SDL backends: Submit click events when focusing the window

Backends/RmlUi_Backend_SDL_GL2.cpp

@@ -166,6 +166,9 @@ bool Backend::Initialize(const char* window_name, int width, int height, bool al
 	if (SDL_Init(SDL_INIT_VIDEO) != 0)
 		return false;
 
+	// Submit click events when focusing the window.
+	SDL_SetHint(SDL_HINT_MOUSE_FOCUS_CLICKTHROUGH, "1");
+
 	// Request stencil buffer of at least 8-bit size to supporting clipping on transformed elements.
 	SDL_GL_SetAttribute(SDL_GL_STENCIL_SIZE, 8);
 	SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);

Backends/RmlUi_Backend_SDL_GL3.cpp

@@ -126,6 +126,9 @@ bool Backend::Initialize(const char* window_name, int width, int height, bool al
 	if (SDL_Init(SDL_INIT_VIDEO) != 0)
 		return false;
 
+	// Submit click events when focusing the window.
+	SDL_SetHint(SDL_HINT_MOUSE_FOCUS_CLICKTHROUGH, "1");
+
 #if defined RMLUI_PLATFORM_EMSCRIPTEN
 	// GLES 3.0 (WebGL 2.0)
 	SDL_GL_SetAttribute(SDL_GL_CONTEXT_FLAGS, 0);

Backends/RmlUi_Backend_SDL_SDLrenderer.cpp

@@ -59,6 +59,9 @@ bool Backend::Initialize(const char* window_name, int width, int height, bool al
 	if (SDL_Init(SDL_INIT_VIDEO) != 0)
 		return false;
 
+	// Submit click events when focusing the window.
+	SDL_SetHint(SDL_HINT_MOUSE_FOCUS_CLICKTHROUGH, "1");
+
 	const Uint32 window_flags = (allow_resize ? SDL_WINDOW_RESIZABLE : 0);
 	SDL_Window* window = SDL_CreateWindow(window_name, SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, width, height, window_flags);
 	if (!window)

Backends/RmlUi_Backend_SDL_VK.cpp

@@ -61,6 +61,9 @@ bool Backend::Initialize(const char* window_name, int width, int height, bool al
 	if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_EVENTS | SDL_INIT_TIMER) != 0)
 		return false;
 
+	// Submit click events when focusing the window.
+	SDL_SetHint(SDL_HINT_MOUSE_FOCUS_CLICKTHROUGH, "1");
+
 	const Uint32 window_flags = (SDL_WINDOW_VULKAN | (allow_resize ? SDL_WINDOW_RESIZABLE : 0));
 
 	SDL_Window* window = SDL_CreateWindow(window_name, SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, width, height, window_flags);