Editor search should match on notebook output by default

[joyceerhl]

Testing #174637

This repros for me with or without experimental scrollable output support enabled.

[amunger]

currently you need to specifically enable searching in cell output, but it might be a good idea to enable that when the focus was in the output when the find widget was opened.

cc @rebornix

[joyceerhl]

Would it make sense to enable searching in cell output by default (or have we received user feedback that it's noisy or undesirable to show those results)?

[amunger]

It's a performance concern, especially now that outputs can be much longer.

[isidorn]

+100 for enabling this by default. If it is a performance concern, could you provide more details why?
I am curious since our editor supports find / replace even when it open 100K+ lines of content.

fyi @rebornix since he might have advice on how Find works in huge editors

[rebornix]

The major concern we have for turning on find in output by default is performance since it requires all outputs to be rendered before searching keywords. I used PythonDataScienceHandbook as a good real world sample to test how much will be spent in rendering all outputs on the reveal of the find widget.

Most of notebooks in PythonDataScienceHandbook has cells between dozens to hundreds and they are good mixes of markdown cell and code cells with outputs. Rendering a cell output ~= 1 to 3ms depending on the output type (text or rich output like image). With a notebook that contains 100 cells, it takes around 200ms to 300ms to finish the full rendering of outputs. This process will block the renderer process for a while to prepare and send the output data to the webview, and then the webview will block for a while to render all outputs. A flame chart for this particular notebook is as below

To avoid the webview to be blocked for too long (which will affect the scrolling or any other user interactions), we want to request the output rendering when Idle, not only checking if the renderer process is Idle, but also if the webview is Idle. Another approach is only giving the output warmup task a small of time frame, for example, 100 ms per 5 seconds, to ensure it's not adding too much CPU cycles for just viewing the notebook.