line drawing

3 files changed, 35 insertions, 0 deletions

diff --git a/src/main.c b/src/main.c
index c3110a4..0e5e502 100644
--- a/src/main.c
+++ b/src/main.c
@@ -61,6 +61,7 @@ main(void)
 		pxPal(3, 11);
 		pxPalt(3, true);
 		pxSpr(&spr, x, y + 8, .flip_x=true, .flip_y=true);
+		pxLine(0, 0, x, y, 2);;
 
 		pxPset(0, 0, 10);
 		pxPset(1, 0, 10);
diff --git a/src/px.c b/src/px.c
index 267b2e0..7458bcd 100644
--- a/src/px.c
+++ b/src/px.c
@@ -181,6 +181,37 @@ pxRectfill(int x0, int y0, int x1, int y1, PxCol col)
 }
 
 void
+pxLine(int x0, int y0, int x1, int y1, PxCol col)
+{
+	int dx, dy, sx, sy, err, e2;
+
+	dx = x1 - x0;
+	dx = (dx < 0) ? (-dx) : (dx);
+	dy = y1 - y0;
+	dy = (dy < 0) ? (dy) : (-dy);
+	sx = (x0 < x1) ? (1) : (-1);
+	sy = (y0 < y1) ? (1) : (-1);
+	err = dx + dy;
+
+	for (;;) {
+		pxPset(x0, y0, col);
+
+		if (x0 == x1 && y0 == y1)
+			break;
+
+		e2 = 2 * err;
+		if (e2 >= dy) {
+			err += dy;
+			x0 += sx;
+		}
+		if (e2 <= dx) {
+			err += dx;
+			y0 += sy;
+		}
+	}
+}
+
+void
 _pxSpr(const PxSprArgs *args)
 {
 	int w = (args->w < 0) ? (int)(args->spr->w) : (args->w);
diff --git a/src/px.h b/src/px.h
index 713f245..9eb9610 100644
--- a/src/px.h
+++ b/src/px.h
@@ -88,6 +88,9 @@ void pxRect(int x0, int y0, int x1, int y1, PxCol col);
 /* Draw filled rectangle. */
 void pxRectfill(int x0, int y0, int x1, int y1, PxCol col);
 
+/* Draw line. */
+void pxLine(int x0, int y0, int x1, int y1, PxCol col);
+
 /* Draw sprite. */
 #define pxSpr(...) _pxSpr(&(const PxSprArgs){ \
 	.x=0, .y=0, .ix=0, .iy=0, .w=-1, .h=-1, .flip_x=false, .flip_x=false, \