fix(ElementHandle.boundingBox): account for margin, padding, and border in element.boxModel (#1017)

This patch starts relying on border quad to compute element's bounding box.

Fixes #1010

lib/ElementHandle.js

@@ -116,20 +116,22 @@ class ElementHandle extends JSHandle {
   }
 
   /**
-   * @return {!Promise<Object>}
+   * @return {!Promise<{x: number, y: number, width: number, height: number}>}
    */
   async boundingBox() {
-    const boxModel = await this._client.send('DOM.getBoxModel', {
+    const {model} = await this._client.send('DOM.getBoxModel', {
       objectId: this._remoteObject.objectId
     });
-    if (!boxModel || !boxModel.model)
-      return null;
-    return {
-      x: boxModel.model.margin[0],
-      y: boxModel.model.margin[1],
-      width: boxModel.model.width,
-      height: boxModel.model.height
-    };
+    if (!model)
+      throw new Error('Node is detached from document');
+
+    const quad = model.border;
+    const x = Math.min(quad[0], quad[2], quad[4], quad[6]);
+    const y = Math.min(quad[1], quad[3], quad[5], quad[7]);
+    const width = Math.max(quad[0], quad[2], quad[4], quad[6]) - x;
+    const height = Math.max(quad[1], quad[3], quad[5], quad[7]) - y;
+
+    return {x, y, width, height};
   }
 
   /**

test/test.js

@@ -1503,6 +1503,33 @@ describe('Page', function() {
       const screenshot = await elementHandle.screenshot();
       expect(screenshot).toBeGolden('screenshot-element-bounding-box.png');
     }));
+    it('should take into account padding and border', SX(async function() {
+      await page.setViewport({width: 500, height: 500});
+      await page.setContent('something above<h1 style="border:2px solid blue; background: green;">&nbsp;</h1>');
+      const elementHandle = await page.$('h1');
+      const screenshot = await elementHandle.screenshot();
+      expect(screenshot).toBeGolden('screenshot-element-padding-border.png');
+    }));
+    it('should work with a rotated element', SX(async function() {
+      await page.setViewport({width: 500, height: 500});
+      await page.setContent(`<div style="position:absolute;
+                                         top: 100px;
+                                         left: 100px;
+                                         width: 100px;
+                                         height: 100px;
+                                        background: green;
+                                        transform: rotateZ(200deg);">&nbsp;</div>`);
+      const elementHandle = await page.$('div');
+      const screenshot = await elementHandle.screenshot();
+      expect(screenshot).toBeGolden('screenshot-element-rotate.png');
+    }));
+    it('should fail to screenshot a detached element', SX(async function() {
+      await page.setContent('<h1>remove this</h1>');
+      const elementHandle = await page.$('h1');
+      await page.evaluate(element => element.remove(), elementHandle);
+      const screenshotError = await elementHandle.screenshot().catch(error => error);
+      expect(screenshotError.message).toBe('Node is detached from document');
+    }));
   });
 
   describe('input', function() {