title: Detecting that installation was aborted/cancelled in Inno Setup
body: <p>I have an Inno Setup installer with some code in the <code>DeinitilizeSetup()</code> procedure. Importantly, this procedure includes calls to create/start a service (that it just installed) that hosts a localhost REST API, and then calls to that API to 'finish' the install (that's sort of a misleading name, but that's not important).</p>
  
  <p>Here's the deal: If the installation aborted for any reason (current test case is if the application was open, so the installer couldn't overwrite the exe/etc), it aborts because it's running in <code>/verysilent</code> mode. But I want to KNOW that it is aborting (vs a happy path ending) and call the RESTAPI with a querystring parameter as true vs false.</p>
  
  <p>I'm all set with a conditional like this:</p>
  
  <pre class="lang-pascal prettyprint-override"><code>if (InstallerCanceled = true) then begin
      Log('Calling Service''s FinishInstall endpoint with errorOccurred=true')
      WinHttpReq.Open('GET', 'http://localhost:5000/api/update/FinishInstall?errorOccurred=true', False)
    end
    else begin
      Log('Calling Service''s FinishInstall endpoint with errorOccurred=false');
      WinHttpReq.Open('GET', 'http://localhost:5000/api/update/FinishInstall?errorOccurred=false', False);
    end
  WinHttpReq.Send('');
  </code></pre>
  
  <p>But I can't figure out how to define the conditional itself...how do I know if the install was cancelled?</p>