Followup to ed556113ce
The issue ed556113ce was trying to solve was that custom masks for
scrollers were used for drawing but not for mouse interaction (so
interaction was not matching drawing in some cases, namely the File
Browser and Spreadsheet).
This was done by "re-using" what was written to v2d->hor & v2d->vert (in
drawing) as a new mask (in interaction). This caused a problem since
this already includes not only those custom masks but other stuff, too.
For example, `view2d_masks` shrinks the rect when
V2D_SCROLL_VERTICAL_HANDLES is used, after ed556113ce this was
effectively done twice.
To resolve, revert the way ed556113ce was "re-using" what was written to
v2d->hor & v2d->vert and instead use the exact same masks that the
FileBrowser and the Spreadsheet set up for drawing in mouse interaction
as well. This way the masks match perfectly for both cases (and we can
fully recalculate all v2d extends without reusing anything that we
shouldnt).
Philipp Oeser