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[Aisano <info@xxxxxxxxxxxxxxxxx>]

I am having this problem on my new notebook running Ubuntu 10.04, and I
did a little source code reading. At least on my hardware the problem is
caused by the processing of mouse move events, where the event state
mask happens to have the 0x2000 bit set. This bit is not defined in the
"gdktypes.h" header, and I do not know what it means. But it causes the
comparison to the mouse button bit masks in "xsane-preview.c" to fail,
so the scan rectangle is never drawn or updated.

A look at the code revealed that there seems to be a little
misunderstanding: Though the "GdkEventMotion.state" value is a bit mask
it is AND-ed with constants such as GDK_Num_Lock or GDK_Caps_Lock, which
are not bit masks but enumerated values. What the author probably meant
was ignoring any modifiers (such as Shift or Ctrl) except for the bare
mouse buttons. This is easily achieved by AND-ing the state value with
the OR-ed mouse button constants (GDK_BUTTON1_MASK | GDK_BUTTON2_MASK |
GDK_BUTTON3_MASK).

I am adding a patch for xsane-preview.c, which solves the problem on my
platform and looks like "doing the right thing", so it should not harm
anybody even if the problem should have different causes on different
platforms.

** Patch added: "Patch for xsane-preview.c"
   http://launchpadlibrarian.net/48345142/xsane-preview.c.patch

-- 
Unable to select scan area in preview window
https://bugs.launchpad.net/bugs/370818
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