Dark Theme has insufficient contrast for Lock buttons on the dockable dialogs

Operating System: All

Summary:

The Dark Theme has insufficient contrast between on and off states for Lock buttons on the dockable dialogs

Detail:

We had a request for help from someone having difficulty with the Dark Theme: https://www.gimp-forum.net/Thread-GIMP-2-10-status-of-locking-icons-difficult-to-see

I provided a work-around for them by editing a local copy of the theme, but it seems sensible to amend the Theme to better indicate when those buttons are activated.

Instructions to patch your local theme aka workaround.

0. Copy the theme to your personal Themes folder and re-name it.
1. Create a new gimp-button-pressed-lock.png image in the ui folder of your copied theme (copy the gimp-button-pressed.png and modify in a way that suits you).
2. Edit the gtkrc file in the copied theme to add the following (below) to the end of the file.

style "highlight-layer-locks" = "gimp-gtkbutton-style"
{
  engine "pixmap"
    {
      image
        {
          function = BOX
          state = ACTIVE
          file = "ui/gimp-button-pressed-lock.png"
          border = { 8, 8, 8, 8 }
          stretch = TRUE
        }
    }
}

widget "*Tree*Button*" style "highlight-layer-locks"

(edit: attached patch and instructions. just in case if the source page went down. SG)