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92 lines
3.1 KiB
Python
92 lines
3.1 KiB
Python
# Copyright (C) 2014, Sugarlabs
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#
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# This library is free software; you can redistribute it and/or
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# modify it under the terms of the GNU Lesser General Public
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# License as published by the Free Software Foundation; either
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# version 2 of the License, or (at your option) any later version.
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#
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# This library is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# Lesser General Public License for more details.
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#
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# You should have received a copy of the GNU Lesser General Public
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# License along with this library; if not, write to the
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# Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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# Boston, MA 02111-1307, USA.
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'''
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ScrollingDetector emits signals when a ScrolledWindow starts and
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finish scrolling. Other widgets can use that information to
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avoid doing performance-expensive operations.
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Example:
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.. literalinclude:: ../examples/scrollingdetector.py
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'''
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from gi.repository import GObject
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from gi.repository import GLib
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class ScrollingDetector(GObject.GObject):
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'''
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The scrolling detector sends signals when a scrolled window is scrolled and
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when a scrolled window stops scrolling. Only one `scroll-start` signal will be
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emitted until scrolling stops.
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The `scroll-start` signal is emitted when scrolling begins and
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The `scroll-end` signal is emitted when scrolling ends
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Neither of these two signals have any arguments
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Args:
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scrolled_window (Gtk.ScrolledWindow): A GTK scrolled window object for which
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scrolling is to be detected
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timeout (int): time in milliseconds to establish the interval for which
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scrolling is detected
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'''
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scroll_start_signal = GObject.Signal('scroll-start')
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scroll_end_signal = GObject.Signal('scroll-end')
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def __init__(self, scrolled_window, timeout=100):
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self._scrolled_window = scrolled_window
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self._timeout = timeout
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self.is_scrolling = False
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self._prev_value = 0
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self.connect_scrolled_window()
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GObject.GObject.__init__(self)
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def connect_scrolled_window(self):
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'''
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Connects scrolling detector to a scrolled window.
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Detects scrolling when the vertical scrollbar
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adjustment value is changed
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Should be used to link an instance of a scrolling detector
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to a Scrolled Window, after setting scrolled_window
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'''
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adj = self._scrolled_window.get_vadjustment()
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adj.connect('value-changed', self._value_changed_cb)
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def _check_scroll_cb(self, adj):
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if (adj.props.value == self._prev_value):
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self.is_scrolling = False
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self.scroll_end_signal.emit()
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return False
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self._prev_value = adj.props.value
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return True
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def _value_changed_cb(self, adj):
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if (self.is_scrolling):
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return
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self.is_scrolling = True
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self.scroll_start_signal.emit()
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self._prev_value = adj.props.value
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GLib.timeout_add(self._timeout, self._check_scroll_cb, adj)
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