Defer text buffer line painting

[skyline75489]

Summary of the Pull Request

Defer painting when writing a lots of text.

References

#2960 #3075

PR Checklist

• Closes #xxx
• CLA signed. If not, go over here and sign the CLA
• Tests added/passed
• Requires documentation to be updated
• I've discussed this with core contributors already. If not checked, I'm ready to accept this work might be rejected in favor of a different grand plan. Issue number where discussion took place: #xxx

Detailed Description of the Pull Request / Additional comments

Calling NotifyPaint for every line is expensive and not really necessary. For performance reason, painting should wait for as much buffer as possible.

Validation Steps Performed

[zadjii-msft]

Won't this not work if the write wraps to the next line? This looks to me like it'll only invalidate the region of the buffer on the initial line, and none of the subsequent lines.

[skyline75489]

It occurs to me that the code base here is doing a lot of paint while writing buffer. Every cell calls NotifyPaint, whick makes render thread and terminal connection thread competing for CPU resource. This isn't right. The paint should be delayed as described in #3075. But I don't know how to achieve it without breaking a lots of things...

[skyline75489]

I'm gonna close this one in favor of #780. Hope it can land soon.