Make map editor more like pico 8

util.ts

@@ -46,10 +46,27 @@ export const drawTransparentRect = (x: number, y: number, w: number, h: number)
 	})
 }
 
-export const subgrid = <T>(array: Array<T>, gridW: number, x: number, y: number, w: number, h: number): Array<T> => {
+export const drawVoidRect = (x: number, y: number, w: number, h: number) => {
+	Array(w*h).fill(0).map((_z, j) => {
+		const jx = j%w;
+		const jy = Math.floor(j/w);
+		setPixelColor(x+jx, y+jy, (jx+jy)%2 ? COLOR.BLACK : COLOR.DARKERBLUE);
+	})
+}
+
+export const subgrid = <T>(array: Array<T>, gridW: number, x: number, y: number, w: number, h: number): Array<T|undefined> => {
 	return Array(h).fill(0).flatMap((_, i) => {
-		const start = (y+i)*gridW+x;
-		return array.slice(start, start+w);
+		if (y+i < 0 || y+i > array.length/gridW) {
+			return Array(w).fill(undefined);
+		}
+		const x0 = Math.max(0, x);
+		const x1 = Math.min(x+w, gridW);
+		const start = (y+i)*gridW+x0;
+		const end = (y+i)*gridW+x1;
+		const before = Array(x0 - x).fill(undefined);
+		const after = Array((x+w) - x1).fill(undefined);
+		const middle = array.slice(start, end);
+		return [...before, ...middle, ...after];
 	})
 }