[Webkit-unassigned] [Bug 14440] New: [CAIRO][QT][CG] Share adjustLineToPixelBoundaries() between all GraphicsContext impls.

[bugzilla-daemon at webkit.org]

http://bugs.webkit.org/show_bug.cgi?id=14440

           Summary: [CAIRO][QT][CG] Share adjustLineToPixelBoundaries()
                    between all GraphicsContext impls.
           Product: WebKit
           Version: 522+ (nightly)
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: Minor
          Priority: P2
         Component: New Bugs
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: alp at atoker.com


Each of the GraphicsContext implementations have duplicated code in
adjustLineToPixelBoundaries().

The block used by Qt and Cairo is:

// FIXME: Now that this is refactored, it should be shared by all contexts.
static void adjustLineToPixelBoundaries(FloatPoint& p1, FloatPoint& p2, float
strokeWidth,
                                        const StrokeStyle& penStyle)
{
    // For odd widths, we add in 0.5 to the appropriate x/y so that the float
arithmetic
    // works out.  For example, with a border width of 3, KHTML will pass us
(y1+y2)/2, e.g.,
    // (50+53)/2 = 103/2 = 51 when we want 51.5.  It is always true that an
even width gave
    // us a perfect position, but an odd width gave us a position that is off
by exactly 0.5.
    if (penStyle == DottedStroke || penStyle == DashedStroke) {
        if (p1.x() == p2.x()) {
            p1.setY(p1.y() + strokeWidth);
            p2.setY(p2.y() - strokeWidth);
        } else {
            p1.setX(p1.x() + strokeWidth);
            p2.setX(p2.x() - strokeWidth);
        }
    }

    if (((int) strokeWidth) % 2) {
        if (p1.x() == p2.x()) {
            // We're a vertical line.  Adjust our x.
            p1.setX(p1.x() + 0.5);
            p2.setX(p2.x() + 0.5);
        } else {
            // We're a horizontal line. Adjust our y.
            p1.setY(p1.y() + 0.5);
            p2.setY(p2.y() + 0.5);
        }
    }
}


On CG:

    // For odd widths, we add in 0.5 to the appropriate x/y so that the float
arithmetic
    // works out.  For example, with a border width of 3, KHTML will pass us
(y1+y2)/2, e.g.,
    // (50+53)/2 = 103/2 = 51 when we want 51.5.  It is always true that an
even width gave
    // us a perfect position, but an odd width gave us a position that is off
by exactly 0.5.
    if (strokeStyle() == DottedStroke || strokeStyle() == DashedStroke) {
        if (isVerticalLine) {
            p1.move(0, width);
            p2.move(0, -width);
        } else {
            p1.move(width, 0);
            p2.move(-width, 0);
        }
    }

    if (((int)width) % 2) {
        if (isVerticalLine) {
            // We're a vertical line.  Adjust our x.
            p1.move(0.5f, 0.0f);
            p2.move(0.5f, 0.0f);
        } else {
            // We're a horizontal line. Adjust our y.
            p1.move(0.0f, 0.5f);
            p2.move(0.0f, 0.5f);
        }
    }


There may be more code that can be shared here.


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