Hi,
My Mesh branch suffered from serious bit rot. This is good as it shows how fast Inkscape code is progressing. But it also required several days of work to get the mesh branch in sync... not so good. I have thus merged the branch with trunk so I won't have to go through this pain again. One major change I made was to create a separate Mesh tool. The editing mode for meshes is significantly different from that for linear and radial gradients that I think this makes the most sense.
By default, the Mesh tool is not shown. You can enable it at compile time by editing the file widgets/toolbox.cpp to define WITH_MESH. To actually see meshes, you must have compiled and linked to a version of Cairo greater to or equal to 1.11.4. Cairo version 12.0 would be preferred as 1.11.4 has bugs that cause frequent Inkscape crashes.
Note, meshes are to be considered experimental. The SVG working group has endorsed their inclusion in SVG2 but the exact syntax has not been fixed. Inkscape is the only program/browser/renderer that supports the proposed SVG mesh syntax. Also, the UI for meshes is rather primitive at the moment.
Please play with the meshes and give your feedback. Bug fixes and interface improvements will be greatly appreciated!
Tav