_class_install_property (gobject_klass, PROP_PIXEL_ASPECT_RATIO,
      gst_param_spec_fraction ("pixel-aspect-ratio", "Pixel Aspect Ratio",
          "The pixel aspect ratio of the device", DEFAULT_PAR_N, DEFAULT_PAR_D,
          G_MAXINT, 1, 1, 1, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));

  g_object_class_install_property (gobject_klass, PROP_IGNORE_ALPHA,
      g_param_spec_boolean ("ignore-alpha", "Ignore Alpha",
          "When enabled, alpha will be ignored and converted to black",
          DEFAULT_IGNORE_ALPHA, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));

  gl_widget_klass->render = gtk_gst_gl_widget_render;

  widget_klass->get_preferred_width = gtk_gst_gl_widget_get_preferred_width;
  widget_klass->get_preferred_height = gtk_gst_gl_widget_get_preferred_height;
}

static void
gtk_gst_gl_widget_init (GtkGstGLWidget * widget)
{
  GdkDisplay *display;

  widget->priv = GTK_GST_GL_WIDGET_GET_PRIVATE (widget);

  widget->priv->force_aspect_ratio = DEFAULT_FORCE_ASPECT_RATIO;
  widget->priv->par_n = DEFAULT_PAR_N;
  widget->priv->par_d = DEFAULT_PAR_D;
  widget->priv->ignore_alpha = DEFAULT_IGNORE_ALPHA;

  g_mutex_init (&widget->priv->lock);

  display = gdk_display_get_default ();

#if GST_GL_HAVE_WINDOW_X11 && defined (GDK_WINDOWING_X11)
  if (GDK_IS_X11_DISPLAY (display))
    widget->priv->display = (GstGLDisplay *)
        gst_gl_display_x11_new_with_display (gdk_x11_display_get_xdisplay
        (display));
#endif
#if GST_GL_HAVE_WINDOW_WAYLAND && defined (GDK_WINDOWING_WAYLAND)
  if (GDK_IS_WAYLAND_DISPLAY (display)) {
    struct wl_display *wayland_display =
        gdk_wayland_display_get_wl_display (display);
    widget->priv->display = (GstGLDisplay *)
        gst_gl_display_wayland_new_with_display (wayland_display);
  }
#endif

  (void) display;

  if (!widget->priv->display)
    widget->priv->display = gst_gl_display_new ();

  gtk_gl_area_set_has_alpha ((GtkGLArea *) widget, !widget->priv->ignore_alpha);
}

GtkWidget *
gtk_gst_gl_widget_new (void)
{
  return (GtkWidget *) g_object_new (GTK_TYPE_GST_GL_WIDGET, NULL);
}

static gboolean
_queue_draw (GtkGstGLWidget * widget)
{
  gtk_widget_queue_draw (GTK_WIDGET (widget));

  return G_SOURCE_REMOVE;
}

void
gtk_gst_gl_widget_set_buffer (GtkGstGLWidget * widget, GstBuffer * buffer)
{
  GMainContext *main_context = g_main_context_default ();

  g_return_if_fail (GTK_IS_GST_GL_WIDGET (widget));
  g_return_if_fail (widget->priv->negotiated);

  g_mutex_lock (&widget->priv->lock);

  gst_buffer_replace (&widget->priv->buffer, buffer);
  widget->priv->new_buffer = TRUE;

  g_mutex_unlock (&widget->priv->lock);

  g_main_context_invoke (main_context, (GSourceFunc) _queue_draw, widget);
}

static void
_get_gl_context (GtkGstGLWidget * gst_widget)
{
  GstGLPlatform platform;
  GstGLAPI gl_api;
  guintptr gl_handle;

  gtk_widget_realize (GTK_WIDGET (gst_widget));

  if (gst_widget->priv->gdk_context)
    g_object_unref (gst_widget->priv->gdk_context);
  gst_widget->priv->gdk_context =
      gtk_gl_area_get_context (GTK_GL_AREA (gst_widget));
  if (gst_widget->priv->gdk_context == NULL) {
    g_assert_not_reached ();
    return;
  }

  g_object_ref (gst_widget->priv->gdk_context);

  gdk_gl_context_make_current (gst_widget->priv->gdk_context);

#if GST_GL_HAVE_WINDOW_X11 && defined (GDK_WINDOWING_X11)
  if (GST_IS_GL_DISPLAY_X11 (gst_widget->priv->display)) {
    platform = GST_GL_PLATFORM_GLX;
    gl_api = gst_gl_context_get_current_gl_api (NULL, NULL);
    gl_handle = gst_gl_context_get_current_gl_context (platform);
    if (gl_handle)
      gst_widget->priv->other_context =
          gst_gl_context_new_wrapped (gst_widget->priv->display, gl_handle,
          platform, gl_api);
  }
#endif
#if GST_GL_HAVE_WINDOW_WAYLAND && defined (GDK_WINDOWING_WAYLAND)
  if (GST_IS_GL_DISPLAY_WAYLAND (gst_widget->priv->display)) {
    platform = GST_GL_PLATFORM_EGL;
    gl_api = gst_gl_context_get_current_gl_api (NULL, NULL);
    gl_handle = gst_gl_context_get_current_gl_context (platform);
    if (gl_handle)
      gst_widget->priv->other_context =
          gst_gl_context_new_wrapped (gst_widget->priv->display, gl_handle,
          platform, gl_api);
  }
#endif

  (void) platform;
  (void) gl_api;
  (void) gl_handle;

  if (gst_widget->priv->other_context) {
    GError *error = NULL;

    gst_gl_context_activate (gst_widget->priv->other_context, TRUE);
    if (!gst_gl_context_fill_info (gst_widget->priv->other_context, &error)) {
      GST_ERROR ("failed to retreive gdk context info: %s", error->message);
      g_object_unref (gst_widget->priv->other_context);
      gst_widget->priv->other_context = NULL;
    } else {
      gst_gl_context_activate (gst_widget->priv->other_context, FALSE);
    }
  }
}

static gboolean
_queue_resize (GtkGstGLWidget * widget)
{
  gtk_widget_queue_resize (GTK_WIDGET (widget));

  return G_SOURCE_REMOVE;
}

gboolean
gtk_gst_gl_widget_init_winsys (GtkGstGLWidget * widget)
{
  g_return_val_if_fail (GTK_IS_GST_GL_WIDGET (widget), FALSE);

  g_mutex_lock (&widget->priv->lock);

  if (widget->priv->display && widget->priv->gdk_context
      && widget->priv->other_context) {
    g_mutex_unlock (&widget->priv->lock);
    return TRUE;
  }

  if (!widget->priv->other_context) {
    _invoke_on_main ((ThreadFunc) _get_gl_context, widget);
  }

  if (!GST_GL_IS_CONTEXT (widget->priv->other_context)) {
    g_mutex_unlock (&widget->priv->lock);
    return FALSE;
  }

  widget->priv->context = gst_gl_context_new (widget->priv->display);

  if (!widget->priv->context) {
    g_mutex_unlock (&widget->priv->lock);
    return FALSE;
  }

  gst_gl_context_create (widget->priv->context, widget->priv->other_context,
      NULL);

  g_mutex_unlock (&widget->priv->lock);
  return TRUE;
}

static gboolean
_calculate_par (GtkGstGLWidget * widget, GstVideoInfo * info)
{
  gboolean ok;
  gint width, height;
  gint par_n, par_d;
  gint display_par_n, display_par_d;
  guint display_ratio_num, display_ratio_den;

  width = GST_VIDEO_INFO_WIDTH (info);
  height = GST_VIDEO_INFO_HEIGHT (info);

  par_n = GST_VIDEO_INFO_PAR_N (info);
  par_d = GST_VIDEO_INFO_PAR_D (info);

  if (!par_n)
    par_n = 1;

  /* get display's PAR */
  if (widget->priv->par_n != 0 && widget->priv->par_d != 0) {
    display_par_n = widget->priv->par_n;
    display_par_d = widget->priv->par_d;
  } else {
    display_par_n = 1;
    display_par_d = 1;
  }

  ok = gst_video_calculate_display_ratio (&display_ratio_num,
      &display_ratio_den, width, height, par_n, par_d, display_par_n,
      display_par_d);

  if (!ok)
    return FALSE;

  GST_LOG ("PAR: %u/%u DAR:%u/%u", par_n, par_d, display_par_n, display_par_d);

  if (height % display_ratio_den == 0) {
    GST_DEBUG ("keeping video height");
    widget->priv->display_width = (guint)
        gst_util_uint64_scale_int (height, display_ratio_num,
        display_ratio_den);
    widget->priv->display_height = height;
  } else if (width % display_ratio_num == 0) {
    GST_DEBUG ("keeping video width");
    widget->priv->display_width = width;
    widget->priv->display_height = (guint)
        gst_util_uint64_scale_int (width, display_ratio_den, display_ratio_num);
  } else {
    GST_DEBUG ("approximating while keeping video height");
    widget->priv->display_width = (guint)
        gst_util_uint64_scale_int (height, display_ratio_num,
        display_ratio_den);
    widget->priv->display_height = height;
  }
  GST_DEBUG ("scaling to %dx%d", widget->priv->display_width,
      widget->priv->display_height);

  return TRUE;
}

gboolean
gtk_gst_gl_widget_set_caps (GtkGstGLWidget * widget, GstCaps * caps)
{
  GMainContext *main_context = g_main_context_default ();
  GstVideoInfo v_info;

  g_return_val_if_fail (GTK_IS_GST_GL_WIDGET (widget), FALSE);
  g_return_val_if_fail (GST_IS_CAPS (caps), FALSE);
  g_return_val_if_fail (gst_caps_is_fixed (caps), FALSE);

  if (widget->priv->caps && gst_caps_is_equal_fixed (widget->priv->caps, caps))
    return TRUE;

  if (!gst_video_info_from_caps (&v_info, caps))
    return FALSE;

  g_mutex_lock (&widget->priv->lock);

  _reset (widget);

  gst_caps_replace (&widget->priv->caps, caps);

  widget->priv->gl_caps = gst_video_info_to_caps (&v_info);
  gst_caps_set_features (widget->priv->gl_caps, 0,
      gst_caps_features_from_string (GST_CAPS_FEATURE_MEMORY_GL_MEMORY));

  if (!_calculate_par (widget, &v_info)) {
    g_mutex_unlock (&widget->priv->lock);
    return FALSE;
  }

  widget->priv->v_info = v_info;
  widget->priv->negotiated = TRUE;

  g_mutex_unlock (&widget->priv->lock);

  g_main_context_invoke (main_context, (GSourceFunc) _queue_resize, widget);

  return TRUE;
}

GstGLContext *
gtk_gst_gl_widget_get_gtk_context (GtkGstGLWidget * gst_widget)
{
  if (!gst_widget->priv->other_context)
    return NULL;

  return gst_object_ref (gst_widget->priv->other_context);
}

GstGLContext *
gtk_gst_gl_widget_get_context (GtkGstGLWidget * gst_widget)
{
  if (!gst_widget->priv->context)
    return NULL;

  return gst_object_ref (gst_widget->priv->context);
}

GstGLDisplay *
gtk_gst_gl_widget_get_display (GtkGstGLWidget * gst_widget)
{
  if (!gst_widget->priv->display)
    return NULL;

  return gst_object_ref (gst_widget->priv->display);
}