NAME¶
Gtk2::ImageView::Tool::Selector - Image tool for selecting rectangular regions
HIERARCHY¶
Glib::Object
+----Gtk2::ImageView::Tool::Selector
INTERFACES¶
Gtk2::ImageView::Tool
DESCRIPTION¶
Gtk2::ImageView::Tool::Selector is a tool for selecting areas of an image. It is
useful for cropping an image, for example. The tool is an implementor of the
Gtk2::ImageView::Tool inteface which means that it can be plugged into a
Gtk2::ImageView by using the
Gtk2::ImageView::Tool::set_tool() method.
Gtk2::ImageView::Tool::Selector changes the default display of the
Gtk2::ImageView. It darkens down the unselected region of the image which
provides a nice effect and makes it clearer what part of the image that is
currently selected. Unfortunately, this effect is somewhat incompatible with
how Gtk2::ImageView::Nav behaves because that widget will show the image
without darkening it.
The tool also changes the default behaviour of the mouse. When a
Gtk2::ImageView::Tool::Selector is set on a Gtk2::ImageView, mouse presses do
not "grab" the image and you cannot scroll by dragging. Instead
mouse presses and dragging is used to resize and move the selection rectangle.
When the mouse drags the selection rectangle to the border of the widget, the
view autoscrolls which is a convenient way for a user to position the
selection.
Please note that Gtk2::ImageView::Tool::Selector draws the image in two layers.
One darkened and the selection rectangle in normal luminosity. Because it uses
two draw operations instead one one like Gtk2::ImageView::Tool::Dragger does,
it is significantly slower than that tool. Therefore, it makes sense for a
user of this library to set the interpolation to GDK_INTERP_NEAREST when using
this tool to ensure that performance is acceptable to the users of the
program.
Zoom bug¶
There is a small bug in Gtk2::ImageView::Tool::Selector that becomes apparent
when the zoom factor is greater than about 30. The edge of the selection
rectangle may in that case intersect a pixel.
The bug is caused by bug 389832 in gdk-pixbuf. There is no way to solve this bug
on Gtk2::ImageView's level (but if someone knows how, I'd really like to
know).
METHODS¶
- •
- $view (Gtk2::ImageView)
Returns a new selector tool for the specified view with the following default
values:
- selection : (0, 0) - [0, 0]
rectangle = $selector-> get_selection¶
Returns a Gtk2::Gdk::Rectangle with the current selection. If either the width
or the height of the selection is zero, then nothing is selected and undef is
returned. See "selection-changed" for an example.
$selector->set_selection ($rect)¶
- •
- $rect (Gtk2::Gdk::Rectangle)
Sets the selection rectangle for the tool. Setting this attribute will cause the
widget to immidiately repaint itself if its view is realized.
This method does nothing under the following circumstances:
- If the views pixbuf is undef.
- If rect is wider or taller than the size of the pixbuf
- If rect equals the current selection rectangle.
If the selection falls outside the pixbufs area, its position is moved so that
it is within the pixbuf.
Calling this method causes the ::selection-changed signal to be emitted.
The default selection is (0,0) - [0,0].
- selector : a Gtk2::ImageView::Tool::Selector
- rect : Selection rectangle in image space coordinates.
PROPERTIES¶
- 'view' (Gtk2::ImageView : default undef : writable / construct-only)
- Image View to navigate
SIGNALS¶
- selection-changed (Gtk2::ImageView::Tool::Selector)
SEE ALSO¶
Gtk2::ImageView, Glib::Object
COPYRIGHT¶
Copyright (C) 2007 by Jeffrey Ratcliffe.
This software is licensed under the GPL-3; see Gtk2::ImageView for a full
notice.