/* * Copyright 2016 Google Inc. * * Use of this source code is governed by a BSD-style license that can be * found in the LICENSE file. */ /* * This GM exercises stroking of paths with large stroke lengths, which is * referred to as "overstroke" for brevity. In Skia as of 8/2016 we offset * each part of the curve the request amount even if it makes the offsets * overlap and create holes. There is not a really great algorithm for this * and several other 2D graphics engines have the same bug. * * The old Nvidia Path Renderer used to yield correct results, so a possible * direction of attack is to use the GPU and a completely different algorithm. * * See crbug.com/589769 skbug.com/5405 skbug.com/5406 */ #include "gm/gm.h" #include "include/core/SkCanvas.h" #include "include/core/SkColor.h" #include "include/core/SkPaint.h" #include "include/core/SkPathBuilder.h" #include "include/core/SkPathMeasure.h" #include "include/core/SkPoint.h" #include "include/core/SkRect.h" #include "include/core/SkScalar.h" #include "src/core/SkPointPriv.h" #include <cstddef> const SkScalar OVERSTROKE_WIDTH = 500.0f; const SkScalar NORMALSTROKE_WIDTH = 3.0f; //////// path and paint builders SkPaint make_normal_paint() { SkPaint p; p.setAntiAlias(true); p.setStyle(SkPaint::kStroke_Style); p.setStrokeWidth(NORMALSTROKE_WIDTH); p.setColor(SK_ColorBLUE); return p; } SkPaint make_overstroke_paint() { SkPaint p; p.setAntiAlias(true); p.setStyle(SkPaint::kStroke_Style); p.setStrokeWidth(OVERSTROKE_WIDTH); return p; } SkPath quad_path() { return SkPathBuilder().moveTo(0, 0) .lineTo(100, 0) .quadTo(50, -40, 0, 0) .close() .detach(); } SkPath cubic_path() { SkPath path; path.moveTo(0, 0); path.cubicTo(25, 75, 75, -50, 100, 0); return path; } SkPath oval_path() { SkRect oval = SkRect::MakeXYWH(0, -25, 100, 50); return SkPathBuilder().arcTo(oval, 0, 359, true).close().detach(); } SkPath ribs_path(SkPath path, SkScalar radius) { SkPath ribs; const SkScalar spacing = 5.0f; float accum = 0.0f; SkPathMeasure meas(path, false); SkScalar length = meas.getLength(); SkPoint pos; SkVector tan; while (accum < length) { if (meas.getPosTan(accum, &pos, &tan)) { tan.scale(radius); SkPointPriv::RotateCCW(&tan); ribs.moveTo(pos.x() + tan.x(), pos.y() + tan.y()); ribs.lineTo(pos.x() - tan.x(), pos.y() - tan.y()); } accum += spacing; } return ribs; } void draw_ribs(SkCanvas *canvas, SkPath path) { SkPath ribs = ribs_path(path, OVERSTROKE_WIDTH/2.0f); SkPaint p = make_normal_paint(); p.setStrokeWidth(1); p.setColor(SK_ColorBLUE); p.setColor(SK_ColorGREEN); canvas->drawPath(ribs, p); } ///////// quads void draw_small_quad(SkCanvas *canvas) { // scaled so it's visible // canvas->scale(8, 8); SkPaint p = make_normal_paint(); SkPath path = quad_path(); draw_ribs(canvas, path); canvas->drawPath(path, p); } void draw_large_quad(SkCanvas *canvas) { SkPaint p = make_overstroke_paint(); SkPath path = quad_path(); canvas->drawPath(path, p); draw_ribs(canvas, path); } void draw_quad_fillpath(SkCanvas *canvas) { SkPath path = quad_path(); SkPaint p = make_overstroke_paint(); SkPaint fillp = make_normal_paint(); fillp.setColor(SK_ColorMAGENTA); SkPath fillpath; p.getFillPath(path, &fillpath); canvas->drawPath(fillpath, fillp); } void draw_stroked_quad(SkCanvas *canvas) { canvas->translate(400, 0); draw_large_quad(canvas); draw_quad_fillpath(canvas); } ////////// cubics void draw_small_cubic(SkCanvas *canvas) { SkPaint p = make_normal_paint(); SkPath path = cubic_path(); draw_ribs(canvas, path); canvas->drawPath(path, p); } void draw_large_cubic(SkCanvas *canvas) { SkPaint p = make_overstroke_paint(); SkPath path = cubic_path(); canvas->drawPath(path, p); draw_ribs(canvas, path); } void draw_cubic_fillpath(SkCanvas *canvas) { SkPath path = cubic_path(); SkPaint p = make_overstroke_paint(); SkPaint fillp = make_normal_paint(); fillp.setColor(SK_ColorMAGENTA); SkPath fillpath; p.getFillPath(path, &fillpath); canvas->drawPath(fillpath, fillp); } void draw_stroked_cubic(SkCanvas *canvas) { canvas->translate(400, 0); draw_large_cubic(canvas); draw_cubic_fillpath(canvas); } ////////// ovals void draw_small_oval(SkCanvas *canvas) { SkPaint p = make_normal_paint(); SkPath path = oval_path(); draw_ribs(canvas, path); canvas->drawPath(path, p); } void draw_large_oval(SkCanvas *canvas) { SkPaint p = make_overstroke_paint(); SkPath path = oval_path(); canvas->drawPath(path, p); draw_ribs(canvas, path); } void draw_oval_fillpath(SkCanvas *canvas) { SkPath path = oval_path(); SkPaint p = make_overstroke_paint(); SkPaint fillp = make_normal_paint(); fillp.setColor(SK_ColorMAGENTA); SkPath fillpath; p.getFillPath(path, &fillpath); canvas->drawPath(fillpath, fillp); } void draw_stroked_oval(SkCanvas *canvas) { canvas->translate(400, 0); draw_large_oval(canvas); draw_oval_fillpath(canvas); } ////////// gm void (*examples[])(SkCanvas *canvas) = { draw_small_quad, draw_stroked_quad, draw_small_cubic, draw_stroked_cubic, draw_small_oval, draw_stroked_oval, }; DEF_SIMPLE_GM(OverStroke, canvas, 500, 500) { const size_t length = sizeof(examples) / sizeof(examples[0]); const size_t width = 2; for (size_t i = 0; i < length; i++) { int x = (int)(i % width); int y = (int)(i / width); canvas->save(); canvas->translate(150.0f * x, 150.0f * y); canvas->scale(0.2f, 0.2f); canvas->translate(300.0f, 400.0f); examples[i](canvas); canvas->restore(); } }