a whole load of work in progress

static/viewport.js

@@ -0,0 +1,47 @@
+export class Viewport {
+    constructor() {
+        this.panX = 0;
+        this.panY = 0;
+        this.zoomLevel = 0;
+    }
+
+    get zoom() {
+        return Math.pow(2, this.zoomLevel * 0.25);
+    }
+
+    panAround(x, y) {
+        this.panX -= x / this.zoom;
+        this.panY -= y / this.zoom;
+    }
+
+    zoomIn(delta) {
+        this.zoomLevel += delta;
+        this.zoomLevel = Math.max(-16, Math.min(20, this.zoomLevel));
+    }
+
+    getVisibleRect(windowSize) {
+        let invZoom = 1 / this.zoom;
+        let width = windowSize.width * invZoom;
+        let height = windowSize.height * invZoom;
+        return {
+            x: this.panX - width / 2,
+            y: this.panY - height / 2,
+            width,
+            height,
+        };
+    }
+
+    toViewportSpace(x, y, windowSize) {
+        return [
+            (x - windowSize.width / 2) / this.zoom + this.panX,
+            (y - windowSize.height / 2) / this.zoom + this.panY,
+        ];
+    }
+
+    toScreenSpace(x, y, windowSize) {
+        return [
+            (x - this.panX) * this.zoom + windowSize.width / 2,
+            (y - this.panY) * this.zoom + windowSize.height / 2,
+        ];
+    }
+}