plugin: Add clapper GStreamer plugin

Add new GStreamer plugin that consists of multiple elements for Clapper video player.

The main difference is that unlike the old one, this does not operate using `GtkGLArea`
anymore, but processes and displays `GdkTextures` directly through `GtkPicture` widget.
Also this one is installed like any other GStreamer plugin, thus can be used via
`gst-launch-1.0` binary or even used by other GTK4 apps if they wish to integrate it.

This commit adds new video sink that uses a new kind of memory as input, called
`ClapperGdkMemory`. With it comes a simple dedicated memory allocator, buffer pool
and a `clapperimport` element that converts system mapped memory frames into
`GdkTextures` that are later passed in our `ClapperGdkMemory` for the sink to display.

lib/gst/plugin/gstclappergdkbufferpool.c

@@ -0,0 +1,173 @@
+/*
+ * Copyright (C) 2022 Rafał Dzięgiel <rafostar.github@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.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include "gstclappergdkbufferpool.h"
+
+#define GST_CAT_DEFAULT gst_clapper_gdk_buffer_pool_debug
+GST_DEBUG_CATEGORY_STATIC (GST_CAT_DEFAULT);
+
+#define parent_class gst_clapper_gdk_buffer_pool_parent_class
+G_DEFINE_TYPE (GstClapperGdkBufferPool, gst_clapper_gdk_buffer_pool, GST_TYPE_BUFFER_POOL);
+
+static void
+gst_clapper_gdk_buffer_pool_init (GstClapperGdkBufferPool *pool)
+{
+}
+
+static const gchar **
+gst_clapper_gdk_buffer_pool_get_options (GstBufferPool *pool)
+{
+  static const gchar *options[] = {
+    GST_BUFFER_POOL_OPTION_VIDEO_META,
+    NULL
+  };
+
+  return options;
+}
+
+static gboolean
+gst_clapper_gdk_buffer_pool_set_config (GstBufferPool *pool, GstStructure *config)
+{
+  GstClapperGdkBufferPool *self = GST_CLAPPER_GDK_BUFFER_POOL_CAST (pool);
+  GstCaps *caps = NULL;
+  guint size, min_buffers, max_buffers;
+  GstVideoInfo info;
+  GstClapperGdkMemory *clapper_mem;
+
+  if (!gst_buffer_pool_config_get_params (config, &caps, &size,
+      &min_buffers, &max_buffers)) {
+    GST_WARNING_OBJECT (self, "Invalid buffer pool config");
+    return FALSE;
+  }
+
+  if (!caps || !gst_video_info_from_caps (&info, caps)) {
+    GST_WARNING_OBJECT (pool, "Could not parse caps into video info");
+    return FALSE;
+  }
+
+  gst_clear_object (&self->allocator);
+  self->allocator = GST_CLAPPER_GDK_ALLOCATOR_CAST (
+      gst_allocator_find (GST_CLAPPER_GDK_MEMORY_TYPE_NAME));
+
+  if (G_UNLIKELY (!self->allocator)) {
+    GST_ERROR_OBJECT (self, "ClapperGdkAllocator is unavailable");
+    return FALSE;
+  }
+
+  clapper_mem = GST_CLAPPER_GDK_MEMORY_CAST (
+      gst_clapper_gdk_allocator_alloc (self->allocator, &info));
+  if (G_UNLIKELY (!clapper_mem)) {
+    GST_ERROR_OBJECT (self, "Cannot create ClapperGdkMemory");
+    return FALSE;
+  }
+
+  gst_buffer_pool_config_set_params (config, caps,
+      GST_VIDEO_INFO_SIZE (&clapper_mem->info), min_buffers, max_buffers);
+  gst_memory_unref (GST_MEMORY_CAST (clapper_mem));
+
+  self->info = info;
+
+  GST_DEBUG_OBJECT (self, "Set buffer pool config: %" GST_PTR_FORMAT, config);
+
+  return GST_BUFFER_POOL_CLASS (parent_class)->set_config (pool, config);
+}
+
+static GstFlowReturn
+gst_clapper_gdk_buffer_pool_alloc (GstBufferPool *pool, GstBuffer **buffer,
+    GstBufferPoolAcquireParams *params)
+{
+  GstClapperGdkBufferPool *self = GST_CLAPPER_GDK_BUFFER_POOL_CAST (pool);
+  GstMemory *mem;
+  GstClapperGdkMemory *clapper_mem;
+
+  mem = gst_clapper_gdk_allocator_alloc (self->allocator, &self->info);
+  if (G_UNLIKELY (!mem)) {
+    GST_ERROR_OBJECT (self, "Cannot create ClapperGdkMemory");
+    return GST_FLOW_ERROR;
+  }
+
+  clapper_mem = GST_CLAPPER_GDK_MEMORY_CAST (mem);
+
+  *buffer = gst_buffer_new ();
+  gst_buffer_append_memory (*buffer, mem);
+
+  gst_buffer_add_video_meta_full (*buffer, GST_VIDEO_FRAME_FLAG_NONE,
+      GST_VIDEO_INFO_FORMAT (&self->info), GST_VIDEO_INFO_WIDTH (&self->info),
+      GST_VIDEO_INFO_HEIGHT (&self->info), GST_VIDEO_INFO_N_PLANES (&self->info),
+      clapper_mem->info.offset, clapper_mem->info.stride);
+
+  GST_TRACE_OBJECT (self, "Allocated %" GST_PTR_FORMAT, *buffer);
+
+  return GST_FLOW_OK;
+}
+
+static void
+gst_clapper_gdk_buffer_reset_buffer (GstBufferPool *pool, GstBuffer *buffer)
+{
+  GstClapperGdkMemory *clapper_mem;
+
+  GST_TRACE ("Reset %" GST_PTR_FORMAT, buffer);
+
+  clapper_mem = GST_CLAPPER_GDK_MEMORY_CAST (gst_buffer_peek_memory (buffer, 0));
+  g_clear_object (&clapper_mem->texture);
+
+  return GST_BUFFER_POOL_CLASS (parent_class)->reset_buffer (pool, buffer);
+}
+
+static void
+gst_clapper_gdk_buffer_pool_dispose (GObject *object)
+{
+  GstClapperGdkBufferPool *self = GST_CLAPPER_GDK_BUFFER_POOL_CAST (object);
+
+  gst_clear_object (&self->allocator);
+
+  GST_CALL_PARENT (G_OBJECT_CLASS, dispose, (object));
+}
+
+static void
+gst_clapper_gdk_buffer_pool_class_init (GstClapperGdkBufferPoolClass *klass)
+{
+  GObjectClass *gobject_class = (GObjectClass *) klass;
+  GstBufferPoolClass *bufferpool_class = (GstBufferPoolClass *) klass;
+
+  gobject_class->dispose = gst_clapper_gdk_buffer_pool_dispose;
+
+  bufferpool_class->get_options = gst_clapper_gdk_buffer_pool_get_options;
+  bufferpool_class->set_config = gst_clapper_gdk_buffer_pool_set_config;
+  bufferpool_class->alloc_buffer = gst_clapper_gdk_buffer_pool_alloc;
+  bufferpool_class->reset_buffer = gst_clapper_gdk_buffer_reset_buffer;
+
+  GST_DEBUG_CATEGORY_INIT (GST_CAT_DEFAULT, "clappergdkbufferpool", 0,
+      "Clapper Gdk Buffer Pool");
+}
+
+GstBufferPool *
+gst_clapper_gdk_buffer_pool_new (void)
+{
+  GstClapperGdkBufferPool *self;
+
+  self = g_object_new (GST_TYPE_CLAPPER_GDK_BUFFER_POOL, NULL);
+  gst_object_ref_sink (self);
+
+  return GST_BUFFER_POOL_CAST (self);
+}