bugfix: KMSDRM fixes for when using a single window (fixes #1411)

Disable integer scaling when opening the GUI, trigger an update of scaling options when resuming

src/osdep/amiberry_gui.cpp

@@ -544,6 +544,10 @@ void gui_display(int shortcut)
 	//rawinput_alloc();
 	struct AmigaMonitor* mon = &AMonitors[0];
 	SDL_SetWindowGrab(mon->amiga_window, SDL_TRUE);
+	if (kmsdrm_detected && amiga_surface != nullptr)
+	{
+		target_graphics_buffer_update(mon->monitor_id, true);
+	}
 	fpscounter_reset();
 	//screenshot_free();
 	//write_disk_history();

src/osdep/gui/main_window.cpp

@@ -346,6 +346,10 @@ void amiberry_gui_init()
 			SDL_FreeSurface(icon_surface);
 		}
 	}
+	else if (kmsdrm_detected)
+	{
+		SDL_SetWindowSize(mon->gui_window, GUI_WIDTH * amiberry_options.window_scaling, GUI_HEIGHT * amiberry_options.window_scaling);
+	}
 
 	if (mon->gui_renderer == nullptr)
 	{
@@ -355,6 +359,8 @@ void amiberry_gui_init()
 
 	// make the scaled rendering look smoother (linear scaling).
 	SDL_SetHint(SDL_HINT_RENDER_SCALE_QUALITY, "linear");
+	// Disable integer scaling for the GUI
+	SDL_RenderSetIntegerScale(mon->gui_renderer, SDL_FALSE);
 
 	gui_texture = SDL_CreateTexture(mon->gui_renderer, gui_screen->format->format, SDL_TEXTUREACCESS_STREAMING, gui_screen->w,
 									gui_screen->h);