Draft: perf: Faster contact switching by caching spell checkers
This commit makes is snappier to switch between chat by caching the Gspell.Checker objects.
It triggers a linter error about a possible memory leak using lru_cache on methods but AFAIU it can be safely ignored since MessageInputTextView and TextBufferManager are singletons, see https://bugs.python.org/issue19859
Maybe 128 is too high a value for this cache, I'm not sure what's a sane size.
Benchmark
Procedure: switching between 2 contacts 20 times
Before patch
| Name | Call Count | Time (ms) | Own time (ms) |
|---|---|---|---|
| _init_spell_checker | 20 | 884 | 883 |
| show_chat | 20 | 1842 | 224 |
| switch_contact | 20 | 1088 | 185 |
After patch
| Name | Call Count | Time (ms) | Own time (ms) |
|---|---|---|---|
| show_chat | 20 | 823 | 223 |
| switch_contact | 20 | 3 | 0 |
| _init_spell_checker | 20 | 100 | 0 |