fix: fix rendering glitches due to interaction with vim-dirvish

This isn't a bug in vim-dirvish, but there is something about the way it
operates that triggers this undesired behavior in Command-T. The repro
isn't 100% reliable but it almost is:

1. Create a tmux split in order to have a narrow window to test inside.
2. Open vim-dirvish with `nvim .`.
3. Split the buffer vertically to make it even thinner (strictly
   speaking, you don't have to do this, but it makes it more likely to
   reproduce).
4. Open Command-T; see that the match listing is acting as though it
   were scrolled to the right (ie. you can't see the text on the left,
   or you can only see the tail end of it).

Now, what vim-dirvish is doing is having potentially very long absolute
paths in its buffer that are very wide, and hiding the bit that
corresponds to the current working directory using Vim's "conceal"
feature. So, you only see relative paths (relative to the current
working directory), but each line in the buffer may be much longer.

So, given a `'textwidth'` of, say, 80, it's easily possibly for you to
have lines longer than that, even if they don't look that long. This
becomes more obvious if you set `'colorcolumn'` to "+0,+1" etc; you
might have a path that looks like "README.md" in the visible spectrum,
but the line is actually prefixed by something way longer, and you can
see the colorcolumn columns not in column 80 (assuming `'textwidth'` is
80) like you would expect, but in something way farther to the left,
like "column" 15 or 20.

If you jump the cursor all the way to the start of the line (with `^`)
then you see the colorcolumn highlighting move to the right, and
Command-T works without the rendering glitch. If you jump to the end
(with `$`), the colorcolumn highlighting moves back to the left and the
bug returns.

I tried various settings of `'sidescroll'` and `'sidescrolloff'` but the
only way I could get the problem to go away was to turn `'wrap'` _on_,
and then trim my lines to avoid the unwanted wrapping. Moving the cursor
to column 0 with `nvim_win_set_cursor` does not solve this problem, even
thought he docs say it will scroll the window if necessary (note: we
were already doing this).

I tried to repro this without vim-dirvish, and didn't succeed. For
example I got a big Markdown file with long lines and tried various
values of all the settings without reproducing the bug. I turned off
various bells and whistles. I updated vim-dirvish. In the end, I don't
have a smoking gun, but I have a correlation. It's a mystery how the
state of the vim-dirvish window could/would affect an independent buffer
(the match listing); that does feel like a bug, in Neovim most likely.
But it seem so edge-casey and speculative that I don't think I can even
formulate a bug report.

doc/command-t.txt

@@ -240,9 +240,6 @@ KNOWN ISSUES                                    *command-t-known-issues*
   to force a re-scan. 6.x does not implement any such caching (which means
   that results are always fresh, but on large directories the re-scanning may
   introduce a noticeable delay).
-- Sometimes the results in the match listing are scrolled to the right,
-  causing the left edge to be cut off; I would love to fix this but haven't
-  identified a cause yet.
 - The documentation for 6.x (ie. this document) is still a work in progress.
 
 

ftplugin/CommandTMatchListing.lua

@@ -6,4 +6,9 @@ vim.bo.textwidth = 0
 vim.wo.concealcursor = ''
 vim.wo.conceallevel = 0
 vim.wo.winhighlight = 'IncSearch:Normal,Search:Normal'
-vim.wo.wrap = false
+
+-- Would like this to be false, but that produces rendering glitches in
+-- conjunction with vim-dirvish, so instead we turn wrapping on but trim our
+-- match listing text so that it is never wide enough to actually cause
+-- wrapping.
+vim.wo.wrap = true

lua/wincent/commandt/private/match_listing.lua

@@ -43,19 +43,45 @@ function MatchListing:close()
   end
 end
 
+local format_line = function(line, width, selected)
+  local prefix = selected and '> ' or '  '
+
+  -- Right pad so that selection highlighting is shown across full width.
+  if width < 104 then
+    if #line > 99 then
+      -- No padding needed.
+      line = prefix .. line
+    else
+      line = prefix .. string.format('%-' .. (width - #prefix) .. 's', line)
+    end
+  else
+    -- Avoid: "invalid option" caused by format argument > 99.
+    line = prefix .. string.format('%-99s', line)
+    local diff = width - line:len()
+    if diff > 0 then
+      line = line .. string.rep(' ', diff)
+    end
+  end
+
+  -- Trim right to make sure we never wrap.
+  return line:sub(1, width)
+end
+
 function MatchListing:select(selected)
   assert(type(selected) == 'number')
   assert(selected > 0)
-  assert(selected <= #self._lines)
+  assert(selected <= #self._results)
   if self._window then
-    local selection = '  ' .. self._lines[self._selected]:sub(3)
-    self._window:replace_line(selection, self._selected)
+    local width = self._window:width() or vim.o.columns -- BUG: width may be cached/stale
+
+    local previous_selection = format_line(self._results[self._selected], width, false)
+    self._window:replace_line(previous_selection, self._selected)
     self._window:unhighlight_line(self._selected)
 
     self._selected = selected
-    selection = '> ' .. self._lines[self._selected]:sub(3)
-    self._window:replace_line(selection, selected)
-    self._window:highlight_line(selected)
+    local new_selection = format_line(self._results[self._selected], width, true)
+    self._window:replace_line(new_selection, self._selected)
+    self._window:highlight_line(self._selected)
   end
 end
 
@@ -112,26 +138,8 @@ function MatchListing:update(results, options)
     local width = self._window:width() or vim.o.columns
     self._lines = {}
     for i, result in ipairs(results) do
-      local prefix = i == self._selected and '> ' or '  '
-      local line = nil
-
-      -- Right pad so that selection highlighting is shown across full width.
-      if width < 104 then
-        if #result > 99 then
-          -- No padding needed.
-          line = prefix .. result
-        else
-          line = prefix .. string.format('%-' .. (width - #prefix) .. 's', result)
-        end
-      else
-        -- Avoid: "invalid option" caused by format argument > 99.
-        line = prefix .. string.format('%-99s', result)
-        local diff = width - line:len()
-        if diff > 0 then
-          line = line .. string.rep(' ', diff)
-        end
-      end
-
+      local selected = i == self._selected
+      local line = format_line(result, width, selected)
       table.insert(self._lines, line)
     end
     self._window:unhighlight()