Add DisplayServerDummy for headless display.

Uses RasterizerDummy internally. This is always compiled in, maybe we
should add a switch to enable/disable it via scons?

drivers/dummy/display_server_headless.h

@@ -0,0 +1,128 @@
+/*************************************************************************/
+/*  display_server_headless.h                                            */
+/*************************************************************************/
+/*                       This file is part of:                           */
+/*                           GODOT ENGINE                                */
+/*                      https://godotengine.org                          */
+/*************************************************************************/
+/* Copyright (c) 2007-2021 Juan Linietsky, Ariel Manzur.                 */
+/* Copyright (c) 2014-2021 Godot Engine contributors (cf. AUTHORS.md).   */
+/*                                                                       */
+/* 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.                */
+/*************************************************************************/
+
+#ifndef DISPLAY_SERVER_HEADLESS_H
+#define DISPLAY_SERVER_HEADLESS_H
+
+#include "servers/display_server.h"
+
+#include "drivers/dummy/rasterizer_dummy.h"
+
+class DisplayServerHeadless : public DisplayServer {
+public:
+	bool has_feature(Feature p_feature) const override { return false; }
+	String get_name() const override { return "headless"; }
+
+	void alert(const String &p_alert, const String &p_title = "ALERT!") override {}
+
+	int get_screen_count() const override { return 0; }
+	Point2i screen_get_position(int p_screen = SCREEN_OF_MAIN_WINDOW) const override { return Point2i(); }
+	Size2i screen_get_size(int p_screen = SCREEN_OF_MAIN_WINDOW) const override { return Size2i(); }
+	Rect2i screen_get_usable_rect(int p_screen = SCREEN_OF_MAIN_WINDOW) const override { return Rect2i(); }
+	int screen_get_dpi(int p_screen = SCREEN_OF_MAIN_WINDOW) const override { return 96; /* 0 might cause issues */ }
+	float screen_get_scale(int p_screen = SCREEN_OF_MAIN_WINDOW) const override { return 1; }
+	float screen_get_max_scale() const override { return 1; }
+
+	Vector<DisplayServer::WindowID> get_window_list() const override { return Vector<DisplayServer::WindowID>(); }
+
+	WindowID get_window_at_screen_position(const Point2i &p_position) const override { return -1; }
+
+	void window_attach_instance_id(ObjectID p_instance, WindowID p_window = MAIN_WINDOW_ID) override {}
+	ObjectID window_get_attached_instance_id(WindowID p_window = MAIN_WINDOW_ID) const override { return ObjectID(); }
+
+	void window_set_rect_changed_callback(const Callable &p_callable, WindowID p_window = MAIN_WINDOW_ID) override {}
+
+	void window_set_window_event_callback(const Callable &p_callable, WindowID p_window = MAIN_WINDOW_ID) override {}
+	void window_set_input_event_callback(const Callable &p_callable, WindowID p_window = MAIN_WINDOW_ID) override {}
+	void window_set_input_text_callback(const Callable &p_callable, WindowID p_window = MAIN_WINDOW_ID) override {}
+	void window_set_drop_files_callback(const Callable &p_callable, WindowID p_window = MAIN_WINDOW_ID) override {}
+
+	void window_set_title(const String &p_title, WindowID p_window = MAIN_WINDOW_ID) override {}
+
+	void window_set_mouse_passthrough(const Vector<Vector2> &p_region, WindowID p_window = MAIN_WINDOW_ID) override {}
+
+	int window_get_current_screen(WindowID p_window = MAIN_WINDOW_ID) const override { return -1; }
+	void window_set_current_screen(int p_screen, WindowID p_window = MAIN_WINDOW_ID) override {}
+
+	Point2i window_get_position(WindowID p_window = MAIN_WINDOW_ID) const override { return Point2i(); }
+	void window_set_position(const Point2i &p_position, WindowID p_window = MAIN_WINDOW_ID) override {}
+
+	void window_set_transient(WindowID p_window, WindowID p_parent) override {}
+
+	void window_set_max_size(const Size2i p_size, WindowID p_window = MAIN_WINDOW_ID) override {}
+	Size2i window_get_max_size(WindowID p_window = MAIN_WINDOW_ID) const override { return Size2i(); }
+
+	void window_set_min_size(const Size2i p_size, WindowID p_window = MAIN_WINDOW_ID) override {}
+	Size2i window_get_min_size(WindowID p_window = MAIN_WINDOW_ID) const override { return Size2i(); };
+
+	void window_set_size(const Size2i p_size, WindowID p_window = MAIN_WINDOW_ID) override {}
+	Size2i window_get_size(WindowID p_window = MAIN_WINDOW_ID) const override { return Size2i(); }
+	Size2i window_get_real_size(WindowID p_window = MAIN_WINDOW_ID) const override { return Size2i(); }
+
+	void window_set_mode(WindowMode p_mode, WindowID p_window = MAIN_WINDOW_ID) override {}
+	WindowMode window_get_mode(WindowID p_window = MAIN_WINDOW_ID) const override { return WINDOW_MODE_MINIMIZED; }
+
+	bool window_is_maximize_allowed(WindowID p_window = MAIN_WINDOW_ID) const override { return false; }
+
+	void window_set_flag(WindowFlags p_flag, bool p_enabled, WindowID p_window = MAIN_WINDOW_ID) override {}
+	virtual bool window_get_flag(WindowFlags p_flag, WindowID p_window = MAIN_WINDOW_ID) const override { return false; }
+
+	void window_request_attention(WindowID p_window = MAIN_WINDOW_ID) override {}
+	void window_move_to_foreground(WindowID p_window = MAIN_WINDOW_ID) override {}
+
+	bool window_can_draw(WindowID p_window = MAIN_WINDOW_ID) const override { return false; }
+
+	bool can_any_window_draw() const override { return false; }
+
+	void process_events() override {}
+
+	void set_icon(const Ref<Image> &p_icon) override {}
+
+	static void register_headless_driver() {
+		register_create_function("headless", create_func, get_rendering_drivers_func);
+	}
+
+	static Vector<String> get_rendering_drivers_func() {
+		Vector<String> drivers;
+		drivers.push_back("dummy");
+		return drivers;
+	}
+
+	static DisplayServer *create_func(const String &p_rendering_driver, DisplayServer::WindowMode p_mode, uint32_t p_flags, const Vector2i &p_resolution, Error &r_error) {
+		r_error = OK;
+		RasterizerDummy::make_current();
+		return memnew(DisplayServerHeadless());
+	}
+
+	DisplayServerHeadless() {}
+	~DisplayServerHeadless() {}
+};
+
+#endif // DISPLAY_SERVER_HEADLESS_H

drivers/register_driver_types.cpp

@@ -30,6 +30,7 @@
 
 #include "register_driver_types.h"
 
+#include "drivers/dummy/display_server_headless.h"
 #include "drivers/png/image_loader_png.h"
 #include "drivers/png/resource_saver_png.h"
 
@@ -37,6 +38,8 @@ static ImageLoaderPNG *image_loader_png;
 static Ref<ResourceSaverPNG> resource_saver_png;
 
 void register_core_driver_types() {
+	DisplayServerHeadless::register_headless_driver();
+
 	image_loader_png = memnew(ImageLoaderPNG);
 	ImageLoader::add_image_format_loader(image_loader_png);