Sadly, the line width depends on the widget's DPI, which seems to
even cause uneven lines on Windows, where virtual printers claim
high DPI. It might also be an unrelated problem.
Similarly, selected objects are exported highlighted.
Other than that, it works quite well.
Add a manifest to make the print dialog look nice with the older
GTK+ bundle we depend upon.
The RC file could theoretically be scanned for /\s+"([^"]+)"\s*$/,
unescaped, and the results configure_file()-stamped.
It turns out the RC detection snippet is no longer necessary
after the recent CMake version bump.
The "name" argument in the UI file is redundant, implied by "action".
