Sample CSS animation property tracks

crates/obscura-render/src/lib.rs

@@ -495,6 +495,14 @@ impl BackgroundPositionAxis {
     pub fn resolve(self, leftover_space: f32) -> f32 {
         self.length + self.percentage * leftover_space
     }
+
+    pub(crate) fn interpolate(self, other: Self, position: f32) -> Self {
+        Self {
+            length: self.length + (other.length - self.length) * position,
+            percentage: self.percentage
+                + (other.percentage - self.percentage) * position,
+        }
+    }
 }
 
 /// The two axes of CSS `background-position`.
@@ -511,6 +519,13 @@ impl BackgroundPosition {
     pub const fn new(x: BackgroundPositionAxis, y: BackgroundPositionAxis) -> Self {
         Self { x, y }
     }
+
+    pub(crate) fn interpolate(self, other: Self, position: f32) -> Self {
+        Self {
+            x: self.x.interpolate(other.x, position),
+            y: self.y.interpolate(other.y, position),
+        }
+    }
 }
 
 /// Fill rule for a CSS `clip-path: polygon(...)`.

crates/obscura-render/src/style.rs

@@ -354,6 +354,17 @@ pub(crate) fn apply_animation_declarations(style: &mut LayoutStyle, css: &str) {
     }
 }
 
+/// Apply one already-cascaded keyframe declaration through the ordinary
+/// computed-style parser. The animation sampler deliberately reuses this
+/// path instead of maintaining a second, subtly different value parser.
+pub(crate) fn apply_animation_property_value(
+    style: &mut LayoutStyle,
+    name: &str,
+    value: &str,
+) {
+    apply_value(style, name, value);
+}
+
 fn apply_color_scheme(
     style: &mut LayoutStyle,
     value: &str,