shithub: wl3d

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don't cargo cult timing shit

- "it's pretty and probably correct, lgtm ship it" → wrong.
- if we are doomed to fail, we should at least time our undoing accurately
- still not sure if this is enough/correct, but it seems to be (ε ≤ 1 ms). but
  i've been wrong before!

--- a/wl3d.c

+++ b/wl3d.c

@@ -16,8 +16,9 @@

 Channel *csc, *kbc, *msc;

 enum{

-	BILLION = 1000000000,

-	MILLION = 1000000

+	Te9 = 1000000000,

+	Te6 = 1000000,

+	Td = Te9/Tb

 };

 static Point p0;

 static Rectangle fbr, grabr;

@@ -170,7 +171,6 @@

 	return p;

 }

-/* use only for shortening buffers, no zeroing done */

 void *

 erealloc(void *p, ulong n)

 {

@@ -234,7 +234,7 @@

 void

 threadmain(int argc, char **argv)

 {

-	vlong t0, t, dt, Δ;

+	vlong t0, t, dt;

 	char *datdir = "/sys/games/lib/wl3d/";

 	step = mstep;

@@ -266,7 +266,7 @@

 		sysfatal("proccreate: %r");

 	init();

-	t0 = Δ = 0;

+	t0 = nsec();

 	for(;;){

 		if(nbrecv(reszc, nil) != 0){

 			if(getwindow(display, Refnone) < 0)

@@ -274,17 +274,12 @@

 			resetfb();

 		}

 		step();

+		t0 += Td;

 		t = nsec();

-		dt = 0;

-		if(t0 != 0){

-			dt = BILLION/Tb - (t - t0) - Δ;

-			if(dt >= MILLION)

-				sleep(dt/MILLION);

-		}

-		t0 = nsec();

-		if(dt != 0){

-			dt = (t0 - t) - (dt / MILLION) * MILLION;

-			Δ += (dt - Δ) / 100;

-		}

+		dt = (t0 - t) / Te6;

+		if(dt > 0)

+			sleep(dt);

+		else

+			t0 = t;

 	}

 }