Chapter 19. The Clipboard

Table of Contents

Simple text copy-paste functionality is provided for free by widgets such as Gtk::Entry and Gtk::TextView, but you might need special code to deal with your own data formats. For instance, a drawing program would need special code to allow copy and paste within a view, or between documents.

You can usually pretend that Gtk::Clipboard is a singleton. You can get the default clipboard instance with Gtk::Clipboard::get(). This is probably the only clipboard you will ever need.

Your application doesn't need to wait for clipboard operations, particularly between the time when the user chooses Copy and then later chooses Paste. Most Gtk::Clipboard methods take sigc::slots which specify callback methods. When Gtk::Clipboard is ready, it will call these methods, either providing the requested data, or asking for data.



Different applications contain different types of data, and they might make that data available in a variety of formats. gtkmm calls these data types targets.

For instance, gedit can supply and receive the "UTF8_STRING" target, so you can paste data into gedit from any application that supplies that target. Or two different image editing applications might supply and receive a variety of image formats as targets. As long as one application can receive one of the targets that the other supplies then you will be able to copy data from one to the other.

A target can be in a variety of binary formats. This chapter, and the examples, assume that the data is 8-bit text. This would allow us to use an XML format for the clipboard data. However this would probably not be appropriate for binary data such as images. Gtk::Clipboard provides overloads that allow you to specify the format in more detail if necessary.

The Drag and Drop API uses the same mechanism. You should probably use the same data targets and formats for both Clipboard and Drag and Drop operations.