Bug 54658 – [gtk] Failing collinear arcTo canvas tests

• Status: RESOLVED
• Resolution: FIXED
• Component: Canvas

[Zan Dobersek]

The following two canvas tests are failing because we do not check for collinearity of the points when arcTo is called.
canvas/philip/tests/2d.path.arcTo.collinear.2.html
canvas/philip/tests/2d.path.arcTo.collinear.3.html

[Zan Dobersek]

Created attachment 82798 [details]
Add collinearity check

This patch adds a collinearity check that checks if the three points used to draw an arc through arcTo method are positioned in a line.

Check is performed by calculating the area of the triangle that the three points construct - if the area equals zero, the lines are collinear.

[Martin Robinson]

Comment on attachment 82798 [details]
Add collinearity check

View in context: https://bugs.webkit.org/attachment.cgi?id=82798&action=review

This is great! We want to make the if statement a little clearer below.

> Source/WebCore/platform/graphics/cairo/PathCairo.cpp:187
> +        || !(p0.x() * (p1.y() - p2.y()) + p1.x() * (p2.y() - p0.y()) + p2.x() * (p0.y() - p1.y()))) {

Please split out the area calculation to a static inline method called something like areaOfTriangleFormedByPoints.

[Zan Dobersek]

Created attachment 82974 [details]
Updated patch

Creates new function for calculating area of a triangle, clears up the checking statement.

[Eric Seidel (no email)]

Comment on attachment 82974 [details]
Updated patch

OK.  rs=me.

[Eric Seidel (no email)]

CCing folks who understand graphics better than I so they can see this go by.

[WebKit Commit Bot]

Comment on attachment 82974 [details]
Updated patch

Clearing flags on attachment: 82974

Committed r79541: <http://trac.webkit.org/changeset/79541>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.