Improve hit test performance by optimizing Y axis #177
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NickEntin
commented
Jan 4, 2024
| @@ -11,7 +11,7 @@ | |||
| <key>com.apple.XCTPerformanceMetric_WallClockTime</key> | |||
| <dict> | |||
| <key>baselineAverage</key> | |||
| <real>48.792810</real> | |||
| <real>17.200000</real> | |||
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This brings the run time to almost (1 / scale factor), so in this case around a 65% improvement for a 3x device over the original implementation in #119.
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Increasing the maxPermissibleMissedRegionHeight to larger values continues to improve the run time, but you get diminishing returns.
2 => 10.259 sec
4 => 8.317 sec
dnagler
reviewed
Jan 4, 2024
| // error, in particular when dealing with bounds with a negative y origin. By striding to a value slightly | ||
| // less than the desired stop (small enough to be less than the density of any screen in the foreseeable | ||
| // future), we can avoid this rounding problem. | ||
| let stopEpsilon: CGFloat = 0.0001 |
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If we ever see screens with density high enough that this is an issue, I will eat my futuristic hat
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Maybe by the iPhone C
dnagler
reviewed
Jan 4, 2024
| } | ||
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| } else { | ||
| // No-op. We'll draw this on the next iteration. |
dnagler
approved these changes
Jan 4, 2024
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This is the first performance optimization for hit test snapshotting, focused on optimizing the Y axis.
Note this optimization introduces a possibility of missing a hit region, specifically in the case where there's a very thin horizontal hit region (for example, a hairline separator view) with the same hit target view on both sides. I think given the huge performance improvement, this is probably acceptable in most cases, but I made it configurable so it's up to consumers to make that trade-off.
Split into three commits: