Codechange: [SDL2] Allow several places to hook into the SDL driver

This allows future subdrivers to use these to manage their
own flow.

src/video/sdl2_v.cpp

@@ -126,9 +126,16 @@ void VideoDriver_SDL::Paint()
 				this->UpdatePalette();
 				break;
 
-			case Blitter::PALETTE_ANIMATION_BLITTER:
+			case Blitter::PALETTE_ANIMATION_BLITTER: {
+				bool need_buf = _screen.dst_ptr == nullptr;
+				if (need_buf) _screen.dst_ptr = this->GetVideoPointer();
 				blitter->PaletteAnimate(this->local_palette);
+				if (need_buf) {
+					this->ReleaseVideoPointer();
+					_screen.dst_ptr = nullptr;
+				}
 				break;
+			}
 
 			case Blitter::PALETTE_ANIMATION_NONE:
 				break;
@@ -248,11 +255,26 @@ static uint FindStartupDisplay(uint startup_display)
 	return 0;
 }
 
-bool VideoDriver_SDL::CreateMainWindow(uint w, uint h)
+void VideoDriver_SDL::ClientSizeChanged(int w, int h, bool force)
+{
+	/* Allocate backing store of the new size. */
+	if (this->AllocateBackingStore(w, h, force)) {
+		/* Mark all palette colours dirty. */
+		_cur_palette.first_dirty = 0;
+		_cur_palette.count_dirty = 256;
+		this->local_palette = _cur_palette;
+
+		BlitterFactory::GetCurrentBlitter()->PostResize();
+
+		GameSizeChanged();
+	}
+}
+
+bool VideoDriver_SDL::CreateMainWindow(uint w, uint h, uint flags)
 {
 	if (this->sdl_window != nullptr) return true;
 
-	Uint32 flags = SDL_WINDOW_SHOWN | SDL_WINDOW_RESIZABLE;
+	flags |= SDL_WINDOW_SHOWN | SDL_WINDOW_RESIZABLE;
 
 	if (_fullscreen) {
 		flags |= SDL_WINDOW_FULLSCREEN;
@@ -302,17 +324,13 @@ bool VideoDriver_SDL::CreateMainSurface(uint w, uint h, bool resize)
 
 	if (!this->CreateMainWindow(w, h)) return false;
 	if (resize) SDL_SetWindowSize(this->sdl_window, w, h);
-
-	if (!this->AllocateBackingStore(w, h, true)) return false;
+	this->ClientSizeChanged(w, h, true);
 
 	/* When in full screen, we will always have the mouse cursor
 	 * within the window, even though SDL does not give us the
 	 * appropriate event to know this. */
 	if (_fullscreen) _cursor.in_window = true;
 
-	BlitterFactory::GetCurrentBlitter()->PostResize();
-
-	GameSizeChanged();
 	return true;
 }
 
@@ -350,13 +368,18 @@ bool VideoDriver_SDL::AllocateBackingStore(int w, int h, bool force)
 	_screen.width = _sdl_surface->w;
 	_screen.height = _sdl_surface->h;
 	_screen.pitch = _sdl_surface->pitch / (bpp / 8);
-	_screen.dst_ptr = _sdl_surface->pixels;
+	_screen.dst_ptr = this->GetVideoPointer();
 
 	this->MakePalette();
 
 	return true;
 }
 
+void *VideoDriver_SDL::GetVideoPointer()
+{
+	return _sdl_surface->pixels;
+}
+
 bool VideoDriver_SDL::ClaimMousePointer()
 {
 	SDL_ShowCursor(0);
@@ -944,11 +967,25 @@ Dimension VideoDriver_SDL::GetScreenSize() const
 
 bool VideoDriver_SDL::LockVideoBuffer()
 {
+	if (this->buffer_locked) return false;
+	this->buffer_locked = true;
+
 	if (this->draw_threaded) this->draw_lock.lock();
+
+	_screen.dst_ptr = this->GetVideoPointer();
+	assert(_screen.dst_ptr != nullptr);
+
 	return true;
 }
 
 void VideoDriver_SDL::UnlockVideoBuffer()
 {
+	if (_screen.dst_ptr != nullptr) {
+		/* Hand video buffer back to the drawing backend. */
+		this->ReleaseVideoPointer();
+		_screen.dst_ptr = nullptr;
+	}
+
 	if (this->draw_threaded) this->draw_lock.unlock();
+	this->buffer_locked = false;
 }

src/video/sdl2_v.h

@@ -52,6 +52,7 @@ protected:
 	std::recursive_mutex *draw_mutex = nullptr; ///< Mutex to keep the access to the shared memory controlled.
 	std::condition_variable_any *draw_signal = nullptr; ///< Signal to draw the next frame.
 	volatile bool draw_continue; ///< Should we keep continue drawing?
+	bool buffer_locked; ///< Video buffer was locked by the main thread.
 
 	Dimension GetScreenSize() const override;
 	void InputLoop() override;
@@ -61,8 +62,17 @@ protected:
 	void PaintThread() override;
 	void CheckPaletteAnim() override;
 
+	/** Indicate to the driver the client-side might have changed. */
+	void ClientSizeChanged(int w, int h, bool force);
+
 	/** (Re-)create the backing store. */
 	virtual bool AllocateBackingStore(int w, int h, bool force = false);
+	/** Get a pointer to the video buffer. */
+	virtual void *GetVideoPointer();
+	/** Hand video buffer back to the painting backend. */
+	virtual void ReleaseVideoPointer() {}
+	/** Create the main window. */
+	virtual bool CreateMainWindow(uint w, uint h, uint flags = 0);
 
 private:
 	int PollEvent();