Source code for enaml.wx.wx_scroll_area

#  Copyright (c) 2012, Enthought, Inc.
#  All rights reserved.
import wx

from .wx_constraints_widget import WxConstraintsWidget
from .wx_container import WxContainer
from .wx_single_widget_sizer import wxSingleWidgetSizer

# The 'always_on' scroll policy is not supported on wx, because it
# requires setting a window style flag which does not dynamically
# toggle in a reliable fashion. Since we only support 'off' or 'auto'
# it's easiest to use this mapping to convert straight from policy
# values into a respective scroll rate. A rate of Zero causes wx not
# to show the scroll bar. A positive rate indicates to scroll that many
# pixels per event. We set the rate to 1 to have smooth scrolling. Wx
# doesn't make a distinction between scroll events caused by the mouse
# or scrollbar and those caused by clicking the scroll buttons (ala qt),
# and thus this rate applies the same to all of those events. Since we
# expect that clicking on a scroll button happens much more infrequently
# than scrolling by dragging the scroll bar, we opt for a lower rate
# in order to get smooth drag scrolling and sacrifice some usability
# on the scroll buttons.
    'as_needed': 1,
    'always_off': 0,
    'always_on': 1,

class wxScrollAreaSizer(wxSingleWidgetSizer):
    """ A wxSingleWidgetSizer subclass which makes adjusts the min
    size to account for a 2 pixel error in Wx.

    def CalcMin(self):
        """ Returns the minimum size for the area owned by the sizer.

        result : wxSize
            The wx size representing the minimum area required by the

        # The effective min size computation is correct, but the wx
        # scrolled window interprets it with an error of 2px. That
        # is we need to make wx think that the min size is 2px smaller
        # than it actually is so that scroll bars should and hide at
        # the appropriate sizes.
        res = super(wxScrollAreaSizer, self).CalcMin()
        if res.IsFullySpecified():
            res.width -= 2
            res.height -= 2
        return res

class wxScrollArea(wx.ScrolledWindow):
    """ A custom wx.ScrolledWindow which is suits Enaml's use case.

    #: The internal best size. The same as QAbstractScrollArea.
    _best_size = wx.Size(256, 192)

    def __init__(self, *args, **kwargs):
        """ Initialize a wxScrollArea.

        *args, **kwargs
            The positional and keyword arguments needed to initialize
            a wxScrolledWindow.

        super(wxScrollArea, self).__init__(*args, **kwargs)
        self._scroll_widget = None

    def GetBestSize(self):
        """ An overridden parent class method which returns a sensible
        best size.

        The default wx implementation returns a best size of (16, 16)
        on Windows; far too small to be useful. So, we just adopt the
        size hint of (256, 192) used in Qt's QAbstractScrollArea.

        return self._best_size

    def GetScrollWidget(self):
        """ Get the scroll widget for this scroll area.

        results : wxWindow
            The wxWindow being scrolled by this scroll area.

        return self._scroll_widget

    def SetScrollWidget(self, widget):
        """ Set the scroll widget for this scroll area.

        widget : wxWindow
            The wxWindow which should be scrolled by this area.

        self._scroll_widget = widget

[docs]class WxScrollArea(WxConstraintsWidget): """ A Wx implementation of an Enaml ScrollArea. """ #: Storage for the horizontal scroll policy _h_scroll = 'as_needed' #: Storage for the vertical scroll policy _v_scroll = 'as_needed'
[docs] def create_widget(self, parent, tree): """ Create the underlying wxScrolledWindow widget. """ style = wx.HSCROLL | wx.VSCROLL | wx.BORDER_SIMPLE return wxScrollArea(parent, style=style)
[docs] def create(self, tree): """ Create and initialize the scroll area widget. """ super(WxScrollArea, self).create(tree) self.set_horizontal_policy(tree['horizontal_policy']) self.set_vertical_policy(tree['vertical_policy']) self.set_widget_resizable(tree['widget_resizable'])
[docs] def init_layout(self): """ Handle the layout initialization for the scroll area. """ super(WxScrollArea, self).init_layout() self.widget().SetScrollWidget(self.scroll_widget()) #-------------------------------------------------------------------------- # Utility Methods #--------------------------------------------------------------------------
[docs] def scroll_widget(self): """ Find and return the scroll widget child for this widget. Returns ------- result : wxWindow or None The scroll widget defined for this widget, or None if one is not defined. """ widget = None for child in self.children(): if isinstance(child, WxContainer): widget = child.widget() return widget #-------------------------------------------------------------------------- # Child Events #--------------------------------------------------------------------------
[docs] def child_removed(self, child): """ Handle the child removed event for a WxScrollArea. """ if isinstance(child, WxContainer): self.widget().SetScrollWidget(self.scroll_widget())
[docs] def child_added(self, child): """ Handle the child added event for a WxScrollArea. """ if isinstance(child, WxContainer): self.widget().SetScrollWidget(self.scroll_widget()) #-------------------------------------------------------------------------- # Overrides #--------------------------------------------------------------------------
[docs] def replace_constraints(self, old_cns, new_cns): """ A reimplemented WxConstraintsWidget layout method. Constraints layout may not cross the boundary of a ScrollArea, so this method is no-op which stops the layout propagation. """ pass #-------------------------------------------------------------------------- # Message Handlers #--------------------------------------------------------------------------
[docs] def on_action_set_horizontal_policy(self, content): """ Handle the 'set_horizontal_policy' action from the Enaml widget. """ self.set_horizontal_policy(content['horizontal_policy'])
[docs] def on_action_set_vertical_policy(self, content): """ Handle the 'set_vertical_policy' action from the Enaml widget. """ self.set_vertical_policy(content['vertical_policy'])
[docs] def on_action_set_widget_resizable(self, content): """ Handle the 'set_widget_resizable' action from the Enaml widget. """ self.set_widget_resizable(content['widget_resizable']) #-------------------------------------------------------------------------- # Widget Update Methods #--------------------------------------------------------------------------
[docs] def set_horizontal_policy(self, policy): """ Set the horizontal scrollbar policy of the widget. """ self._h_scroll = policy horiz = SCROLLBAR_MAP[policy] vert = SCROLLBAR_MAP[self._v_scroll] self.widget().SetScrollRate(horiz, vert)
[docs] def set_vertical_policy(self, policy): """ Set the vertical scrollbar policy of the widget. """ self._v_scroll = policy horiz = SCROLLBAR_MAP[self._h_scroll] vert = SCROLLBAR_MAP[policy] self.widget().SetScrollRate(horiz, vert)
[docs] def set_widget_resizable(self, resizable): """ Set whether or not the scroll widget is resizable. """ # Not currently implemented on Wx pass