gfx/skia/skia/src/gpu/GrSwizzle.h
author Wes Kocher <wkocher@mozilla.com>
Wed, 10 May 2017 10:01:18 -0700
changeset 407965 ce2218406119c36a551e3faea4e192186ee46cc5
permissions -rw-r--r--
Backed out 9 changesets (bug 1340627) for graphical glitches a=backout Backed out changeset 0b1371055c7f (bug 1340627) Backed out changeset f152be1fadb7 (bug 1340627) Backed out changeset c691e2ab6a0c (bug 1340627) Backed out changeset 3cb4bceb8d79 (bug 1340627) Backed out changeset 026aadd76d06 (bug 1340627) Backed out changeset fdbd5d281287 (bug 1340627) Backed out changeset 75fb0d9858a9 (bug 1340627) Backed out changeset 0d4ec7d38a00 (bug 1340627) Backed out changeset af6f19870b2a (bug 1340627) MozReview-Commit-ID: 9dHr7xMZezY

/*
 * Copyright 2016 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef GrSwizzle_DEFINED
#define GrSwizzle_DEFINED

#include "GrColor.h"
#include "SkRandom.h"

/** Represents a rgba swizzle. It can be converted either into a string or a eight bit int.
    Currently there is no way to specify an arbitrary swizzle, just some static swizzles and an
    assignment operator. That could be relaxed. */
class GrSwizzle {
public:
    GrSwizzle() { *this = RGBA(); }

    GrSwizzle(const GrSwizzle& that) { *this = that; }

    GrSwizzle& operator=(const GrSwizzle& that) {
        memcpy(this, &that, sizeof(GrSwizzle));
        return *this;
    }

    /** Recreates a GrSwizzle from the output of asKey() */
    void setFromKey(uint8_t key) {
        fKey = key;
        for (int i = 0; i < 4; ++i) {
            fSwiz[i] = IdxToChar(key & 3);
            key >>= 2;
        }
        SkASSERT(fSwiz[4] == 0);
    }

    bool operator==(const GrSwizzle& that) const { return this->asUInt() == that.asUInt(); }

    bool operator!=(const GrSwizzle& that) const { return !(*this == that); }

    /** Compact representation of the swizzle suitable for a key. */
    uint8_t asKey() const { return fKey; }

    /** 4 char null terminated string consisting only of chars 'r', 'g', 'b', 'a'. */
    const char* c_str() const { return fSwiz; }

    /** Applies this swizzle to the input color and returns the swizzled color. */
    GrColor applyTo(GrColor color) const {
        int idx;
        uint32_t key = fKey;
        // Index of the input color that should be mapped to output r.
        idx = (key & 3);
        uint32_t outR = (color >> idx * 8)  & 0xFF;
        key >>= 2;
        idx = (key & 3);
        uint32_t outG = (color >> idx * 8)  & 0xFF;
        key >>= 2;
        idx = (key & 3);
        uint32_t outB = (color >> idx * 8)  & 0xFF;
        key >>= 2;
        idx = (key & 3);
        uint32_t outA = (color >> idx * 8)  & 0xFF;
        return GrColorPackRGBA(outR, outG, outB, outA);
    }

    static const GrSwizzle& RGBA() {
        static GrSwizzle gRGBA("rgba");
        return gRGBA;
    }

    static const GrSwizzle& AAAA() {
        static GrSwizzle gAAAA("aaaa");
        return gAAAA;
    }

    static const GrSwizzle& RRRR() {
        static GrSwizzle gRRRR("rrrr");
        return gRRRR;
    }

    static const GrSwizzle& BGRA() {
        static GrSwizzle gBGRA("bgra");
        return gBGRA;
    }

    static const GrSwizzle& CreateRandom(SkRandom* random) {
        switch (random->nextU() % 4) {
            case 0:
                return RGBA();
            case 1:
                return BGRA();
            case 2:
                return RRRR();
            case 3:
                return AAAA();
            default:
                SkFAIL("Mod is broken?!?");
                return RGBA();
        }
    }

private:
    char fSwiz[5];
    uint8_t fKey;

    static int CharToIdx(char c) {
        switch (c) {
            case 'r':
                return (GrColor_SHIFT_R / 8);
            case 'g':
                return (GrColor_SHIFT_G / 8);
            case 'b':
                return (GrColor_SHIFT_B / 8);
            case 'a':
                return (GrColor_SHIFT_A / 8);
            default:
                SkFAIL("Invalid swizzle char");
                return 0;
        }
    }

    static /* constexpr */ char IToC(int idx) {
        return (8*idx) == GrColor_SHIFT_R ? 'r' :
               (8*idx) == GrColor_SHIFT_G ? 'g' :
               (8*idx) == GrColor_SHIFT_B ? 'b' : 'a';
    }

    static char IdxToChar(int c) {
        // Hopefully this array gets computed at compile time.
        static const char gStr[4] = { IToC(0), IToC(1), IToC(2), IToC(3) };
        return gStr[c];
    }

    explicit GrSwizzle(const char* str) {
        SkASSERT(strlen(str) == 4);
        fSwiz[0] = str[0];
        fSwiz[1] = str[1];
        fSwiz[2] = str[2];
        fSwiz[3] = str[3];
        fSwiz[4] = 0;
        fKey = SkToU8(CharToIdx(fSwiz[0]) | (CharToIdx(fSwiz[1]) << 2) |
                      (CharToIdx(fSwiz[2]) << 4) | (CharToIdx(fSwiz[3]) << 6));
    }

    uint32_t* asUIntPtr() { return SkTCast<uint32_t*>(fSwiz); }
    uint32_t asUInt() const { return *SkTCast<const uint32_t*>(fSwiz); }

    GR_STATIC_ASSERT(sizeof(char[4]) == sizeof(uint32_t));
};

#endif