entry.intersectionRatio is not exactly 1.0

[aminya]

Details

• Browser and browser version: Electron 6
• OS version: Win 10
• xterm.js version: 4.9.0

Steps to reproduce

We hit a strange bug that was blocking us for a couple of days. Until we found the intersectionRatio is sometimes near to 1.0 (like 0.99) but not exactly 1.0.

atom-community/terminal#5 (comment)
atom-community/terminal#5

I just wanted to let you know about this behavior.

We had a condition to create xterm Element only if intersectionRatio === 1.0 which was not being triggered (this condition was to avoid bus-stop/x-terminal#57).

Suggestion

Introduce a boolean value that shows if the intersectionRatio is almost 1.

[UziTech]

This is probably a bug in chrome not xterm.

[aminya]

Where can we report this bug? Should it be chromium? https://chromium.googlesource.com/chromium/src/

[aminya]

There seems to exist a isIntersecting property:

xterm.js/src/browser/services/RenderService.ts

Line 89 in b89d4b1

this._isPaused = entry.isIntersecting === undefined ? (entry.intersectionRatio === 0) : !entry.isIntersecting;

But seems to have its own issues: #2998 (comment)

[Tyriar]

Looks like you've already fixed it, no?

atom-community/terminal@7a05451

We only care if it's partially visible (entry.intersectionRatio === 0):

xterm.js/src/browser/services/RenderService.ts

Line 89 in b89d4b1

this._isPaused = entry.isIntersecting === undefined ? (entry.intersectionRatio === 0) : !entry.isIntersecting;

[aminya]

We solved it by a workaround, but this is a xterm issue. xterm should not allow the following error:
bus-stop/x-terminal#57 (comment)

[UziTech]

That error comes from the fit addon. Running fit when the canvas that has a 0 width or height will throw the error Uncaught Error: This API only accepts integers

[Tyriar]

We could handle that better but in the end the right behavior is probably still throw, just with a better message about NaN terminal dimensions.

[UziTech]

I feel like fit being called on a hidden element or one with 0 width or height shouldn't throw an error. It should just check for that situation and return early without doing anything. I can't see a situation where that would be a problem.

[UziTech]

It already seems to do something similar if the terminal isn't connected to the dom

xterm.js/addons/xterm-addon-fit/src/FitAddon.ts

Lines 36 to 38 in 4e18a78

	if (!dims || !this._terminal) {
	return;
	}