title: Make nvim popup menu appear with only one character
body: <p>I'm using NCM2 as my autocomplete plugin at the moment, but I'm not sure if the issue is with popup menus in general or NCM2.</p>
  
  <p>When I am trying to auto-complete a filename, the pop-up menu will only appear after I've entered at least 3 characters. Even if the extra third character doesn't limit the suggestions.</p>
  
  <p>Example, I have the following directory:</p>
  
  <pre><code>- 4822283_ERCOFTAC_m3c1_SST.dat 
  - 4822299_ERCOFTAC_m3c1_SBES.log
  - 4822299_FluentSBES.jou
  - ERCOFTAC_m3c1_SBES.cas
  - ERCOFTAC_m3c1_SBES.o4822299
  - fluentSBES.sh
  </code></pre>
  
  <p>If I type in <code>48</code>, nothing comes up:</p>
  
  <p><a href="https://i.stack.imgur.com/wjkRb.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/wjkRb.png" alt="2 characters"></a></p>
  
  <p>If I type <code>482</code>, then I get the auto-complete menu:</p>
  
  <p><a href="https://i.stack.imgur.com/rTHja.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/rTHja.png" alt="3 characters"></a></p>
  
  <p>This is very consistent behavior. I at least notice it the most when dealing with file names that start with numbers.</p>
  
  <p>So the question is whether I can </p>
  
  <p>A) change the number of characters required for the auto complete menu to appear or </p>
  
  <p>B) find whatever shortcut opens the auto-complete menu (similar to "Trigger Suggest" command in VS Code)</p>
  
  <p>You can see a copy of my <code>init.vim</code> <a href="https://github.com/u2berggeist/dotfiles/blob/master/nvim/init.vim" rel="nofollow noreferrer">here</a>.</p>
  
  <h2>Edit:</h2>
  
  <p>Yedhin's answer addresses method A), however it also causes the auto-popup menu to be open at all times, which is fairly annoying to be honest.</p>
  
  <p>For addressing item B), which would be the ideal, I found the <code>ncm2_manual_trigger</code> function. So theoretically, by putting the following in <code>init.vim</code>, you can manual trigger the auto-popup at anytime.</p>
  
  <pre><code>let g:ncm2#auto_popup = 0
  imap &lt;C-a&gt; &lt;Plug&gt;(ncm2_manual_trigger)
  </code></pre>
  
  <p>However, as detailed in <a href="https://github.com/ncm2/ncm2/issues/70" rel="nofollow noreferrer">this issue posted on the ncm2 repo</a>, the manual_trigger is still dependent on the <code>ncm2#complete_length</code> parameter to figure out what to display. This causes the manual trigger to not display the popup-menu if the auto-trigger hasn't already triggered the popup-menu. We'll just have to wait for the issue to be resolved for now (which as of writing should be fairly soon judging off the "my-next-task" tag on the issue).</p>