Updates VideoDecoder plugin API to GDExtension.

Adds VideoStream and relevant resource loaders to migrate
external GDNative plugins to GDExtension.

Adds a VideoStreamLoader as a specialization of ResourceFormatLoader
as ClassDB::is_parent_class is inaccessible from GDExtension currently.

Using Object* instead of Ref<T> in order to avoid the refcount bug
(godotengine/godot-cpp#652)
Also another bug is in ResourceLoader in use on the extension side that
requires fixing.

2 files changed, 255 insertions, 19 deletions

diff --git a/scene/resources/video_stream.cpp b/scene/resources/video_stream.cpp
new file mode 100644
index 0000000000..ee1a47c338
--- /dev/null
+++ b/scene/resources/video_stream.cpp
@@ -0,0 +1,198 @@
+/**************************************************************************/
+/*  video_stream.cpp                                                      */
+/**************************************************************************/
+/*                         This file is part of:                          */
+/*                             GODOT ENGINE                               */
+/*                        https://godotengine.org                         */
+/**************************************************************************/
+/* Copyright (c) 2014-present Godot Engine contributors (see AUTHORS.md). */
+/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur.                  */
+/*                                                                        */
+/* Permission is hereby granted, free of charge, to any person obtaining  */
+/* a copy of this software and associated documentation files (the        */
+/* "Software"), to deal in the Software without restriction, including    */
+/* without limitation the rights to use, copy, modify, merge, publish,    */
+/* distribute, sublicense, and/or sell copies of the Software, and to     */
+/* permit persons to whom the Software is furnished to do so, subject to  */
+/* the following conditions:                                              */
+/*                                                                        */
+/* The above copyright notice and this permission notice shall be         */
+/* included in all copies or substantial portions of the Software.        */
+/*                                                                        */
+/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,        */
+/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF     */
+/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. */
+/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY   */
+/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,   */
+/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE      */
+/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                 */
+/**************************************************************************/
+
+#include "video_stream.h"
+
+#include "core/config/project_settings.h"
+#include "servers/audio_server.h"
+
+// VideoStreamPlayback starts here.
+
+void VideoStreamPlayback::_bind_methods() {
+	ClassDB::bind_method(D_METHOD("mix_audio", "num_frames", "buffer", "offset"), &VideoStreamPlayback::mix_audio, DEFVAL(PackedFloat32Array()), DEFVAL(0));
+	GDVIRTUAL_BIND(_stop);
+	GDVIRTUAL_BIND(_play);
+	GDVIRTUAL_BIND(_is_playing);
+	GDVIRTUAL_BIND(_set_paused, "paused");
+	GDVIRTUAL_BIND(_is_paused);
+	GDVIRTUAL_BIND(_get_length);
+	GDVIRTUAL_BIND(_get_playback_position);
+	GDVIRTUAL_BIND(_seek, "time");
+	GDVIRTUAL_BIND(_set_audio_track, "idx");
+	GDVIRTUAL_BIND(_get_texture);
+	GDVIRTUAL_BIND(_update, "delta");
+	GDVIRTUAL_BIND(_get_channels);
+	GDVIRTUAL_BIND(_get_mix_rate);
+}
+
+VideoStreamPlayback::VideoStreamPlayback() {
+}
+
+VideoStreamPlayback::~VideoStreamPlayback() {
+}
+
+void VideoStreamPlayback::stop() {
+	GDVIRTUAL_CALL(_stop);
+}
+
+void VideoStreamPlayback::play() {
+	GDVIRTUAL_CALL(_play);
+}
+
+bool VideoStreamPlayback::is_playing() const {
+	bool ret;
+	if (GDVIRTUAL_CALL(_is_playing, ret)) {
+		return ret;
+	}
+	return false;
+}
+
+void VideoStreamPlayback::set_paused(bool p_paused) {
+	GDVIRTUAL_CALL(_is_playing, p_paused);
+}
+
+bool VideoStreamPlayback::is_paused() const {
+	bool ret;
+	if (GDVIRTUAL_CALL(_is_paused, ret)) {
+		return ret;
+	}
+	return false;
+}
+
+double VideoStreamPlayback::get_length() const {
+	double ret;
+	if (GDVIRTUAL_CALL(_get_length, ret)) {
+		return ret;
+	}
+	return 0;
+}
+
+double VideoStreamPlayback::get_playback_position() const {
+	double ret;
+	if (GDVIRTUAL_CALL(_get_playback_position, ret)) {
+		return ret;
+	}
+	return 0;
+}
+
+void VideoStreamPlayback::seek(double p_time) {
+	GDVIRTUAL_CALL(_seek, p_time);
+}
+
+void VideoStreamPlayback::set_audio_track(int p_idx) {
+	GDVIRTUAL_CALL(_set_audio_track, p_idx);
+}
+
+Ref<Texture2D> VideoStreamPlayback::get_texture() const {
+	Ref<Texture2D> ret;
+	if (GDVIRTUAL_CALL(_get_texture, ret)) {
+		return ret;
+	}
+	return nullptr;
+}
+
+void VideoStreamPlayback::update(double p_delta) {
+	if (!GDVIRTUAL_CALL(_update, p_delta)) {
+		ERR_FAIL_MSG("VideoStreamPlayback::update unimplemented");
+	}
+}
+
+void VideoStreamPlayback::set_mix_callback(AudioMixCallback p_callback, void *p_userdata) {
+	mix_callback = p_callback;
+	mix_udata = p_userdata;
+}
+
+int VideoStreamPlayback::get_channels() const {
+	int ret;
+	if (GDVIRTUAL_CALL(_get_channels, ret)) {
+		_channel_count = ret;
+		return ret;
+	}
+	return 0;
+}
+
+int VideoStreamPlayback::get_mix_rate() const {
+	int ret;
+	if (GDVIRTUAL_CALL(_get_mix_rate, ret)) {
+		return ret;
+	}
+	return 0;
+}
+
+int VideoStreamPlayback::mix_audio(int num_frames, PackedFloat32Array buffer, int offset) {
+	if (num_frames <= 0) {
+		return 0;
+	}
+	if (!mix_callback) {
+		return -1;
+	}
+	ERR_FAIL_INDEX_V(offset, buffer.size(), -1);
+	ERR_FAIL_INDEX_V((_channel_count < 1 ? 1 : _channel_count) * num_frames - 1, buffer.size() - offset, -1);
+	return mix_callback(mix_udata, buffer.ptr() + offset, num_frames);
+}
+
+/* --- NOTE VideoStream starts here. ----- */
+
+Ref<VideoStreamPlayback> VideoStream::instantiate_playback() {
+	Ref<VideoStreamPlayback> ret;
+	if (GDVIRTUAL_CALL(_instantiate_playback, ret)) {
+		ERR_FAIL_COND_V_MSG(ret.is_null(), nullptr, "Plugin returned null playback");
+		ret->set_audio_track(audio_track);
+		return ret;
+	}
+	return nullptr;
+}
+
+void VideoStream::set_file(const String &p_file) {
+	file = p_file;
+}
+
+String VideoStream::get_file() {
+	return file;
+}
+
+void VideoStream::_bind_methods() {
+	ClassDB::bind_method(D_METHOD("set_file", "file"), &VideoStream::set_file);
+	ClassDB::bind_method(D_METHOD("get_file"), &VideoStream::get_file);
+
+	ADD_PROPERTY(PropertyInfo(Variant::STRING, "file"), "set_file", "get_file");
+
+	GDVIRTUAL_BIND(_instantiate_playback);
+}
+
+VideoStream::VideoStream() {
+}
+
+VideoStream::~VideoStream() {
+}
+
+void VideoStream::set_audio_track(int p_track) {
+	audio_track = p_track;
+}
diff --git a/scene/resources/video_stream.h b/scene/resources/video_stream.h
index f83c621d0a..b91a7acf35 100644
--- a/scene/resources/video_stream.h
+++ b/scene/resources/video_stream.h
@@ -31,6 +31,7 @@
 #ifndef VIDEO_STREAM_H
 #define VIDEO_STREAM_H
 
+#include "core/io/file_access.h"
 #include "scene/resources/texture.h"
 
 class VideoStreamPlayback : public Resource {
@@ -39,40 +40,77 @@ class VideoStreamPlayback : public Resource {
 public:
 	typedef int (*AudioMixCallback)(void *p_udata, const float *p_data, int p_frames);
 
-	virtual void stop() = 0;
-	virtual void play() = 0;
+protected:
+	AudioMixCallback mix_callback = nullptr;
+	void *mix_udata = nullptr;
+	mutable int _channel_count = 0; // Used only to assist with bounds checking in mix_audio.
+
+	static void _bind_methods();
+	GDVIRTUAL0(_stop);
+	GDVIRTUAL0(_play);
+	GDVIRTUAL0RC(bool, _is_playing);
+	GDVIRTUAL1(_set_paused, bool);
+	GDVIRTUAL0RC(bool, _is_paused);
+	GDVIRTUAL0RC(double, _get_length);
+	GDVIRTUAL0RC(double, _get_playback_position);
+	GDVIRTUAL1(_seek, double);
+	GDVIRTUAL1(_set_audio_track, int);
+	GDVIRTUAL0RC(Ref<Texture2D>, _get_texture);
+	GDVIRTUAL1(_update, double);
+	GDVIRTUAL0RC(int, _get_channels);
+	GDVIRTUAL0RC(int, _get_mix_rate);
+
+	int mix_audio(int num_frames, PackedFloat32Array buffer = {}, int offset = 0);
 
-	virtual bool is_playing() const = 0;
+public:
+	VideoStreamPlayback();
+	virtual ~VideoStreamPlayback();
 
-	virtual void set_paused(bool p_paused) = 0;
-	virtual bool is_paused() const = 0;
+	virtual void stop();
+	virtual void play();
 
-	virtual void set_loop(bool p_enable) = 0;
-	virtual bool has_loop() const = 0;
+	virtual bool is_playing() const;
 
-	virtual double get_length() const = 0;
+	virtual void set_paused(bool p_paused);
+	virtual bool is_paused() const;
 
-	virtual double get_playback_position() const = 0;
-	virtual void seek(double p_time) = 0;
+	virtual double get_length() const;
 
-	virtual void set_audio_track(int p_idx) = 0;
+	virtual double get_playback_position() const;
+	virtual void seek(double p_time);
 
-	virtual Ref<Texture2D> get_texture() const = 0;
+	virtual void set_audio_track(int p_idx);
 
-	virtual void update(double p_delta) = 0;
+	virtual Ref<Texture2D> get_texture() const;
+	virtual void update(double p_delta);
 
-	virtual void set_mix_callback(AudioMixCallback p_callback, void *p_userdata) = 0;
-	virtual int get_channels() const = 0;
-	virtual int get_mix_rate() const = 0;
+	virtual void set_mix_callback(AudioMixCallback p_callback, void *p_userdata);
+	virtual int get_channels() const;
+	virtual int get_mix_rate() const;
 };
 
 class VideoStream : public Resource {
 	GDCLASS(VideoStream, Resource);
-	OBJ_SAVE_TYPE(VideoStream); // Saves derived classes with common type so they can be interchanged.
+	OBJ_SAVE_TYPE(VideoStream);
+
+protected:
+	static void
+	_bind_methods();
+
+	GDVIRTUAL0R(Ref<VideoStreamPlayback>, _instantiate_playback);
+
+	String file;
+	int audio_track = 0;
 
 public:
-	virtual void set_audio_track(int p_track) = 0;
-	virtual Ref<VideoStreamPlayback> instantiate_playback() = 0;
+	void set_file(const String &p_file);
+	String get_file();
+
+	virtual void set_audio_track(int p_track);
+	virtual Ref<VideoStreamPlayback> instantiate_playback();
+
+	VideoStream();
+	~VideoStream();
 };
 
 #endif // VIDEO_STREAM_H