fix(display/bézier): make control points wider to cover whole canvas

perhaps in the future it would be best to specify bounds

Author: ulahello

display/rendering/canvas.h

@@ -31,13 +31,12 @@ struct line {
 	struct color c;
 };
 
-// TODO: control points are not tight to the bounds of the curve, so either
-// 1) explicitly pass bounds, infer i32 control points from that, or
-// 2) explicitly pass control points as i32s
 struct bezier2 {
-	uint16_t x0, y0;
-	uint16_t x1, y1;
-	uint16_t x2, y2;
+	// Control points are wider than u16 to allow expressing
+	// curves across the whole canvas.
+	int32_t x0, y0;
+	int32_t x1, y1;
+	int32_t x2, y2;
 	struct color c;
 };
 

display/testing.c

@@ -305,7 +305,7 @@ static void test_bezier2(struct canvas *c)
 		.x0 = c->width / 4,
 		.y0 = c->height * 3 / 4,
 		.x1 = c->width / 2,
-		.y1 = 0,
+		.y1 = -c->height / 3,
 		.x2 = c->width * 3 / 4,
 		.y2 = c->height * 3 / 4,
 		.c = FG,