Bug 96015 – 2D canvas strokeRect: negative width or height should affect winding direction

• Status: NEW
• Component: Canvas

[Justin Novosad]

From whatwg strokeRect spec:
"the path has a single subpath are four points, with coordinates (x, y), (x+w, y), (x+w, y+h), and (x, y+h), connected to each other in that order by straight lines"

Emphasis on: "in that order"

This means that if w is negative xor y is negative, then the vertices should be drawn in counter clockwise order. This has an effect on how line dashes are drawn.  This is currently broken because CanvasRenderingContext2D::strokeRect calls validateRectForCanvas, which normalizes the rectangle to make w and h positive.

When fixing the, care must be taken not to regress any of the graphics ports.  The skia port of GraphicsContext is capable of handling negative w/h, haven't looked at the others yet.

[Dirk Schulze]

Created attachment 228677 [details]
Example

Example file.

[Brent Fulgham]

WebKit still doesn't seem to handle this properly.

[Radar WebKit Bug Importer]

<rdar://problem/97219927>