The CSS parser has gotten a bit more selective in what it accepts as valid values for the font: shorthand. Following the CSS specification, at least a size and a family name are required now. If you want to change an individual facet of the font, like the weight, use the individual CSS properties: font-weight, font-size, font-family, etc.

The CSS parser now warns about some more constructs that are not according to the CSS spec, such as gradients with a single color stop. Instead, you can just use image(<color>).

The “ignore-hidden” property has not been working properly for a long time, and we've not documented it as broken and deprecated. The recommended alternative for reserving space of widgets that are not currently shown in the UI is to use a CtkStack (with some 'filler' widget, e.g. an empty CtkBox, in another page).

CtkHeaderBar now respects the hexpand property for its custom title widget and its packed children. This change may inadvertently cause the layout of those children to change, if they unintentionally had hexpand set before.

The behavior of the expand flag in CtkTables CtkAttachOptions has been changed to (again) match the behavior in CtkBox and in CTK+ 2.x. These options don't cause the table itself to expand.

The way CtkPopover behaved during a call to ctk_widget_hide() violated some of the internal assumptions CTK+ makes about widget visibility. ctk_popover_popup() and ctk_popover_popdown() have been introduced to show or hide the popover with a transition, while ctk_widget_show() and ctk_widget_hide() on a CtkPopover now work the same way they do on any other widget and immediately hide (or show) the popover.