447806 Fix inconsistency in preview visibility on AppImages

In AppImages, the Qt file picker will always be used regardless of the value of QFileDialog::DontUseNativeDialog. This commit ensures the preview is shown if there's a layout() present when the checkbox isn't ticked, and disables the checkbox altogether on AppImages.

BUG: 447806 CCMAIL: kimageshop@kde.org

Test Plan

Package an AppImage and check that the preview widget is always shown, and that it's impossible to enable the native file dialog checkbox on Preferences.

Formalities Checklist

  • I confirmed this builds.
  • I confirmed Krita ran and the relevant functions work.
  • I tested the relevant unit tests and can confirm they are not broken. (If not possible, don't hesitate to ask for help!)
  • I made sure my commits build individually and have good descriptions as per KDE guidelines.
  • I made sure my code conforms to the standards set in the HACKING file.
  • I can confirm the code is licensed and attributed appropriately, and that unattributed code is mine, as per KDE Licensing Policy.
Edited by Amy spark

Merge request reports