The fiber will pause until the image has been written.
An easy way show a QR code on screen is to save it as SVG then open in with the Dialog web block, confine the Viewport width for proper scaling. Most apps displaying a black & white PNG image will use interpolated scaling that makes it blurry when enlarged, use the Image rescale block to quadruple its size, or more, to make it appear less so.
To scan a QR code use the App decision block with
the result will then be in the extras output variable.
If no app is capable of handling the action, i.e. an
then install the Barcode scanner app.