demo: add demo_nanosleep() for HUD

src/demo/demo.h

@@ -124,6 +124,10 @@ int hud_schedule(const char* demoname);
 // demo_render(), which will ensure the HUD stays on the top of the z-stack.
 int demo_render(struct notcurses* nc);
 
+// if you won't be doing things, and it's a long sleep, consider using
+// demo_nanosleep(). it updates the HUD, which looks better to the user.
+int demo_nanosleep(struct notcurses* nc, const struct timespec *ts);
+
 int demo_fader(struct notcurses* nc, struct ncplane* ncp, void* curry);
 
 // grab the hud with the mouse

src/demo/hud.c

@@ -185,6 +185,26 @@ int hud_schedule(const char* demoname){
   return 0;
 }
 
+// wake up every 100ms and render a frame so the HUD doesn't look locked up
+int demo_nanosleep(struct notcurses* nc, const struct timespec *ts){
+  uint64_t nstotal = timespec_to_ns(ts);
+  uint64_t deadline;
+  struct timespec fsleep, now;
+
+  clock_gettime(CLOCK_MONOTONIC_RAW, &now);
+  deadline = timespec_to_ns(&now) + nstotal;
+  while(deadline - timespec_to_ns(&now) > GIG / 10){
+    fsleep.tv_sec = 0;
+    fsleep.tv_nsec = GIG / 10;
+    nanosleep(&fsleep, NULL);
+    demo_render(nc);
+    clock_gettime(CLOCK_MONOTONIC_RAW, &now);
+  }
+  ns_to_timespec(deadline - timespec_to_ns(&now), &fsleep);
+  nanosleep(&fsleep, NULL);
+  return 0;
+}
+
 int demo_render(struct notcurses* nc){
   if(hud){
     int plen = HUD_COLS - 4 - NSLEN;

src/demo/intro.c

@@ -94,7 +94,7 @@ int intro(struct notcurses* nc){
   if(demo_render(nc)){
     return -1;
   }
-  nanosleep(&demodelay, NULL);
+  demo_nanosleep(nc, &demodelay);
   struct timespec fade = demodelay;
   ncplane_fadeout(ncp, &fade, demo_fader, NULL);
   return 0;

src/demo/outro.c

@@ -49,7 +49,7 @@ fadethread(void* vnc){
   ncplane_erase(ncp);
   fade.tv_sec = 2;
   fade.tv_nsec = 0;
-  nanosleep(&fade, NULL);
+  demo_nanosleep(nc, &fade);
   ncplane_destroy(apiap);
   return vnc;
 }

src/demo/view.c

@@ -111,8 +111,8 @@ int view_demo(struct notcurses* nc){
     return -1;
   }
   demo_render(nc);
+  demo_nanosleep(nc, &demodelay);
   ncplane_move_bottom(dsplane);
-  nanosleep(&demodelay, NULL);
   if(ncvisual_render(ncv, 0, 0, 0, 0)){
     ncvisual_destroy(ncv);
     ncvisual_destroy(ncv2);
@@ -123,14 +123,14 @@ int view_demo(struct notcurses* nc){
   cell_set_fg_alpha(&b, CELL_ALPHA_TRANSPARENT);
   cell_set_bg_alpha(&b, CELL_ALPHA_TRANSPARENT);
   ncplane_set_base(ncvisual_plane(ncv2), &b);
+  demo_render(nc);
+  demo_nanosleep(nc, &demodelay);
   ncvisual_destroy(ncv);
   ncvisual_destroy(ncv2);
-  demo_render(nc);
-  nanosleep(&demodelay, NULL);
   ncplane_move_top(dsplane);
   demo_render(nc);
+  demo_nanosleep(nc, &demodelay);
   ncplane_destroy(dsplane);
-  nanosleep(&demodelay, NULL);
   struct ncplane* ncpl = legend(nc, dimy, dimx);
   if(ncpl == NULL){
     return -1;