Avoid polling in main GUI loop

mjs commented 5 years ago

Description

Instead of waking up regularly using WaitEventsTimeout, WaitEvents and PostEmptyEvent are used to make the main loop event driven. The maximum rate of redraws due to terminal activity can be tweaked via the new wakePeriod const.

This leads to some significant performance improvements: Aminal now consumes:

no CPU when idle (previously ~2.7% on my laptop)
~8.5% CPU on my laptop when running htop full screen on a large monitor (previously ~18.5%)
scrolling large amounts of output is an order of magnitude faster

This change also incidentally fixes data races around the terminal dirty flag (which is now gone).

Type of change

[x] Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

This has seen extensive manual testing on Windows and Linux using cmd.exe, Windows SSH to Linux host, zsh and bash on Linux.

Test Configuration:

OS: Linux and Windows
OS version: Ubuntu 18.04 and Windows 1809
Go version: 1.12

Checklist:

[x] My code follows the style guidelines of this project
[x] I have performed a self-review of my own code
[x] I have commented my code, particularly in hard-to-understand areas
[ ] I have made corresponding changes to the documentation
[x] My changes generate no new warnings
[x] I have added tests that prove my fix is effective or that my feature works
[x] New and existing unit tests pass locally with my changes
[ ] Any dependent changes have been merged and published in downstream modules

rrrooommmaaa commented 5 years ago

@mjs Why didn't you put dirty notifier to TerminalState? Terminal and buffer share this object already. No need for extra argument in constructor. @MaxRis I suggest we optimize this

maxhora commented 5 years ago

@rrrooommmaaa will it be fine to add improvements as new separate PR?

mjs commented 5 years ago

@rrrooommmaaa I considered putting dirty onto TerminalState but given that the dirty state was set for several conditions that don't involve a change to TerminalState it didn't seem like the right place for it.

I'm happy to revisit this later if you think it's worthwhile.

rrrooommmaaa commented 5 years ago

@mjs What conditions? Can you give examples, please?

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