# -*- coding: utf-8 -*-
"""
Copyright (C) 2013 Oliver Tengler
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
"""
from typing import Any, List, Iterator, Tuple, Dict, DefaultDict, Optional
from abc import ABC,abstractmethod
import bisect
import collections
from PyQt5.QtCore import Qt, QSize
from PyQt5.QtGui import QResizeEvent
from PyQt5.QtWidgets import QLabel, QLayout, QScrollArea, QWidget
def doLinesIntersect (y1: int, length1: int, y2: int, length2: int) -> bool:
if y1 < y2:
return y1+length1 > y2
else:
return y2+length2 > y1
class ScrollAreaItem (ABC):
def __init__ (self, height: int) -> None:
self.height = height
self.id: int = 0
@abstractmethod
def generateItem (self, parent: QWidget) -> QWidget:
pass
@abstractmethod
def configureItem(self, item: QWidget) -> None:
pass
@abstractmethod
def getType(self) -> Any:
pass
class Labeltem (ScrollAreaItem):
def __init__(self, text: str, bIsBold: bool, height: int) -> None:
super ().__init__(height)
self.text = text
self.bIsBold = bIsBold
def generateItem (self, parent: QWidget) -> QWidget:
return QLabel("", parent)
def configureItem(self, item: QWidget) -> None:
item.setFixedHeight(self.height)
if self.bIsBold:
text = "<b>" + self.text + "</b>"
else:
text = self.text
item.setText(text)
def getType(self) -> Any:
return QLabel
class SrollAreaItemList:
def __init__(self, spacing:int = 7) -> None:
self.spacing = spacing
self.clear()
def clear(self) -> None:
self.items: List[ScrollAreaItem] = []
self.yStarts: List[int] = []
self.y = self.spacing
self.nextId = 1
def __len__(self) -> int:
return len(self.items)
def addItem (self, item: ScrollAreaItem) -> int:
"""Adds an item to the list and returns its index in the item list."""
item.id = self.nextId
self.nextId += 1
self.items.append(item)
self.yStarts.append(self.y)
self.y += (item.height+self.spacing)
return len(self.items)-1
def itemYPos (self, index: int) -> int:
if index>=len(self.yStarts):
return 0
return self.yStarts[index]
def height(self) -> int:
if not self.items:
return 0
last = len(self.items)-1
return self.yStarts[last]+self.items[last].height+self.spacing
def visibleItems (self, y: int, height: int) -> Iterator[Tuple[int, ScrollAreaItem]]:
index = self.__indexBeforePos (y)
while index<len(self.items):
item = self.items[index]
itemY = self.yStarts[index]
if doLinesIntersect(y, height, itemY, item.height):
yield itemY, item
else:
if itemY > y+height:
break
index += 1
def __indexBeforePos(self, yPos: int) -> int:
index = bisect.bisect_left(self.yStarts, yPos)
if index > 0:
index -= 1
return index
class EmptyLayout(QLayout):
"""
This layout works around the problem that child wigets of the scrollarea widget are invisible if the scrollarea widget
has no layout. If this is a bug or as designed - I don't know.
"""
def itemAt(self, _: int) -> None:
return None
def takeAt(self, _: int) -> None:
return None
def count(self) -> int:
return 0
def sizeHint(self) -> QSize:
return self.parent().size()
class RecyclingVerticalScrollArea(QScrollArea):
def __init__(self, parent: QWidget=None) -> None:
super().__init__(parent)
self.setVerticalScrollBarPolicy(Qt.ScrollBarAlwaysOn)
self.items: Optional[SrollAreaItemList] = None
self.activeWidgets: Dict[int, QWidget] = {} # id to widget
self.reservedWidgets: DefaultDict[str, QWidget] = collections.defaultdict(list) # type name to widgets
w = QWidget(self)
w.setLayout(EmptyLayout(w))
self.setWidget(w)
def scrollToNthItem (self, index: int) -> None:
if self.items:
self.ensureVisible (0, self.items.itemYPos(index), 0, int(self.height()/2))
def resizeEvent(self, event: QResizeEvent) -> None:
super().resizeEvent(event)
self.__refreshItems()
def scrollContentsBy (self, dx: int, dy: int) -> None:
super().scrollContentsBy(dx, dy)
self.__refreshItems()
def setItems (self, items: SrollAreaItemList) -> None:
self.__reset()
self.items = items
self.widget().setFixedHeight(self.items.height())
self.__refreshItems()
def __reset (self) -> None:
for w in self.activeWidgets.values():
w.close()
self.activeWidgets.clear()
for wlist in self.reservedWidgets.values():
for w in wlist:
w.close()
self.reservedWidgets.clear()
def __refreshItems (self) -> None:
if not self.items:
return
y = self.verticalScrollBar().value()
size = self.size()
width = size.width()
height = size.height()
# Iterate all widgets, those which are no longer visible are returned under their class name to
# the map self.reservedWidgets for future use.
inactive: List[int] = []
for ident, w in self.activeWidgets.items():
wg = w.geometry()
if not doLinesIntersect (y, height, wg.top(), wg.height()):
self.reservedWidgets[w.__class__].append(w)
inactive.append(ident)
for ident in inactive:
del self.activeWidgets[ident]
for itemY, item in self.items.visibleItems (y, height):
margin = self.__getScrollViewWidthMargin()
if not item.id in self.activeWidgets:
reserve = self.reservedWidgets[item.getType()]
if reserve:
w = reserve.pop()
else:
# No element left, create a new one
w = item.generateItem (self.widget())
w.setAttribute(Qt.WA_DeleteOnClose)
item.configureItem(w)
w.move(self.items.spacing, itemY)
w.setFixedSize(width-margin, item.height)
w.show()
self.activeWidgets[item.id] = w
else:
self.activeWidgets[item.id].setFixedWidth(width-margin)
def __getScrollViewWidthMargin (self) -> int:
# Again not so nice. Without adding 7 pixels the text edit is too close to the scrollbar
if not self.items:
return 0
width: int = 2*self.items.spacing+7+self.verticalScrollBar().width()
return width
def main() -> None:
import sys
from PyQt5.QtWidgets import QApplication
app = QApplication(sys.argv)
items = SrollAreaItemList()
for i in range(1000):
labelItem = Labeltem("%u" % (i+1, ), False, 14)
items.addItem(labelItem)
w = RecyclingVerticalScrollArea(None)
w.setItems(items)
w.show()
sys.exit(app.exec_())
if __name__ == "__main__":
main()
