Black bar appears in terminal "empty rows" when its resized

[octref]

Issue Type: Bug

• Run tsc --watch
• Terminal split

VS Code version: Code - Insiders 1.24.0-insider (9275422, 2018-06-01T13:37:15.690Z)
OS version: Darwin x64 17.5.0

System Info

Item	Value
CPUs	Intel(R) Core(TM) i7-4770HQ CPU @ 2.20GHz (8 x 2200)
GPU Status	2d_canvas: enabled flash_3d: enabled flash_stage3d: enabled flash_stage3d_baseline: enabled gpu_compositing: enabled multiple_raster_threads: enabled_on native_gpu_memory_buffers: enabled rasterization: enabled video_decode: enabled video_encode: enabled vpx_decode: enabled webgl: enabled webgl2: enabled
Load (avg)	3, 2, 2
Memory (System)	16.00GB (0.98GB free)
Process Argv	/Applications/Visual Studio Code - Insiders.app/Contents/MacOS/Electron -psn_0_1364301
Screen Reader	no
VM	0%

Extensions (14)

Extension	Author (truncated)	Version
markdown-emoji	bie	0.0.7
tslint	eg2	1.0.30
vsc-material-theme	Equ	2.1.0
prettier-vscode	esb	1.4.0
theme-monokai-pro-vscode	mon	1.1.6
vscode-scss	mrm	0.6.2
debugger-for-chrome	msj	4.5.0
vetur	oct	0.12.3
vscode-proun	oct	0.0.1
polacode	pnp	0.2.2
vscode-sort-json	ric	1.11.0
vscode-csstree	sme	0.7.0
language-stylus	sys	1.9.2
vim	vsc	0.12.0

(2 theme extensions excluded)

[octref]

The shadowy scorllbar persists even after closing split terminal.

[chrmarti]

Removing from May milestone after checking with @Tyriar.

[Tyriar]

@bgw any idea what this could be? It appears to be a recent regression:

[bgw]

😕 😱 Given the artifacts that's manifesting with, this looks like it might be an electron/chromium bug, and not an xterm.js bug. We shouldn't even be doing any drawing work (aside from the initial background fill) to regions without text...

This is with the canvas renderer, right?

[Tyriar]

@bgw yes this is the canvas renderer. My first impression was it's a Chromium thing but it looks like the black columns are lining up with the terminal columns which makes me think it's our bug.

[Tyriar]

Updating to latest xterm.js doesn't appear to fix this.

[Tyriar]

May be related to #51602

[Tyriar]

It's definitely the text layer that has the issue.

[Tyriar]

This is looking more and more like a Chromium bug. If I change this line to be #FF0000, I do not get the bars. changing it to #888888 however and I do:

https://github.com/xtermjs/xterm.js/blob/1487b8d02d42a3aef6b7225d7745bbc488015aaa/src/renderer/BaseRenderLayer.ts#L177

[Tyriar]

Moving to June as it appears to be a Chrome issue, needs a workaround inside xterm.js and it's less impact than I first thought. It only impacts "null" rows, this does not happen when the viewport has been filled (you see a flicker but it goes away the next frame).

[bgw]

@Tyriar, what was the workaround for this?

[Tyriar]

@bgw the workaround didn't fix it, I tried to use clearRect in TextRenderLayer.onGridChanged which seemed to work on macOS, but didn't on other platforms #51749 (comment)

[Tyriar]

Can't repro this out of sources anymore 😕

[octref]

I'm on e585e4b

[Tyriar]

Yeah I see it in insiders, no running out of sources though 😕

[Tyriar]

I've also seen this happen:

[Tyriar]

Something similar can also happen in the color picker:

[Tyriar]

I think this one is fixed in Electron 3

[Tyriar]

This is also fixed by the webgl renderer I just build xtermjs/xterm.js#1790, not sure if we would ship that before Electron 3 though.

[bpasero]

Closing this issue given that we plan to release VSCode stable early February with Electron 3.x. If you want to benefit from the fix already, consider to use our insiders version that already contains the fix: https://code.visualstudio.com/insiders/