1 files changed, 304 insertions, 0 deletions
diff --git a/servo/ports/geckolib/tests/piecewise_linear.rs b/servo/ports/geckolib/tests/piecewise_linear.rs
new file mode 100644
index 0000000000..53a905f7ab
--- /dev/null
+++ b/servo/ports/geckolib/tests/piecewise_linear.rs
@@ -0,0 +1,304 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+use euclid::approxeq::ApproxEq;
+use style::piecewise_linear::{PiecewiseLinearFunction, PiecewiseLinearFunctionBuilder};
+
+fn get_linear_keyword_equivalent() -> PiecewiseLinearFunction {
+    PiecewiseLinearFunctionBuilder::new().build()
+}
+#[test]
+fn linear_keyword_equivalent_in_bound() {
+    let function = get_linear_keyword_equivalent();
+    assert!(function.at(0.).approx_eq(&0.));
+    assert!(function.at(0.5).approx_eq(&0.5));
+    assert!(function.at(1.0).approx_eq(&1.0));
+}
+
+#[test]
+fn linear_keyword_equivalent_out_of_bounds() {
+    let function = get_linear_keyword_equivalent();
+    assert!(function.at(-0.1).approx_eq(&-0.1));
+    assert!(function.at(1.1).approx_eq(&1.1));
+}
+
+fn get_const_function() -> PiecewiseLinearFunction {
+    PiecewiseLinearFunctionBuilder::new()
+        .push(CONST_VALUE as f32, None)
+        .build()
+}
+
+const CONST_VALUE: f32 = 0.2;
+
+#[test]
+fn const_function() {
+    let function = get_const_function();
+    assert!(function.at(0.).approx_eq(&CONST_VALUE));
+    assert!(function.at(0.5).approx_eq(&CONST_VALUE));
+    assert!(function.at(1.0).approx_eq(&CONST_VALUE));
+}
+
+#[test]
+fn const_function_out_of_bounds() {
+    let function = get_const_function();
+    assert!(function.at(-0.1).approx_eq(&CONST_VALUE));
+    assert!(function.at(1.1).approx_eq(&CONST_VALUE));
+}
+
+#[test]
+fn implied_input_spacing() {
+    let explicit_spacing = PiecewiseLinearFunctionBuilder::new()
+        .push(0.0, Some(0.0))
+        .push(1.0, Some(1.0))
+        .build();
+    let implied_spacing = PiecewiseLinearFunctionBuilder::new()
+        .push(0.0, None)
+        .push(1.0, None)
+        .build();
+    assert!(implied_spacing.at(0.).approx_eq(&explicit_spacing.at(0.)));
+    assert!(implied_spacing.at(0.5).approx_eq(&explicit_spacing.at(0.5)));
+    assert!(implied_spacing.at(1.0).approx_eq(&explicit_spacing.at(1.0)));
+}
+
+#[test]
+fn interpolation() {
+    let interpolate = PiecewiseLinearFunctionBuilder::new()
+        .push(0.0, None)
+        .push(0.7, None)
+        .push(1.0, None)
+        .build();
+    assert!(interpolate.at(0.1).approx_eq(&0.14));
+    assert!(interpolate.at(0.25).approx_eq(&0.35));
+    assert!(interpolate.at(0.45).approx_eq(&0.63));
+    assert!(interpolate.at(0.7).approx_eq(&0.82));
+    assert!(interpolate.at(0.75).approx_eq(&0.85));
+    assert!(interpolate.at(0.95).approx_eq(&0.97));
+}
+
+#[test]
+fn implied_multiple_input_spacing() {
+    let multiple_implied = PiecewiseLinearFunctionBuilder::new()
+        .push(0.0, None)
+        .push(0.8, None)
+        .push(0.6, None)
+        .push(0.4, None)
+        .push(0.5, Some(0.4))
+        .push(0.1, None)
+        .push(0.9, None)
+        .push(1.0, None)
+        .build();
+    assert!(multiple_implied.at(0.1).approx_eq(&0.8));
+    assert!(multiple_implied.at(0.2).approx_eq(&0.6));
+    assert!(multiple_implied.at(0.3).approx_eq(&0.4));
+    assert!(multiple_implied.at(0.4).approx_eq(&0.5));
+    assert!(multiple_implied.at(0.6).approx_eq(&0.1));
+    assert!(multiple_implied.at(0.8).approx_eq(&0.9));
+    assert!(multiple_implied.at(1.).approx_eq(&1.));
+}
+
+#[test]
+fn nonzero_edge_values() {
+    let nonzero_edges = PiecewiseLinearFunctionBuilder::new()
+        .push(0.1, Some(0.0))
+        .push(0.7, Some(1.0))
+        .build();
+    assert!(nonzero_edges.at(0.).approx_eq(&0.1));
+    assert!(nonzero_edges.at(0.5).approx_eq(&0.4));
+    assert!(nonzero_edges.at(1.0).approx_eq(&0.7));
+}
+
+#[test]
+fn out_of_bounds_extrapolate() {
+    // General case: extrapolate from the edges' slope
+    let oob_extend = PiecewiseLinearFunctionBuilder::new()
+        .push(0.0, None)
+        .push(0.7, None)
+        .push(1.0, None)
+        .build();
+    assert!(oob_extend.at(-0.25).approx_eq(&-0.35));
+    assert!(oob_extend.at(1.25).approx_eq(&1.15));
+}
+
+#[test]
+fn out_of_bounds_flat() {
+    // Repeated endpoints: flat extrapolation out-of-bounds
+    let oob_flat = PiecewiseLinearFunctionBuilder::new()
+        .push(0.0, Some(0.0))
+        .push(0.0, Some(0.0))
+        .push(0.7, None)
+        .push(1.0, Some(1.0))
+        .push(1.0, Some(1.0))
+        .build();
+    assert!(oob_flat.at(0.0).approx_eq(&oob_flat.at(-0.25)));
+    assert!(oob_flat.at(1.0).approx_eq(&oob_flat.at(1.25)));
+}
+
+#[test]
+fn flat_region() {
+    let flat = PiecewiseLinearFunctionBuilder::new()
+        .push(0.0, Some(0.0))
+        .push(0.5, Some(0.25))
+        .push(0.5, Some(0.7))
+        .push(1.0, Some(1.0))
+        .build();
+    assert!(flat.at(0.125).approx_eq(&0.25));
+    assert!(flat.at(0.5).approx_eq(&0.5));
+    assert!(flat.at(0.85).approx_eq(&0.75));
+}
+
+#[test]
+fn step() {
+    let step = PiecewiseLinearFunctionBuilder::new()
+        .push(0.0, Some(0.0))
+        .push(0.0, Some(0.5))
+        .push(1.0, Some(0.5))
+        .push(1.0, Some(1.0))
+        .build();
+    assert!(step.at(0.25).approx_eq(&0.0));
+    // At the discontinuity, take the right hand side value
+    assert!(step.at(0.5).approx_eq(&1.0));
+    assert!(step.at(0.75).approx_eq(&1.0));
+}
+
+#[test]
+fn step_multiple_conflicting() {
+    let step = PiecewiseLinearFunctionBuilder::new()
+        .push(0.0, Some(0.0))
+        .push(0.0, Some(0.5))
+        .push(0.75, Some(0.5))
+        .push(0.75, Some(0.5))
+        .push(1.0, Some(0.5))
+        .push(1.0, Some(1.0))
+        .build();
+    assert!(step.at(0.25).approx_eq(&0.0));
+    assert!(step.at(0.5).approx_eq(&1.0));
+    assert!(step.at(0.75).approx_eq(&1.0));
+}
+
+#[test]
+fn always_monotonic() {
+    let monotonic = PiecewiseLinearFunctionBuilder::new()
+        .push(0.0, Some(0.0))
+        .push(0.3, Some(0.5))
+        .push(0.4, Some(0.4))
+        .push(1.0, Some(1.0))
+        .build();
+    assert!(monotonic.at(0.25).approx_eq(&0.15));
+    // A discontinuity at x = 0.5 from y = 0.3 to 0.4
+    assert!(monotonic.at(0.5).approx_eq(&0.4));
+    assert!(monotonic.at(0.6).approx_eq(&0.52));
+}
+
+#[test]
+fn always_monotonic_flat() {
+    let monotonic = PiecewiseLinearFunctionBuilder::new()
+        .push(0.0, Some(0.0))
+        .push(0.2, Some(0.2))
+        .push(0.4, Some(0.1))
+        .push(0.4, Some(0.15))
+        .push(1.0, Some(1.0))
+        .build();
+    assert!(monotonic.at(0.2).approx_eq(&0.4));
+    // A discontinuity at x = 0.2 from y = 0.2 to 0.4
+    assert!(monotonic.at(0.3).approx_eq(&0.475));
+}
+
+#[test]
+fn always_monotonic_flat_backwards() {
+    let monotonic = PiecewiseLinearFunctionBuilder::new()
+        .push(0.0, Some(0.0))
+        .push(0.2, Some(0.2))
+        .push(0.3, Some(0.3))
+        .push(0.3, Some(0.2))
+        .push(1.0, Some(1.0))
+        .build();
+    assert!(monotonic.at(0.2).approx_eq(&0.2));
+    assert!(monotonic.at(0.3).approx_eq(&0.3));
+    assert!(monotonic.at(0.4).approx_eq(&0.4));
+}
+
+#[test]
+fn input_out_of_bounds() {
+    let oob = PiecewiseLinearFunctionBuilder::new()
+        .push(0.0, Some(-0.5))
+        .push(1.0, Some(1.5))
+        .build();
+    assert!(oob.at(-0.5).approx_eq(&0.0));
+    assert!(oob.at(0.0).approx_eq(&0.25));
+    assert!(oob.at(0.5).approx_eq(&0.5));
+    assert!(oob.at(1.0).approx_eq(&0.75));
+    assert!(oob.at(1.5).approx_eq(&1.0));
+}
+
+#[test]
+fn invalid_builder_input() {
+    let built_from_invalid = PiecewiseLinearFunctionBuilder::new()
+        .push(0.0, Some(f32::NEG_INFINITY))
+        .push(0.7, Some(f32::NAN))
+        .push(1.0, Some(f32::INFINITY))
+        .build();
+    let equivalent = PiecewiseLinearFunctionBuilder::new()
+        .push(0.0, None)
+        .push(0.7, None)
+        .push(1.0, None)
+        .build();
+
+    assert!(built_from_invalid.at(0.0).approx_eq(&equivalent.at(0.0)));
+    assert!(built_from_invalid.at(0.25).approx_eq(&equivalent.at(0.25)));
+    assert!(built_from_invalid.at(0.5).approx_eq(&equivalent.at(0.5)));
+    assert!(built_from_invalid.at(0.75).approx_eq(&equivalent.at(0.75)));
+    assert!(built_from_invalid.at(1.0).approx_eq(&equivalent.at(1.0)));
+}
+
+#[test]
+fn input_domain_not_complete() {
+    let not_covered = PiecewiseLinearFunctionBuilder::new()
+        .push(0.2, Some(0.2))
+        .push(0.8, Some(0.8))
+        .build();
+    assert!(not_covered.at(0.0).approx_eq(&0.0));
+    assert!(not_covered.at(0.5).approx_eq(&0.5));
+    assert!(not_covered.at(1.0).approx_eq(&1.0));
+}
+
+#[test]
+fn input_second_negative() {
+    let function = PiecewiseLinearFunctionBuilder::new()
+        .push(0.0, None)
+        .push(0.0, Some(-0.1))
+        .push(0.3, Some(-0.05))
+        .push(0.5, None)
+        .push(0.2, Some(0.6))
+        .push(1.0, None)
+        .build();
+    let equivalent = PiecewiseLinearFunctionBuilder::new()
+        .push(0.0, Some(0.0))
+        .push(0.0, Some(0.0))
+        .push(0.3, Some(0.0))
+        .push(0.5, Some(0.3))
+        .push(0.2, Some(0.6))
+        .push(1.0, Some(1.0))
+        .build();
+    assert!(function.at(-0.1).approx_eq(&equivalent.at(-0.1)));
+    assert!(function.at(0.0).approx_eq(&equivalent.at(0.0)));
+    assert!(function.at(0.3).approx_eq(&equivalent.at(0.3)));
+    assert!(function.at(0.6).approx_eq(&equivalent.at(0.6)));
+    assert!(function.at(1.0).approx_eq(&equivalent.at(1.0)));
+}
+
+#[test]
+fn input_second_last_above_1() {
+    let function = PiecewiseLinearFunctionBuilder::new()
+        .push(0.0, Some(0.0))
+        .push(1.0, Some(2.0))
+        .push(1.0, None)
+        .build();
+    assert!(function.at(-0.5).approx_eq(&-0.25));
+    assert!(function.at(0.0).approx_eq(&0.0));
+    assert!(function.at(0.5).approx_eq(&0.25));
+    assert!(function.at(1.0).approx_eq(&0.5));
+    assert!(function.at(1.5).approx_eq(&0.75));
+    assert!(function.at(2.0).approx_eq(&1.0));
+    assert!(function.at(3.0).approx_eq(&1.0));
+}