src/core/SkDraw_atlas.cpp

/*
 * Copyright 2019 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "include/core/SkAlphaType.h"
#include "include/core/SkColor.h"
#include "include/core/SkMaskFilter.h"
#include "include/core/SkMatrix.h"
#include "include/core/SkPaint.h"
#include "include/core/SkPath.h"
#include "include/core/SkPixmap.h"
#include "include/core/SkPoint.h"
#include "include/core/SkRSXform.h"
#include "include/core/SkRect.h"
#include "include/core/SkRefCnt.h"
#include "include/core/SkScalar.h"
#include "include/core/SkShader.h"
#include "include/core/SkSurfaceProps.h"
#include "src/base/SkArenaAlloc.h"
#include "src/core/SkBlendModePriv.h"
#include "src/core/SkBlenderBase.h"
#include "src/core/SkColorSpacePriv.h"
#include "src/core/SkColorSpaceXformSteps.h"
#include "src/core/SkCoreBlitters.h"
#include "src/core/SkDraw.h"
#include "src/core/SkEffectPriv.h"
#include "src/core/SkRasterClip.h"
#include "src/core/SkRasterPipeline.h"
#include "src/core/SkRasterPipelineOpContexts.h"
#include "src/core/SkRasterPipelineOpList.h"
#include "src/core/SkScan.h"
#include "src/core/SkSurfacePriv.h"
#include "src/shaders/SkShaderBase.h"
#include "src/shaders/SkTransformShader.h"

#include <cstdint>
#include <optional>

class SkBlender;
class SkBlitter;
enum class SkBlendMode;

static void fill_rect(const SkMatrix& ctm, const SkRasterClip& rc,
                      const SkRect& r, SkBlitter* blitter, SkPath* scratchPath) {
    if (ctm.rectStaysRect()) {
        SkRect dr;
        ctm.mapRect(&dr, r);
        SkScan::FillRect(dr, rc, blitter);
    } else {
        SkPoint pts[4];
        r.toQuad(pts);
        ctm.mapPoints(pts, pts, 4);

        scratchPath->rewind();
        scratchPath->addPoly(pts, 4, true);
        SkScan::FillPath(*scratchPath, rc, blitter);
    }
}

static void load_color(SkRasterPipeline_UniformColorCtx* ctx, const float rgba[]) {
    // only need one of these. can I query the pipeline to know if its lowp or highp?
    ctx->rgba[0] = SkScalarRoundToInt(rgba[0]*255); ctx->r = rgba[0];
    ctx->rgba[1] = SkScalarRoundToInt(rgba[1]*255); ctx->g = rgba[1];
    ctx->rgba[2] = SkScalarRoundToInt(rgba[2]*255); ctx->b = rgba[2];
    ctx->rgba[3] = SkScalarRoundToInt(rgba[3]*255); ctx->a = rgba[3];
}

void SkDraw::drawAtlas(const SkRSXform xform[],
                       const SkRect textures[],
                       const SkColor colors[],
                       int count,
                       sk_sp<SkBlender> blender,
                       const SkPaint& paint) {
    sk_sp<SkShader> atlasShader = paint.refShader();
    if (!atlasShader) {
        return;
    }

    SkSTArenaAlloc<256> alloc;

    SkPaint p(paint);
    p.setAntiAlias(false);  // we never respect this for drawAtlas(or drawVertices)
    p.setStyle(SkPaint::kFill_Style);
    p.setShader(nullptr);
    p.setMaskFilter(nullptr);

    // The RSXForms can't contain perspective - only the CTM can.
    const bool perspective = fCTM->hasPerspective();

    auto transformShader = alloc.make<SkTransformShader>(*as_SB(atlasShader), perspective);

    SkRasterPipeline pipeline(&alloc);
    SkSurfaceProps props = SkSurfacePropsCopyOrDefault(fProps);
    SkStageRec rec = {&pipeline, &alloc, fDst.colorType(), fDst.colorSpace(),
                      p.getColor4f(), props};
    // We pass an identity matrix here rather than the CTM. The CTM gets folded into the
    // per-triangle matrix.
    if (!as_SB(transformShader)->appendRootStages(rec, SkMatrix::I())) {
        return;
    }

    SkRasterPipeline_UniformColorCtx* uniformCtx = nullptr;
    SkColorSpaceXformSteps steps(sk_srgb_singleton(), kUnpremul_SkAlphaType,
                                 rec.fDstCS, kUnpremul_SkAlphaType);
    if (colors) {
        // we will late-bind the values in ctx, once for each color in the loop
        uniformCtx = alloc.make<SkRasterPipeline_UniformColorCtx>();
        rec.fPipeline->append(SkRasterPipelineOp::uniform_color_dst, uniformCtx);
        std::optional<SkBlendMode> bm = as_BB(blender)->asBlendMode();
        if (!bm.has_value()) {
            return;
        }
        SkBlendMode_AppendStages(*bm, rec.fPipeline);
    }

    bool isOpaque = !colors && transformShader->isOpaque();
    if (p.getAlphaf() != 1) {
        rec.fPipeline->append(SkRasterPipelineOp::scale_1_float, alloc.make<float>(p.getAlphaf()));
        isOpaque = false;
    }

    auto blitter = SkCreateRasterPipelineBlitter(fDst, p, pipeline, isOpaque, &alloc,
                                                 fRC->clipShader());
    if (!blitter) {
        return;
    }
    SkPath scratchPath;

    for (int i = 0; i < count; ++i) {
        if (colors) {
            SkColor4f c4 = SkColor4f::FromColor(colors[i]);
            steps.apply(c4.vec());
            load_color(uniformCtx, c4.premul().vec());
        }

        SkMatrix mx;
        mx.setRSXform(xform[i]);
        mx.preTranslate(-textures[i].fLeft, -textures[i].fTop);
        mx.postConcat(*fCTM);
        SkMatrix inv;
        if (!mx.invert(&inv)) {
            return;
        }
        if (transformShader->update(inv)) {
            fill_rect(mx, *fRC, textures[i], blitter, &scratchPath);
        }
    }
}