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Text animators: Tracking Amount in pixels, Subtract selectors stop at 0, as After Effects

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A text animator's Tracking Amount is in pixels in After Effects 2026, not in
1/1000 em like the Character panel's tracking: Amount 30 on every character
adds 30 px between neighbours (half before, half after each) at 80 px and at
40 px. And a Subtract range selector over characters the first selector
leaves out keeps them at 0 instead of selecting them negatively. With both,
the EXPORTER's t8 layer D (Tracking 30 on characters 2-4 by index, Subtract
over the last 20 %) puts every glyph where AE does (it ended 88 px short,
1553 vs 1641; now 1641).

The "Tracking In" text preset animates 40 -> 0 px (was 400 -> 0 thousandths
of an em, about the same at 100 px text); Lottie export writes a style run's
tracking (1/1000 em) as pixels for its tracking animator, which Lottie
players add in pixels.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
This commit is contained in:
vangel76
2026-10-19 16:41:15 +02:00
co-authored by Claude Opus 5.5
parent 83b134cdc8
commit 8ea876914d
6 changed files with 55 additions and 11 deletions
Download Patch File Download Diff File Expand all files Collapse all files
crates/text/src/selectors.rs
+7
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@@ -71,6 +71,10 @@ impl Mode {
pub fn combine(self, acc: f64, v: f64) -> f64 {
let r = match self {
Mode::Add => acc + v,
// Subtracting more than is selected leaves nothing, not a negative selection (After
// Effects 2026: a Subtract selector over unselected characters leaves their
// Tracking at 0, EXPORTER read-back t8).
Mode::Subtract if acc >= 0.0 => (acc - v).max(0.0),
Mode::Subtract => acc - v,
Mode::Intersect => acc * v,
Mode::Min => acc.min(v),
@@ -352,6 +356,9 @@ mod tests {
// A lone Subtract inverts.
assert_eq!(Mode::Subtract.combine(Mode::Subtract.initial(), 1.0), 0.0);
assert_eq!(Mode::Subtract.combine(Mode::Subtract.initial(), 0.0), 1.0);
// Subtracting from what is not selected leaves 0, not a negative selection (AE t8).
assert_eq!(Mode::Subtract.combine(0.0, 1.0), 0.0);
assert_eq!(Mode::Subtract.combine(0.25, 1.0), 0.0);
assert_eq!(Mode::from_index(5), Mode::Difference);
}