I think I fixed now the various bugs reported by Mental and others about the use of tablet pen in various tools:

http://sourceforge.net/tracker/index.php?func=detail&aid=1455685&gro...

(and probably other reports too).

Turns out "it's not a bug, it's a feature". This affected everything that dragged knots plus the rect tool; this also probably affected guideline dragging but nobody noticed that.

The reason is that only knot.cpp, rect-context.cpp and the ruler/guideline code grabbed canvas with a mask that included GDK_POINTER_MOTION_HINT_MASK. And this mask, per documentation, is exactly for this: it passes only the first motion event and suppresses all others, until you call gdk_window_get_pointer. Only ruler code cared to call; there's also a call in canvas motion event handler but it seems to have no effect.

Now, I have no time nor desire to figure out why this worked before (the hint mask was there since Sodipodi times), or why it broke with newer GTK versions, or why it broke only for tablet pens and not mice. Someone who likes GTK more than me might enjoy the exercise :) For now I simply removed the hint masks wherever I could find them, and everything seems to work fine for me (though for me it always worked fine, because I have a rather old gtk) and for a person on IRC who had troubles with pen before.

Of course this change is somewhat risky, so please test all tools and all kinds of dragging thoroughly. Let me know at once if you find something broken.