GTK+ Reference Manual
<<< Previous Page | Home | Up | Next Page >>>

# Clipboards

## Name

Clipboards -- Storing data on clipboards.

## Synopsis

    #include <gtk/gtk.h>

    struct      GtkClipboard;
    void        (*GtkClipboardReceivedFunc)     (GtkClipboard *clipboard,
                                                 GtkSelectionData *selection_data,
                                                 gpointer data);
    void        (*GtkClipboardTextReceivedFunc) (GtkClipboard *clipboard,
                                                 const gchar *text,
                                                 gpointer data);
    void        (*GtkClipboardGetFunc)          (GtkClipboard *clipboard,
                                                 GtkSelectionData *selection_data,
                                                 guint info,
                                                 gpointer user_data_or_owner);
    void        (*GtkClipboardClearFunc)        (GtkClipboard *clipboard,
                                                 gpointer user_data_or_owner);
    GtkClipboard* gtk_clipboard_get             (GdkAtom selection);
    GtkClipboard* gtk_clipboard_get_for_display (GdkDisplay *display,
                                                 GdkAtom selection);
    GdkDisplay* gtk_clipboard_get_display       (GtkClipboard *clipboard);
    gboolean    gtk_clipboard_set_with_data     (GtkClipboard *clipboard,
                                                 const GtkTargetEntry *targets,
                                                 guint n_targets,
                                                 GtkClipboardGetFunc get_func,
                                                 GtkClipboardClearFunc clear_func,
                                                 gpointer user_data);
    gboolean    gtk_clipboard_set_with_owner    (GtkClipboard *clipboard,
                                                 const GtkTargetEntry *targets,
                                                 guint n_targets,
                                                 GtkClipboardGetFunc get_func,
                                                 GtkClipboardClearFunc clear_func,
                                                 GObject *owner);
    GObject*    gtk_clipboard_get_owner         (GtkClipboard *clipboard);
    void        gtk_clipboard_clear             (GtkClipboard *clipboard);
    void        gtk_clipboard_set_text          (GtkClipboard *clipboard,
                                                 const gchar *text,
                                                 gint len);
    void        gtk_clipboard_request_contents  (GtkClipboard *clipboard,
                                                 GdkAtom target,
                                                 GtkClipboardReceivedFunc callback,
                                                 gpointer user_data);
    void        gtk_clipboard_request_text      (GtkClipboard *clipboard,
                                                 GtkClipboardTextReceivedFunc callback,
                                                 gpointer user_data);
    GtkSelectionData* gtk_clipboard_wait_for_contents
                                                (GtkClipboard *clipboard,
                                                 GdkAtom target);
    gchar*      gtk_clipboard_wait_for_text     (GtkClipboard *clipboard);
    gboolean    gtk_clipboard_wait_is_text_available
                                                (GtkClipboard *clipboard);

## Description

The GtkClipboard object represents a clipboard of data shared between different processes or between different widgets in the same process. Each clipboard is identified by a name encoded as a GdkAtom. (Conversion to and from strings can be done with gdk_atom_intern() and gdk_atom_name().) The default clipboard corresponds to the "CLIPBOARD" atom; another commonly used clipboard is the "PRIMARY" clipboard, which, in X, traditionally contains the currently selected text.

To support having a number of different formats on the clipboard at the same time, the clipboard mechanism allows providing callbacks instead of the actual data. When you set the contents of the clipboard, you can either supply the data directly (via functions like gtk_clipboard_set_text()), or you can supply a callback to be called at a later time when the data is needed (via gtk_clipboard_set_with_data() or gtk_clipboard_set_with_owner().) Providing a callback also avoids having to make copies of the data when it is not needed.

gtk_clipboard_set_with_data() and gtk_clipboard_set_with_owner() are quite similar; the choice between the two depends mostly on which is more convenient in a particular situation. The former is most useful when you want to have a blob of data with callbacks to convert it into the various data types that you advertise. When the `clear_func` you provided is called, you simply free the data blob. The latter is more useful when the contents of clipboard reflect the internal state of a GObject (As an example, for the PRIMARY clipboard, when an entry widget provides the clipboard's contents the contents are simply the text within the selected region.) If the contents change, the entry widget can call gtk_clipboard_set_with_owner() to update the timestamp for clipboard ownership, without having to worry about `clear_func` being called.

Requesting the data from the clipboard is essentially asynchronous. If the contents of the clipboard are provided within the same process, then a direct function call will be made to retrieve the data, but if they are provided by another process, then the data needs to be retrieved from the other process, which may take some time. To avoid blocking the user interface, the call to request the selection, gtk_clipboard_request_contents() takes a callback that will be called when the contents are received (or when the request fails.) If you don't want to deal with providing a separate callback, you can also use gtk_clipboard_wait_for_contents(). What this does is run the GLib main loop recursively waiting for the contents. This can simplify the code flow, but you still have to be aware that other callbacks in your program can be called while this recursive mainloop is running.

Along with the functions to get the clipboard contents as an arbitrary data chunk, there are also functions to retrieve it as text, gtk_clipboard_request_text() and gtk_clipboard_wait_for_text(). These functions take care of determining which formats are advertised by the clipboard provider, asking for the clipboard in the best available format and converting the results into the UTF-8 encoding. (The standard form for representing strings in GTK+.)

## Details

### struct GtkClipboard

    struct GtkClipboard;

### GtkClipboardReceivedFunc ()

    void        (*GtkClipboardReceivedFunc)     (GtkClipboard *clipboard,
                                                 GtkSelectionData *selection_data,
                                                 gpointer data);

A function to be called when the results of gtk_clipboard_request_contents() are received, or when the request fails.

`clipboard` : | the GtkClipboard
`selection_data` : | a GtkSelectionData containing the data was received. If retrieving the data failed, then then length field of `selection_data` will be negative.
`data` : | the `user_data` supplied to gtk_clipboard_request_contents().

### GtkClipboardTextReceivedFunc ()

    void        (*GtkClipboardTextReceivedFunc) (GtkClipboard *clipboard,
                                                 const gchar *text,
                                                 gpointer data);

A function to be called when the results of gtk_clipboard_request_text() are received, or when the request fails.

`clipboard` : | the GtkClipboard
`text` : | the text received, as a UTF-8 encoded string, or `NULL` if retrieving the data failed.
`data` : | the `user_data` supplied to gtk_clipboard_request_text().

### GtkClipboardGetFunc ()

    void        (*GtkClipboardGetFunc)          (GtkClipboard *clipboard,
                                                 GtkSelectionData *selection_data,
                                                 guint info,
                                                 gpointer user_data_or_owner);

A function that will be called to provide the contents of the selection. If multiple types of data were advertised, the requested type can be determined from the `info` parameter or by checking the target field of `selection_data`. If the data could successfully be converted into then it should be stored into the `selection_data` object by calling gtk_selection_data_set() (or related functions such as gtk_selection_data_set_text()). If no data is set, the requestor will be informed that the attempt to get the data failed.

`clipboard` : | the GtkClipboard
`selection_data` : | a GtkSelectionData argument in which the requested data should be stored.
`info` : | the info field corresponding to the requested target from the GtkTargetEntry array passed to gtk_clipboard_set_with_data() or gtk_clipboard_set_with_owner().
`user_data_or_owner` : | the `user_data` argument passed to gtk_clipboard_set_with_data(), or the `owner` argument passed to gtk_clipboard_set_with_owner()

### GtkClipboardClearFunc ()

    void        (*GtkClipboardClearFunc)        (GtkClipboard *clipboard,
                                                 gpointer user_data_or_owner);

A function that will be called when the contents of the clipboard are changed or cleared. Once this has called, the `user_data_or_owner` argument will not be used again.

`clipboard` : | the GtkClipboard
`user_data_or_owner` : | the `user_data` argument passed to gtk_clipboard_set_with_data(), or the `owner` argument passed to gtk_clipboard_set_with_owner()

### gtk_clipboard_get ()

    GtkClipboard* gtk_clipboard_get             (GdkAtom selection);

Returns the clipboard object for the given selection. See gtk_clipboard_get_for_display() for complete details.

`selection` : | a GdkAtom which identifies the clipboard to use.
Returns : | the appropriate clipboard object. If no clipboard already exists, a new one will be created. Once a clipboard object has been created, it is persistent for all time and cannot be freed.

### gtk_clipboard_get_for_display ()

    GtkClipboard* gtk_clipboard_get_for_display (GdkDisplay *display,
                                                 GdkAtom selection);

Returns the clipboard object for the given selection. Cut/copy/paste menu items and keyboard shortcuts should use the default clipboard, returned by passing `GDK_SELECTION_CLIPBOARD` for `selection`. (`GDK_NONE` is supported as a synonym for GDK_SELECTION_CLIPBOARD for backwards compatibility reasons.) The currently-selected object or text should be provided on the clipboard identified by GDK_SELECTION_PRIMARY. Cut/copy/paste menu items conceptually copy the contents of the GDK_SELECTION_PRIMARY clipboard to the default clipboard, i.e. they copy the selection to what the user sees as the clipboard.

(Passing GDK_NONE is the same as using `gdk_atom_intern ("CLIPBOARD", FALSE)`. See http://www.freedesktop.org/standards/clipboards.txt for a detailed discussion of the "CLIPBOARD" vs. "PRIMARY" selections under the X window system. On Win32 the GDK_SELECTION_PRIMARY clipboard is essentially ignored.)

It's possible to have arbitrary named clipboards; if you do invent new clipboards, you should prefix the selection name with an underscore (because the ICCCM requires that nonstandard atoms are underscore-prefixed), and namespace it as well. For example, if your application called "Foo" has a special-purpose clipboard, you might call it "_FOO_SPECIAL_CLIPBOARD".

`display` : | the display for which the clipboard is to be retrieved or created
`selection` : | a GdkAtom which identifies the clipboard to use.
Returns : | the appropriate clipboard object. If no clipboard already exists, a new one will be created. Once a clipboard object has been created, it is persistent for all time and cannot be freed.

### gtk_clipboard_get_display ()

    GdkDisplay* gtk_clipboard_get_display       (GtkClipboard *clipboard);

Gets the GdkDisplay associated with `clipboard`

`clipboard` : | a GtkClipboard
Returns : | the GdkDisplay associated with `clipboard`

### gtk_clipboard_set_with_data ()

    gboolean    gtk_clipboard_set_with_data     (GtkClipboard *clipboard,
                                                 const GtkTargetEntry *targets,
                                                 guint n_targets,
                                                 GtkClipboardGetFunc get_func,
                                                 GtkClipboardClearFunc clear_func,
                                                 gpointer user_data);

Virtually sets the contents of the specified clipboard by providing a list of supported formats for the clipboard data and a function to call to get the actual data when it is requested.

`clipboard` : | a GtkClipboard
`targets` : | array containing information about the available forms for the clipboard data
`n_targets` : | number of elements in `targets`
`get_func` : | function to call to get the actual clipboard data
`clear_func` : | when the clipboard contents are set again, this function will be called, and `get_func` will not be subsequently called.
`user_data` : | user data to pass to `get_func` and `clear_func`.
Returns : | `TRUE` if setting the clipboard data succeeded. If setting the clipboard data failed the provided callback functions will be ignored.

### gtk_clipboard_set_with_owner ()

    gboolean    gtk_clipboard_set_with_owner    (GtkClipboard *clipboard,
                                                 const GtkTargetEntry *targets,
                                                 guint n_targets,
                                                 GtkClipboardGetFunc get_func,
                                                 GtkClipboardClearFunc clear_func,
                                                 GObject *owner);

Virtually sets the contents of the specified clipboard by providing a list of supported formats for the clipboard data and a function to call to get the actual data when it is requested.

The difference between this function and gtk_clipboard_set_with_data() is that instead of an generic `user_data` pointer, a GObject is passed in.

`clipboard` : | a GtkClipboard
`targets` : | array containing information about the available forms for the clipboard data
`n_targets` : | number of elements in `targets`
`get_func` : | function to call to get the actual clipboard data
`clear_func` : | when the clipboard contents are set again, this function will be called, and `get_func` will not be subsequently called.
`owner` : | an object that "owns" the data. This object will be passed to the callbacks when called.
Returns : | `TRUE` if setting the clipboard data succeeded. If setting the clipboard data failed the provided callback functions will be ignored.

### gtk_clipboard_get_owner ()

    GObject*    gtk_clipboard_get_owner         (GtkClipboard *clipboard);

If the clipboard contents callbacks were set with gtk_clipboard_set_with_owner(), and the gtk_clipboard_set_with_data() or gtk_clipboard_clear() has not subsequently called, returns the owner set by gtk_clipboard_set_with_owner().

`clipboard` : | a GtkClipboard
Returns : | the owner of the clipboard, if any; otherwise `NULL`.

### gtk_clipboard_clear ()

    void        gtk_clipboard_clear             (GtkClipboard *clipboard);

Clears the contents of the clipboard. Generally this should only be called between the time you call gtk_clipboard_set_with_owner() or gtk_clipboard_set_with_data(), and when the `clear_func` you supplied is called. Otherwise, the clipboard may be owned by someone else.

`clipboard` : | a GtkClipboard

### gtk_clipboard_set_text ()

    void        gtk_clipboard_set_text          (GtkClipboard *clipboard,
                                                 const gchar *text,
                                                 gint len);

Sets the contents of the clipboard to the given UTF-8 string. GTK+ will make a copy of the text and take responsibility for responding for requests for the text, and for converting the text into the requested format.

`clipboard` : | a GtkClipboard object
`text` : | a UTF-8 string.
`len` : | length of `text`, in bytes, or -1, in which case the length will be determined with `strlen()`.

### gtk_clipboard_request_contents ()

    void        gtk_clipboard_request_contents  (GtkClipboard *clipboard,
                                                 GdkAtom target,
                                                 GtkClipboardReceivedFunc callback,
                                                 gpointer user_data);

Requests the contents of clipboard as the given target. When the results of the result are later received the supplied callback will be called.

`clipboard` : | a GtkClipboard
`target` : | an atom representing the form into which the clipboard owner should convert the selection.
`callback` : | A function to call when the results are received (or the retrieval fails). If the retrieval fails the length field of `selection_data` will be negative.
`user_data` : | user data to pass to `callback`

### gtk_clipboard_request_text ()

    void        gtk_clipboard_request_text      (GtkClipboard *clipboard,
                                                 GtkClipboardTextReceivedFunc callback,
                                                 gpointer user_data);

Requests the contents of the clipboard as text. When the text is later received, it will be converted to UTF-8 if necessary, and `callback` will be called.

The `text` parameter to `callback` will contain the resulting text if the request succeeded, or `NULL` if it failed. This could happen for various reasons, in particular if the clipboard was empty or if the contents of the clipboard could not be converted into text form.

`clipboard` : | a GtkClipboard
`callback` : | a function to call when the text is received, or the retrieval fails. (It will always be called one way or the other.)
`user_data` : | user data to pass to `callback`.

### gtk_clipboard_wait_for_contents ()

    GtkSelectionData* gtk_clipboard_wait_for_contents
                                                (GtkClipboard *clipboard,
                                                 GdkAtom target);

Requests the contents of the clipboard using the given target. This function waits for the data to be received using the main loop, so events, timeouts, etc, may be dispatched during the wait.

`clipboard` : | a GtkClipboard
`target` : | an atom representing the form into which the clipboard owner should convert the selection.
Returns : | a newly-allocated GtkSelectionData object or `NULL` if retrieving the given target failed. If non-`NULL`, this value must be freed with gtk_selection_data_free() when you are finished with it.

### gtk_clipboard_wait_for_text ()

    gchar*      gtk_clipboard_wait_for_text     (GtkClipboard *clipboard);

Requests the contents of the clipboard as text and converts the result to UTF-8 if necessary. This function waits for the data to be received using the main loop, so events, timeouts, etc, may be dispatched during the wait.

`clipboard` : | a GtkClipboard
Returns : | a newly-allocated UTF-8 string which must be freed with g_free(), or `NULL` if retrieving the selection data failed. (This could happen for various reasons, in particular if the clipboard was empty or if the contents of the clipboard could not be converted into text form.)

### gtk_clipboard_wait_is_text_available ()

    gboolean    gtk_clipboard_wait_is_text_available
                                                (GtkClipboard *clipboard);

Test to see if there is text available to be pasted This is done by requesting the TARGETS atom and checking if it contains any of the names: STRING, TEXT, COMPOUND_TEXT, UTF8_STRING. This function waits for the data to be received using the main loop, so events, timeouts, etc, may be dispatched during the wait.

This function is a little faster than calling gtk_clipboard_wait_for_text() since it doesn't need to retrieve the actual text.

`clipboard` : | a GtkClipboard
Returns : | `TRUE` is there is text available, `FALSE` otherwise.

## See Also

GtkSelection

  GtkClipboard provides a high-level wrapper around the lower level routines that deal with X selections. It is also possibly to directly manipulate the X selections, though it is seldom necessary to do so.

<<< Previous Page | Home | Up | Next Page >>>
Accelerator Maps | Drag and Drop