Allow toggling fullscreen without restart and add keybind (#14714)

irr/include/IrrlichtDevice.h

@@ -179,6 +179,11 @@ public:
 	/** \return True if window is fullscreen. */
 	virtual bool isFullscreen() const = 0;
 
+	//! Enables or disables fullscreen mode.
+	/** Only works on SDL.
+	\return True on success. */
+	virtual bool setFullscreen(bool fullscreen) { return false; }
+
 	//! Checks if the window could possibly be visible.
 	/** If this returns false, you should not do any rendering. */
 	virtual bool isWindowVisible() const { return true; };

irr/src/CIrrDeviceSDL.cpp

@@ -463,13 +463,7 @@ bool CIrrDeviceSDL::createWindowWithContext()
 {
 	u32 SDL_Flags = 0;
 
-	if (CreationParams.Fullscreen) {
-#ifdef _IRR_EMSCRIPTEN_PLATFORM_
-		SDL_Flags |= SDL_WINDOW_FULLSCREEN;
-#else
-		SDL_Flags |= SDL_WINDOW_FULLSCREEN_DESKTOP;
-#endif
-	}
+	SDL_Flags |= getFullscreenFlag(CreationParams.Fullscreen);
 	if (Resizable)
 		SDL_Flags |= SDL_WINDOW_RESIZABLE;
 	if (CreationParams.WindowMaximized)
@@ -889,6 +883,14 @@ bool CIrrDeviceSDL::run()
 			IsInBackground = false;
 			break;
 
+		case SDL_RENDER_TARGETS_RESET:
+			os::Printer::log("Received SDL_RENDER_TARGETS_RESET. Rendering is probably broken.", ELL_ERROR);
+			break;
+
+		case SDL_RENDER_DEVICE_RESET:
+			os::Printer::log("Received SDL_RENDER_DEVICE_RESET. Rendering is probably broken.", ELL_ERROR);
+			break;
+
 		default:
 			break;
 		} // end switch
@@ -1157,14 +1159,37 @@ bool CIrrDeviceSDL::isWindowMaximized() const
 
 bool CIrrDeviceSDL::isFullscreen() const
 {
-#ifdef _IRR_EMSCRIPTEN_PLATFORM_
-	return SDL_GetWindowFlags(0) == SDL_WINDOW_FULLSCREEN;
-#else
+	if (!Window)
+		return false;
+	u32 flags = SDL_GetWindowFlags(Window);
+	return (flags & SDL_WINDOW_FULLSCREEN) != 0 ||
+			(flags & SDL_WINDOW_FULLSCREEN_DESKTOP) != 0;
+}
 
-	return CIrrDeviceStub::isFullscreen();
+u32 CIrrDeviceSDL::getFullscreenFlag(bool fullscreen)
+{
+	if (!fullscreen)
+		return 0;
+#ifdef _IRR_EMSCRIPTEN_PLATFORM_
+	return SDL_WINDOW_FULLSCREEN;
+#else
+	return SDL_WINDOW_FULLSCREEN_DESKTOP;
 #endif
 }
 
+bool CIrrDeviceSDL::setFullscreen(bool fullscreen)
+{
+	if (!Window)
+		return false;
+	// The SDL wiki says that this may trigger SDL_RENDER_TARGETS_RESET, but
+	// looking at the SDL source, this only happens with D3D, so it's not
+	// relevant to us.
+	bool success = SDL_SetWindowFullscreen(Window, getFullscreenFlag(fullscreen)) == 0;
+	if (!success)
+		os::Printer::log("SDL_SetWindowFullscreen failed", SDL_GetError(), ELL_ERROR);
+	return success;
+}
+
 bool CIrrDeviceSDL::isWindowVisible() const
 {
 	return !IsInBackground;

irr/src/CIrrDeviceSDL.h

@@ -86,6 +86,10 @@ public:
 	/** \return True if window is fullscreen. */
 	bool isFullscreen() const override;
 
+	//! Enables or disables fullscreen mode.
+	/** \return True on success. */
+	bool setFullscreen(bool fullscreen) override;
+
 	//! Checks if the window could possibly be visible.
 	bool isWindowVisible() const override;
 
@@ -299,6 +303,8 @@ private:
 
 	bool Resizable;
 
+	static u32 getFullscreenFlag(bool fullscreen);
+
 	core::rect<s32> lastElemPos;
 
 	struct SKeyMap