RFR: 8280020: Underline and line-through not straight in WebView

[yosbits]

On Thu, 10 Feb 2022 11:36:38 GMT, Jay Bhaskar <duke at openjdk.java.net> wrote:

> Issue: The end point of  line in drawLinesForText , add thickness to the endPoint.y(). In this case origin which is start point and the end point would not be same, and line would be drawn not straight.
> Solution: Do not add thickness to the y position of end point of line.
> Start Point(x,y) ----------End Point(x + width, 0)

Looking at the GraphicsContexCG source, we can see that the
It looks correct to call fill rect instead of draw line.

The GraphicsContexJava implementation seems to be the cause of the underline tilt.
Also, there seems to be no need to call drawLine() multiple times by referring to last().

``` cpp
void GraphicsContextCG::drawLinesForText(const FloatPoint& point, float thickness, const DashArray& widths, bool printing, bool doubleLines, StrokeStyle strokeStyle)
{
    if (!widths.size())
        return;

    Color localStrokeColor(strokeColor());

    FloatRect bounds = computeLineBoundsAndAntialiasingModeForText(FloatRect(point, FloatSize(widths.last(), thickness)), printing, localStrokeColor);
    if (bounds.isEmpty())
        return;

    bool fillColorIsNotEqualToStrokeColor = fillColor() != localStrokeColor;
    
    Vector<CGRect, 4> dashBounds;
    ASSERT(!(widths.size() % 2));
    dashBounds.reserveInitialCapacity(dashBounds.size() / 2);

    float dashWidth = 0;
    switch (strokeStyle) {
    case DottedStroke:
        dashWidth = bounds.height();
        break;
    case DashedStroke:
        dashWidth = 2 * bounds.height();
        break;
    case SolidStroke:
    default:
        break;
    }

    for (size_t i = 0; i < widths.size(); i += 2) {
        auto left = widths[i];
        auto width = widths[i+1] - widths[i];
        if (!dashWidth)
            dashBounds.append(CGRectMake(bounds.x() + left, bounds.y(), width, bounds.height()));
        else {
            auto startParticle = static_cast<int>(std::ceil(left / (2 * dashWidth)));
            auto endParticle = static_cast<int>((left + width) / (2 * dashWidth));
            for (auto j = startParticle; j < endParticle; ++j)
                dashBounds.append(CGRectMake(bounds.x() + j * 2 * dashWidth, bounds.y(), dashWidth, bounds.height()));
        }
    }

    if (doubleLines) {
        // The space between double underlines is equal to the height of the underline
        for (size_t i = 0; i < widths.size(); i += 2)
            dashBounds.append(CGRectMake(bounds.x() + widths[i], bounds.y() + 2 * bounds.height(), widths[i+1] - widths[i], bounds.height()));
    }

    if (fillColorIsNotEqualToStrokeColor)
        setCGFillColor(platformContext(), localStrokeColor);

    CGContextFillRects(platformContext(), dashBounds.data(), dashBounds.size());

    if (fillColorIsNotEqualToStrokeColor)
        setCGFillColor(platformContext(), fillColor());
}

-------------

PR: https://git.openjdk.java.net/jfx/pull/731