Gtk2::Ex::WidgetCursor -- mouse pointer cursor management for widgets


 use Gtk2::Ex::WidgetCursor;
 my $wc = Gtk2::Ex::WidgetCursor->new (widget => $mywidget,
                                       cursor => 'fleur',
                                       active => 1);

 # show wristwatch everywhere while number crunching

 # bonus invisible cursor creator
 my $cursor = Gtk2::Ex::WidgetCursor->invisible_cursor;


Gtk2::Ex::WidgetCursor is a subclass of Glib::Object.



WidgetCursor manages the mouse pointer cursor shown in widget windows as per Gtk2::Gdk::Window set_cursor. A "busy" mechanism can display a wristwatch in all windows when the whole application is blocked.

With the plain window set_cursor it's difficult for widget add-ons or independent parts of an application to cooperate with what should be shown at different times or in different modes.

A Gtk2::Ex::WidgetCursor object represents a desired cursor in one or more widgets. When "active" and when it's the newest or highest priority then the specified cursor is set onto those widget window(s). If the WidgetCursor object is later made inactive or destroyed then the next remaining highest WidgetCursor takes effect, etc.

The idea is to have say a base WidgetCursor for an overall mode, then something else temporarily while dragging, and perhaps a wristwatch "busy" indication trumping one or both (like the global "busy" mechanism below).

The examples subdirectory in the WidgetCursor sources has some variously contrived sample programs.



$wc = Gtk2::Ex::WidgetCursor->new (key => value, ...)

Create and return a new WidgetCursor object. Optional key/value parameters set initial properties as per Glib::Object->new (see Glib::Object).

    $wc = Gtk2::Ex::WidgetCursor->new (widget => $mywidget,
                                       cursor => 'fleur',
                                       active => 1);

Note that active is false by default and the WidgetCursor does nothing to the widgets until made active by the property or the method call below.

WidgetCursor objects can be applied to unrealized widgets. The cursor settings take effect if/when the widgets are realized.


$bool = $wc->active ()
$wc->active ($newval)

Get or set the "active" state of $wc. This is the active property.

$cursor = $wc->cursor ()
$wc->cursor ($cursor)

Get or set the cursor of $wc. This is the cursor property, see "PROPERTIES" below for possible values. Eg.

    $wc->cursor ('umbrella');
@widgets = $wc->widgets ()

Return a list of the widgets currently in $wc. Eg.

    my @array = $wc->widgets;

or if you know you're only acting on one widget then say

    my ($widget) = $wc->widgets;
$wc->add_widgets ($widget, $widget, ...)

Add widgets to $wc. Any widgets given which are already in $wc are ignored.


widget (Gtk2::Widget, default undef)
widgets (scalar arrayref of Gtk2::Widget, default undef)

The widget or widgets to act on.

A WidgetCursor object only keeps weak references to its widget(s), so the mere fact there's a desired cursor won't keep a widget alive forever. Garbage collected widgets drop out of the widgets list. In particular this means it's safe to hold a WidgetCursor within a widget's own hash without creating a circular reference. Eg.

    my $widget = Gtk2::DrawingArea->new;
    $widget->{'base_cursor'} = Gtk2::Ex::WidgetCursor->new
                                 (widget => $widget,
                                  cursor => 'hand1',
                                  active => 1,
                                  priority => -10);
add-widget (Gtk2::Widget, write-only)

Add a widget to those to act on. This is a write-only pseudo-property calling add_widget above. It's good for Gtk2::Builder where the widgets property can't be used since it's a Perl scalar type.

cursor (scalar string name or Gtk2::Gdk::Cursor object)

The cursor to show in the widgets. This can be

cursor-name (string, default undef)
cursor-object (Gtk2::Gdk::Cursor, default undef)

The cursor to show in the widgets, as a plain Glib string or object property. These are designed for use from Gtk2::Builder where the scalar type cursor property can't be set.

Reading from cursor-name when a cursor object has been set gives the type nick if it has one, or if it's a pixmap then currently undef.

Reading from cursor-object when a cursor name string has been set gives undef currently. It'd be possible to make or return the cursor object in use (or which will be used when realized) but that doesn't seem worth bothering with as yet.

active (boolean, default false)

Whether to apply the cursor to the widgets. This can be set before widgets are added or before they're realized, in which case the cursor is applied later as soon as they're realized.

priority (number, default 0)

The priority level of this WidgetCursor among multiple WidgetCursors acting on a widget.

Higher values are higher priority. A low value (perhaps negative) can act as a fallback, or a high value can trump other added cursors.

include-children (boolean, default false)

Whether to apply the cursor to child widgets of the given widgets too. Normally the cursor in a child widget overrides its parents (as set_cursor does at the window level). But with include-children a setting in a parent applies to the children too, with priority+newest applied as usual.


The busy mechanism sets a "watch" cursor on all windows to tell the user the program is doing CPU-intensive work and might not run the main loop to draw or interact for a while.

If your busy state isn't CPU-intensive, but instead perhaps a Glib timer or an I/O watch on a socket, then this is not what you want, it'll turn off too soon. (Instead simply make a WidgetCursor with a "watch" and turn it on or off at your start and end points. See examples/ in the sources for an example of that sort of thing.)

Gtk2::Ex::WidgetCursor->busy ()

Show the "watch" cursor (a little wristwatch) in all the application's widget windows (toplevels, dialogs, popups, etc). An idle handler (Glib::Idle->add) removes the watch automatically upon returning to the main loop.

The X queue is flushed to set the cursor immediately, so the program can go straight into its work. For example

    foreach my $i (1 .. 1_000_000) {
      # do much number crunching

If you create new windows within a busy then they too get the busy cursor (or they're supposed to, something fishy in Gtk 2.20 and maybe 2.18 has broken it). You can even go busy before creating any windows at all. But note WidgetCursor doesn't do any extra X flush for new creations; if you want them to show immediately then you must flush in the usual way.

busy uses a WidgetCursor object as described above and so cooperates with application uses of that. Priority level 1000 is set to trump other cursor settings.

Gtk2::Ex::WidgetCursor->unbusy ()

Explicitly remove the watch cursor setup by busy above. The X request queue is flushed to ensure any cursor change appears immediately. If busy is not active then do nothing.

It's unlikely you'll need unbusy, because if your program hasn't yet reached the idle handler in the main loop then it's probably still busy! But perhaps if most of your work is done then you could unbusy while the remainder is finishing up.


The following invisible cursor is used by WidgetCursor for the "invisible" cursor and is made available for general use.

$cursor = Gtk2::Ex::WidgetCursor->invisible_cursor ()
$cursor = Gtk2::Ex::WidgetCursor->invisible_cursor ($target)

Return a Gtk2::Gdk::Cursor object which is invisible, ie. displays no cursor at all. This is the blank-cursor in Gtk 2.16 and up, or for earlier versions a "no pixels set" cursor as described by gdk_cursor_new.

With no arguments (or undef) the cursor is for the default display Gtk2::Gdk::Display->get_default. If your program only uses one display then that's all you need.

    my $cursor = Gtk2::Ex::WidgetCursor->invisible_cursor;

For multiple displays a cursor is a per-display resource so you must pass a $target. This can be a Gtk2::Gdk::Display, or anything with a get_display method, including Gtk2::Widget, Gtk2::Gdk::Window, Gtk2::Gdk::Drawable, another Gtk2::Gdk::Cursor, etc.

    my $cursor = Gtk2::Ex::WidgetCursor->invisible_cursor ($widget);

When passing a widget note the display comes from its toplevel Gtk2::Window parent and until added as a child somewhere under a toplevel its get_display is the default display and invisible_cursor will give a cursor for that display.

The invisible cursor is cached against the display so repeated calls don't make a new one every time.

Gtk had its own "no pixels set" cursor constructor code in GtkEntry and GtkTextView prior to "blank-cursor" but didn't make it available to applications.


WidgetCursor is a Glib::Object and can be created by Gtk2::Builder in the usual way. Each is a separate toplevel object and the widget property sets what it should act on. The add-widget pseudo-property allows multiple widgets to be set.

    <object class="Gtk2__Ex__WidgetCursor" id="wcursor">
      <property name="widget">mywidget</property>
      <property name="active">1</property>

See examples/ and examples/ in the WidgetCursor sources for complete sample programs.


WidgetCursor settings are applied to the widget windows without paying attention to which among them are "no-window" and thus using their parents' windows. If different no-window children have a common windowed parent then WidgetCursor won't notice and the result will probably come out wrong. For now it's suggested you either always give a windowed widget, or at least always the same no-window child.

An exception to the no-window rule is Gtk2::Button. It has the no-window flag but in fact keeps a private input-only event window over its allocated space. WidgetCursor digs that out and uses it to put the cursor on the intended area. But an exception to this exception is Gtk2::LinkButton where a setting on the button works fine, but any WidgetCursor on its parent widget is messed up.

In the future it might be possible to have cursors on no-window widgets by following motion-notify events within the container parent in order to update the cursor as it goes across different children. Something similar might allow certain regions of a window to have a particular cursor, such as hyperlinked clickable text. But windowed widgets are normally best, since they let the X server take care of the display as the mouse moves around.

Reparenting widgets under an include_children probably doesn't quite work. If it involves a new realize then it may work (as for reparenting to a different screen). Moving widgets is unusual, so in practice this isn't too bad. Doing the right thing in all cases might need a lot of add or parent signal connections.

Widgets calling $window->set_cursor themselves generally don't work with the WidgetCursor mechanism. WidgetCursor has some special handling for Gtk2::Entry and Gtk2::TextView (their insertion point cursor), but a few other core widgets have problems. The worst currently is Gtk2::LinkButton per above. Hopefully this can improve in the future, though ill effects are often as modest as an include_children merely not working on children of offending types.


Gtk2::Gdk::Cursor, Gtk2::Widget, Gtk2::Gdk::Window, Gtk2::Gdk::Display



Copyright 2007, 2008, 2009, 2010 Kevin Ryde

Gtk2-Ex-WidgetCursor is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version.

Gtk2-Ex-WidgetCursor is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with Gtk2-Ex-WidgetCursor. If not, see