Remove Mozilla specific setFocus implementation which waits for a focus event before returning. #10584
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…us event before returning. This was added in nvaccess#8678 to mitigate focus "rubber-banding" and spurious switching to focus mode when moving fast in browse mode. However, this degrades performance. Removing this code, this no longer seems to be a problem. It's likely that changes in Firefox, NVDA or both mitigated this. The changes to Firefox to avoid extraneous tree re-creation are a likely candidate.
michaelDCurran
approved these changes
Dec 9, 2019
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Link to issue number:
None.
Summary of the issue:
This setFocus override was added in #8678 to mitigate focus "rubber-banding" and spurious switching to focus mode when moving fast in browse mode. However, this degrades performance in Firefox.
Description of how this pull request fixes the issue:
This PR simply removes this code. We (@MarcoZehe and I) tested with this code removed for several hours in both normal daily usage and intentionally rapid usage. The rubber-banding/spurious focus mode switching no longer seem to be a problem.
It's likely that changes in Firefox, NVDA or both mitigated this. The changes to Firefox to avoid extraneous tree re-creation are a likely candidate, though I know there was also some refactoring of NVDA's focus handling code for browse mode.
Testing performed:
See above.
Known issues with pull request:
It's possible that we'll see the same issues this code was originally added to mitigate. However, it's worth noting that Chrome also sets focus asynchronously. I confirmed this by calling setFocus and then checking the focused state immediately afterwards. My best guess is that extraneous tree re-creation in older Firefox versions was causing enough of a perf hit to trigger these problems in Firefox... or perhaps Firefox was actually generating a new accessible for the focus when this occurred, which would have been even worse.
Change log entry:
Bug fixes:
- In Mozilla Firefox, moving focus in browse mode is faster. This makes moving the cursor in browse mode more responsive in many cases.