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examples/js/util.js

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+const pixelRatio = 2;
+let isDown = false, moveX = 0, moveY = 0, offsetX = 0, offsetY = 0;
+let canvas, ctx;
+let renderer, stage;
+let sw = document.body.clientWidth;
+let sh = document.body.clientHeight;
+
+function generateCanvas() {
+    canvas = document.createElement('canvas');
+    document.body.appendChild(canvas);
+    ctx = canvas.getContext("2d");
+
+    window.addEventListener('resize', canvasResize, false);
+    canvasResize();
+
+    moveEvent(canvas);
+}
+
+function canvasResize() {
+    sw = document.body.clientWidth;
+    sh = document.body.clientHeight;
+
+    canvas.width = sw * pixelRatio;
+    canvas.height = sh * pixelRatio;
+    canvas.style.width = sw + 'px';
+    canvas.style.height = sh + 'px';
+    ctx.scale(pixelRatio, pixelRatio);
+}
+
+function generatePixi(bgcolor) {
+    renderer = new PIXI.Renderer({
+        width: sw,
+        height: sh,
+        antialias: true,
+        transparent: false,
+        autoDensity: true,
+        resolution: pixelRatio,//window.devicePixelRatio > 1 ? 2 : 1,
+        powerPreference: "high-performance",
+        backgroundColor: bgcolor
+    });
+    document.body.appendChild(renderer.view);
+    stage = new PIXI.Container();
+
+    window.addEventListener('resize', pixiResize, false);
+    pixiResize();
+
+    moveEvent(renderer.view);
+}
+
+function pixiResize() {
+    sw = document.body.clientWidth;
+    sh = document.body.clientHeight;
+
+    renderer.resize(sw, sh);
+}
+
+function moveEvent(canvas) {
+    const hammer = new Hammer(canvas);
+    hammer.add(new Hammer.Pan({direction: Hammer.DIRECTION_ALL, threshold: 0}));
+    hammer.on("pan", (e) => {                
+        moveX = e.deltaX + offsetX;
+        moveY = e.deltaY + offsetY;
+        if (e.isFinal) {
+            offsetX = moveX;
+            offsetY = moveY;
+        }
+    });
+}
+
+function getSize(size) {
+    let ratio = Math.sqrt(sw * sw + sh * sh) / 1800;
+    if (ratio > 1) ratio = 1;
+    else if (ratio < 0.5) ratio = 0.5;
+    return size * ratio;
+}