App layout is laggy when the window is being resized

[larz0]

See Reflow for comparison. I spoke to Anirudh of Reflow and he said it took them awhile to get Reflow into that state.

They did benchmarked some perf stuff and found that taking out heavy assets and resize listeners helped them smooth out resizing.

To reproduce:

1. Rename extensions folder to isolate the issue
2. Expand Brackets /src folder
3. Resize the window

Actual result:

• Text glitches in the project panel
• Layout is slightly laggy on edges

Expected result:

• See Reflow CC (:pray: @anirudhsasikumar)

[jasonsanjose]

Reviewed. Medium priority to @jasonsanjose.

[larz0]

@jasonsanjose this is slightly better now without any extensions installed.

[JeffryBooher]

@larz0 Is this worse with the new CEF build (Sprint 30 daily)? or are you seing this with Sprint 29 build? Corey posted something yesterday about serious redraw flicker due to resize and performance in CEF 1547 especially on Retina.

[larz0]

@JeffryBooher just tried the new CEF build and it's about the same. It's quite noticeable when you resize the window with the extension manager open.

[njx]

The resize performance doesn't seem significantly worse to me in the newest CEF (it was always bad :)), but the file tree redraw issue does look new--I don't recall seeing that before. I wonder if that's just a separate issue.

[peterflynn]

Fwiw, we will probably always have worse resize performance than Reflow (or most other HTML layouts, for that matter) because CodeMirror needs to actively do JS work on resize -- rather than letting browser-native layout take care of everything.

We could try to be clever and, for example, not fully refresh CodeMirror until the resize has crossed the boundaries of the extra-rendered-lines buffer that CodeMirror has available. That would not eliminate the lag from CM resizing, but it might possibly reduce it a whole lot.