cairo-overlay-example/cairo.c

/* GStreamer
 * Copyright (C) 2011 Jon Nordby <jononor@gmail.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.
 */

/*
 * Example showing usage of the cairooverlay element
 */

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

#include <cairo-gobject.h>
#include <cairo.h>

#include <glib.h>

static gboolean on_message(GstBus *bus, GstMessage *message,
                           gpointer user_data) {
  GMainLoop *loop = (GMainLoop *)user_data;

  switch (GST_MESSAGE_TYPE(message)) {
  case GST_MESSAGE_ERROR: {
    GError *err = NULL;
    gchar *debug;

    gst_message_parse_error(message, &err, &debug);
    g_critical("Got ERROR: %s (%s)", err->message, GST_STR_NULL(debug));
    g_main_loop_quit(loop);
    break;
  }
  case GST_MESSAGE_WARNING: {
    GError *err = NULL;
    gchar *debug;

    gst_message_parse_warning(message, &err, &debug);
    g_warning("Got WARNING: %s (%s)", err->message, GST_STR_NULL(debug));
    g_main_loop_quit(loop);
    break;
  }
  case GST_MESSAGE_EOS:
    g_main_loop_quit(loop);
    break;
  default:
    break;
  }

  return TRUE;
}

/* Datastructure to share the state we are interested in between
 * prepare and render function. */
typedef struct {
  gboolean valid;
  GstVideoInfo vinfo;
} CairoOverlayState;

/* Store the information from the caps that we are interested in. */
static void prepare_overlay(GstElement *overlay, GstCaps *caps,
                            gpointer user_data) {
  CairoOverlayState *state = (CairoOverlayState *)user_data;

  state->valid = gst_video_info_from_caps(&state->vinfo, caps);
}

/* Draw the overlay.
 * This function draws a cute "beating" heart. */
static void draw_overlay(GstElement *overlay, cairo_t *cr, guint64 timestamp,
                         guint64 duration, gpointer user_data) {
  CairoOverlayState *s = (CairoOverlayState *)user_data;
  double scale;
  int width, height;

  if (!s->valid)
    return;

  width = GST_VIDEO_INFO_WIDTH(&s->vinfo);
  height = GST_VIDEO_INFO_HEIGHT(&s->vinfo);

  scale = 2 * (((timestamp / (int)1e7) % 70) + 30) / 100.0;
  cairo_translate(cr, width / 2, (height / 2) - 30);

  /* FIXME: this assumes a pixel-aspect-ratio of 1/1 */
  cairo_scale(cr, scale, scale);

  cairo_move_to(cr, 0, 0);
  cairo_curve_to(cr, 0, -30, -50, -30, -50, 0);
  cairo_curve_to(cr, -50, 30, 0, 35, 0, 60);
  cairo_curve_to(cr, 0, 35, 50, 30, 50, 0);
  cairo_curve_to(cr, 50, -30, 0, -30, 0, 0);
  cairo_set_source_rgba(cr, 0.9, 0.0, 0.1, 0.7);
  cairo_fill(cr);
}

static GstElement *setup_gst_pipeline(CairoOverlayState *overlay_state) {
  GstElement *pipeline;
  GstElement *cairo_overlay;
  GstElement *source, *adaptor1, *adaptor2, *sink;

  pipeline = gst_pipeline_new("cairo-overlay-example");

  /* Adaptors needed because cairooverlay only supports ARGB data */
  source = gst_element_factory_make("videotestsrc", "source");
  adaptor1 = gst_element_factory_make("videoconvert", "adaptor1");
  cairo_overlay = gst_element_factory_make("cairooverlay", "overlay");
  adaptor2 = gst_element_factory_make("videoconvert", "adaptor2");
  sink = gst_element_factory_make("ximagesink", "sink");
  if (sink == NULL)
    sink = gst_element_factory_make("autovideosink", "sink");

  /* If failing, the element could not be created */
  g_assert(cairo_overlay);

  /* Hook up the necessary signals for cairooverlay */
  g_signal_connect(cairo_overlay, "draw", G_CALLBACK(draw_overlay),
                   overlay_state);
  g_signal_connect(cairo_overlay, "caps-changed", G_CALLBACK(prepare_overlay),
                   overlay_state);

  gst_bin_add_many(GST_BIN(pipeline), source, adaptor1, cairo_overlay, adaptor2,
                   sink, NULL);

  if (!gst_element_link_many(source, adaptor1, cairo_overlay, adaptor2, sink,
                             NULL)) {
    g_warning("Failed to link elements!");
  }

  return pipeline;
}

int main(int argc, char **argv) {
  GMainLoop *loop;
  GstElement *pipeline;
  GstBus *bus;
  CairoOverlayState *overlay_state;

  gst_init(&argc, &argv);
  loop = g_main_loop_new(NULL, FALSE);

  /* allocate on heap for pedagogical reasons, makes code easier to transfer */
  overlay_state = g_new0(CairoOverlayState, 1);

  pipeline = setup_gst_pipeline(overlay_state);

  bus = gst_pipeline_get_bus(GST_PIPELINE(pipeline));
  gst_bus_add_signal_watch(bus);
  g_signal_connect(G_OBJECT(bus), "message", G_CALLBACK(on_message), loop);
  gst_object_unref(GST_OBJECT(bus));

  gst_element_set_state(pipeline, GST_STATE_PLAYING);
  g_main_loop_run(loop);

  gst_element_set_state(pipeline, GST_STATE_NULL);
  gst_object_unref(pipeline);

  g_free(overlay_state);
  return 0;
}