Tickled to Death

My last post was written rather hastily, and the Lazy Web indeed noticed some silly mistakes; for one thing, the || operator makes 'if' statements much smaller, and the code that configures your GdkWindow.Devices should be handled on Realize, not on Configure.

I was also rather ambiguous as to what I meant about applying a gradient to a stroke (as opposed to a fill). Yes, it is possible, and quite straightforward:

Code for that is available here.

Cairo gives you a radial gradient and a linear gradient for free. The gradient, however, is applied to the image as a whole. What I want to be able to do is draw a stroke and have the gradient be applied along the path of the stroke itself, rather than what you see in the above screenshot. So, if I set a black color stop at 0.0 and a red color stop at 1.0 (as I did above), I would want the black to start at the top-left corner of the square, and change to red along the path itself, ending as red back where it started in the top-left. If I fill that square using the same linear gradient, you can see what is actually happening:

Anyway, just because I wanted to see pressure-sensitive results in Virtual Paper, I reworked the stroke drawing code to stroke for each line segment with the color (pressure) of that line segment. It actually looks really nice, and doesn't slow down like I was afraid it would:

This screenshot shows why I'd like to be able to apply a gradient to a stroke. Fortunately, it also shows that the results without a gradient are still pretty spectacular:

Since it looks decent without gradients and the performance doesn't take any noticeable hit with extra calls to Stroke() (and am I insane for thinking there would be a noticeable hit?), this one will be on the back burner for a little while.  It'll become important again for things like SVG export, since you want to actually have a scalable vector graphic and not a bunch of line segments that don't flow with each other.

This entry was posted on Wednesday, May 23rd, 2007 at 12:39 am and is filed under Life, Public. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.