Add support for 2 point conical gradients (#164)

Author: wmedrano

CHANGELOG.md

@@ -5,6 +5,14 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased]
+### Added
+- 2-point conical gradient support for (`RadialGradient`).
+  Thanks to [@wmedrano](https://github.com/wmedrano)
+
+### Changed
+- The `RadialGradient::new` requires a start radius now. Set the second argument
+  to 0.0 to preserve the old behavior.
+
 
 ## [0.11.4] - 2024-02-04
 ### Fixed

benches/src/gradients.rs

@@ -538,6 +538,7 @@ fn simple_radial_tiny_skia(bencher: &mut Bencher) {
     paint.anti_alias = false;
     paint.shader = RadialGradient::new(
         Point::from_xy(500.0, 500.0),
+        0.0,
         Point::from_xy(500.0, 500.0),
         500.0,
         vec![
@@ -692,6 +693,7 @@ fn two_point_radial_tiny_skia(bencher: &mut Bencher) {
     paint.anti_alias = false;
     paint.shader = RadialGradient::new(
         Point::from_xy(400.0, 400.0),
+        0.0,
         Point::from_xy(500.0, 500.0),
         500.0,
         vec![

path/src/scalar.rs

@@ -24,6 +24,7 @@ pub trait Scalar {
     fn invert(self) -> Self;
     fn bound(self, min: Self, max: Self) -> Self;
     fn is_nearly_equal(self, other: Self) -> bool;
+    fn is_nearly_equal_within_tolerance(self, other: Self, tolerance: Self) -> bool;
     fn is_nearly_zero(self) -> bool;
     fn is_nearly_zero_within_tolerance(self, tolerance: Self) -> bool;
     fn almost_dequal_ulps(self, other: Self) -> bool;
@@ -56,6 +57,10 @@ impl Scalar for f32 {
         (self - other).abs() <= SCALAR_NEARLY_ZERO
     }
 
+    fn is_nearly_equal_within_tolerance(self, other: Self, tolerance: Self) -> bool {
+        (self - other).abs() <= tolerance
+    }
+
     fn is_nearly_zero(self) -> bool {
         self.is_nearly_zero_within_tolerance(SCALAR_NEARLY_ZERO)
     }

src/pipeline/highp.rs

@@ -116,9 +116,16 @@ pub const STAGES: &[StageFn; super::STAGES_COUNT] = &[
     xy_to_radius,
     xy_to_2pt_conical_focal_on_circle,
     xy_to_2pt_conical_well_behaved,
+    xy_to_2pt_conical_smaller,
     xy_to_2pt_conical_greater,
+    xy_to_2pt_conical_strip,
+    mask_2pt_conical_nan,
     mask_2pt_conical_degenerates,
     apply_vector_mask,
+    alter_2pt_conical_compensate_focal,
+    alter_2pt_conical_unswap,
+    negate_x,
+    apply_concentric_scale_bias,
     gamma_expand_2,
     gamma_expand_dst_2,
     gamma_compress_2,
@@ -1017,25 +1024,44 @@ fn xy_to_2pt_conical_greater(p: &mut Pipeline) {
     p.next_stage();
 }
 
+fn xy_to_2pt_conical_smaller(p: &mut Pipeline) {
+    let ctx = &p.ctx.two_point_conical_gradient;
+
+    let x = p.r;
+    let y = p.g;
+    p.r = -(x * x - y * y).sqrt() - x * f32x8::splat(ctx.p0);
+
+    p.next_stage();
+}
+
+fn xy_to_2pt_conical_strip(p: &mut Pipeline) {
+    let ctx = &p.ctx.two_point_conical_gradient;
+
+    let x = p.r;
+    let y = p.g;
+    p.r = x + (f32x8::splat(ctx.p0) - y * y).sqrt();
+
+    p.next_stage();
+}
+
+fn mask_2pt_conical_nan(p: &mut Pipeline) {
+    let ctx = &mut p.ctx.two_point_conical_gradient;
+
+    let t = p.r;
+    let is_degenerate = t.cmp_ne(t);
+    p.r = is_degenerate.blend(f32x8::default(), t);
+    ctx.mask = cond_to_mask(!is_degenerate.to_u32x8_bitcast());
+
+    p.next_stage();
+}
+
 fn mask_2pt_conical_degenerates(p: &mut Pipeline) {
     let ctx = &mut p.ctx.two_point_conical_gradient;
 
     let t = p.r;
     let is_degenerate = t.cmp_le(f32x8::default()) | t.cmp_ne(t);
     p.r = is_degenerate.blend(f32x8::default(), t);
-
-    let is_not_degenerate = !is_degenerate.to_u32x8_bitcast();
-    let is_not_degenerate: [u32; 8] = bytemuck::cast(is_not_degenerate);
-    ctx.mask = bytemuck::cast([
-        if is_not_degenerate[0] != 0 { !0 } else { 0 },
-        if is_not_degenerate[1] != 0 { !0 } else { 0 },
-        if is_not_degenerate[2] != 0 { !0 } else { 0 },
-        if is_not_degenerate[3] != 0 { !0 } else { 0 },
-        if is_not_degenerate[4] != 0 { !0 } else { 0 },
-        if is_not_degenerate[5] != 0 { !0 } else { 0 },
-        if is_not_degenerate[6] != 0 { !0 } else { 0 },
-        if is_not_degenerate[7] != 0 { !0 } else { 0 },
-    ]);
+    ctx.mask = cond_to_mask(!is_degenerate.to_u32x8_bitcast());
 
     p.next_stage();
 }
@@ -1051,6 +1077,36 @@ fn apply_vector_mask(p: &mut Pipeline) {
     p.next_stage();
 }
 
+fn alter_2pt_conical_compensate_focal(p: &mut Pipeline) {
+    let ctx = &p.ctx.two_point_conical_gradient;
+
+    p.r = p.r + f32x8::splat(ctx.p1);
+
+    p.next_stage();
+}
+
+fn alter_2pt_conical_unswap(p: &mut Pipeline) {
+    p.r = f32x8::splat(1.0) - p.r;
+
+    p.next_stage();
+}
+
+fn negate_x(p: &mut Pipeline) {
+    p.r = -p.r;
+
+    p.next_stage();
+}
+
+fn apply_concentric_scale_bias(p: &mut Pipeline) {
+    let ctx = &p.ctx.two_point_conical_gradient;
+
+    // Apply t = t * scale + bias for concentric gradients
+    let x = p.r;
+    p.r = x * f32x8::splat(ctx.p0) + f32x8::splat(ctx.p1);
+
+    p.next_stage();
+}
+
 fn gamma_expand_2(p: &mut Pipeline) {
     p.r = p.r * p.r;
     p.g = p.g * p.g;
@@ -1141,6 +1197,21 @@ pub fn just_return(_: &mut Pipeline) {
     // Ends the loop.
 }
 
+#[inline(always)]
+fn cond_to_mask(cond: u32x8) -> u32x8 {
+    let cond: [u32; 8] = bytemuck::cast(cond);
+    bytemuck::cast([
+        if cond[0] != 0 { !0 } else { 0 },
+        if cond[1] != 0 { !0 } else { 0 },
+        if cond[2] != 0 { !0 } else { 0 },
+        if cond[3] != 0 { !0 } else { 0 },
+        if cond[4] != 0 { !0 } else { 0 },
+        if cond[5] != 0 { !0 } else { 0 },
+        if cond[6] != 0 { !0 } else { 0 },
+        if cond[7] != 0 { !0 } else { 0 },
+    ])
+}
+
 #[inline(always)]
 fn load_8888(
     data: &[PremultipliedColorU8; STAGE_WIDTH],

src/pipeline/lowp.rs

@@ -129,9 +129,16 @@ pub const STAGES: &[StageFn; super::STAGES_COUNT] = &[
     xy_to_radius,
     null_fn, // XYTo2PtConicalFocalOnCircle
     null_fn, // XYTo2PtConicalWellBehaved
+    null_fn, // XYTo2PtConicalSmaller
     null_fn, // XYTo2PtConicalGreater
+    null_fn, // XYTo2PtConicalStrip
+    null_fn, // Mask2PtConicalNan
     null_fn, // Mask2PtConicalDegenerates
     null_fn, // ApplyVectorMask
+    null_fn, // Alter2PtConicalCompensateFocal
+    null_fn, // Alter2PtConicalUnswap
+    null_fn, // NegateX
+    null_fn, // ApplyConcentricScaleBias
     null_fn, // GammaExpand2
     null_fn, // GammaExpandDestination2
     null_fn, // GammaCompress2

src/pipeline/mod.rs

@@ -127,9 +127,16 @@ pub enum Stage {
     XYToRadius,
     XYTo2PtConicalFocalOnCircle,
     XYTo2PtConicalWellBehaved,
+    XYTo2PtConicalSmaller,
     XYTo2PtConicalGreater,
+    XYTo2PtConicalStrip,
+    Mask2PtConicalNan,
     Mask2PtConicalDegenerates,
     ApplyVectorMask,
+    Alter2PtConicalCompensateFocal,
+    Alter2PtConicalUnswap,
+    NegateX,
+    ApplyConcentricScaleBias,
     GammaExpand2,
     GammaExpandDestination2,
     GammaCompress2,
@@ -327,6 +334,7 @@ pub struct TwoPointConicalGradientCtx {
     // This context is used only in highp, where we use Tx4.
     pub mask: u32x8,
     pub p0: f32,
+    pub p1: f32,
 }
 
 #[derive(Copy, Clone, Default, Debug)]