Sometimes image is not output in Safari

[sasanquaneuf]

• [o] You are using the latest version
• [o] You are testing using the non-minified version of html2canvas and checked any potential issues reported in the console

Bug reports:

Safari (iOS/Mac) fail to write image to canvas sometimes. The structure of html-element is following (simplified):

<div class="render-root">
  <img src="somefile.png" />
</div>

and pass the render-root div to html2canvas.
The image is already loaded and displayed, but the canvas didn't contain the image sometimes. I tried one hundred, and nearly eighty are succeed, bu other twenty there is no image in canvas.
I investigated this. In canvas-renderer.ts, renderReplacedElement() function has the input check image && container.intrinsicWidth > 0 && container.intrinsicHeight > 0, sometimes container.intrinsicWidth and container.intrinsicHeight are 0.

Specifications:

• html2canvas version tested with: 1.0.0-rc.7
• Browser & version: Safari 13.1(iOS), 13.1.1(Mac)
• Operating system: iOS/Mac

Note:

When I re-called html2canvas, then the phenomenon was disappeared. So, when container.intrinsicWidth === 0 || container.intrinsicHeight === 0 I hope to reject the result promise.
For this purpose, I'll create pull-request that add option for reject image loading error (contains width/height are zero).

[niklasvh]

Should be fixed with #2577