Fix Linux Folder Dialog Reopening After Cancel

Util/OS/FolderDialogUtil.cs

@@ -18,8 +18,8 @@ namespace ADOFAIRenderer.Util.OS;
 /// </para>
 /// <para>- <b>macOS</b>: <c>osascript</c> running AppleScript <c>choose folder</c>.</para>
 /// <para>
-/// - <b>Linux</b>: <c>zenity --file-selection --directory</c>; when zenity does not return an existing directory (not installed,
-///   cancelled or failed), <c>kdialog --getexistingdirectory</c>.
+/// - <b>Linux</b>: <c>zenity --file-selection --directory</c>; when zenity is not installed or fails (exit code other than 0
+///   or 1), <c>kdialog --getexistingdirectory</c>. A cancelled zenity dialog (exit code 1) ends the selection.
 /// </para>
 /// <para>
 /// The dialog runs off the main Unity thread so the game keeps rendering frames while it is open. Only one dialog can be open
@@ -688,13 +688,13 @@ internal static class FolderDialogUtil
 
     /// <summary>
     /// Runs <c>zenity --file-selection --directory --title=... [--filename=initialDirectory]</c> and blocks until it exits.
-    /// When zenity cannot be started, exits with a non-zero code (cancel or error) or prints a path that is not an existing
-    /// directory, runs <c>kdialog --getexistingdirectory [initialDirectory] --title ...</c> instead. Both commands print the
+    /// Exit code 0 returns the printed path when it is an existing directory, and exit code 1 (cancelled or closed) returns null
+    /// without opening a second dialog. When zenity cannot be started or exits with any other code, runs <c>kdialog --getexistingdirectory [initialDirectory] --title ...</c> instead. Both commands print the
     /// selected path to standard output.
     /// </summary>
     /// <param name="initialDirectory">Folder shown first; used only when it is an existing directory.</param>
     /// <returns>
-    /// The selected existing directory; null when both dialogs return nothing, when kdialog cannot be started, or on an
+    /// The selected existing directory; null when the dialog is cancelled, when kdialog cannot be started, or on an
     /// exception (logged as a warning).
     /// </returns>
     private static string? OpenLinuxFolderBrowser(string initialDirectory)
@@ -725,15 +725,19 @@ internal static class FolderDialogUtil
                     var output = process.StandardOutput.ReadToEnd().Trim();
                     process.WaitForExit();
 
-                    if (process.ExitCode == 0 && !string.IsNullOrEmpty(output) && Directory.Exists(output))
+                    if (process.ExitCode == 0)
                     {
-                        return output;
+                        return !string.IsNullOrEmpty(output) && Directory.Exists(output) ? output : null;
                     }
+
+                    // zenity exit code 1: the dialog was cancelled or closed.
+                    // Reference: https://gitlab.gnome.org/GNOME/zenity/-/raw/master/src/util.c (ZENITY_OK_DEFAULT 0, ZENITY_CANCEL_DEFAULT 1, ZENITY_ESC_DEFAULT 1, ZENITY_ERROR_DEFAULT -1).
+                    if (process.ExitCode == 1) return null;
                 }
             }
             catch
             {
-                // Fallback to kdialog if zenity fails to start
+                // Falls back to kdialog when zenity is not installed or cannot be started.
             }
 
             var kdialogInfo = new ProcessStartInfo