skia2/gm/shadowutils.cpp

/*
 * Copyright 2017 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "gm.h"
#include "SkCanvas.h"
#include "SkPath.h"
#include "SkResourceCache.h"
#include "SkShadowUtils.h"

void draw_shadow(SkCanvas* canvas, const SkPath& path, SkScalar height, SkColor color,
                 SkPoint3 lightPos, SkScalar lightR, bool isAmbient, uint32_t flags) {
    SkScalar ambientAlpha = isAmbient ? .5f : 0.f;
    SkScalar spotAlpha = isAmbient ? 0.f : .5f;
    SkColor ambientColor = SkColorSetARGB(ambientAlpha*SkColorGetA(color), SkColorGetR(color),
                                          SkColorGetG(color), SkColorGetB(color));
    SkColor spotColor = SkColorSetARGB(spotAlpha*SkColorGetA(color), SkColorGetR(color),
                                       SkColorGetG(color), SkColorGetB(color));
    SkShadowUtils::DrawShadow(canvas, path, SkPoint3{ 0, 0, height}, lightPos, lightR,
                              ambientColor, spotColor, flags);
}

static constexpr int kW = 800;
static constexpr int kH = 960;

enum ShadowMode {
    kDebugColorNoOccluders,
    kDebugColorOccluders,
    kGrayscale
};

void draw_paths(SkCanvas* canvas, ShadowMode mode) {
    SkTArray<SkPath> paths;
    paths.push_back().addRoundRect(SkRect::MakeWH(50, 50), 10, 10);
    SkRRect oddRRect;
    oddRRect.setNinePatch(SkRect::MakeWH(50, 50), 9, 13, 6, 16);
    paths.push_back().addRRect(oddRRect);
    paths.push_back().addRect(SkRect::MakeWH(50, 50));
    paths.push_back().addCircle(25, 25, 25);
    paths.push_back().cubicTo(100, 50, 20, 100, 0, 0);
    paths.push_back().addOval(SkRect::MakeWH(20, 60));

    // star
    SkTArray<SkPath> concavePaths;
    concavePaths.push_back().moveTo(0.0f, -33.3333f);
    concavePaths.back().lineTo(9.62f, -16.6667f);
    concavePaths.back().lineTo(28.867f, -16.6667f);
    concavePaths.back().lineTo(19.24f, 0.0f);
    concavePaths.back().lineTo(28.867f, 16.6667f);
    concavePaths.back().lineTo(9.62f, 16.6667f);
    concavePaths.back().lineTo(0.0f, 33.3333f);
    concavePaths.back().lineTo(-9.62f, 16.6667f);
    concavePaths.back().lineTo(-28.867f, 16.6667f);
    concavePaths.back().lineTo(-19.24f, 0.0f);
    concavePaths.back().lineTo(-28.867f, -16.6667f);
    concavePaths.back().lineTo(-9.62f, -16.6667f);
    concavePaths.back().close();

    // dumbbell
    concavePaths.push_back().moveTo(50, 0);
    concavePaths.back().cubicTo(100, 25, 60, 50, 50, 0);
    concavePaths.back().cubicTo(0, -25, 40, -50, 50, 0);

    static constexpr SkScalar kPad = 15.f;
    static constexpr SkScalar kLightR = 100.f;
    static constexpr SkScalar kHeight = 50.f;

    // transform light position relative to canvas to handle tiling
    SkPoint lightXY = canvas->getTotalMatrix().mapXY(250, 400);
    SkPoint3 lightPos = { lightXY.fX, lightXY.fY, 500 };

    canvas->translate(3 * kPad, 3 * kPad);
    canvas->save();
    SkScalar x = 0;
    SkScalar dy = 0;
    SkTDArray<SkMatrix> matrices;
    matrices.push()->reset();
    SkMatrix* m = matrices.push();
    m->setRotate(33.f, 25.f, 25.f);
    m->postScale(1.2f, 0.8f, 25.f, 25.f);
    for (auto& m : matrices) {
        for (int flags : { kNone_ShadowFlag, kTransparentOccluder_ShadowFlag }) {
            for (const auto& path : paths) {
                SkRect postMBounds = path.getBounds();
                m.mapRect(&postMBounds);
                SkScalar w = postMBounds.width() + kHeight;
                SkScalar dx = w + kPad;
                if (x + dx > kW - 3 * kPad) {
                    canvas->restore();
                    canvas->translate(0, dy);
                    canvas->save();
                    x = 0;
                    dy = 0;
                }

                canvas->save();
                canvas->concat(m);

                if (kDebugColorNoOccluders == mode || kDebugColorOccluders == mode) {
                    draw_shadow(canvas, path, kHeight, SK_ColorRED, lightPos, kLightR,
                                true, flags);
                    draw_shadow(canvas, path, kHeight, SK_ColorBLUE, lightPos, kLightR,
                                false, flags);
                } else if (kGrayscale == mode) {
                    SkColor ambientColor = SkColorSetARGB(0.1f * 255, 0, 0, 0);
                    SkColor spotColor = SkColorSetARGB(0.25f * 255, 0, 0, 0);
                    SkShadowUtils::DrawShadow(canvas, path, SkPoint3{0, 0, kHeight}, lightPos,
                                              kLightR, ambientColor, spotColor, flags);
                }

                SkPaint paint;
                paint.setAntiAlias(true);
                if (kDebugColorNoOccluders == mode) {
                    // Draw the path outline in green on top of the ambient and spot shadows.
                    if (SkToBool(flags & kTransparentOccluder_ShadowFlag)) {
                        paint.setColor(SK_ColorCYAN);
                    } else {
                        paint.setColor(SK_ColorGREEN);
                    }
                    paint.setStyle(SkPaint::kStroke_Style);
                    paint.setStrokeWidth(0);
                } else {
                    paint.setColor(kDebugColorOccluders == mode ? SK_ColorLTGRAY : SK_ColorWHITE);
                    if (SkToBool(flags & kTransparentOccluder_ShadowFlag)) {
                        paint.setAlpha(128);
                    }
                    paint.setStyle(SkPaint::kFill_Style);
                }
                canvas->drawPath(path, paint);
                canvas->restore();

                canvas->translate(dx, 0);
                x += dx;
                dy = SkTMax(dy, postMBounds.height() + kPad + kHeight);
            }
        }
    }

    // concave paths
    canvas->restore();
    canvas->translate(kPad, dy);
    canvas->save();
    x = kPad;
    dy = 0;
    for (auto& m : matrices) {
        // for the concave paths we are not clipping, so transparent and opaque are the same
        for (const auto& path : concavePaths) {
            SkRect postMBounds = path.getBounds();
            m.mapRect(&postMBounds);
            SkScalar w = postMBounds.width() + kHeight;
            SkScalar dx = w + kPad;

            canvas->save();
            canvas->concat(m);

            if (kDebugColorNoOccluders == mode || kDebugColorOccluders == mode) {
                draw_shadow(canvas, path, kHeight, SK_ColorRED, lightPos, kLightR,
                            true, kNone_ShadowFlag);
                draw_shadow(canvas, path, kHeight, SK_ColorBLUE, lightPos, kLightR,
                            false, kNone_ShadowFlag);
            } else if (kGrayscale == mode) {
                SkColor ambientColor = SkColorSetARGB(0.1f * 255, 0, 0, 0);
                SkColor spotColor = SkColorSetARGB(0.25f * 255, 0, 0, 0);
                SkShadowUtils::DrawShadow(canvas, path, SkPoint3{ 0, 0, kHeight }, lightPos,
                                          kLightR, ambientColor, spotColor, kNone_ShadowFlag);
            }

            SkPaint paint;
            paint.setAntiAlias(true);
            if (kDebugColorNoOccluders == mode) {
                // Draw the path outline in green on top of the ambient and spot shadows.
                paint.setColor(SK_ColorGREEN);
                paint.setStyle(SkPaint::kStroke_Style);
                paint.setStrokeWidth(0);
            } else {
                paint.setColor(kDebugColorOccluders == mode ? SK_ColorLTGRAY : SK_ColorWHITE);
                paint.setStyle(SkPaint::kFill_Style);
            }
            canvas->drawPath(path, paint);
            canvas->restore();

            canvas->translate(dx, 0);
            x += dx;
            dy = SkTMax(dy, postMBounds.height() + kPad + kHeight);
        }
    }

    // Show where the light is in x,y as a circle (specified in device space).
    SkMatrix invCanvasM = canvas->getTotalMatrix();
    if (invCanvasM.invert(&invCanvasM)) {
        canvas->save();
        canvas->concat(invCanvasM);
        SkPaint paint;
        paint.setColor(SK_ColorBLACK);
        paint.setAntiAlias(true);
        canvas->drawCircle(lightPos.fX, lightPos.fY, kLightR / 10.f, paint);
        canvas->restore();
    }
}

DEF_SIMPLE_GM(shadow_utils, canvas, kW, kH) {
    draw_paths(canvas, kDebugColorNoOccluders);
}

DEF_SIMPLE_GM(shadow_utils_occl, canvas, kW, kH) {
    draw_paths(canvas, kDebugColorOccluders);
}

DEF_SIMPLE_GM(shadow_utils_gray, canvas, kW, kH) {
    draw_paths(canvas, kGrayscale);
}