🚸 TFT backlight PWM / brightness (#22841)

Marlin/src/lcd/dogm/marlinui_DOGM.cpp

@@ -338,6 +338,15 @@ void MarlinUI::draw_kill_screen() {
 
 void MarlinUI::clear_lcd() { } // Automatically cleared by Picture Loop
 
+#if HAS_LCD_BRIGHTNESS
+  void MarlinUI::_set_brightness() {
+    #if PIN_EXISTS(TFT_BACKLIGHT)
+      if (PWM_PIN(TFT_BACKLIGHT_PIN))
+        analogWrite(pin_t(TFT_BACKLIGHT_PIN), brightness);
+    #endif
+  }
+#endif
+
 #if HAS_LCD_MENU
 
   #include "../menu/menu.h"