first pass on making rendering user-configurable

plugin/buftabline.vim

@@ -44,42 +44,56 @@ function! buftabline#user_buffers() " help buffers are always unlisted, but quic
 	return filter(range(1,bufnr('$')),'buflisted(v:val) && "quickfix" !=? getbufvar(v:val, "&buftype")')
 endfunction
 
-let s:dirsep = fnamemodify(getcwd(),':p')[-1:]
-let s:centerbuf = winbufnr(0)
-function! buftabline#render()
+function! s:visible_width(s)
+	" remove '%#highlight#' groups, '%1*' hl-user groups, '%*' endings
+	let pattern = '\V\(%#\w\+#\)\|\(%\d\{-0,1}*\)'
+	return strwidth(strtrans(substitute(a:s, pattern, '', 'g')))
+endfunction
+
+function! buftabline#default_format(opts)
+	let opts = a:opts
 	let show_num = g:buftabline_numbers == 1
 	let show_ord = g:buftabline_numbers == 2
 	let show_mod = g:buftabline_indicators
-	let lpad     = g:buftabline_separators ? nr2char(0x23B8) : ' '
+	if strlen(opts.name)
+		let mod = show_mod && opts.modified ? '+' : ''
+		let num = show_num ? opts.bufnum : show_ord ? opts.ordnum : ''
+		let pre = mod . num
+		if strlen(pre)
+			let pre .= ' '
+		endif
+		let rv = pre . opts.name
+	elseif -1 < index(['nofile', 'acwrite'], opts.buftype)
+		let rv = show_mod ? '!' . opts.ordnum : opts.ordnum ? opts.ordnum . '!' : '!'
+	else
+		let mod = show_mod && opts.modified ? '+' : ''
+		let num = show_num ? opts.bufnum : show_ord ? opts.ordnum : '*'
+		let rv = mod . num
+	endif
+	let hl = opts.current ? 'Current' : opts.active ? 'Active' : 'Hidden'
+	let lpad = opts.ordnum > 1 && g:buftabline_separators ? nr2char(0x23B8) : ' '
+	return '%#BufTabLine' . hl . '#' . lpad . rv . ' %#BufTabLineFill#'
+endfunction
 
-	let bufnums = buftabline#user_buffers()
+let s:dirsep = fnamemodify(getcwd(),':p')[-1:]
+let s:centerbuf = winbufnr(0)
+function! buftabline#render()
 	let centerbuf = s:centerbuf " prevent tabline jumping around when non-user buffer current (e.g. help)
-
-	" pick up data on all the buffers
 	let tabs = []
 	let path_tabs = []
 	let tabs_per_tail = {}
 	let currentbuf = winbufnr(0)
-	let screen_num = 0
-	for bufnum in bufnums
-		let screen_num = show_num ? bufnum : show_ord ? screen_num + 1 : ''
-		let tab = { 'num': bufnum }
-		let tab.hilite = currentbuf == bufnum ? 'Current' : bufwinnr(bufnum) > 0 ? 'Active' : 'Hidden'
+
+	for bufnum in buftabline#user_buffers()
+		let tab = { 'num': bufnum, 'label': '' }
 		if currentbuf == bufnum | let [centerbuf, s:centerbuf] = [bufnum, bufnum] | endif
 		let bufpath = bufname(bufnum)
 		if strlen(bufpath)
 			let tab.path = fnamemodify(bufpath, ':p:~:.')
 			let tab.sep = strridx(tab.path, s:dirsep, strlen(tab.path) - 2) " keep trailing dirsep
 			let tab.label = tab.path[tab.sep + 1:]
-			let pre = ( show_mod && getbufvar(bufnum, '&mod') ? '+' : '' ) . screen_num
-			let tab.pre = strlen(pre) ? pre . ' ' : ''
 			let tabs_per_tail[tab.label] = get(tabs_per_tail, tab.label, 0) + 1
 			let path_tabs += [tab]
-		elseif -1 < index(['nofile','acwrite'], getbufvar(bufnum, '&buftype')) " scratch buffer
-			let tab.label = ( show_mod ? '!' . screen_num : screen_num ? screen_num . ' !' : '!' )
-		else " unnamed file
-			let tab.label = ( show_mod && getbufvar(bufnum, '&mod') ? '+' : '' )
-			\             . ( screen_num ? screen_num : '*' )
 		endif
 		let tabs += [tab]
 	endfor
@@ -96,6 +110,20 @@ function! buftabline#render()
 		endfor
 	endwhile
 
+	let ordnum = 0
+	for tab in tabs
+		let ordnum += 1
+		let tab.opts = {
+			\ 'name': tab.label,
+			\ 'bufnum': tab.num,
+			\ 'ordnum': ordnum,
+			\ 'modified': getbufvar(bufnum, '&modified'),
+			\ 'buftype': getbufvar(bufnum, '&buftype'),
+			\ 'current': currentbuf == tab.num,
+			\ 'active': bufwinnr(bufnum) > 0,
+			\ }
+	endfor
+
 	" now keep the current buffer center-screen as much as possible:
 
 	" 1. setup
@@ -104,9 +132,10 @@ function! buftabline#render()
 
 	" 2. sum the string lengths for the left and right halves
 	let currentside = lft
+	let formatter = get(g:, 'buftabline_format', 'buftabline#default_format')
 	for tab in tabs
-		let tab.label = lpad . get(tab, 'pre', '') . tab.label . ' '
-		let tab.width = strwidth(strtrans(tab.label))
+		execute printf('let tab.label = %s(tab.opts)', formatter)
+		let tab.width = s:visible_width(tab.label)
 		if centerbuf == tab.num
 			let halfwidth = tab.width / 2
 			let lft.width += halfwidth
@@ -135,17 +164,15 @@ function! buftabline#render()
 			endwhile
 			" then snip at the last one to make it fit
 			let endtab = tabs[side.lasttab]
-			while delta > ( endtab.width - strwidth(strtrans(endtab.label)) )
+			while delta > ( endtab.width - s:visible_width(endtab.label) )
 				let endtab.label = substitute(endtab.label, side.cut, '', '')
 			endwhile
 			let endtab.label = substitute(endtab.label, side.cut, side.indicator, '')
 		endfor
 	endif
 
-	if len(tabs) | let tabs[0].label = substitute(tabs[0].label, lpad, ' ', '') | endif
-
 	let swallowclicks = '%'.(1 + tabpagenr('$')).'X'
-	return swallowclicks . join(map(tabs,'printf("%%#BufTabLine%s#%s",v:val.hilite,strtrans(v:val.label))'),'') . '%#BufTabLineFill#'
+	return swallowclicks . join(map(tabs,'strtrans(v:val.label)'),'')
 endfunction
 
 function! buftabline#update(zombie)