When you click on the Share widget that is placed anywhere, in this case the header, the pop-up is displayed out of bounds.
And you have to swipe left to see the entire thing.
Hi Min-Hung Chou,
Are you seeing this in builder or after launched?
From your screenshot it looks like you are seeing this in builder. And based on my assumption, your page may be zoomed in a little bit and part of page is hide. If so I am afraid it is as expected. (Please correct if I am wrong. Below explanation is based on the assumption.)
What the share popup does is that it will first validate the distance between the share button and the page's right edge. If the distance is enough for the popup, it will open at right side. Otherwise, it will open left side. Note that it does not measure to the working window edge but page.
In the case, though if the page is partially hidden, the distance/ space from share button to page edge is enough to display a popup, it opens to that orientation, and it looks like cut same as your page.
What I suggest is that you can fit the page width to the current window, so you can see everything.
I am seeing this both in builder and after launched on mobile devices.
I am also doing all my edits in the small screen devices view, instead of the large default one.
Without clicking on the share button, everything is fix.
When you click on it, the frame expands, which you can see from the scroll bar at the bottom.
You are welcome to test it out yourself on your mobile device.
Maybe there is an option to lock the page that I am missing?