96 lines
3.5 KiB
Python
96 lines
3.5 KiB
Python
# -*- coding: utf-8 -*-
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"""This module implements a scroll bar capability for widgets"""
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from __future__ import division
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from __future__ import absolute_import
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from __future__ import print_function
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from __future__ import unicode_literals
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from builtins import range
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from builtins import object
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class _ScrollBar(object):
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"""
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Internal object to provide vertical scroll bars for widgets.
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"""
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def __init__(self, canvas, palette, x, y, height, get_pos, set_pos, absolute=False):
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"""
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:param canvas: The canvas on which to draw the scroll bar.
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:param palette: The palette of the parent Frame.
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:param x: The x location of the top of the scroll bar.
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:param y: The y location of the top of the scroll bar.
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:param height: The height of the scroll bar.
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:param get_pos: A function to return the current position of the scroll bar.
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:param set_pos: A function to set the current position of the scroll bar.
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:param absolute: Whether the scroll bar should use absolute co-ordinates when handling mouse
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events.
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The current position for the scroll bar is defined to be 0.0 at the top and 1.0 at the
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bottom. The scroll bar will call `get_pos` to find the current position when drawing and
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uses `set_pos` to update this position on a mouse click.
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The widget using the scroll bar is responsible for maintaining its own state of where the
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current view is scrolled (e.g. which is the top line in a text box) and for providing
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these two functions to translate that internal state into a form the scroll bar can use.
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"""
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self._canvas = canvas
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self.palette = palette
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self.max_height = 0
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self._x = x
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self._y = y
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self._height = height
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self._absolute = absolute
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self._get_pos = get_pos
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self._set_pos = set_pos
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def update(self):
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"""
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Draw the scroll bar.
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"""
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# Sort out chars
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cursor = u"█" if self._canvas.unicode_aware else "O"
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back = u"░" if self._canvas.unicode_aware else "|"
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# Now draw...
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try:
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sb_pos = self._get_pos()
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sb_pos = min(1, max(0, sb_pos))
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sb_pos = max(int(self._height * sb_pos) - 1, 0)
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except ZeroDivisionError:
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sb_pos = 0
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(colour, attr, bg) = self.palette["scroll"]
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y = self._canvas.start_line if self._absolute else 0
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for dy in range(self._height):
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self._canvas.print_at(cursor if dy == sb_pos else back,
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self._x, y + self._y + dy,
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colour, attr, bg)
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def is_mouse_over(self, event):
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"""
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Check whether a MouseEvent is over thus scroll bar.
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:param event: The MouseEvent to check.
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:returns: True if the mouse event is over the scroll bar.
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"""
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return event.x == self._x and self._y <= event.y < self._y + self._height
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def process_event(self, event):
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"""
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Handle input on the scroll bar.
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:param event: the event to be processed.
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:returns: True if the scroll bar handled the event.
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"""
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# Convert into absolute coordinates if needed.
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new_event = event
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if self._absolute:
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new_event.y -= self._canvas.start_line
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# Process event if needed.
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if self.is_mouse_over(new_event) and event.buttons != 0:
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self._set_pos((new_event.y - self._y) / (self._height - 1))
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return True
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return False
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