# Copyright 2006 James Tauber and contributors
# Copyright (C) 2009 Luke Kenneth Casson Leighton <lkcl@lkcl.net>
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
from pyjamas import DOM
from pyjamas import Factory

from pyjamas.ui.SimplePanel import SimplePanel
from pyjamas.ui import Event

class ScrollPanel(SimplePanel):

    _props = [("always", "Always show scroll bars",
                              "AlwaysShowScrollBars", None),
             ("position", "Vertical Scroll Position",
                              "ScrollPosition", None),
             ("horizPos", "Horizontal Scroll Position",
                              "HorizontalScrollPosition", None),
            ]

    def __init__(self, child=None, **kwargs):
        self.scrollListeners = []

        if child is not None:
            kwargs['Widget'] = child
        if not kwargs.has_key('AlwaysShowScrollBars'):
             kwargs['AlwaysShowScrollBars'] = False

        SimplePanel.__init__(self, **kwargs)
        self.sinkEvents(Event.ONSCROLL)

    @classmethod
    def _getProps(self):
        return SimplePanel._getProps() + self._props

    # next three functions are part of the standard Builder API for panels
    def addIndexedItem(self, index, item):
        self.setWidget(item)
    
    def getWidgetIndex(self, index):
        return 0

    def getIndexedChild(self, index):
        return self.getWidget()

    def addScrollListener(self, listener):
        self.scrollListeners.append(listener)

    def ensureVisible(self, item):
        scroll = self.getElement()
        element = item.getElement()
        self.ensureVisibleImpl(scroll, element)

    def getScrollPosition(self):
        return DOM.getIntAttribute(self.getElement(), "scrollTop")

    def getHorizontalScrollPosition(self):
        return DOM.getIntAttribute(self.getElement(), "scrollLeft")

    def onBrowserEvent(self, event):
        type = DOM.eventGetType(event)
        if type == "scroll":
            for listener in self.scrollListeners:
                listener.onScroll(self, self.getHorizontalScrollPosition(),
                                        self.getScrollPosition())

    def removeScrollListener(self, listener):
        self.scrollListeners.remove(listener)

    def setAlwaysShowScrollBars(self, alwaysShow):
        if alwaysShow:
            style = "scroll"
        else:
            style = "auto"
        DOM.setStyleAttribute(self.getElement(), "overflow", style)

    def setScrollPosition(self, position):
        DOM.setIntAttribute(self.getElement(), "scrollTop", position)

    def setHorizontalScrollPosition(self, position):
        DOM.setIntAttribute(self.getElement(), "scrollLeft", position)

    def ensureVisibleImpl(self, scroll, e):
        if not e:
            return
        item = e
        realOffset = 0
        while item and (item != scroll):
            realOffset += item.offsetTop
            item = item.offsetParent
        scroll.scrollTop = realOffset - scroll.offsetHeight / 2

Factory.registerClass('pyjamas.ui.ScrollPanel', 'ScrollPanel', ScrollPanel)

