Codechange: use (Un)LockVideoBuffer() to manage video buffer

src/video/sdl2_v.cpp

@@ -801,9 +801,9 @@ void VideoDriver_SDL::LoopOnce()
 
 		/* The gameloop is the part that can run asynchronously. The rest
 		 * except sleeping can't. */
-		if (_draw_mutex != nullptr) draw_lock.unlock();
+		this->UnlockVideoBuffer();
 		GameLoop();
-		if (_draw_mutex != nullptr) draw_lock.lock();
+		this->LockVideoBuffer();
 	}
 
 	/* Prevent drawing when switching mode, as windows can be removed when they should still appear. */
@@ -834,9 +834,9 @@ void VideoDriver_SDL::LoopOnce()
 		auto now = std::chrono::steady_clock::now();
 
 		if (next_tick > now) {
-			if (_draw_mutex != nullptr) draw_lock.unlock();
+			this->UnlockVideoBuffer();
 			std::this_thread::sleep_for(next_tick - now);
-			if (_draw_mutex != nullptr) draw_lock.lock();
+			this->LockVideoBuffer();
 		}
 	}
 #endif
@@ -986,3 +986,14 @@ Dimension VideoDriver_SDL::GetScreenSize() const
 
 	return { static_cast<uint>(mode.w), static_cast<uint>(mode.h) };
 }
+
+bool VideoDriver_SDL::LockVideoBuffer()
+{
+	if (_draw_threaded) this->draw_lock.lock();
+	return true;
+}
+
+void VideoDriver_SDL::UnlockVideoBuffer()
+{
+	if (_draw_threaded) this->draw_lock.unlock();
+}

src/video/sdl2_v.h

@@ -44,6 +44,8 @@ public:
 protected:
 	Dimension GetScreenSize() const override;
 	void InputLoop() override;
+	bool LockVideoBuffer() override;
+	void UnlockVideoBuffer() override;
 
 private:
 	int PollEvent();

src/video/sdl_v.cpp

@@ -706,7 +706,6 @@ void VideoDriver_SDL::MainLoop()
 	CheckPaletteAnim();
 
 	std::thread draw_thread;
-	std::unique_lock<std::recursive_mutex> draw_lock;
 	if (_draw_threaded) {
 		/* Initialise the mutex first, because that's the thing we *need*
 		 * directly in the newly created thread. */
@@ -714,7 +713,7 @@ void VideoDriver_SDL::MainLoop()
 		if (_draw_mutex == nullptr) {
 			_draw_threaded = false;
 		} else {
-			draw_lock = std::unique_lock<std::recursive_mutex>(*_draw_mutex);
+			this->draw_lock = std::unique_lock<std::recursive_mutex>(*_draw_mutex);
 			_draw_signal = new std::condition_variable_any();
 			_draw_continue = true;
 
@@ -722,8 +721,8 @@ void VideoDriver_SDL::MainLoop()
 
 			/* Free the mutex if we won't be able to use it. */
 			if (!_draw_threaded) {
-				draw_lock.unlock();
-				draw_lock.release();
+				this->draw_lock.unlock();
+				this->draw_lock.release();
 				delete _draw_mutex;
 				delete _draw_signal;
 				_draw_mutex = nullptr;
@@ -763,9 +762,9 @@ void VideoDriver_SDL::MainLoop()
 
 			/* The gameloop is the part that can run asynchronously. The rest
 			 * except sleeping can't. */
-			if (_draw_mutex != nullptr) draw_lock.unlock();
+			this->UnlockVideoBuffer();
 			GameLoop();
-			if (_draw_mutex != nullptr) draw_lock.lock();
+			this->LockVideoBuffer();
 		}
 
 		/* Prevent drawing when switching mode, as windows can be removed when they should still appear. */
@@ -794,9 +793,9 @@ void VideoDriver_SDL::MainLoop()
 			auto now = std::chrono::steady_clock::now();
 
 			if (next_tick > now) {
-				if (_draw_mutex != nullptr) draw_lock.unlock();
+				this->UnlockVideoBuffer();
 				std::this_thread::sleep_for(next_tick - now);
-				if (_draw_mutex != nullptr) draw_lock.lock();
+				this->LockVideoBuffer();
 			}
 		}
 	}
@@ -806,8 +805,8 @@ void VideoDriver_SDL::MainLoop()
 		/* Sending signal if there is no thread blocked
 		 * is very valid and results in noop */
 		_draw_signal->notify_one();
-		if (draw_lock.owns_lock()) draw_lock.unlock();
-		draw_lock.release();
+		if (this->draw_lock.owns_lock()) this->draw_lock.unlock();
+		this->draw_lock.release();
 		draw_thread.join();
 
 		delete _draw_mutex;
@@ -858,4 +857,15 @@ void VideoDriver_SDL::ReleaseBlitterLock()
 	if (_draw_mutex != nullptr) _draw_mutex->unlock();
 }
 
+bool VideoDriver_SDL::LockVideoBuffer()
+{
+	if (_draw_threaded) this->draw_lock.lock();
+	return true;
+}
+
+void VideoDriver_SDL::UnlockVideoBuffer()
+{
+	if (_draw_threaded) this->draw_lock.unlock();
+}
+
 #endif /* WITH_SDL */

src/video/sdl_v.h

@@ -39,8 +39,12 @@ public:
 
 protected:
 	void InputLoop() override;
+	bool LockVideoBuffer() override;
+	void UnlockVideoBuffer() override;
 
 private:
+	std::unique_lock<std::recursive_mutex> draw_lock;
+
 	int PollEvent();
 	bool CreateMainSurface(uint w, uint h);
 	void SetupKeyboard();

src/video/video_driver.hpp

@@ -161,6 +161,19 @@ protected:
 	 */
 	virtual void InputLoop() {}
 
+	/**
+	 * Make sure the video buffer is ready for drawing.
+	 * @returns True if the video buffer has to be unlocked.
+	 */
+	virtual bool LockVideoBuffer() {
+		return false;
+	}
+
+	/**
+	 * Unlock a previously locked video buffer.
+	 */
+	virtual void UnlockVideoBuffer() {}
+
 	std::chrono::steady_clock::duration GetGameInterval()
 	{
 		return std::chrono::milliseconds(MILLISECONDS_PER_TICK);

src/video/win32_v.cpp

@@ -1161,7 +1161,6 @@ void VideoDriver_Win32::MainLoop()
 	auto next_draw_tick = cur_ticks;
 
 	std::thread draw_thread;
-	std::unique_lock<std::recursive_mutex> draw_lock;
 
 	if (_draw_threaded) {
 		/* Initialise the mutex first, because that's the thing we *need*
@@ -1174,15 +1173,15 @@ void VideoDriver_Win32::MainLoop()
 		}
 
 		if (_draw_threaded) {
-			draw_lock = std::unique_lock<std::recursive_mutex>(*_draw_mutex);
+			this->draw_lock = std::unique_lock<std::recursive_mutex>(*_draw_mutex);
 
 			_draw_continue = true;
 			_draw_threaded = StartNewThread(&draw_thread, "ottd:draw-win32", &PaintWindowThread);
 
 			/* Free the mutex if we won't be able to use it. */
 			if (!_draw_threaded) {
-				draw_lock.unlock();
-				draw_lock.release();
+				this->draw_lock.unlock();
+				this->draw_lock.release();
 				delete _draw_mutex;
 				delete _draw_signal;
 				_draw_mutex = nullptr;
@@ -1231,9 +1230,9 @@ void VideoDriver_Win32::MainLoop()
 
 			/* The game loop is the part that can run asynchronously.
 			 * The rest except sleeping can't. */
-			if (_draw_threaded) draw_lock.unlock();
+			this->UnlockVideoBuffer();
 			GameLoop();
-			if (_draw_threaded) draw_lock.lock();
+			this->LockVideoBuffer();
 		}
 
 		/* Prevent drawing when switching mode, as windows can be removed when they should still appear. */
@@ -1269,9 +1268,9 @@ void VideoDriver_Win32::MainLoop()
 				/* Flush GDI buffer to ensure we don't conflict with the drawing thread. */
 				GdiFlush();
 
-				if (_draw_mutex != nullptr) draw_lock.unlock();
+				this->UnlockVideoBuffer();
 				std::this_thread::sleep_for(next_tick - now);
-				if (_draw_mutex != nullptr) draw_lock.lock();
+				this->LockVideoBuffer();
 			}
 		}
 	}
@@ -1281,8 +1280,8 @@ void VideoDriver_Win32::MainLoop()
 		/* Sending signal if there is no thread blocked
 		 * is very valid and results in noop */
 		_draw_signal->notify_all();
-		if (draw_lock.owns_lock()) draw_lock.unlock();
-		draw_lock.release();
+		if (this->draw_lock.owns_lock()) this->draw_lock.unlock();
+		this->draw_lock.release();
 		draw_thread.join();
 
 		delete _draw_mutex;
@@ -1383,3 +1382,14 @@ float VideoDriver_Win32::GetDPIScale()
 
 	return cur_dpi > 0 ? cur_dpi / 96.0f : 1.0f; // Default Windows DPI value is 96.
 }
+
+bool VideoDriver_Win32::LockVideoBuffer()
+{
+	if (_draw_threaded) this->draw_lock.lock();
+	return true;
+}
+
+void VideoDriver_Win32::UnlockVideoBuffer()
+{
+	if (_draw_threaded) this->draw_lock.unlock();
+}

src/video/win32_v.h

@@ -45,9 +45,15 @@ protected:
 	Dimension GetScreenSize() const override;
 	float GetDPIScale() override;
 	void InputLoop() override;
+	bool LockVideoBuffer() override;
+	void UnlockVideoBuffer() override;
 
 private:
+	std::unique_lock<std::recursive_mutex> draw_lock;
+
 	void CheckPaletteAnim();
+
+	static void PaintThreadThunk(VideoDriver_Win32 *drv);
 };
 
 /** The factory for Windows' video driver. */