skia2/tests/EmptyPathTest.cpp

/*
 * Copyright 2011 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/SkBitmap.h"
#include "include/core/SkCanvas.h"
#include "include/core/SkPath.h"
#include "tests/Test.h"

#define DIMENSION   32

static void drawAndTest(skiatest::Reporter* reporter, const SkPath& path,
                        const SkPaint& paint, bool shouldDraw) {
    SkBitmap bm;
    bm.allocN32Pixels(DIMENSION, DIMENSION);
    SkASSERT(DIMENSION*4 == bm.rowBytes()); // ensure no padding on each row
    bm.eraseColor(SK_ColorTRANSPARENT);

    SkCanvas canvas(bm);
    SkPaint p(paint);
    p.setColor(SK_ColorWHITE);

    canvas.drawPath(path, p);

    size_t count = DIMENSION * DIMENSION;
    const SkPMColor* ptr = bm.getAddr32(0, 0);

    SkPMColor andValue = ~0U;
    SkPMColor orValue = 0;
    for (size_t i = 0; i < count; ++i) {
        SkPMColor c = ptr[i];
        andValue &= c;
        orValue |= c;
    }

    // success means we drew everywhere or nowhere (depending on shouldDraw)
    bool success = shouldDraw ? (~0U == andValue) : (0 == orValue);

    if (!success) {
        const char* str;
        if (shouldDraw) {
            str = "Path expected to draw everywhere, but didn't. ";
        } else {
            str = "Path expected to draw nowhere, but did. ";
        }
        ERRORF(reporter, "%s style[%d] cap[%d] join[%d] antialias[%d]"
               " filltype[%d] ptcount[%d]", str, paint.getStyle(),
               paint.getStrokeCap(), paint.getStrokeJoin(),
               paint.isAntiAlias(), (int)path.getFillType(), path.countPoints());
// uncomment this if you want to step in to see the failure
//        canvas.drawPath(path, p);
    }
}

enum DrawCaps {
    kDontDrawCaps,
    kDrawCaps
};

static void iter_paint(skiatest::Reporter* reporter, const SkPath& path, bool shouldDraw,
                       DrawCaps drawCaps) {
    static const SkPaint::Cap gCaps[] = {
        SkPaint::kButt_Cap,
        SkPaint::kRound_Cap,
        SkPaint::kSquare_Cap
    };
    static const SkPaint::Join gJoins[] = {
        SkPaint::kMiter_Join,
        SkPaint::kRound_Join,
        SkPaint::kBevel_Join
    };
    static const SkPaint::Style gStyles[] = {
        SkPaint::kFill_Style,
        SkPaint::kStroke_Style,
        SkPaint::kStrokeAndFill_Style
    };
    for (size_t cap = 0; cap < std::size(gCaps); ++cap) {
        for (size_t join = 0; join < std::size(gJoins); ++join) {
            for (size_t style = 0; style < std::size(gStyles); ++style) {
                if (drawCaps && SkPaint::kButt_Cap != gCaps[cap]
                        && SkPaint::kFill_Style != gStyles[style]) {
                    continue;
                }

                SkPaint paint;
                paint.setStrokeWidth(SkIntToScalar(10));

                paint.setStrokeCap(gCaps[cap]);
                paint.setStrokeJoin(gJoins[join]);
                paint.setStyle(gStyles[style]);

                paint.setAntiAlias(false);
                drawAndTest(reporter, path, paint, shouldDraw);
                paint.setAntiAlias(true);
                drawAndTest(reporter, path, paint, shouldDraw);
            }
        }
    }
}

#define CX  (SkIntToScalar(DIMENSION) / 2)
#define CY  (SkIntToScalar(DIMENSION) / 2)

static void make_empty(SkPath*) {}
static void make_M(SkPath* path) { path->moveTo(CX, CY); }
static void make_MM(SkPath* path) { path->moveTo(CX, CY).moveTo(CX, CY); }
static void make_MZM(SkPath* path) { path->moveTo(CX, CY).close().moveTo(CX, CY); }
static void make_L(SkPath* path) { path->moveTo(CX, CY).lineTo(CX, CY); }
static void make_Q(SkPath* path) { path->moveTo(CX, CY).quadTo(CX, CY, CX, CY); }
static void make_C(SkPath* path) { path->moveTo(CX, CY).cubicTo(CX, CY, CX, CY, CX, CY); }

/*  Two invariants are tested: How does an empty/degenerate path draw?
 *  - if the path is drawn inverse, it should draw everywhere
 *  - if the path is drawn non-inverse, it should draw nowhere
 *
 *  Things to iterate on:
 *  - path (empty, degenerate line/quad/cubic w/ and w/o close
 *  - paint style
 *  - path filltype
 *  - path stroke variants (e.g. caps, joins, width)
 */
static void test_emptydrawing(skiatest::Reporter* reporter) {
    static void (*gMakeProc[])(SkPath*) = {
        make_empty, make_M, make_MM, make_MZM, make_L, make_Q, make_C
    };
    static SkPathFillType gFills[] = {
        SkPathFillType::kWinding,
        SkPathFillType::kEvenOdd,
        SkPathFillType::kInverseWinding,
        SkPathFillType::kInverseEvenOdd
    };
    for (int doClose = 0; doClose < 2; ++doClose) {
        for  (size_t i = 0; i < std::size(gMakeProc); ++i) {
            SkPath path;
            gMakeProc[i](&path);
            if (doClose) {
                path.close();
            }
            /* zero length segments and close following moves draw round and square caps */
            bool allowCaps = make_L == gMakeProc[i] || make_Q == gMakeProc[i]
                    || make_C == gMakeProc[i] || make_MZM == gMakeProc[i];
            allowCaps |= SkToBool(doClose);
            for (size_t fill = 0; fill < std::size(gFills); ++fill) {
                path.setFillType(gFills[fill]);
                bool shouldDraw = path.isInverseFillType();
                iter_paint(reporter, path, shouldDraw, allowCaps ? kDrawCaps : kDontDrawCaps);
            }
        }
    }
}

DEF_TEST(EmptyPath, reporter) {
    test_emptydrawing(reporter);
}