Created attachment 488488 [details]
Patch to fix text glyph output from Cairo to be visible in all SVG clients

An R user reported a bug on RHEL-5 where a simple graph plot, written by R via cairo generated an SVG that did not appear to have text labels. Upon analysis, I discovered that on modern Fedora, R would output a valid SVG with text labels.

To reproduce this issue, install "R-core" from EPEL, and run R, then enter:

svg("plot.svg");
plot(cars);
dev.off(); 

This will output "plot.svg". Some clients seemed able to properly view this RHEL-5 SVG (inkscape, gimp), but others could not (firefox, chromium).

When I diff'd the two files (the RHEL-5 generated SVG and the Fedora 14 generated SVG), I discovered that the glyph entries in the RHEL-5 generated SVG were missing the overflow="visible" attribute. Sure enough, this was a bug identified and fixed in Cairo 1.4.0:

"SVG: Fix bug preventing text from appearing in many viewers"

http://cairographics.org/news/cairo-1.4.0/

When I looked to see how the bug was fixed, the fix was to simply add the overflow="visible" attribute when writing out glyphs. I backported this one-line fix to the RHEL-5 cairo package, rebuilt, and confirmed that it now generated SVG files which can be viewed with text labels in all SVG clients I could find.

I have attached a fixed SPEC, patch, and before/after SVG files. This patch should not affect API. Please consider this for a future update.