flutter_flutter/sky/engine/platform/graphics/StrokeData.cpp

// Copyright (C) 2013 Google Inc. All rights reserved.
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#include "flutter/sky/engine/platform/graphics/StrokeData.h"

#include "flutter/sky/engine/platform/graphics/skia/SkiaUtils.h"
#include "flutter/sky/engine/wtf/OwnPtr.h"
#include "flutter/sky/engine/wtf/PassOwnPtr.h"

namespace blink {

static const int dashRatio = 3; // Ratio of the length of a dash to its width.

void StrokeData::setLineDash(const DashArray& dashes, float dashOffset)
{
    // FIXME: This is lifted directly off SkiaSupport, lines 49-74
    // so it is not guaranteed to work correctly.
    size_t dashLength = dashes.size();
    if (!dashLength) {
        // If no dash is set, revert to solid stroke
        // FIXME: do we need to set NoStroke in some cases?
        m_style = SolidStroke;
        m_dash.reset();
        return;
    }

    size_t count = !(dashLength % 2) ? dashLength : dashLength * 2;
    OwnPtr<SkScalar[]> intervals = adoptArrayPtr(new SkScalar[count]);

    for (unsigned i = 0; i < count; i++)
        intervals[i] = dashes[i % dashLength];

    m_dash = SkDashPathEffect::Make(intervals.get(), count, dashOffset);
}

void StrokeData::setupPaint(SkPaint* paint, int length) const
{
    paint->setStyle(SkPaint::kStroke_Style);
    paint->setStrokeWidth(SkFloatToScalar(m_thickness));
    paint->setStrokeCap(m_lineCap);
    paint->setStrokeJoin(m_lineJoin);
    paint->setStrokeMiter(SkFloatToScalar(m_miterLimit));

    setupPaintDashPathEffect(paint, length);
}

void StrokeData::setupPaintDashPathEffect(SkPaint* paint, int length) const
{
    float width = m_thickness;
    if (m_dash) {
        paint->setPathEffect(m_dash);
    } else {
        switch (m_style) {
        case NoStroke:
        case SolidStroke:
        case DoubleStroke:
        case WavyStroke: // FIXME: https://code.google.com/p/chromium/issues/detail?id=229574
            paint->setPathEffect(0);
            return;
        case DashedStroke:
            width = dashRatio * width;
            // Fall through.
        case DottedStroke:
            // Truncate the width, since we don't want fuzzy dots or dashes.
            int dashLength = static_cast<int>(width);
            // Subtract off the endcaps, since they're rendered separately.
            int distance = length - 2 * static_cast<int>(m_thickness);
            int phase = 1;
            if (dashLength > 1) {
                // Determine how many dashes or dots we should have.
                int numDashes = distance / dashLength;
                int remainder = distance % dashLength;
                // Adjust the phase to center the dashes within the line.
                if (numDashes % 2) {
                    // Odd: shift right a full dash, minus half the remainder.
                    phase = dashLength - remainder / 2;
                } else {
                    // Even: shift right half a dash, minus half the remainder.
                    phase = (dashLength - remainder) / 2;
                }
            }
            SkScalar dashLengthSk = SkIntToScalar(dashLength);
            SkScalar intervals[2] = { dashLengthSk, dashLengthSk };
            paint->setPathEffect(SkDashPathEffect::Make(intervals, 2, SkIntToScalar(phase)));
        }
    }
}

} // namespace blink