Add the external filetype warning to about:downloads

In #40701 (closed) we deprecated the external filetype dialog, and incorporated the warning into the Downloads wingpanel instead. @henry suggested in MR !595 (comment 2892920) that we could add the same warning to about:downloads too.

I think a standard grey messagebar would be fine.

added 12.5 stable Backlog Feature UX Team Q2 UX labels

mentioned in merge request !595 (merged)

marked this issue as related to #40701 (closed)

changed the description

added Desktop label

NOTE: With this change there will be multiple points of entry for the same pref, so we probably want to switch to using Services.pref.addObserver. See !595 (comment 2894310).

assigned to @dan

mentioned in issue #41350 (closed)

henry has suggested altering download.js lines around 139 the (!595 (comment 2894310))

let showDownloadWarning = Services.prefs.getBoolPref(
      PREF_SHOW_DOWNLOAD_WARNING
    );
if (!showDownloadWarning) {
      document.getElementById("downloadsWarning").hidden = true;
    } else {
      document.getElementById("downloadsWarning").hidden = false;
    }

"since we will have multiple entry points for this pref with we might want to make this change using Services.prefs.addObserver instead in preparation."

"For reference for now or the next patch, it would be something like this, where we move all the hiding and focus logic out of the "click" handler and into the preference observer:"

initialize() {
    /* ... */

    this._torWarningPrefObserver = () => {
      const warningMessage = document.getElementById("downloadsWarning");
      if (Services.prefs.getBoolPref(PREF_SHOW_DOWNLOAD_WARNING)) {
        warningMessage.hidden = false;
      } else {
        // Re-assign focus if it is about to be lost.
        if (warningMessage.contains(document.activeElement)) {
          this._focusPanel(true);
        }
        warningMessage.hidden = true;
      }
    };
    Services.prefs.addObserver(
      PREF_SHOW_DOWNLOAD_WARNING,
      this._torWarningPrefObserver
    );
    // Initialize.
    this._torWarningPrefObserver();

    if (!this._torWarningInitialized) {
      /* ... */

      dismissBtn.addEventListener("click", event => {
        Services.prefs.setBoolPref(PREF_SHOW_DOWNLOAD_WARNING, false);
      });

      /* ... */
    }
    
    /* ... */
  },
  /* ... */
  terminate() {
    /* ... */

    Services.prefs.removeObserver(
      PREF_SHOW_DOWNLOAD_WARNING,
      this._torWarningPrefObserver
    );

    /* ... */
  },

mentioned in merge request !634 (closed)

marked this issue as related to #41800 (closed)

mentioned in issue #41800 (closed)

removed Q2 label

removed Backlog label

added Doing label

assigned to @henry and unassigned @dan

mentioned in merge request !664 (merged)

marked this issue as related to tor-browser-build#40865 (closed)

closed

mentioned in issue #41820 (closed)

marked this issue as related to #41820 (closed)