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skia2/modules/sksg/samples/SampleSVGPong.cpp
Mike Klein 8aa0edfed2 move SkTPin to include/private 
Change-Id: Ib0dc823d331a7cddc5da1d1be83136ce803a7871
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/327783
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Mike Reed <reed@google.com>
2020-10-16 19:45:11 +00:00

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/*
* Copyright 2016 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/SkCanvas.h"
#include "include/core/SkPathBuilder.h"
#include "include/core/SkRRect.h"
#include "include/private/SkTPin.h"
#include "include/utils/SkRandom.h"
#include "samplecode/Sample.h"
#include "tools/timer/TimeUtils.h"
#include "modules/sksg/include/SkSGDraw.h"
#include "modules/sksg/include/SkSGGroup.h"
#include "modules/sksg/include/SkSGInvalidationController.h"
#include "modules/sksg/include/SkSGPaint.h"
#include "modules/sksg/include/SkSGPath.h"
#include "modules/sksg/include/SkSGRect.h"
#include "modules/sksg/include/SkSGScene.h"
#include "modules/sksg/include/SkSGTransform.h"
namespace {
static const SkRect kBounds = SkRect::MakeLTRB(0.1f, 0.1f, 0.9f, 0.9f);
static const SkSize kPaddleSize = SkSize::Make(0.03f, 0.1f);
static const SkScalar kBallSize = 0.04f;
static const SkScalar kShadowOpacity = 0.40f;
static const SkScalar kShadowParallax = 0.04f;
static const SkScalar kBackgroundStroke = 0.01f;
static const uint32_t kBackgroundDashCount = 20;
static const SkScalar kBallSpeedMax = 0.0020f;
static const SkScalar kBallSpeedMin = 0.0005f;
static const SkScalar kBallSpeedFuzz = 0.0002f;
static const SkScalar kTimeScaleMin = 0.0f;
static const SkScalar kTimeScaleMax = 5.0f;
// Box the value within [min, max), by applying infinite reflection on the interval endpoints.
SkScalar box_reflect(SkScalar v, SkScalar min, SkScalar max) {
const SkScalar intervalLen = max - min;
SkASSERT(intervalLen > 0);
// f(v) is periodic in 2 * intervalLen: one normal progression + one reflection
const SkScalar P = intervalLen * 2;
// relative to P origin
const SkScalar vP = v - min;
// map to [0, P)
const SkScalar vMod = (vP < 0) ? P - SkScalarMod(-vP, P) : SkScalarMod(vP, P);
// reflect if needed, to map to [0, intervalLen)
const SkScalar vInterval = vMod < intervalLen ? vMod : P - vMod;
// finally, reposition relative to min
return vInterval + min;
}
// Compute <t, y> for the trajectory intersection with the next vertical edge.
std::tuple<SkScalar, SkScalar> find_yintercept(const SkPoint& pos, const SkVector& spd,
const SkRect& box) {
const SkScalar edge = spd.fX > 0 ? box.fRight : box.fLeft;
const SkScalar t = (edge - pos.fX) / spd.fX;
SkASSERT(t >= 0);
const SkScalar dY = t * spd.fY;
return std::make_tuple(t, box_reflect(pos.fY + dY, box.fTop, box.fBottom));
}
void update_pos(const sk_sp<sksg::RRect>& rr, const SkPoint& pos) {
// TODO: position setters on RRect?
const auto r = rr->getRRect().rect();
const auto offsetX = pos.x() - r.x(),
offsetY = pos.y() - r.y();
rr->setRRect(rr->getRRect().makeOffset(offsetX, offsetY));
}
} // namespace
class PongView final : public Sample {
public:
PongView() = default;
protected:
void onOnceBeforeDraw() override {
const SkRect fieldBounds = kBounds.makeOutset(kBallSize / 2, kBallSize / 2);
const SkRRect ball = SkRRect::MakeOval(SkRect::MakeWH(kBallSize, kBallSize));
const SkRRect paddle = SkRRect::MakeRectXY(SkRect::MakeWH(kPaddleSize.width(),
kPaddleSize.height()),
kPaddleSize.width() / 2,
kPaddleSize.width() / 2);
fBall.initialize(ball,
SkPoint::Make(kBounds.centerX(), kBounds.centerY()),
SkVector::Make(fRand.nextRangeScalar(kBallSpeedMin, kBallSpeedMax),
fRand.nextRangeScalar(kBallSpeedMin, kBallSpeedMax)));
fPaddle0.initialize(paddle,
SkPoint::Make(fieldBounds.left() - kPaddleSize.width() / 2,
fieldBounds.centerY()),
SkVector::Make(0, 0));
fPaddle1.initialize(paddle,
SkPoint::Make(fieldBounds.right() + kPaddleSize.width() / 2,
fieldBounds.centerY()),
SkVector::Make(0, 0));
// Background decoration.
SkPathBuilder bgPath;
bgPath.moveTo(kBounds.left() , fieldBounds.top())
.lineTo(kBounds.right(), fieldBounds.top())
.moveTo(kBounds.left() , fieldBounds.bottom())
.lineTo(kBounds.right(), fieldBounds.bottom());
// TODO: stroke-dash support would come in handy right about now.
for (uint32_t i = 0; i < kBackgroundDashCount; ++i) {
bgPath.moveTo(kBounds.centerX(),
kBounds.top() + (i + 0.25f) * kBounds.height() / kBackgroundDashCount)
.lineTo(kBounds.centerX(),
kBounds.top() + (i + 0.75f) * kBounds.height() / kBackgroundDashCount);
}
auto bg_path = sksg::Path::Make(bgPath.detach());
auto bg_paint = sksg::Color::Make(SK_ColorBLACK);
bg_paint->setStyle(SkPaint::kStroke_Style);
bg_paint->setStrokeWidth(kBackgroundStroke);
auto ball_paint = sksg::Color::Make(SK_ColorGREEN),
paddle0_paint = sksg::Color::Make(SK_ColorBLUE),
paddle1_paint = sksg::Color::Make(SK_ColorRED),
shadow_paint = sksg::Color::Make(SK_ColorBLACK);
ball_paint->setAntiAlias(true);
paddle0_paint->setAntiAlias(true);
paddle1_paint->setAntiAlias(true);
shadow_paint->setAntiAlias(true);
shadow_paint->setOpacity(kShadowOpacity);
// Build the scene graph.
auto group = sksg::Group::Make();
group->addChild(sksg::Draw::Make(std::move(bg_path), std::move(bg_paint)));
group->addChild(sksg::Draw::Make(fPaddle0.shadowNode, shadow_paint));
group->addChild(sksg::Draw::Make(fPaddle1.shadowNode, shadow_paint));
group->addChild(sksg::Draw::Make(fBall.shadowNode, shadow_paint));
group->addChild(sksg::Draw::Make(fPaddle0.objectNode, paddle0_paint));
group->addChild(sksg::Draw::Make(fPaddle1.objectNode, paddle1_paint));
group->addChild(sksg::Draw::Make(fBall.objectNode, ball_paint));
// Handle everything in a normalized 1x1 space.
fContentMatrix = sksg::Matrix<SkMatrix>::Make(
SkMatrix::MakeRectToRect(SkRect::MakeWH(1, 1),
SkRect::MakeIWH(this->width(), this->height()),
SkMatrix::kFill_ScaleToFit));
auto root = sksg::TransformEffect::Make(std::move(group), fContentMatrix);
fScene = sksg::Scene::Make(std::move(root));
// Off we go.
this->updatePaddleStrategy();
}
SkString name() override { return SkString("SGPong"); }
bool onChar(SkUnichar uni) override {
switch (uni) {
case '[':
fTimeScale = SkTPin(fTimeScale - 0.1f, kTimeScaleMin, kTimeScaleMax);
return true;
case ']':
fTimeScale = SkTPin(fTimeScale + 0.1f, kTimeScaleMin, kTimeScaleMax);
return true;
case 'I':
fShowInval = !fShowInval;
return true;
default:
break;
}
return false;
}
void onSizeChange() override {
if (fContentMatrix) {
fContentMatrix->setMatrix(SkMatrix::MakeRectToRect(SkRect::MakeWH(1, 1),
SkRect::MakeIWH(this->width(),
this->height()),
SkMatrix::kFill_ScaleToFit));
}
this->INHERITED::onSizeChange();
}
void onDrawContent(SkCanvas* canvas) override {
sksg::InvalidationController ic;
fScene->render(canvas);
if (fShowInval) {
SkPaint fill, stroke;
fill.setAntiAlias(true);
fill.setColor(0x40ff0000);
stroke.setAntiAlias(true);
stroke.setColor(0xffff0000);
stroke.setStyle(SkPaint::kStroke_Style);
for (const auto& r : ic) {
canvas->drawRect(r, fill);
canvas->drawRect(r, stroke);
}
}
}
bool onAnimate(double nanos) override {
// onAnimate may fire before the first draw.
if (fScene) {
SkScalar dt = (TimeUtils::NanosToMSec(nanos) - fLastTick) * fTimeScale;
fLastTick = TimeUtils::NanosToMSec(nanos);
fPaddle0.posTick(dt);
fPaddle1.posTick(dt);
fBall.posTick(dt);
this->enforceConstraints();
fPaddle0.updateDom();
fPaddle1.updateDom();
fBall.updateDom();
}
return true;
}
private:
struct Object {
void initialize(const SkRRect& rrect, const SkPoint& p, const SkVector& s) {
objectNode = sksg::RRect::Make(rrect);
shadowNode = sksg::RRect::Make(rrect);
pos = p;
spd = s;
size = SkSize::Make(rrect.width(), rrect.height());
}
void posTick(SkScalar dt) {
pos += spd * dt;
}
void updateDom() {
const SkPoint corner = pos - SkPoint::Make(size.width() / 2, size.height() / 2);
update_pos(objectNode, corner);
// Simulate parallax shadow for a centered light source.
SkPoint shadowOffset = pos - SkPoint::Make(kBounds.centerX(), kBounds.centerY());
shadowOffset.scale(kShadowParallax);
const SkPoint shadowCorner = corner + shadowOffset;
update_pos(shadowNode, shadowCorner);
}
sk_sp<sksg::RRect> objectNode,
shadowNode;
SkPoint pos;
SkVector spd;
SkSize size;
};
void enforceConstraints() {
// Perfect vertical reflection.
if (fBall.pos.fY < kBounds.fTop || fBall.pos.fY >= kBounds.fBottom) {
fBall.spd.fY = -fBall.spd.fY;
fBall.pos.fY = box_reflect(fBall.pos.fY, kBounds.fTop, kBounds.fBottom);
}
// Horizontal bounce - introduces a speed fuzz.
if (fBall.pos.fX < kBounds.fLeft || fBall.pos.fX >= kBounds.fRight) {
fBall.spd.fX = this->fuzzBallSpeed(-fBall.spd.fX);
fBall.spd.fY = this->fuzzBallSpeed(fBall.spd.fY);
fBall.pos.fX = box_reflect(fBall.pos.fX, kBounds.fLeft, kBounds.fRight);
this->updatePaddleStrategy();
}
}
SkScalar fuzzBallSpeed(SkScalar spd) {
// The speed limits are absolute values.
const SkScalar sign = spd >= 0 ? 1.0f : -1.0f;
const SkScalar fuzzed = fabs(spd) + fRand.nextRangeScalar(-kBallSpeedFuzz, kBallSpeedFuzz);
return sign * SkTPin(fuzzed, kBallSpeedMin, kBallSpeedMax);
}
void updatePaddleStrategy() {
Object* pitcher = fBall.spd.fX > 0 ? &fPaddle0 : &fPaddle1;
Object* catcher = fBall.spd.fX > 0 ? &fPaddle1 : &fPaddle0;
SkScalar t, yIntercept;
std::tie(t, yIntercept) = find_yintercept(fBall.pos, fBall.spd, kBounds);
// The pitcher aims for a neutral/centered position.
pitcher->spd.fY = (kBounds.centerY() - pitcher->pos.fY) / t;
// The catcher goes for the ball. Duh.
catcher->spd.fY = (yIntercept - catcher->pos.fY) / t;
}
std::unique_ptr<sksg::Scene> fScene;
sk_sp<sksg::Matrix<SkMatrix>> fContentMatrix;
Object fPaddle0, fPaddle1, fBall;
SkRandom fRand;
SkMSec fLastTick = 0;
SkScalar fTimeScale = 1.0f;
bool fShowInval = false;
using INHERITED = Sample;
};
DEF_SAMPLE( return new PongView(); )
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