Old bodymovin compat

docs/compat.md

@@ -0,0 +1,70 @@
+# Compatibility with older versions
+
+This page describes breaking changes that have been introduced over time.
+
+You'd need to check `v` from {ref-link:animation/animation} to see the
+the lottie is so old to need to worry about these.
+
+The code examples are just for illustrative purposes and are not to be
+taken as a complete conversion code.
+
+## [0,255] Colors
+
+Until `v` 4.1.9.
+
+Modern Lotties have [color](concepts.md#colors) components in the [0, 1] range.
+Older ones have components in the [0, 255] range.
+
+Fix: Divide all color components by 255.
+
+## Static text document
+
+Until `v` 4.4.14.
+
+In {ref-link:text/text-data}, `d` was not animated.
+
+Fix: Wrap into an animated property
+
+`text_layer.t.d = {"a": 0, "k": text_layer.t.d}`
+
+## Shape closing
+
+Until `v` 4.4.18.
+
+{ref-link:shapes/path} objects had a boolean `closed` property and `c` was not
+present in the bezier data.
+
+Similarly, {ref-link:helpers/mask} had `cl` that worked the same way.
+
+Fix: For each {ref-link:shapes/path}, update all the keyframes
+(or the non-animated value) of `ks`.
+Do the same to fix `pt` in each {ref-link:helpers/mask}.
+
+`shape.ks.k.c = shape.closed ? 1 : 0`
+
+## Old keyframe style
+
+Until `v` 5.0.0 (?).
+
+[Keyframes](concepts.md#keyframe) had an `e` property that specified
+the end value for that keyframe (`s` marking the start value),
+and the last keyframe would not have `s`.
+
+Fix: Ignore all the `e` in keyframes, but copy the `e` from the keyframe
+before last into the last keyframe.
+
+`keyframes[keyframes.length - 1].s = keyframes[keyframes.length - 2].e`
+
+
+
+## Static text layer properties
+
+Until `v` 5.7.15.
+
+In {ref-link:text/text-follow-path} properties `r`, `a`, and `p` were
+plain numbers instead of animated properties.
+
+Fix: Wrap all of those into animated properties
+
+`text_layer.t.p.a + {"a": 0, "k": text_layer.t.p.a}`
+

mkdocs.yml

@@ -42,6 +42,7 @@ nav:
         - constants.md
         - text.md
         - expressions.md
+        - compat.md
     - "Playground":
         - "Builder": playground/builder.md
         - "JSON Editor": playground/json_editor.md