Simplify GetRuntimeBlendForBlendMode.

Now that we support sampling from an SkBlender inside a Runtime Effect,
we can leverage that to reuse the blends from SkBlender::Mode. This lets
us avoid hard-coding copies of every built-in blend function.

Change-Id: I51f380490611fbde943c16648999b4fd4e6a14a9
Bug: skia:12257, skia:12085
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/434472
Commit-Queue: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
diff --git a/tools/RuntimeBlendUtils.cpp b/tools/RuntimeBlendUtils.cpp
index a82c9f0..2eb35dd 100644
--- a/tools/RuntimeBlendUtils.cpp
+++ b/tools/RuntimeBlendUtils.cpp
@@ -7,364 +7,19 @@
 
 #include "include/core/SkBlendMode.h"
 #include "include/core/SkRefCnt.h"
-#include "include/core/SkString.h"
 #include "include/effects/SkRuntimeEffect.h"
 
-static sk_sp<SkBlender> blender_func(std::initializer_list<const char*> code) {
-    SkString concat;
-    for (const char* part : code) {
-        concat.append(part);
-    }
-    SkRuntimeEffect::Result result = SkRuntimeEffect::MakeForBlender(std::move(concat));
-    SkASSERTF(result.effect, "%s", result.errorText.c_str());
-    return result.effect->makeBlender(/*uniforms=*/nullptr);
-}
-
-static sk_sp<SkBlender> blender_expr(const char* returnExpr) {
-    return blender_func({"half4 main(half4 src, half4 dst) {\n"
-                         "    return ", returnExpr, ";\n"
-                         "}"});
-}
-
 sk_sp<SkBlender> GetRuntimeBlendForBlendMode(SkBlendMode mode) {
-    static constexpr char kGuardedDivide[] = R"(
-        half _guarded_divide(half n, half d) {
-            return n/(d + 0.00000001);
+    static auto result = SkRuntimeEffect::MakeForBlender(SkString(R"(
+        uniform blender b;
+        half4 main(half4 src, half4 dst) {
+            return sample(b, src, dst);
         }
+    )"));
 
-        half3 _guarded_divide(half3 n, half d) {
-            return n/(d + 0.00000001);
-        }
-    )";
+    SkASSERTF(result.effect, "%s", result.errorText.c_str());
 
-    static constexpr char kHSLCSharedCode[] = R"(
-        half _blend_color_luminance(half3 color) { return dot(half3(0.3, 0.59, 0.11), color); }
-
-        half3 _blend_set_color_luminance(half3 hueSatColor, half alpha, half3 lumColor) {
-            half lum = _blend_color_luminance(lumColor);
-            half3 result = lum - _blend_color_luminance(hueSatColor) + hueSatColor;
-            half minComp = min(min(result.r, result.g), result.b);
-            half maxComp = max(max(result.r, result.g), result.b);
-            if (minComp < 0 && lum != minComp) {
-                result = lum + (result - lum) * _guarded_divide(lum, (lum - minComp));
-            }
-            if (maxComp > alpha && maxComp != lum) {
-                return lum + _guarded_divide((result - lum) * (alpha - lum), (maxComp - lum));
-            } else {
-                return result;
-            }
-        }
-
-        half _blend_color_saturation(half3 color) {
-            return max(max(color.r, color.g), color.b) - min(min(color.r, color.g), color.b);
-        }
-
-        half3 _blend_set_color_saturation_helper(half3 minMidMax, half sat) {
-            if (minMidMax.r < minMidMax.b) {
-                return half3(0,
-                            _guarded_divide(sat*(minMidMax.g - minMidMax.r),
-                                            (minMidMax.b - minMidMax.r)),
-                            sat);
-            } else {
-                return half3(0);
-            }
-        }
-
-        half3 _blend_set_color_saturation(half3 hueLumColor, half3 satColor) {
-            half sat = _blend_color_saturation(satColor);
-            if (hueLumColor.r <= hueLumColor.g) {
-                if (hueLumColor.g <= hueLumColor.b) {
-                    return _blend_set_color_saturation_helper(hueLumColor.rgb, sat);
-                } else if (hueLumColor.r <= hueLumColor.b) {
-                    return _blend_set_color_saturation_helper(hueLumColor.rbg, sat).rbg;
-                } else {
-                    return _blend_set_color_saturation_helper(hueLumColor.brg, sat).gbr;
-                }
-            } else if (hueLumColor.r <= hueLumColor.b) {
-               return _blend_set_color_saturation_helper(hueLumColor.grb, sat).grb;
-            } else if (hueLumColor.g <= hueLumColor.b) {
-               return _blend_set_color_saturation_helper(hueLumColor.gbr, sat).brg;
-            } else {
-               return _blend_set_color_saturation_helper(hueLumColor.bgr, sat).bgr;
-            }
-        }
-    )";
-
-    switch (mode) {
-        case SkBlendMode::kClear: {
-            static auto blender = blender_expr("half4(0)");
-            return blender;
-        }
-        case SkBlendMode::kSrc: {
-            static auto blender = blender_expr("src");
-            return blender;
-        }
-        case SkBlendMode::kDst: {
-            static auto blender = blender_expr("dst");
-            return blender;
-        }
-        case SkBlendMode::kSrcOver: {
-            static auto blender = blender_expr("src + (1 - src.a)*dst");
-            return blender;
-        }
-        case SkBlendMode::kDstOver: {
-            static auto blender = blender_expr("(1 - dst.a)*src + dst");
-            return blender;
-        }
-        case SkBlendMode::kSrcIn: {
-            static auto blender = blender_expr("(src == half4(0) ? half4(0) : src*dst.a)");
-            return blender;
-        }
-        case SkBlendMode::kDstIn: {
-            static auto blender = blender_expr("(dst == half4(0) ? half4(0) : dst*src.a)");
-            return blender;
-        }
-        case SkBlendMode::kSrcOut: {
-            static auto blender = blender_expr("(1 - dst.a)*src");
-            return blender;
-        }
-        case SkBlendMode::kDstOut: {
-            static auto blender = blender_expr("(1 - src.a)*dst");
-            return blender;
-        }
-        case SkBlendMode::kSrcATop: {
-            static auto blender = blender_expr("dst.a*src + (1 - src.a)*dst");
-            return blender;
-        }
-        case SkBlendMode::kDstATop: {
-            static auto blender = blender_expr("(1 - dst.a) * src + src.a*dst");
-            return blender;
-        }
-        case SkBlendMode::kXor: {
-            static auto blender = blender_expr("(1 - dst.a)*src + (1 - src.a)*dst");
-            return blender;
-        }
-        case SkBlendMode::kPlus: {
-            static auto blender = blender_expr("min(src + dst, 1)");
-            return blender;
-        }
-        case SkBlendMode::kModulate: {
-            static auto blender = blender_expr("src*dst");
-            return blender;
-        }
-        case SkBlendMode::kScreen: {
-            static auto blender = blender_expr("src + (1 - src)*dst");
-            return blender;
-        }
-        case SkBlendMode::kOverlay: {
-            static auto blender = blender_func({R"(
-                half _blend_overlay_component(half2 s, half2 d) {
-                    return (2*d.x <= d.y)
-                            ? 2*s.x*d.x
-                            : s.y*d.y - 2*(d.y - d.x)*(s.y - s.x);
-                }
-
-                half4 main(half4 src, half4 dst) {
-                    half4 result = half4(_blend_overlay_component(src.ra, dst.ra),
-                                         _blend_overlay_component(src.ga, dst.ga),
-                                         _blend_overlay_component(src.ba, dst.ba),
-                                         src.a + (1 - src.a)*dst.a);
-                    result.rgb += dst.rgb*(1 - src.a) + src.rgb*(1 - dst.a);
-                    return result;
-                }
-            )"});
-            return blender;
-        }
-        case SkBlendMode::kDarken: {
-            static auto blender = blender_func({R"(
-                half4 main(half4 src, half4 dst) {
-                    half4 result = src + (1 - src.a)*dst;
-                    result.rgb = min(result.rgb, (1 - dst.a)*src.rgb + dst.rgb);
-                    return result;
-                }
-            )"});
-            return blender;
-        }
-        case SkBlendMode::kLighten: {
-            static auto blender = blender_func({R"(
-                half4 main(half4 src, half4 dst) {
-                    half4 result = src + (1 - src.a)*dst;
-                    result.rgb = max(result.rgb, (1 - dst.a)*src.rgb + dst.rgb);
-                    return result;
-                }
-            )"});
-            return blender;
-        }
-        case SkBlendMode::kColorDodge: {
-            static auto blender = blender_func({kGuardedDivide, R"(
-                half _color_dodge_component(half2 s, half2 d) {
-                    if (d.x == 0) {
-                        return s.x*(1 - d.y);
-                    } else {
-                        half delta = s.y - s.x;
-                        if (delta == 0) {
-                             return s.y*d.y + s.x*(1 - d.y) + d.x*(1 - s.y);
-                        } else {
-                            delta = min(d.y, _guarded_divide(d.x*s.y, delta));
-                            return delta*s.y + s.x*(1 - d.y) + d.x*(1 - s.y);
-                        }
-                    }
-                }
-
-                half4 main(half4 src, half4 dst) {
-                    return half4(_color_dodge_component(src.ra, dst.ra),
-                                 _color_dodge_component(src.ga, dst.ga),
-                                 _color_dodge_component(src.ba, dst.ba),
-                                 src.a + (1 - src.a)*dst.a);
-                }
-            )"});
-            return blender;
-        }
-        case SkBlendMode::kColorBurn: {
-            static auto blender = blender_func({kGuardedDivide, R"(
-                half _color_burn_component(half2 s, half2 d) {
-                    if (d.y == d.x) {
-                        return s.y*d.y + s.x*(1 - d.y) + d.x*(1 - s.y);
-                    } else if (s.x == 0) {
-                        return d.x*(1 - s.y);
-                    } else {
-                        half delta = max(0, d.y - _guarded_divide((d.y - d.x)*s.y, s.x));
-                        return delta*s.y + s.x*(1 - d.y) + d.x*(1 - s.y);
-                    }
-                }
-
-                half4 main(half4 src, half4 dst) {
-                    return half4(_color_burn_component(src.ra, dst.ra),
-                                 _color_burn_component(src.ga, dst.ga),
-                                 _color_burn_component(src.ba, dst.ba),
-                                 src.a + (1 - src.a)*dst.a);
-                }
-            )"});
-            return blender;
-        }
-        case SkBlendMode::kHardLight: {
-            static auto blender = blender_func({R"(
-                half _blend_overlay_component(half2 s, half2 d) {
-                    return (2*d.x <= d.y)
-                            ? 2*s.x*d.x
-                            : s.y*d.y - 2*(d.y - d.x)*(s.y - s.x);
-                }
-
-                half4 main(half4 dst, half4 src) {
-                    half4 result = half4(_blend_overlay_component(src.ra, dst.ra),
-                                         _blend_overlay_component(src.ga, dst.ga),
-                                         _blend_overlay_component(src.ba, dst.ba),
-                                         src.a + (1 - src.a)*dst.a);
-                    result.rgb += dst.rgb*(1 - src.a) + src.rgb*(1 - dst.a);
-                    return result;
-                }
-            )"});
-            return blender;
-        }
-        case SkBlendMode::kSoftLight: {
-            static auto blender = blender_func({kGuardedDivide, R"(
-                half _soft_light_component(half2 s, half2 d) {
-                    if (2*s.x <= s.y) {
-                        return _guarded_divide(d.x*d.x*(s.y - 2*s.x), d.y) +
-                               (1 - d.y)*s.x + d.x*(-s.y + 2*s.x + 1);
-                    } else if (4.0 * d.x <= d.y) {
-                        half DSqd = d.x*d.x;
-                        half DCub = DSqd*d.x;
-                        half DaSqd = d.y*d.y;
-                        half DaCub = DaSqd*d.y;
-                        return _guarded_divide(DaSqd*(s.x - d.x*(3*s.y - 6*s.x - 1))
-                                               + 12*d.y*DSqd*(s.y - 2*s.x)
-                                               - 16*DCub * (s.y - 2*s.x) - DaCub*s.x, DaSqd);
-                    } else {
-                        return d.x*(s.y - 2*s.x + 1) + s.x - sqrt(d.y*d.x)*(s.y - 2*s.x) - d.y*s.x;
-                    }
-                }
-
-                half4 main(half4 src, half4 dst) {
-                    return (dst.a == 0) ? src : half4(_soft_light_component(src.ra, dst.ra),
-                                                      _soft_light_component(src.ga, dst.ga),
-                                                      _soft_light_component(src.ba, dst.ba),
-                                                      src.a + (1 - src.a)*dst.a);
-                }
-            )"});
-            return blender;
-        }
-        case SkBlendMode::kDifference: {
-            static auto blender = blender_func({R"(
-                half4 main(half4 src, half4 dst) {
-                    return half4(src.rgb + dst.rgb - 2*min(src.rgb*dst.a, dst.rgb*src.a),
-                                 src.a + (1 - src.a)*dst.a);
-                }
-            )"});
-            return blender;
-        }
-        case SkBlendMode::kExclusion: {
-            static auto blender = blender_func({R"(
-                half4 main(half4 src, half4 dst) {
-                    return half4(dst.rgb + src.rgb - 2*dst.rgb*src.rgb, src.a + (1 - src.a)*dst.a);
-                }
-            )"});
-            return blender;
-        }
-        case SkBlendMode::kMultiply: {
-            static auto blender = blender_func({R"(
-                half4 main(half4 src, half4 dst) {
-                    return half4((1 - src.a)*dst.rgb + (1 - dst.a)*src.rgb + src.rgb*dst.rgb,
-                                 src.a + (1 - src.a)*dst.a);
-                }
-            )"});
-            return blender;
-        }
-        case SkBlendMode::kHue: {
-            static auto blender = blender_func({kGuardedDivide, kHSLCSharedCode, R"(
-                half4 main(half4 src, half4 dst) {
-                    half alpha = dst.a*src.a;
-                    half3 sda = src.rgb*dst.a;
-                    half3 dsa = dst.rgb*src.a;
-                    return half4(_blend_set_color_luminance(_blend_set_color_saturation(sda, dsa),
-                                                            alpha, dsa) +
-                                 dst.rgb - dsa + src.rgb - sda,
-                                 src.a + dst.a - alpha);
-                                }
-            )"});
-            return blender;
-        }
-        case SkBlendMode::kSaturation: {
-            static auto blender = blender_func({kGuardedDivide, kHSLCSharedCode, R"(
-                half4 main(half4 src, half4 dst) {
-                    half alpha = dst.a*src.a;
-                    half3 sda = src.rgb*dst.a;
-                    half3 dsa = dst.rgb*src.a;
-                    return half4(_blend_set_color_luminance(_blend_set_color_saturation(dsa, sda),
-                                                            alpha, dsa) +
-                                 dst.rgb - dsa + src.rgb - sda,
-                                 src.a + dst.a - alpha);
-                }
-            )"});
-            return blender;
-        }
-        case SkBlendMode::kColor: {
-            static auto blender = blender_func({kGuardedDivide, kHSLCSharedCode, R"(
-                half4 main(half4 src, half4 dst)  {
-                    half alpha = dst.a*src.a;
-                    half3 sda = src.rgb*dst.a;
-                    half3 dsa = dst.rgb*src.a;
-                    return half4(_blend_set_color_luminance(sda, alpha, dsa) + dst.rgb
-                                 - dsa + src.rgb - sda, src.a + dst.a - alpha);
-                }
-            )"});
-            return blender;
-        }
-        case SkBlendMode::kLuminosity: {
-            static auto blender = blender_func({kGuardedDivide, kHSLCSharedCode, R"(
-                half4 main(half4 src, half4 dst) {
-                    half alpha = dst.a*src.a;
-                    half3 sda = src.rgb*dst.a;
-                    half3 dsa = dst.rgb*src.a;
-                    return half4(_blend_set_color_luminance(dsa, alpha, sda) + dst.rgb - dsa
-                                 + src.rgb - sda, src.a + dst.a - alpha);
-                }
-            )"});
-            return blender;
-        }
-        default:
-            SkDEBUGFAILF("unrecognized blend mode %d", (int)mode);
-            return nullptr;
-    }
+    SkRuntimeBlendBuilder builder(result.effect);
+    builder.child("b") = SkBlender::Mode(mode);
+    return builder.makeBlender();
 }
-