ttyplot.c: Call gettimeofday only once per loop

ttyplot.c

@@ -456,6 +456,7 @@ int main(int argc, char *argv[]) {
     int i;
     bool stdin_is_open = true;
     time_t prev_paint_at_seconds = 0;
+    long timeout_nanos = 0;
     int cached_opterr;
     const char *optstring = "2rc:e:E:s:m:M:t:u:vh";
     int show_ver;
@@ -613,17 +614,6 @@ int main(int argc, char *argv[]) {
                 select_nfds = tty + 1;
         }
 
-        // Determine how long we can allow `select` to sleep.  The rules are:
-        // 1. If we find the system clock has already advanced on seconds level,
-        //    there should be no delay, we should get the clock redrawn asap.
-        // 2. Otherwise wait (more or less) exactly until the system clock
-        //    has advanced, only then redraw the clock.
-        gettimeofday(&now, NULL);
-        int timeout_nanos = 0;
-        if (now.tv_sec == prev_paint_at_seconds) {
-            const suseconds_t microseconds_until_full_second = 1000 * 1000 - now.tv_usec;
-            timeout_nanos = 1000 * microseconds_until_full_second;
-        }
         struct timespec timeout = {
             .tv_sec = 0,
             .tv_nsec = timeout_nanos
@@ -666,6 +656,21 @@ int main(int argc, char *argv[]) {
 
         gettimeofday(&now, NULL);  // for input handling and also drawing
 
+        // Determine how long we can allow the next call to `select` to sleep.
+        // The rules are:
+        // 1. If we find the system clock has already advanced on seconds level,
+        //    there should be no delay, we should get the clock redrawn asap.
+        // 2. Otherwise wait (more or less) exactly until the system clock
+        //    has advanced, only then redraw the clock.
+        // 3. Consider input handling and drawing fast enough to be ignored
+        //    altogether.  That's Edgar's idea, Sebastian doesn't like it at all :)
+        if (now.tv_sec == prev_paint_at_seconds) {
+            const suseconds_t microseconds_until_full_second = 1000 * 1000 - now.tv_usec;
+            timeout_nanos = 1000 * microseconds_until_full_second;
+        } else {
+            timeout_nanos = 0;
+        }
+
         // Handle input data.
         if (select_ret > 0 && FD_ISSET(STDIN_FILENO, &read_fds)) {
             bool input_closed = handle_input_event();