Give live surfaces a clock and run timers; add a stopwatch

The terminal and the web page set the time events see to the wall clock
and tick an app's timers on time: each round ticks what is due, draws,
then waits for input, a frame or the next tick, and a tick is news to
every open page at once. Scripts have no clock: time MS sets the time
the next events see and tick TIMER ticks, so an app that uses time
replays exactly. A module swap reschedules the timers.

examples/stopwatch.aup runs on every surface; the checks drive it by
script, on a pseudo-terminal by the clock, and on the web page.

1 files changed, 29 insertions, 0 deletions

diff --git a/src/screen.c b/src/screen.c
index 56c2cf9..fdecaf4 100644
--- a/src/screen.c
+++ b/src/screen.c
@@ -1,7 +1,36 @@
+#define _POSIX_C_SOURCE 200809L
 #include "vega.h"
 #include "module-text.h"
 #include <math.h>
 #include <string.h>
+#include <time.h>
+
+double vega_now(void) {
+    struct timespec t;
+    clock_gettime(CLOCK_REALTIME, &t);
+    return floor((double)t.tv_sec * 1000 + (double)t.tv_nsec / 1e6);
+}
+
+void vega_timers_start(VegaTimers *timers, const PureModule *m, double now) {
+    for (uint32_t i = 0; i < m->inputs; ++i)
+        timers->next[i] = m->input[i].kind == PURE_KIND_TIMER ? now + m->input[i].period : 0;
+}
+
+long vega_timers_run(VegaTimers *timers, PureApp *app, double now, bool *ticked) {
+    const PureModule *m = app->module;
+    double soonest = -1;
+    for (uint32_t i = 0; i < m->inputs; ++i) {
+        if (m->input[i].kind != PURE_KIND_TIMER) continue;
+        if (timers->next[i] <= now) {
+            app->now = now;
+            pure_app_tick(app, i); /* a failed tick changes nothing, as any failed event */
+            *ticked = true;
+            timers->next[i] = now + m->input[i].period;
+        }
+        if (soonest < 0 || timers->next[i] - now < soonest) soonest = timers->next[i] - now;
+    }
+    return soonest < 0 ? -1 : (long)ceil(soonest);
+}
 
 static unsigned long evaluations;