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Unified Diff: samplecode/SamplePathClip.cpp

Issue 1367373002: EdgeClip demo to show scan-converter clipping behavior (Closed) Base URL: https://skia.googlesource.com/skia.git@master
Patch Set: Created 5 years, 3 months ago
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Index: samplecode/SamplePathClip.cpp
diff --git a/samplecode/SamplePathClip.cpp b/samplecode/SamplePathClip.cpp
index 27f1f307ef395d92d0ac9aceacf8aa262984df87..09f1c9705c758f11410c35801b07478f88034cda 100644
--- a/samplecode/SamplePathClip.cpp
+++ b/samplecode/SamplePathClip.cpp
@@ -26,17 +26,9 @@ public:
SkRect fOval;
SkPoint fCenter;
- PathClipView() {
- fOval.set(0, 0, SkIntToScalar(200), SkIntToScalar(50));
- fCenter.set(SkIntToScalar(250), SkIntToScalar(250));
-
-// test_ats();
- }
-
- virtual ~PathClipView() {}
+ PathClipView() : fOval(SkRect::MakeWH(200, 50)), fCenter(SkPoint::Make(250, 250)) {}
protected:
- // overrides from SkEventSink
bool onQuery(SkEvent* evt) override {
if (SampleCode::TitleQ(*evt)) {
SampleCode::TitleR(evt, "PathClip");
@@ -46,8 +38,8 @@ protected:
}
void onDrawContent(SkCanvas* canvas) override {
- SkRect oval = fOval;
- oval.offset(fCenter.fX - oval.centerX(), fCenter.fY - oval.centerY());
+ const SkRect oval = fOval.makeOffset(fCenter.fX - fOval.centerX(),
+ fCenter.fY - fOval.centerY());
SkPaint p;
p.setAntiAlias(true);
@@ -55,9 +47,7 @@ protected:
p.setStyle(SkPaint::kStroke_Style);
canvas->drawOval(oval, p);
- SkRect r;
- r.set(SkIntToScalar(200), SkIntToScalar(200),
- SkIntToScalar(300), SkIntToScalar(300));
+ const SkRect r = SkRect::MakeLTRB(200, 200, 300, 300);
canvas->clipRect(r);
p.setStyle(SkPaint::kFill_Style);
@@ -65,8 +55,6 @@ protected:
canvas->drawRect(r, p);
p.setColor(0x800000FF);
- r.set(SkIntToScalar(150), SkIntToScalar(10),
- SkIntToScalar(250), SkIntToScalar(400));
canvas->drawOval(oval, p);
}
@@ -83,8 +71,251 @@ protected:
private:
typedef SampleView INHERITED;
};
+DEF_SAMPLE( return new PathClipView; )
//////////////////////////////////////////////////////////////////////////////
-static SkView* MyFactory() { return new PathClipView; }
-static SkViewRegister reg(MyFactory);
+static int clip_line(const SkRect& bounds, SkPoint p0, SkPoint p1, SkPoint edges[]) {
+ SkPoint* edgesStart = edges;
+
+ if (p0.fY == p1.fY) {
+ return 0;
+ }
+
+ if (p0.fY > p1.fY) {
+ SkTSwap(p0, p1);
+ }
+ // now we're monotonic in Y: p0 <= p1
+ if (p1.fY <= bounds.top() || p0.fY >= bounds.bottom()) {
+ return 0;
+ }
+
+ double dxdy = (double)(p1.fX - p0.fX) / (p1.fY - p0.fY);
+ if (p0.fY < bounds.top()) {
+ p0.fX = SkDoubleToScalar(p0.fX + dxdy * (bounds.top() - p0.fY));
+ p0.fY = bounds.top();
+ }
+ if (p1.fY > bounds.bottom()) {
+ p1.fX = SkDoubleToScalar(p1.fX + dxdy * (bounds.bottom() - p1.fY));
+ p1.fY = bounds.bottom();
+ }
+
+ // Now p0...p1 is strictly inside bounds vertically, so we just need to clip horizontally
+
+ if (p0.fX > p1.fX) {
+ SkTSwap(p0, p1);
+ }
+ // now we're left-to-right: p0 .. p1
+
+ if (p1.fX <= bounds.left()) { // entirely to the left
+ p0.fX = p1.fX = bounds.left();
+ *edges++ = p0;
+ *edges++ = p1;
+ return 2;
+ }
+ if (p0.fX >= bounds.right()) { // entirely to the right
+ p0.fX = p1.fX = bounds.right();
+ *edges++ = p0;
+ *edges++ = p1;
+ return 2;
+ }
+
+ if (p0.fX < bounds.left()) {
+ float y = SkDoubleToScalar(p0.fY + (bounds.left() - p0.fX) / dxdy);
+ *edges++ = SkPoint::Make(bounds.left(), p0.fY);
+ *edges++ = SkPoint::Make(bounds.left(), y);
+ p0.set(bounds.left(), y);
+ }
+ if (p1.fX > bounds.right()) {
+ float y = SkDoubleToScalar(p0.fY + (bounds.right() - p0.fX) / dxdy);
+ *edges++ = p0;
+ *edges++ = SkPoint::Make(bounds.right(), y);
+ *edges++ = SkPoint::Make(bounds.right(), p1.fY);
+ } else {
+ *edges++ = p0;
+ *edges++ = p1;
+ }
+ return SkToInt(edges - edgesStart);
+}
+
+static void draw_clipped_line(SkCanvas* canvas, const SkRect& bounds,
+ SkPoint p0, SkPoint p1, const SkPaint& paint) {
+ SkPoint verts[6];
+ int count = clip_line(bounds, p0, p1, verts);
+
+ SkPath path;
+ path.addPoly(verts, count, false);
+ canvas->drawPath(path, paint);
+}
+
+// Demonstrate edge-clipping that is used in the scan converter
+//
+class EdgeClipView : public SampleView {
+ enum {
+ N = 3
+ };
+public:
+ SkPoint fPoly[N];
+ SkRect fClip;
+ SkColor fEdgeColor[N];
+
+ EdgeClipView() : fClip(SkRect::MakeLTRB(150, 150, 550, 450)) {
+ fPoly[0].set(300, 40);
+ fPoly[1].set(550, 250);
+ fPoly[2].set(40, 450);
+
+ fEdgeColor[0] = 0xFFFF0000;
+ fEdgeColor[1] = 0xFF00FF00;
+ fEdgeColor[2] = 0xFF0000FF;
+ }
+
+protected:
+ bool onQuery(SkEvent* evt) override {
+ if (SampleCode::TitleQ(*evt)) {
+ SampleCode::TitleR(evt, "EdgeClip");
+ return true;
+ }
+ return this->INHERITED::onQuery(evt);
+ }
+
+ static SkScalar snap(SkScalar x) {
+ return SkScalarRoundToScalar(x * 0.5f) * 2;
+ }
+ static SkPoint snap(const SkPoint& pt) {
+ return SkPoint::Make(snap(pt.x()), snap(pt.y()));
+ }
+ static void snap(SkPoint dst[], const SkPoint src[], int count) {
+ for (int i = 0; i < count; ++i) {
+ dst[i] = snap(src[i]);
+ }
+ }
+
+ void onDrawContent(SkCanvas* canvas) override {
+ SkPath path;
+ path.addPoly(fPoly, N, true);
+
+ // Draw the full triangle, stroked and filled
+ SkPaint p;
+ p.setAntiAlias(true);
+ p.setColor(0xFFE0E0E0);
+ canvas->drawPath(path, p);
+ p.setStyle(SkPaint::kStroke_Style);
+ p.setStrokeWidth(2);
+ for (int i = 0; i < N; ++i) {
+ const int j = (i + 1) % N;
+ p.setColor(fEdgeColor[i]);
+ p.setAlpha(0x88);
+ canvas->drawLine(fPoly[i].x(), fPoly[i].y(), fPoly[j].x(), fPoly[j].y(), p);
+ }
+ p.setStyle(SkPaint::kFill_Style);
+
+ // Draw the clip itself
+ p.setColor(0xFF8888CC);
+ canvas->drawRect(fClip, p);
+
+ // Draw the filled triangle through the clip
+ p.setColor(0xFF88CC88);
+ canvas->save();
+ canvas->clipRect(fClip);
+ canvas->drawPath(path, p);
+ canvas->restore();
+
+ p.setStyle(SkPaint::kStroke_Style);
+ p.setStrokeWidth(6);
+
+ // Draw each of the "Edges" that survived the clipping
+ // We use a layer, so we can PLUS the different edge-colors, showing where two edges
+ // canceled each other out.
+ canvas->saveLayer(nullptr, nullptr);
+ p.setXfermodeMode(SkXfermode::kPlus_Mode);
+ for (int i = 0; i < N; ++i) {
+ const int j = (i + 1) % N;
+ p.setColor(fEdgeColor[i]);
+ draw_clipped_line(canvas, fClip, fPoly[i], fPoly[j], p);
+ }
+ canvas->restore();
+ }
+
+ class MyClick : public Click {
+ public:
+ MyClick(SkView* view) : Click(view) {}
+ virtual void handleMove() = 0;
+ };
+
+ class VertClick : public MyClick {
+ SkPoint* fPt;
+ public:
+ VertClick(SkView* view, SkPoint* pt) : MyClick(view), fPt(pt) {}
+ void handleMove() override { *fPt = snap(fCurr); }
+ };
+
+ class DragRectClick : public MyClick {
+ SkRect* fRect;
+ public:
+ DragRectClick(SkView* view, SkRect* rect) : MyClick(view), fRect(rect) {}
+ void handleMove() override { fRect->offset(fCurr.x() - fPrev.x(), fCurr.y() - fPrev.y()); }
+ };
+
+ class DragPolyClick : public MyClick {
+ SkPoint fSrc[100];
+ SkPoint* fPoly;
+ int fCount;
+ public:
+ DragPolyClick(SkView* view, SkPoint poly[], int count)
+ : MyClick(view), fPoly(poly), fCount(count)
+ {
+ SkASSERT((size_t)count <= SK_ARRAY_COUNT(fSrc));
+ memcpy(fSrc, poly, count * sizeof(SkPoint));
+ }
+ void handleMove() override {
+ const SkScalar dx = fCurr.x() - fOrig.x();
+ const SkScalar dy = fCurr.y() - fOrig.y();
+ for (int i = 0; i < fCount; ++i) {
+ fPoly[i].set(snap(fSrc[i].x() + dx), snap(fSrc[i].y() + dy));
+ }
+ }
+ };
+
+ class DoNothingClick : public MyClick {
+ public:
+ DoNothingClick(SkView* view) : MyClick(view) {}
+ void handleMove() override {}
+ };
+
+ static bool hit_test(const SkPoint& pt, SkScalar x, SkScalar y) {
+ const SkScalar rad = 8;
+ const SkScalar dx = pt.x() - x;
+ const SkScalar dy = pt.y() - y;
+ return dx*dx + dy*dy <= rad*rad;
+ }
+
+ SkView::Click* onFindClickHandler(SkScalar x, SkScalar y, unsigned) override {
+ for (int i = 0; i < N; ++i) {
+ if (hit_test(fPoly[i], x, y)) {
+ return new VertClick(this, &fPoly[i]);
+ }
+ }
+
+ SkPath path;
+ path.addPoly(fPoly, N, true);
+ if (path.contains(x, y)) {
+ return new DragPolyClick(this, fPoly, N);
+ }
+
+ if (fClip.intersects(SkRect::MakeLTRB(x - 1, y - 1, x + 1, y + 1))) {
+ return new DragRectClick(this, &fClip);
+ }
+ return new DoNothingClick(this);
+ }
+
+ bool onClick(Click* click) override {
+ ((MyClick*)click)->handleMove();
+ this->inval(nullptr);
+ return false;
+ }
+
+private:
+ typedef SampleView INHERITED;
+};
+DEF_SAMPLE( return new EdgeClipView; )
+
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