[dev nov 8] When using multitab style "one row, arrows", the
upper/lower borders of tabs are chosen poorly and look ugly. See
attached screenshot. Note that (1) the Property Sheet is using a plain
TabbedPaneUI, so this can serve as a basis for comparison; (2) the
original value of the constant SPACE_TAB was 5, which looked horrible
(upper margin was huge); I made it 0, but actually -2 is required to
make the upper border the same size as with the normal UI; (3) the
lower border appears to be too slim; (4) while in the Editor and
Output Window it looks tolerable, in the Explorer for some reason the
spacing is substantially larger and uglier. Probably the constants
need to be tweaked and/or changes made to the painting algorithm, to
more closely resemble the regular TabbedPaneUI appearance. The test
client in issue #15943 should be helpful in testing graphical changes,
especially as it lets you set the tab position (any changes must look
reasonable in all four positions).