Rerender frequently via extra ever-present event

This method has a small, but definite, performance impact.
The performance should be evaluated before this gets merged.

Consideration: This could be #ifdef'd for steam, but some people
might run non-steam games via steam and expect the overlay work
well which would be a paint for making it the default, not an ifdef

src/PonscripterLabel_event.cpp

@@ -36,8 +36,10 @@
 #define ONS_WAVE_EVENT (SDL_USEREVENT + 4)
 #define ONS_MUSIC_EVENT (SDL_USEREVENT + 5)
 
+#define INTERNAL_REDRAW_EVENT (SDL_USEREVENT + 6)
+
 // This sets up the fadeout event flag for use in mp3 fadeout.  Recommend for integration.  [Seung Park, 20060621]
-#define ONS_FADE_EVENT (SDL_USEREVENT + 6)
+#define ONS_FADE_EVENT (SDL_USEREVENT + 7)
 
 #define EDIT_MODE_PREFIX "[EDIT MODE]  "
 #define EDIT_SELECT_STRING "MP3 vol (m)  SE vol (s)  Voice vol (v)  Numeric variable (n)"
@@ -92,7 +94,6 @@ extern "C" Uint32 SDLCALL timerCallback(Uint32 interval, void* param)
     return interval;
 }
 
-
 extern "C" Uint32 cdaudioCallback(Uint32 interval, void* param)
 {
     SDL_RemoveTimer(timer_cdaudio_id);
@@ -1150,6 +1151,10 @@ int PonscripterLabel::eventLoop()
 {
     SDL_Event event, tmp_event;
 
+    SDL_Event redraw_event;
+    redraw_event.type = INTERNAL_REDRAW_EVENT;
+    SDL_PushEvent(&redraw_event);
+
     advancePhase();
 
     while (SDL_WaitEvent(&event)) {
@@ -1235,6 +1240,13 @@ int PonscripterLabel::eventLoop()
             flushEventSub(event);
             break;
 
+        case INTERNAL_REDRAW_EVENT:
+            rerender();
+            SDL_Event event;
+            event.type = INTERNAL_REDRAW_EVENT;
+            SDL_PushEvent(&event);
+            break;
+
         case ONS_WAVE_EVENT:
             flushEventSub(event);
             //printf("ONS_WAVE_EVENT %d: %x %d %x\n", event.user.code, wave_sample[0], automode_flag, event_mode);