Created attachment 329117 [details]
Glade file demonstrating broken minimum content sizes

I suspect this regressed a long time ago when moving minimum content sizes from the GtkScrollable iface to GtkScrolledWindow, as of commit 0d9ebb501.

Explanation: The reason why we have a minimum content size in the first place, is to allow one to declare the minimum amount of _visible_ area in the scrolled window content, which is to say, regardless of how the scrolled window is configured and whether scrollbars appear, we ensure the content is at least that minimum size.

The current behavior of min-content-size instead has the same effect as setting a width-request on the scrolled window with gtk_widget_set_size_request().

The attached glade file demonstrates the issue as such:

  GtkWindow
    GtkScrolledWindow (min-content-width = 300, overlay-scrollbar = FALSE)
      GtkViewport
        GtkBox
          GtkLabel (width-request = 300, long ellipsis label)
          GtkLabel (width-request = 300, long ellipsis label)
          GtkLabel (width-request = 300, long ellipsis label)
          GtkLabel (width-request = 300, long ellipsis label)
          GtkLabel (width-request = 300, long ellipsis label)
          GtkLabel (width-request = 300, long ellipsis label)

When displaying this glade file, we can observe that when the window is at it's minimum size, the vertical scrollbar overlaps the GtkLabels and we do not see the ellipsis at the end as they are hidden below the scrollbar.