Gtk2::Ex::Lasso -- drag the mouse to lasso a rectangular region
use Gtk2::Ex::Lasso; my $lasso = Gtk2::Ex::Lasso->new (widget => $widget); $lasso->signal_connect (ended => sub { some_code() }); $lasso->start ($event);
Gtk2::Ex::Lasso
is a subclass of Glib::Object
.
Glib::Object Gtk2::Ex::Lasso
A Gtk2::Ex::Lasso
object implements a "lasso" style user selection of a rectangular region in a widget window, drawing dashed lines as visual feedback while selecting.
+-------------------------+ | | | +-----------+ | | | | | | | | | | +-----------* | | \mouse | | | | | +-------------------------+
The lasso is activated by the start()
function (see "FUNCTIONS" below), normally called from a mouse button press or keypress event handler. When started from a mouse button the lasso is active while the button is held down, ie. a drag. This is usual, but it can also begin from a keypress or even something strange like a menu entry.
The following keys are recognised while lassoing,
Return end selection Esc abort the selection Space swap the mouse pointer to the opposite corner
Other keys are propagated to normal processing. The space for "swap" lets the user move the initial corner if it wasn't quite right. (This requires $display->warp_pointer()
and so is only possible in Gtk 2.8 and up.)
See examples/lasso-area.pl for a complete sample program.
Gtk2::Ex::Lasso->new (key => value, ...)
Create and return a new Lasso object. Optional key/value pairs set initial properties as per Glib::Object->new
. Eg.
my $ch = Gtk2::Ex::Lasso->new (widget => $widget);
$lasso->start ()
$lasso->start ($event)
Start a lasso selection with $lasso
. If $event
is a Gtk2::Gdk::Event::Button
then releasing that button ends the selection. For other event types or for undef
or omitted the selection ends only with the Return key or an end()
call.
$lasso->end ()
$lasso->end ($event)
End the $lasso
selection and emit the ended
signal, or if $lasso
is already inactive then do nothing. This end is the user Return key or button release.
If you end a lasso in response to a button release, button press, motion notify, or similar, then pass the Gtk2::Gdk::Event
as the optional $event
parameter so that end()
can use it for a final X,Y position and for a server timestamp if ungrabbing. Both are important if event processing in the client is lagged for any reason.
$lasso->abort ()
Abort the $lasso
selection and emit the aborted
signal, or if $lasso
is already inactive then do nothing. This is the user Esc key.
$lasso->swap_corners()
Swap the mouse pointer to the opposite corner of the selection by a "warp" of the pointer (ie. a forcible movement). This is the user Space key.
For Gtk 2.6 and earlier there's no $display->warp_pointer
and currently this method does nothing in that case.
widget
(a Gtk2::Widget
or undef
)The target widget to act on. This can be changed to act on a different widget. Setting a new widget target is even possible when the lasso is active, though doing so might confuse the user.
active
(boolean, default false)True while lasso selection is in progress. Turning this on or off is the same as calling start()
or end()
above (except you can't pass events).
foreground
(scalar, default undef
)foreground-name
(string, default undef
)foreground-gdk
(Gtk2::Gdk::Color
object, default undef
)The colour for the lasso. This can be
undef
(the default) for the widget style fg
foreground colour (see Gtk2::Style).Gtk2::Gdk::Color->parse()
(see Gtk2::Gdk::Color).Gtk2::Gdk::Color
object with red
, green
, blue
fields set. (A pixel value will be looked up for the particular widget in use.)All three foreground
, foreground-name
and foreground-gdk
access the same underlying setting. foreground-name
and foreground-gdk
help Gtk2::Builder
since the generic Perl scalar foreground
property can't be set from a Builder.
In the current code, if the foreground is a Gtk2::Gdk::Color
object then foreground-name
reads as its to_string()
form such as "#11112222333", or if foreground is a string name then foreground-gdk
reads as parsed to a Gtk2::Gdk::Color
. Is this a good idea? Perhaps it will change in the future.
cursor
(scalar, default "hand1")cursor-name
(string, cursor enum nick or "invisible", default "hand1")cursor-object
(Gtk2::Gdk::Cursor
)The mouse cursor type to display while lassoing. This can be any string or object understood by Gtk2::Ex::WidgetCursor
, or undef
for no cursor change.
A different cursor is highly desirable because when starting a lasso it's normally too small for the user to see and so needs another visual indication that selection has begun. The default "hand1"
is meant to be reasonable.
The cursor
, cursor-name
and cursor-object
properties all access the same underlying setting but with string or cursor object type respectively. cursor-name
and cursor-object
can be used from a Gtk2::Builder
specification.
If using a Gtk2::Gdk::Cursor
object then remember cursor objects are a per-display resource and the cursor must be on the same display as the target widget
.
The cursor can be changed while the lasso is active. Doing so is probably unusual but works and could be used for something creative like further visual feedback or maybe keeping an arrow outwards so as not to obscure the selected region.
moved
, parameters: lasso, x1, y1, x2, y2, userdataEmitted whenever the in-progress selected region changes (but not when it ends). x2,y2 is the corner with the mouse.
ended
, parameters: lasso, x1, y1, x2, y2, userdataEmitted when a selection is complete and accepted by the user (not when aborted). x2,y2 is the corner where the mouse finished, though it's unusual to care which way around the corners are.
aborted
, parameters: lasso, userdataEmitted when a region selection ends by user abort, which normally means the user doesn't want any action.
Lasso can be created from Gtk2::Builder
the same as other objects. The class name is Gtk2__Ex__Lasso
. It will normally be a top-level object with the widget
property telling it what to act on.
<object class="Gtk2__Ex__Lasso" id="mylasso"> <property name="widget">drawingwidget</property> <property name="foreground-name">orange</property> <property name="cursor-name">umbrella</property> <signal name="ended" handler="do_lasso_ended"/> </object>
See examples/lasso-builder.pl for a complete program.
The foreground-name
property is the best way to control the colour. The generic foreground
can't be used because it's a Perl scalar type. foreground-gdk
works too since Gtk2::Builder
knows how to parse a colour name to a Gtk2::Gdk::Color
object, but in that case the Builder also allocates a pixel in the default colormap, which is unnecessary since the Lasso will do that itself on the target widget's colormap.
The cursor-name
property is similarly the best way to control the mouse cursor type, if the default hand is not wanted. The generic cursor
property can't be used because it's a Perl scalar type. The cursor-object
probably can't be used since the Builder doesn't support cursor creation (as of Gtk circa 2.16).
The lasso is drawn using xors in the widget window. See Gtk2::Ex::Xor for notes on this.
Keypresses are obtained from the Gtk "snooper" mechanism (Gtk2->key_snooper_install()
), so they work even if the lasso target widget doesn't have the focus. Keys not for the lasso are propagated in the usual way.
When the lasso is started from a keypress etc, rather than a button press, an explicit pointer grab is used so motion events outside the widget window are seen. In the current code a further start()
call with a button press event will switch to drag mode, so the corresponding release has the expected effect. This does the right thing, but is a bit obscure.
If start()
needs an explicit grab but can't get it (because another application or a button held down has a grab) then in the current code carps a warning and continues anyway. Perhaps that will change, though it only affects the slightly unusual case of a keyboard initiated lasso.
Gtk2::Ex::CrossHair, Gtk2::Ex::Xor, Glib::Object, Gtk2::Ex::WidgetCursor
http://user42.tuxfamily.org/gtk2-ex-xor/index.html
Copyright 2007, 2008, 2009, 2010, 2011, 2012, 2017, 2019 Kevin Ryde
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