CellRendererRef

public struct CellRendererRef : CellRendererProtocol, GWeakCapturing

An object for rendering a single cell

The GtkCellRenderer is a base class of a set of objects used for rendering a cell to a cairo_t. These objects are used primarily by the GtkTreeView widget, though they aren’t tied to them in any specific way. It is worth noting that GtkCellRenderer is not a GtkWidget and cannot be treated as such.

The primary use of a GtkCellRenderer is for drawing a certain graphical elements on a cairo_t. Typically, one cell renderer is used to draw many cells on the screen. To this extent, it isn’t expected that a CellRenderer keep any permanent state around. Instead, any state is set just prior to use using GObjects property system. Then, the cell is measured using gtk_cell_renderer_get_preferred_size(). Finally, the cell is rendered in the correct location using gtk_cell_renderer_snapshot().

There are a number of rules that must be followed when writing a new GtkCellRenderer. First and foremost, it’s important that a certain set of properties will always yield a cell renderer of the same size, barring a style change. The GtkCellRenderer also has a number of generic properties that are expected to be honored by all children.

Beyond merely rendering a cell, cell renderers can optionally provide active user interface elements. A cell renderer can be “activatable” like GtkCellRendererToggle, which toggles when it gets activated by a mouse click, or it can be “editable” like GtkCellRendererText, which allows the user to edit the text using a widget implementing the GtkCellEditable interface, e.g. GtkEntry. To make a cell renderer activatable or editable, you have to implement the GtkCellRendererClass.activate or GtkCellRendererClass.start_editing virtual functions, respectively.

Many properties of GtkCellRenderer and its subclasses have a corresponding “set” property, e.g. “cell-background-set” corresponds to “cell-background”. These “set” properties reflect whether a property has been set or not. You should not set them independently.

The CellRendererRef type acts as a lightweight Swift reference to an underlying GtkCellRenderer instance. It exposes methods that can operate on this data type through CellRendererProtocol conformance. Use CellRendererRef only as an unowned reference to an existing GtkCellRenderer instance.