From 70e12b926f24f5eed93d9e35db515dd1887b994d Mon Sep 17 00:00:00 2001
From: Alexandre Constantino <dreaming.about.electric.sheep@gmail.com>
Date: Thu, 14 Jan 2016 14:56:00 +0000
Subject: [PATCH] Implement TOC window auto-fit

Allow the user, to set an option, to have the TOC window shrink its size
in order to auto-fit to contents.
---
 README.md              |  9 +++++++
 ftplugin/markdown.vim  | 13 +++++++++-
 test/toc-autofit.vader | 57 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 78 insertions(+), 1 deletion(-)
 create mode 100644 test/toc-autofit.vader

diff --git a/README.md b/README.md
index 1a6fd1d..87fef46 100644
--- a/README.md
+++ b/README.md
@@ -104,6 +104,15 @@ let g:vim_markdown_no_default_key_mappings = 1
 
 You can also map them by yourself with `<Plug>` mappings.
 
+### Enable TOC window auto-fit
+
+Allow for the TOC window to auto-fit when it's possible for it to shrink.
+It never increases its default size (half screen), it only shrinks.
+
+```vim
+let g:vim_markdown_toc_autofit = 1
+```
+
 ### Syntax extensions
 
 The following options control which syntax extensions will be turned on. They are off by default.
diff --git a/ftplugin/markdown.vim b/ftplugin/markdown.vim
index 3f084f2..ae81c80 100644
--- a/ftplugin/markdown.vim
+++ b/ftplugin/markdown.vim
@@ -307,6 +307,7 @@ function! s:Toc(...)
     let b:fenced_block = 0
     let b:header_list = []
     let l:header_max_len = 0
+    let g:vim_markdown_toc_autofit = get(g:, "vim_markdown_toc_autofit", 0)
     for i in range(1, line('$'))
         let l:lineraw = getline(i)
         let l:l1 = getline(i+1)
@@ -327,6 +328,11 @@ function! s:Toc(...)
             " append line to location list
             let b:item = {'lnum': i, 'text': l:line, 'valid': 1, 'bufnr': b:bufnr, 'col': 1}
             let b:header_list = b:header_list + [b:item]
+            " keep track of the longest header size (heading level + title)
+            let b:total_len = stridx(l:line, ' ') + len(l:line)
+            if b:total_len > l:header_max_len
+                let l:header_max_len = b:total_len
+            endif
         endif
     endfor
     if len(b:header_list) == 0
@@ -339,7 +345,12 @@ function! s:Toc(...)
         lopen
     elseif l:window_type ==# 'vertical'
         vertical lopen
-        let &winwidth=(&columns/2)
+        " auto-fit toc window when possible to shrink it
+        if (&columns/2) > l:header_max_len && g:vim_markdown_toc_autofit == 1
+            let &winwidth = (l:header_max_len + 1)
+        else
+            let &winwidth = (&columns/2)
+        endif
     elseif l:window_type ==# 'tab'
         tab lopen
     else
diff --git a/test/toc-autofit.vader b/test/toc-autofit.vader
new file mode 100644
index 0000000..005a13f
--- /dev/null
+++ b/test/toc-autofit.vader
@@ -0,0 +1,57 @@
+" Tests toc window auto-fit to longest header, but without exceeding half screen.
+
+Before:
+  source ../after/ftplugin/markdown.vim
+
+After:
+  setlocal foldexpr=0
+  setlocal foldmethod=manual
+
+Given markdown;
+# chap 1
+
+# chap 2
+
+# chap 3
+
+# chap 4
+
+# chap 5
+
+# chap 6
+
+# chap 7
+
+# chap 8
+
+# chap 9
+
+# chap 10
+
+# chap 11
+
+# chap 12
+
+## chap 12.1
+
+### chap 12.1.1
+
+#### chap 12.1.1.1
+
+##### chap 12.1.1.1.1
+
+###### chap 12.1.1.1.1.1
+
+# chap 13
+
+Execute (toc window autofit width):
+  set number
+  let g:vim_markdown_toc_autofit = 1
+  let line = '###### chap 12.1.1.1.1.1'
+  AssertEqual getline('33'), line
+  :Toc
+  let expected_width = len(line) + 2*5 + 1 + 3 - 7
+  AssertEqual &winwidth, expected_width
+" 2 spaces * 5 additional header levels + 1 space for first header +
+" 3 spaces for line numbers - 7 chars ('###### ') that don't show up on the TOC
+
-- 
2.39.2