Add Overstroke gm

gm/OverStroke.cpp

+/*
+ * 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 "gm.h"
+#include "SkPaint.h"
+#include "SkPath.h"
+
+//////// path and paint builders
+
+SkPaint make_overstroke_paint() {
+    SkPaint p;
+    p.setAntiAlias(true);
+    p.setStyle(SkPaint::kStroke_Style);
+    p.setStrokeWidth(500);
+
+    return p;
+}
+
+SkPath quad_path() {
+    SkPoint p1 = SkPoint::Make(0, 0);

[reed1, 2016/08/02 15:21:31]

nit: I think it hurts readability a little to name these points and then use
them once, rather than just inline the values...

e.g.
    path.moveTo(0, 0);
    path.lineTo(100, 0);
    ...

[Harry Stern, 2016/08/02 15:44:02]

I actually think the exact opposite. seeing a bunch of random values, especially
for the cubicTo, just makes my brain freeze up. I'm going to try to
indent/newline to make it clear which are the points and see if that helps.

+    SkPoint p2 = SkPoint::Make(100, 0);
+    SkPoint p3 = SkPoint::Make(50, -40);
+
+    SkPath path;
+    path.moveTo(p1);
+    path.lineTo(p2);
+    path.quadTo(p3, p1);
+
+    return path;
+}
+
+SkPath cubic_path() {
+    SkPoint p1 = SkPoint::Make(0, 0);

[reed1, 2016/08/02 15:21:31]

ditto

[Harry Stern, 2016/08/02 15:44:02]

Done.

+    SkPoint p2 = SkPoint::Make(25, 75);
+    SkPoint p3 = SkPoint::Make(75, -50);
+    SkPoint p4 = SkPoint::Make(100, 0);
+
+    SkPath path;
+    path.moveTo(p1);
+    path.cubicTo(p2, p3, p4);
+
+    return path;
+}
+
+SkPath oval_path() {
+    SkRect oval = SkRect::MakeWH(100, 50);

[reed1, 2016/08/02 15:21:31]

nit: use SkRect::MakeXYWH(0, -25, 100, 50);

[Harry Stern, 2016/08/02 15:44:02]

Done.

+    oval.offset(0, -25);
+
+    SkPath path;
+    path.arcTo(oval, 0, 359, true);

[Harry Stern, 2016/08/02 15:44:02]

There's no way to make a complete oval just with arcTo is there? If I do
path.close() it looks complete, which I guess it good enough.

+
+    return path;
+}
+
+///////// quads
+
+void draw_small_quad(SkCanvas *canvas) {
+    // scaled so it's visible
+    canvas->scale(8, 8);
+
+    SkPaint p;
+    p.setAntiAlias(true);
+    p.setStyle(SkPaint::kStroke_Style);
+    p.setStrokeWidth(3);
+
+    SkPath path = quad_path();
+
+    canvas->drawPath(path, p);
+}
+
+void draw_large_quad(SkCanvas *canvas) {
+    SkPaint p = make_overstroke_paint();
+    SkPath path = quad_path();
+
+    canvas->drawPath(path, p);
+}
+
+void draw_quad_fillpath(SkCanvas *canvas) {
+    SkPath path = quad_path();
+    SkPaint p = make_overstroke_paint();
+
+    SkPaint fillp;
+    fillp.setAntiAlias(true);
+    fillp.setStyle(SkPaint::kStroke_Style);
+    fillp.setColor(SK_ColorMAGENTA);
+
+    SkPath fillpath;
+    p.getFillPath(path, &fillpath);
+
+    canvas->drawPath(fillpath, fillp);
+}
+
+void draw_stroked_quad(SkCanvas *canvas) {
+    canvas->translate(200, 0);
+    draw_large_quad(canvas);
+    draw_quad_fillpath(canvas);
+}
+
+////////// cubics
+
+void draw_small_cubic(SkCanvas *canvas) {
+    // scaled so it's visible
+    canvas->scale(8, 8);
+
+    SkPaint p;
+    p.setAntiAlias(true);
+    p.setStyle(SkPaint::kStroke_Style);
+    p.setStrokeWidth(3);
+
+    SkPath path = cubic_path();
+
+    canvas->drawPath(path, p);
+}
+
+void draw_large_cubic(SkCanvas *canvas) {
+    SkPaint p = make_overstroke_paint();
+    SkPath path = cubic_path();
+
+    canvas->drawPath(path, p);
+}
+
+void draw_cubic_fillpath(SkCanvas *canvas) {
+    SkPath path = cubic_path();
+    SkPaint p = make_overstroke_paint();
+
+    SkPaint fillp;
+    fillp.setAntiAlias(true);
+    fillp.setStyle(SkPaint::kStroke_Style);
+    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) {
+    // scaled so it's visible
+    canvas->scale(8, 8);
+
+    SkPaint p;
+    p.setAntiAlias(true);
+    p.setStyle(SkPaint::kStroke_Style);
+    p.setStrokeWidth(3);
+
+    SkPath path = oval_path();
+
+    canvas->drawPath(path, p);
+}
+
+void draw_large_oval(SkCanvas *canvas) {
+    SkPaint p = make_overstroke_paint();
+    SkPath path = oval_path();
+
+    canvas->drawPath(path, p);
+}
+
+void draw_oval_fillpath(SkCanvas *canvas) {
+    SkPath path = oval_path();
+    SkPaint p = make_overstroke_paint();
+
+    SkPaint fillp;
+    fillp.setAntiAlias(true);
+    fillp.setStyle(SkPaint::kStroke_Style);
+    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) {

[reed1, 2016/08/02 15:21:31]

// overstroke means ... and that's why I want to exercise it

[Harry Stern, 2016/08/02 15:44:02]

Done, at top of file.

+    const size_t length = sizeof(examples) / sizeof(examples[0]);
+    const size_t width = 2;
+
+    printf("length %ld\n", length);
+
+    for (size_t i = 0; i < length; i++) {
+        int x = i % width;
+        int y = i / width;
+
+        canvas->save();
+        canvas->translate(200 * x, 150 * y);
+        canvas->scale(0.25f, 0.25f);
+        canvas->translate(100, 400);
+
+        examples[i](canvas);
+
+        canvas->restore();
+    }
+}