Console Host redraws the current line after every character

Steps to reproduce

Launch powershell. Type a command. Observe that the cursor flickers left and right, back and forth, for every character you type. This may require a terminal with slower refresh.

Expected behavior

The input is only redrawn when it becomes necessary.

Actual behavior

The input is redrawn for every input character.

I profiled this, and found that for the input (and output):

PS > powershell redraws a lot

… which is a paltry few bytes, we emit 52,501 bytes of ANSI escape sequences repositioning the cursor, drawing colours, repositioning the cursor some more, etc.

Environment data

root@f49460ec9455:/# powershell -c '$PSVersionTable'

Name                           Value
----                           -----
PSVersion                      6.0.0-alpha
PSEdition                      Core
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0...}
BuildVersion                   3.0.0.0
GitCommitId                    v6.0.0-alpha.9
CLRVersion
WSManStackVersion              3.0
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1

[DHowett]

Thought: perhaps this is to mimic the Windows console’s support for drawing characters at any coordinates (without cursor moves)? It looks like we could be trying to do the same thing, but because it’s being used to such a high degree we’re emitting a veritable boatload of CSIs.

It’s especially noticeable over remote links with nonzero latency.

[iSazonov]

@masaeedu I cannot repo this. So you can open Issue in this repo. Later we can move it in PSReadLine repo.