def show_tab(idx)
if index(idx) == 0
self.start = 0
return
end
reutrn unless @canvas ||= self.winfo_children[0]
delta = 1 if (delta = cget(:gap)) == 'overlap' ||
(delta = self.winfo_pixels(delta) + 1) <= 0
case cget(:tabpos)
when 's', 'n'
if (head = tabcget(idx, :left)) < 0
self.start -= head
return
end
tabs_size = @canvas.winfo_width
tab_start, tab_end = @canvas .
find_overlapping(head, 0, head + delta, @canvas.winfo_height) .
find_all{|id| @canvas.itemtype(id) == TkcPolygon} .
map!{|id| bbox = @canvas.bbox(id); [bbox[0], bbox[2]]} . max
when 'e', 'w'
if (head = tabcget(idx, :top)) < 0
self.start -= head
return
end
tabs_size = @canvas.winfo_height
tab_start, tab_end = @canvas .
find_overlapping(0, head, @canvas.winfo_width, head + delta) .
find_all{|id| @canvas.itemtype(id) == TkcPolygon} .
map!{|id| bbox = @canvas.bbox(id); [bbox[1], bbox[3]]} . max
end
if (size = tab_end - tab_start + 1) > tabs_size
self.start -= tab_start
elsif head + size > tabs_size
self.start -= head + size - tabs_size
end
self
end