eric6/HexEdit/HexEditWidget.py

Sat, 27 Feb 2021 12:08:23 +0100

author
Detlev Offenbach <detlev@die-offenbachs.de>
date
Sat, 27 Feb 2021 12:08:23 +0100
changeset 8138
169e65a6787c
parent 7923
91e843545d9a
child 8143
2c730d5fd177
permissions
-rw-r--r--

Shell: added functionality to show a prompt when the main client process has exited (e.g. a script ended).

# -*- coding: utf-8 -*-

# Copyright (c) 2016 - 2021 Detlev Offenbach <detlev@die-offenbachs.de>
#

"""
Module implementing an editor for binary data.
"""

import math

from PyQt5.QtCore import (
    pyqtSignal, pyqtSlot, Qt, QByteArray, QTimer, QRect, QBuffer, QIODevice
)
from PyQt5.QtGui import (
    QBrush, QPen, QColor, QFont, QPalette, QKeySequence, QPainter
)
from PyQt5.QtWidgets import QAbstractScrollArea, QApplication

from .HexEditChunks import HexEditChunks
from .HexEditUndoStack import HexEditUndoStack

import Globals


class HexEditWidget(QAbstractScrollArea):
    """
    Class implementing an editor for binary data.
    
    @signal currentAddressChanged(address) emitted to indicate the new
        cursor position
    @signal currentSizeChanged(size) emitted to indicate the new size of
        the data
    @signal dataChanged(modified) emitted to indicate a change of the data
    @signal overwriteModeChanged(state) emitted to indicate a change of
        the overwrite mode
    @signal readOnlyChanged(state) emitted to indicate a change of the
        read only state
    @signal canRedoChanged(bool) emitted after the redo status has changed
    @signal canUndoChanged(bool) emitted after the undo status has changed
    @signal selectionAvailable(bool) emitted to signal a change of the
        selection
    """
    currentAddressChanged = pyqtSignal(int)
    currentSizeChanged = pyqtSignal(int)
    dataChanged = pyqtSignal(bool)
    overwriteModeChanged = pyqtSignal(bool)
    readOnlyChanged = pyqtSignal(bool)
    canRedoChanged = pyqtSignal(bool)
    canUndoChanged = pyqtSignal(bool)
    selectionAvailable = pyqtSignal(bool)
    
    HEXCHARS_PER_LINE = 47
    BYTES_PER_LINE = 16
    
    def __init__(self, parent=None):
        """
        Constructor
        
        @param parent refernce to the parent widget
        @type QWidget
        """
        super(HexEditWidget, self).__init__(parent)
        
        # Properties
        self.__addressArea = True
        # switch the address area on/off
        self.__addressAreaBrush = QBrush()
        self.__addressAreaPen = QPen()
        # background and pen of the address area
        self.__addressOffset = 0
        # offset into the shown address range
        self.__addressWidth = 4
        # address area width in characters
        self.__asciiArea = True
        # switch the ASCII area on/off
        self.__data = bytearray()
        # contents of the hex editor
        self.__highlighting = True
        # switch the highlighting feature on/off
        self.__highlightingBrush = QBrush()
        self.__highlightingPen = QPen()
        # background and pen of highlighted text
        self.__overwriteMode = True
        # set overwrite mode on/off
        self.__selectionBrush = QBrush()
        self.__selectionPen = QPen()
        # background and pen of selected text
        self.__readOnly = False
        # set read only mode on/off
        self.__cursorPosition = 0
        # absolute position of cursor, 1 Byte == 2 tics
        
        self.__addrDigits = 0
        self.__addrSeparators = 0
        self.__blink = True
        self.__bData = QBuffer()
        self.__cursorRect = QRect()
        self.__cursorRectAscii = QRect()
        self.__dataShown = bytearray()
        self.__hexDataShown = bytearray()
        self.__lastEventSize = 0
        self.__markedShown = bytearray()
        self.__modified = False
        self.__rowsShown = 0
        
        # pixel related attributes (starting with __px)
        self.__pxCharWidth = 0
        self.__pxCharHeight = 0
        self.__pxPosHexX = 0
        self.__pxPosAdrX = 0
        self.__pxPosAsciiX = 0
        self.__pxGapAdr = 0
        self.__pxGapAdrHex = 0
        self.__pxGapHexAscii = 0
        self.__pxSelectionSub = 0
        self.__pxCursorWidth = 0
        self.__pxCursorX = 0
        self.__pxCursorY = 0
        
        # absolute byte position related attributes (starting with __b)
        self.__bSelectionBegin = 0
        self.__bSelectionEnd = 0
        self.__bSelectionInit = 0
        self.__bPosFirst = 0
        self.__bPosLast = 0
        self.__bPosCurrent = 0
        
        self.__chunks = HexEditChunks()
        self.__undoStack = HexEditUndoStack(self.__chunks, self)
        if Globals.isWindowsPlatform():
            self.setFont(QFont("Courier", 10))
        else:
            self.setFont(QFont("Monospace", 10))
        
        self.setAddressAreaColors(
            self.palette().color(QPalette.WindowText),
            self.palette().alternateBase().color())
        self.setHighlightColors(
            self.palette().color(QPalette.WindowText),
            QColor(0xff, 0xff, 0x99, 0xff))
        self.setSelectionColors(
            self.palette().highlightedText().color(),
            self.palette().highlight().color())
        
        self.__cursorTimer = QTimer()
        self.__cursorTimer.timeout.connect(self.__updateCursor)
        
        self.verticalScrollBar().valueChanged.connect(self.__adjust)
        
        self.__undoStack.indexChanged.connect(self.__dataChangedPrivate)
        self.__undoStack.canRedoChanged.connect(self.__canRedoChanged)
        self.__undoStack.canUndoChanged.connect(self.__canUndoChanged)
        
        self.readOnlyChanged.connect(self.__canRedoChanged)
        self.readOnlyChanged.connect(self.__canUndoChanged)
        
        self.__cursorTimer.setInterval(500)
        self.__cursorTimer.start()
        
        self.setAddressWidth(4)
        self.setAddressArea(True)
        self.setAsciiArea(True)
        self.setOverwriteMode(True)
        self.setHighlighting(True)
        self.setReadOnly(False)
        
        self.__initialize()
    
    def undoStack(self):
        """
        Public method to get a reference to the undo stack.
        
        @return reference to the undo stack
        @rtype HexEditUndoStack
        """
        return self.__undoStack
    
    @pyqtSlot()
    def __canRedoChanged(self):
        """
        Private slot handling changes of the Redo state.
        """
        self.canRedoChanged.emit(
            self.__undoStack.canRedo() and not self.__readOnly)
    
    @pyqtSlot()
    def __canUndoChanged(self):
        """
        Private slot handling changes of the Undo state.
        """
        self.canUndoChanged.emit(
            self.__undoStack.canUndo() and not self.__readOnly)
    
    def addressArea(self):
        """
        Public method to get the address area visibility.
        
        @return flag indicating the address area visibility
        @rtype bool
        """
        return self.__addressArea
    
    def setAddressArea(self, on):
        """
        Public method to set the address area visibility.
        
        @param on flag indicating the address area visibility
        @type bool
        """
        self.__addressArea = on
        self.__adjust()
        self.setCursorPosition(self.__cursorPosition)
        self.viewport().update()
    
    def addressAreaColors(self):
        """
        Public method to get the address area colors.
        
        @return address area foreground and background colors
        @rtype tuple of 2 QColor
        """
        return self.__addressAreaPen.color(), self.__addressAreaBrush.color()
    
    def setAddressAreaColors(self, foreground, background):
        """
        Public method to set the address area colors.
        
        @param foreground address area foreground color
        @type QColor
        @param background address area background color
        @type QColor
        """
        self.__addressAreaPen = QPen(foreground)
        self.__addressAreaBrush = QBrush(background)
        self.viewport().update()
    
    def addressOffset(self):
        """
        Public method to get the address offset.
        
        @return address offset
        @rtype int
        """
        return self.__addressOffset
    
    def setAddressOffset(self, offset):
        """
        Public method to set the address offset.
        
        @param offset address offset
        @type int
        """
        self.__addressOffset = offset
        self.__adjust()
        self.setCursorPosition(self.__cursorPosition)
        self.viewport().update()
    
    def addressWidth(self):
        """
        Public method to get the width of the address area in
        characters.
        
        Note: The address area width is always a multiple of four.
        
        @return minimum width of the address area
        @rtype int
        """
        size = self.__chunks.size()
        n = 1
        if size > 0x100000000:
            n += 8
            size //= 0x100000000
        if size > 0x10000:
            n += 4
            size //= 0x10000
        if size > 0x100:
            n += 2
            size //= 0x100
        if size > 0x10:
            n += 1
            size //= 0x10
        n = int(math.ceil(n / 4)) * 4
        
        if n > self.__addressWidth:
            return n
        else:
            return self.__addressWidth
    
    def setAddressWidth(self, width):
        """
        Public method to set the width of the address area.
        
        Note: The address area width is always a multiple of four.
        The given value will be adjusted as required.
        
        @param width width of the address area in characters
        @type int
        """
        self.__addressWidth = int(math.ceil(width / 4)) * 4
        self.__adjust()
        self.setCursorPosition(self.__cursorPosition)
        self.viewport().update()
    
    def asciiArea(self):
        """
        Public method to get the visibility of the ASCII area.
        
        @return visibility of the ASCII area
        @rtype bool
        """
        return self.__asciiArea
    
    def setAsciiArea(self, on):
        """
        Public method to set the visibility of the ASCII area.
        
        @param on flag indicating the visibility of the ASCII area
        @type bool
        """
        self.__asciiArea = on
        self.viewport().update()
    
    def cursorPosition(self):
        """
        Public method to get the cursor position.
        
        @return cursor position
        @rtype int
        """
        return self.__cursorPosition
    
    def setCursorPosition(self, pos):
        """
        Public method to set the cursor position.
        
        @param pos cursor position
        @type int
        """
        # step 1: delete old cursor
        self.__blink = False
        self.viewport().update(self.__cursorRect)
        if self.__asciiArea:
            self.viewport().update(self.__cursorRectAscii)
        
        # step 2: check, if cursor is in range
        if self.__overwriteMode and pos > (self.__chunks.size() * 2 - 1):
            pos = self.__chunks.size() * 2 - 1
        if (not self.__overwriteMode) and pos > (self.__chunks.size() * 2):
            pos = self.__chunks.size() * 2
        if pos < 0:
            pos = 0
        
        # step 3: calculate new position of cursor
        self.__cursorPosition = pos
        self.__bPosCurrent = pos // 2
        self.__pxCursorY = (
            ((pos // 2 - self.__bPosFirst) // self.BYTES_PER_LINE + 1) *
            self.__pxCharHeight)
        x = (pos % (2 * self.BYTES_PER_LINE))
        self.__pxCursorX = (
            (((x // 2) * 3) + (x % 2)) * self.__pxCharWidth + self.__pxPosHexX)
        
        self.__setHexCursorRect()
        
        # step 4: calculate position of ASCII cursor
        x = self.__bPosCurrent % self.BYTES_PER_LINE
        self.__cursorRectAscii = QRect(
            self.__pxPosAsciiX + x * self.__pxCharWidth - 1,
            self.__pxCursorY - self.__pxCharHeight + 4,
            self.__pxCharWidth + 1, self.__pxCharHeight + 1)
        
        # step 5: draw new cursors
        self.__blink = True
        self.viewport().update(self.__cursorRect)
        if self.__asciiArea:
            self.viewport().update(self.__cursorRectAscii)
        self.currentAddressChanged.emit(self.__bPosCurrent)
    
    def __setHexCursorRect(self):
        """
        Private method to set the cursor.
        """
        if self.__overwriteMode:
            self.__cursorRect = QRect(
                self.__pxCursorX, self.__pxCursorY + self.__pxCursorWidth,
                self.__pxCharWidth, self.__pxCursorWidth)
        else:
            self.__cursorRect = QRect(
                self.__pxCursorX, self.__pxCursorY - self.__pxCharHeight + 4,
                self.__pxCursorWidth, self.__pxCharHeight)
    
    def cursorBytePosition(self):
        """
        Public method to get the cursor position in bytes.
        
        @return cursor position in bytes
        @rtype int
        """
        return self.__bPosCurrent
    
    def setCursorBytePosition(self, pos):
        """
        Public method to set the cursor position in bytes.
        
        @param pos cursor position in bytes
        @type int
        """
        self.setCursorPosition(pos * 2)
    
    def goto(self, offset, fromCursor=False, backwards=False,
             extendSelection=False):
        """
        Public method to move the cursor.
        
        @param offset offset to move to
        @type int
        @param fromCursor flag indicating a move relative to the current cursor
        @type bool
        @param backwards flag indicating a backwards move
        @type bool
        @param extendSelection flag indicating to extend the selection
        @type bool
        """
        if fromCursor:
            if backwards:
                newPos = self.cursorBytePosition() - offset
            else:
                newPos = self.cursorBytePosition() + offset
        else:
            if backwards:
                newPos = self.__chunks.size() - offset
            else:
                newPos = offset
        
        self.setCursorBytePosition(newPos)
        if extendSelection:
            self.__setSelection(self.__cursorPosition)
        else:
            self.__resetSelection(self.__cursorPosition)
        
        self.__refresh()
    
    def data(self):
        """
        Public method to get the binary data.
        
        @return binary data
        @rtype bytearray
        """
        return self.__chunks.data(0, -1)
    
    def setData(self, dataOrDevice):
        """
        Public method to set the data to show.
        
        @param dataOrDevice byte array or device containing the data
        @type bytearray, QByteArray or QIODevice
        @return flag indicating success
        @rtype bool
        @exception TypeError raised to indicate a wrong parameter type
        """
        if isinstance(dataOrDevice, (bytearray, QByteArray)):
            self.__data = bytearray(dataOrDevice)
            self.__bData.setData(self.__data)
            return self.__setData(self.__bData)
        elif isinstance(dataOrDevice, QIODevice):
            return self.__setData(dataOrDevice)
        else:
            raise TypeError(
                "setData: parameter must be bytearray, "
                "QByteArray or QIODevice")
    
    def __setData(self, ioDevice):
        """
        Private method to set the data to show.
        
        @param ioDevice device containing the data
        @type QIODevice
        @return flag indicating success
        @rtype bool
        """
        ok = self.__chunks.setIODevice(ioDevice)
        self.__initialize()
        self.__dataChangedPrivate()
        return ok
    
    def highlighting(self):
        """
        Public method to get the highlighting state.
        
        @return highlighting state
        @rtype bool
        """
        return self.__highlighting
    
    def setHighlighting(self, on):
        """
        Public method to set the highlighting state.
        
        @param on new highlighting state
        @type bool
        """
        self.__highlighting = on
        self.viewport().update()
    
    def highlightColors(self):
        """
        Public method to get the highlight colors.
        
        @return highlight foreground and background colors
        @rtype tuple of 2 QColor
        """
        return self.__highlightingPen.color(), self.__highlightingBrush.color()
    
    def setHighlightColors(self, foreground, background):
        """
        Public method to set the highlight colors.
        
        @param foreground highlight foreground color
        @type QColor
        @param background highlight background color
        @type QColor
        """
        self.__highlightingPen = QPen(foreground)
        self.__highlightingBrush = QBrush(background)
        self.viewport().update()
    
    def overwriteMode(self):
        """
        Public method to get the overwrite mode.
        
        @return overwrite mode
        @rtype bool
        """
        return self.__overwriteMode
    
    def setOverwriteMode(self, on):
        """
        Public method to set the overwrite mode.
        
        @param on flag indicating the new overwrite mode
        @type bool
        """
        self.__overwriteMode = on
        self.overwriteModeChanged.emit(self.__overwriteMode)
        
        # step 1: delete old cursor
        self.__blink = False
        self.viewport().update(self.__cursorRect)
        # step 2: change the cursor rectangle
        self.__setHexCursorRect()
        # step 3: draw new cursors
        self.__blink = True
        self.viewport().update(self.__cursorRect)
    
    def selectionColors(self):
        """
        Public method to get the selection colors.
        
        @return selection foreground and background colors
        @rtype tuple of 2 QColor
        """
        return self.__selectionPen.color(), self.__selectionBrush.color()
    
    def setSelectionColors(self, foreground, background):
        """
        Public method to set the selection colors.
        
        @param foreground selection foreground color
        @type QColor
        @param background selection background color
        @type QColor
        """
        self.__selectionPen = QPen(foreground)
        self.__selectionBrush = QBrush(background)
        self.viewport().update()
    
    def isReadOnly(self):
        """
        Public method to test the read only state.
        
        @return flag indicating the read only state
        @rtype bool
        """
        return self.__readOnly
    
    def setReadOnly(self, on):
        """
        Public method to set the read only state.
        
        @param on new read only state
        @type bool
        """
        self.__readOnly = on
        self.readOnlyChanged.emit(self.__readOnly)
    
    def font(self):
        """
        Public method to get the font used to show the data.
        
        @return font used to show the data
        @rtype QFont
        """
        return super(HexEditWidget, self).font()
    
    def setFont(self, font):
        """
        Public method to set the font used to show the data.
        
        @param font font used to show the data
        @type QFont
        """
        super(HexEditWidget, self).setFont(font)
        try:
            self.__pxCharWidth = self.fontMetrics().horizontalAdvance("2")
        except AttributeError:
            self.__pxCharWidth = self.fontMetrics().width("2")
        self.__pxCharHeight = self.fontMetrics().height()
        self.__pxGapAdr = self.__pxCharWidth // 2
        self.__pxGapAdrHex = self.__pxCharWidth
        self.__pxGapHexAscii = 2 * self.__pxCharWidth
        self.__pxCursorWidth = self.__pxCharHeight // 7
        self.__pxSelectionSub = self.fontMetrics().descent()
        self.__adjust()
        self.viewport().update()
    
    def dataAt(self, pos, count=-1):
        """
        Public method to get data from a given position.
        
        @param pos position to get data from
        @type int
        @param count amount of bytes to get
        @type int
        @return requested data
        @rtype bytearray
        """
        return bytearray(self.__chunks.data(pos, count))
    
    def write(self, device, pos=0, count=-1):
        """
        Public method to write data from a given position to a device.
        
        @param device device to write to
        @type QIODevice
        @param pos position to start the write at
        @type int
        @param count amount of bytes to write
        @type int
        @return flag indicating success
        @rtype bool
        """
        return self.__chunks.write(device, pos, count)
    
    def insert(self, pos, ch):
        """
        Public method to insert a byte.
        
        @param pos position to insert the byte at
        @type int
        @param ch byte to insert
        @type int in the range 0x00 to 0xff
        """
        if ch in range(0, 256):
            self.__undoStack.insert(pos, ch)
            self.__refresh()
    
    def remove(self, pos, length=1):
        """
        Public method to remove bytes.
        
        @param pos position to remove bytes from
        @type int
        @param length amount of bytes to remove
        @type int
        """
        self.__undoStack.removeAt(pos, length)
        self.__refresh()
    
    def replace(self, pos, ch):
        """
        Public method to replace a byte.
        
        @param pos position to replace the byte at
        @type int
        @param ch byte to replace with
        @type int in the range 0x00 to 0xff
        """
        if ch in range(0, 256):
            self.__undoStack.overwrite(pos, ch)
            self.__refresh()
    
    def insertByteArray(self, pos, byteArray):
        """
        Public method to insert bytes.
        
        @param pos position to insert the bytes at
        @type int
        @param byteArray bytes to be insert
        @type bytearray or QByteArray
        """
        self.__undoStack.insertByteArray(pos, bytearray(byteArray))
        self.__refresh()
    
    def replaceByteArray(self, pos, length, byteArray):
        """
        Public method to replace bytes.
        
        @param pos position to replace the bytes at
        @type int
        @param length amount of bytes to replace
        @type int
        @param byteArray bytes to replace with
        @type bytearray or QByteArray
        """
        self.__undoStack.overwriteByteArray(pos, length, bytearray(byteArray))
        self.__refresh()
    
    def cursorPositionFromPoint(self, point):
        """
        Public method to calculate a cursor position from a graphics position.
        
        @param point graphics position
        @type QPoint
        @return cursor position
        @rtype int
        """
        result = -1
        if (point.x() >= self.__pxPosHexX) and (
            point.x() < (self.__pxPosHexX + (1 + self.HEXCHARS_PER_LINE) *
                         self.__pxCharWidth)):
            x = (
                (point.x() - self.__pxPosHexX - self.__pxCharWidth // 2) //
                self.__pxCharWidth
            )
            x = (x // 3) * 2 + x % 3
            y = (
                ((point.y() - 3) // self.__pxCharHeight) * 2 *
                self.BYTES_PER_LINE
            )
            result = self.__bPosFirst * 2 + x + y
        return result
    
    def ensureVisible(self):
        """
        Public method to ensure, that the cursor is visible.
        """
        if self.__cursorPosition < 2 * self.__bPosFirst:
            self.verticalScrollBar().setValue(
                self.__cursorPosition // 2 // self.BYTES_PER_LINE)
        if self.__cursorPosition > (
            (self.__bPosFirst + (self.__rowsShown - 1) *
             self.BYTES_PER_LINE) * 2):
            self.verticalScrollBar().setValue(
                self.__cursorPosition // 2 // self.BYTES_PER_LINE -
                self.__rowsShown + 1)
        self.viewport().update()
    
    def indexOf(self, byteArray, start):
        """
        Public method to find the first occurrence of a byte array in our data.
        
        @param byteArray data to search for
        @type bytearray or QByteArray
        @param start start position of the search
        @type int
        @return position of match (or -1 if not found)
        @rtype int
        """
        byteArray = bytearray(byteArray)
        pos = self.__chunks.indexOf(byteArray, start)
        if pos > -1:
            curPos = pos * 2
            self.setCursorPosition(curPos + len(byteArray) * 2)
            self.__resetSelection(curPos)
            self.__setSelection(curPos + len(byteArray) * 2)
            self.ensureVisible()
        return pos
    
    def lastIndexOf(self, byteArray, start):
        """
        Public method to find the last occurrence of a byte array in our data.
        
        @param byteArray data to search for
        @type bytearray or QByteArray
        @param start start position of the search
        @type int
        @return position of match (or -1 if not found)
        @rtype int
        """
        byteArray = bytearray(byteArray)
        pos = self.__chunks.lastIndexOf(byteArray, start)
        if pos > -1:
            curPos = pos * 2
            self.setCursorPosition(curPos - 1)
            self.__resetSelection(curPos)
            self.__setSelection(curPos + len(byteArray) * 2)
            self.ensureVisible()
        return pos
    
    def isModified(self):
        """
        Public method to check for any modification.
        
        @return flag indicating a modified state
        @rtype bool
        """
        return self.__modified
    
    def setModified(self, modified, setCleanState=False):
        """
        Public slot to set the modified flag.
        
        @param modified flag indicating the new modification status
        @type bool
        @param setCleanState flag indicating to set the undo stack to clean
        @type bool
        """
        self.__modified = modified
        self.dataChanged.emit(modified)
        
        if not modified and setCleanState:
            self.__undoStack.setClean()
    
    def selectionToHexString(self):
        """
        Public method to get a hexadecimal representation of the selection.
        
        @return hexadecimal representation of the selection
        @rtype str
        """
        byteArray = self.__chunks.data(self.getSelectionBegin(),
                                       self.getSelectionLength())
        return self.__toHex(byteArray).decode(encoding="ascii")
    
    def selectionToReadableString(self):
        """
        Public method to get a formatted representation of the selection.
        
        @return formatted representation of the selection
        @rtype str
        """
        byteArray = self.__chunks.data(self.getSelectionBegin(),
                                       self.getSelectionLength())
        return self.__toReadable(byteArray)
    
    def toReadableString(self):
        """
        Public method to get a formatted representation of our data.
        
        @return formatted representation of our data
        @rtype str
        """
        byteArray = self.__chunks.data()
        return self.__toReadable(byteArray)
    
    @pyqtSlot()
    def redo(self):
        """
        Public slot to redo the last operation.
        """
        self.__undoStack.redo()
        self.setCursorPosition(self.__chunks.pos() * 2)
        self.__refresh()
    
    @pyqtSlot()
    def undo(self):
        """
        Public slot to undo the last operation.
        """
        self.__undoStack.undo()
        self.setCursorPosition(self.__chunks.pos() * 2)
        self.__refresh()
    
    @pyqtSlot()
    def revertToUnmodified(self):
        """
        Public slot to revert all changes.
        """
        cleanIndex = self.__undoStack.cleanIndex()
        if cleanIndex >= 0:
            self.__undoStack.setIndex(cleanIndex)
        self.setCursorPosition(self.__chunks.pos() * 2)
        self.__refresh()
    
    ####################################################
    ## Cursor movement commands
    ####################################################
    
    def moveCursorToNextChar(self):
        """
        Public method to move the cursor to the next byte.
        """
        self.setCursorPosition(self.__cursorPosition + 1)
        self.__resetSelection(self.__cursorPosition)
    
    def moveCursorToPreviousChar(self):
        """
        Public method to move the cursor to the previous byte.
        """
        self.setCursorPosition(self.__cursorPosition - 1)
        self.__resetSelection(self.__cursorPosition)
    
    def moveCursorToEndOfLine(self):
        """
        Public method to move the cursor to the end of the current line.
        """
        self.setCursorPosition(self.__cursorPosition |
                               (2 * self.BYTES_PER_LINE - 1))
        self.__resetSelection(self.__cursorPosition)
    
    def moveCursorToStartOfLine(self):
        """
        Public method to move the cursor to the beginning of the current line.
        """
        self.setCursorPosition(
            self.__cursorPosition -
            (self.__cursorPosition % (2 * self.BYTES_PER_LINE)))
        self.__resetSelection(self.__cursorPosition)
    
    def moveCursorToPreviousLine(self):
        """
        Public method to move the cursor to the previous line.
        """
        self.setCursorPosition(self.__cursorPosition - 2 * self.BYTES_PER_LINE)
        self.__resetSelection(self.__cursorPosition)
    
    def moveCursorToNextLine(self):
        """
        Public method to move the cursor to the next line.
        """
        self.setCursorPosition(self.__cursorPosition + 2 * self.BYTES_PER_LINE)
        self.__resetSelection(self.__cursorPosition)
    
    def moveCursorToNextPage(self):
        """
        Public method to move the cursor to the next page.
        """
        self.setCursorPosition(
            self.__cursorPosition +
            (self.__rowsShown - 1) * 2 * self.BYTES_PER_LINE)
        self.__resetSelection(self.__cursorPosition)
    
    def moveCursorToPreviousPage(self):
        """
        Public method to move the cursor to the previous page.
        """
        self.setCursorPosition(
            self.__cursorPosition -
            (self.__rowsShown - 1) * 2 * self.BYTES_PER_LINE)
        self.__resetSelection(self.__cursorPosition)
    
    def moveCursorToEndOfDocument(self):
        """
        Public method to move the cursor to the end of the data.
        """
        self.setCursorPosition(self.__chunks.size() * 2)
        self.__resetSelection(self.__cursorPosition)
    
    def moveCursorToStartOfDocument(self):
        """
        Public method to move the cursor to the start of the data.
        """
        self.setCursorPosition(0)
        self.__resetSelection(self.__cursorPosition)
    
    ####################################################
    ## Selection commands
    ####################################################
    
    def deselectAll(self):
        """
        Public method to deselect all data.
        """
        self.__resetSelection(0)
        self.__refresh()
    
    def selectAll(self):
        """
        Public method to select all data.
        """
        self.__resetSelection(0)
        self.__setSelection(2 * self.__chunks.size() + 1)
        self.__refresh()
    
    def selectNextChar(self):
        """
        Public method to extend the selection by one byte right.
        """
        pos = self.__cursorPosition + 1
        self.setCursorPosition(pos)
        self.__setSelection(pos)
    
    def selectPreviousChar(self):
        """
        Public method to extend the selection by one byte left.
        """
        pos = self.__cursorPosition - 1
        self.setCursorPosition(pos)
        self.__setSelection(pos)
    
    def selectToEndOfLine(self):
        """
        Public method to extend the selection to the end of line.
        """
        pos = (
            self.__cursorPosition -
            (self.__cursorPosition % (2 * self.BYTES_PER_LINE)) +
            2 * self.BYTES_PER_LINE
        )
        self.setCursorPosition(pos)
        self.__setSelection(pos)
    
    def selectToStartOfLine(self):
        """
        Public method to extend the selection to the start of line.
        """
        pos = (
            self.__cursorPosition -
            (self.__cursorPosition % (2 * self.BYTES_PER_LINE))
        )
        self.setCursorPosition(pos)
        self.__setSelection(pos)
    
    def selectPreviousLine(self):
        """
        Public method to extend the selection one line up.
        """
        pos = self.__cursorPosition - 2 * self.BYTES_PER_LINE
        self.setCursorPosition(pos)
        self.__setSelection(pos)
    
    def selectNextLine(self):
        """
        Public method to extend the selection one line down.
        """
        pos = self.__cursorPosition + 2 * self.BYTES_PER_LINE
        self.setCursorPosition(pos)
        self.__setSelection(pos)
    
    def selectNextPage(self):
        """
        Public method to extend the selection one page down.
        """
        pos = (
            self.__cursorPosition +
            ((self.viewport().height() // self.__pxCharHeight) - 1) *
            2 * self.BYTES_PER_LINE
        )
        self.setCursorPosition(pos)
        self.__setSelection(pos)
    
    def selectPreviousPage(self):
        """
        Public method to extend the selection one page up.
        """
        pos = (
            self.__cursorPosition -
            ((self.viewport().height() // self.__pxCharHeight) - 1) *
            2 * self.BYTES_PER_LINE
        )
        self.setCursorPosition(pos)
        self.__setSelection(pos)
    
    def selectEndOfDocument(self):
        """
        Public method to extend the selection to the end of the data.
        """
        pos = self.__chunks.size() * 2
        self.setCursorPosition(pos)
        self.__setSelection(pos)
    
    def selectStartOfDocument(self):
        """
        Public method to extend the selection to the start of the data.
        """
        pos = 0
        self.setCursorPosition(pos)
        self.__setSelection(pos)
    
    ####################################################
    ## Edit commands
    ####################################################
    
    def cut(self):
        """
        Public method to cut the selected bytes and move them to the clipboard.
        """
        if not self.__readOnly:
            byteArray = self.__toHex(self.__chunks.data(
                self.getSelectionBegin(), self.getSelectionLength()))
            idx = 32
            while idx < len(byteArray):
                byteArray.insert(idx, "\n")
                idx += 33
            cb = QApplication.clipboard()
            cb.setText(byteArray.decode(encoding="latin1"))
            if self.__overwriteMode:
                length = self.getSelectionLength()
                self.replaceByteArray(self.getSelectionBegin(), length,
                                      bytearray(length))
            else:
                self.remove(self.getSelectionBegin(),
                            self.getSelectionLength())
            self.setCursorPosition(2 * self.getSelectionBegin())
            self.__resetSelection(2 * self.getSelectionBegin())
    
    def copy(self):
        """
        Public method to copy the selected bytes to the clipboard.
        """
        byteArray = self.__toHex(self.__chunks.data(
            self.getSelectionBegin(), self.getSelectionLength()))
        idx = 32
        while idx < len(byteArray):
            byteArray.insert(idx, "\n")
            idx += 33
        cb = QApplication.clipboard()
        cb.setText(byteArray.decode(encoding="latin1"))
    
    def paste(self):
        """
        Public method to paste bytes from the clipboard.
        """
        if not self.__readOnly:
            cb = QApplication.clipboard()
            byteArray = self.__fromHex(cb.text().encode(encoding="latin1"))
            if self.__overwriteMode:
                self.replaceByteArray(self.__bPosCurrent, len(byteArray),
                                      byteArray)
            else:
                self.insertByteArray(self.__bPosCurrent, byteArray)
            self.setCursorPosition(
                self.__cursorPosition + 2 * len(byteArray))
            self.__resetSelection(2 * self.getSelectionBegin())
    
    def deleteByte(self):
        """
        Public method to delete the current byte.
        """
        if not self.__readOnly:
            if self.hasSelection():
                self.__bPosCurrent = self.getSelectionBegin()
                if self.__overwriteMode:
                    byteArray = bytearray(self.getSelectionLength())
                    self.replaceByteArray(self.__bPosCurrent, len(byteArray),
                                          byteArray)
                else:
                    self.remove(self.__bPosCurrent,
                                self.getSelectionLength())
            else:
                if self.__overwriteMode:
                    self.replace(self.__bPosCurrent, 0)
                else:
                    self.remove(self.__bPosCurrent, 1)
            self.setCursorPosition(2 * self.__bPosCurrent)
            self.__resetSelection(2 * self.__bPosCurrent)
    
    def deleteByteBack(self):
        """
        Public method to delete the previous byte.
        """
        if not self.__readOnly:
            if self.hasSelection():
                self.__bPosCurrent = self.getSelectionBegin()
                self.setCursorPosition(2 * self.__bPosCurrent)
                if self.__overwriteMode:
                    byteArray = bytearray(self.getSelectionLength())
                    self.replaceByteArray(self.__bPosCurrent, len(byteArray),
                                          byteArray)
                else:
                    self.remove(self.__bPosCurrent,
                                self.getSelectionLength())
            else:
                self.__bPosCurrent -= 1
                if self.__overwriteMode:
                    self.replace(self.__bPosCurrent, 0)
                else:
                    self.remove(self.__bPosCurrent, 1)
                self.setCursorPosition(2 * self.__bPosCurrent)
            self.__resetSelection(2 * self.__bPosCurrent)
    
    ####################################################
    ## Event handling methods
    ####################################################
    
    def keyPressEvent(self, evt):
        """
        Protected method to handle key press events.
        
        @param evt reference to the key event
        @type QKeyEvent
        """
        # Cursor movements
        if evt.matches(QKeySequence.MoveToNextChar):
            self.moveCursorToNextChar()
        elif evt.matches(QKeySequence.MoveToPreviousChar):
            self.moveCursorToPreviousChar()
        elif evt.matches(QKeySequence.MoveToEndOfLine):
            self.moveCursorToEndOfLine()
        elif evt.matches(QKeySequence.MoveToStartOfLine):
            self.moveCursorToStartOfLine()
        elif evt.matches(QKeySequence.MoveToPreviousLine):
            self.moveCursorToPreviousLine()
        elif evt.matches(QKeySequence.MoveToNextLine):
            self.moveCursorToNextLine()
        elif evt.matches(QKeySequence.MoveToNextPage):
            self.moveCursorToNextPage()
        elif evt.matches(QKeySequence.MoveToPreviousPage):
            self.moveCursorToPreviousPage()
        elif evt.matches(QKeySequence.MoveToEndOfDocument):
            self.moveCursorToEndOfDocument()
        elif evt.matches(QKeySequence.MoveToStartOfDocument):
            self.moveCursorToStartOfDocument()
        
        # Selection commands
        elif evt.matches(QKeySequence.SelectAll):
            self.selectAll()
        elif evt.matches(QKeySequence.SelectNextChar):
            self.selectNextChar()
        elif evt.matches(QKeySequence.SelectPreviousChar):
            self.selectPreviousChar()
        elif evt.matches(QKeySequence.SelectEndOfLine):
            self.selectToEndOfLine()
        elif evt.matches(QKeySequence.SelectStartOfLine):
            self.selectToStartOfLine()
        elif evt.matches(QKeySequence.SelectPreviousLine):
            self.selectPreviousLine()
        elif evt.matches(QKeySequence.SelectNextLine):
            self.selectNextLine()
        elif evt.matches(QKeySequence.SelectNextPage):
            self.selectNextPage()
        elif evt.matches(QKeySequence.SelectPreviousPage):
            self.selectPreviousPage()
        elif evt.matches(QKeySequence.SelectEndOfDocument):
            self.selectEndOfDocument()
        elif evt.matches(QKeySequence.SelectStartOfDocument):
            self.selectStartOfDocument()
        
        # Edit commands
        elif evt.matches(QKeySequence.Copy):
            self.copy()
        elif (
            evt.key() == Qt.Key_Insert and
            evt.modifiers() == Qt.NoModifier
        ):
            self.setOverwriteMode(not self.overwriteMode())
            self.setCursorPosition(self.__cursorPosition)
        
        elif not self.__readOnly:
            if evt.matches(QKeySequence.Cut):
                self.cut()
            elif evt.matches(QKeySequence.Paste):
                self.paste()
            elif evt.matches(QKeySequence.Delete):
                self.deleteByte()
            elif (
                evt.key() == Qt.Key_Backspace and
                evt.modifiers() == Qt.NoModifier
            ):
                self.deleteByteBack()
            elif evt.matches(QKeySequence.Undo):
                self.undo()
            elif evt.matches(QKeySequence.Redo):
                self.redo()
            
            elif QApplication.keyboardModifiers() in [
                    Qt.NoModifier, Qt.KeypadModifier]:
                # some hex input
                key = evt.text()
                if key and key in "0123456789abcdef":
                    if self.hasSelection():
                        if self.__overwriteMode:
                            length = self.getSelectionLength()
                            self.replaceByteArray(
                                self.getSelectionBegin(), length,
                                bytearray(length))
                        else:
                            self.remove(self.getSelectionBegin(),
                                        self.getSelectionLength())
                            self.__bPosCurrent = self.getSelectionBegin()
                        self.setCursorPosition(2 * self.__bPosCurrent)
                        self.__resetSelection(2 * self.__bPosCurrent)
                    
                    # if in insert mode, insert a byte
                    if not self.__overwriteMode:
                        if (self.__cursorPosition % 2) == 0:
                            self.insert(self.__bPosCurrent, 0)
                    
                    # change content
                    if self.__chunks.size() > 0:
                        hexValue = self.__toHex(
                            self.__chunks.data(self.__bPosCurrent, 1))
                        if (self.__cursorPosition % 2) == 0:
                            hexValue[0] = ord(key)
                        else:
                            hexValue[1] = ord(key)
                        self.replace(self.__bPosCurrent,
                                     self.__fromHex(hexValue)[0])
                        
                        self.setCursorPosition(self.__cursorPosition + 1)
                        self.__resetSelection(self.__cursorPosition)
                    else:
                        return
                else:
                    return
            else:
                return
        else:
            return
        
        self.__refresh()
    
    def mouseMoveEvent(self, evt):
        """
        Protected method to handle mouse moves.
        
        @param evt reference to the mouse event
        @type QMouseEvent
        """
        self.__blink = False
        self.viewport().update()
        actPos = self.cursorPositionFromPoint(evt.pos())
        if actPos >= 0:
            self.setCursorPosition(actPos)
            self.__setSelection(actPos)
    
    def mousePressEvent(self, evt):
        """
        Protected method to handle mouse button presses.
        
        @param evt reference to the mouse event
        @type QMouseEvent
        """
        self.__blink = False
        self.viewport().update()
        cPos = self.cursorPositionFromPoint(evt.pos())
        if cPos >= 0:
            if evt.modifiers() == Qt.ShiftModifier:
                self.__setSelection(cPos)
            else:
                self.__resetSelection(cPos)
            self.setCursorPosition(cPos)
    
    def paintEvent(self, evt):
        """
        Protected method to handle paint events.
        
        @param evt reference to the paint event
        @type QPaintEvent
        """
        painter = QPainter(self.viewport())
        
        if (
            evt.rect() != self.__cursorRect and
            evt.rect() != self.__cursorRectAscii
        ):
            pxOfsX = self.horizontalScrollBar().value()
            pxPosStartY = self.__pxCharHeight
            
            # draw some patterns if needed
            painter.fillRect(
                evt.rect(), self.viewport().palette().color(QPalette.Base))
            if self.__addressArea:
                painter.fillRect(
                    QRect(-pxOfsX, evt.rect().top(),
                          self.__pxPosHexX - self.__pxGapAdrHex // 2 - pxOfsX,
                          self.height()),
                    self.__addressAreaBrush)
            if self.__asciiArea:
                linePos = self.__pxPosAsciiX - (self.__pxGapHexAscii // 2)
                painter.setPen(Qt.gray)
                painter.drawLine(linePos - pxOfsX, evt.rect().top(),
                                 linePos - pxOfsX, self.height())
            
            painter.setPen(
                self.viewport().palette().color(QPalette.WindowText))
            
            # paint the address area
            if self.__addressArea:
                painter.setPen(self.__addressAreaPen)
                address = ""
                row = 0
                pxPosY = self.__pxCharHeight
                while row <= len(self.__dataShown) // self.BYTES_PER_LINE:
                    address = "{0:0{1}x}".format(
                        self.__bPosFirst + row * self.BYTES_PER_LINE,
                        self.__addrDigits)
                    address = Globals.strGroup(address, ":", 4)
                    painter.drawText(self.__pxPosAdrX - pxOfsX, pxPosY,
                                     address)
                    # increment loop variables
                    row += 1
                    pxPosY += self.__pxCharHeight
            
            # paint hex and ascii area
            colStandard = QPen(
                self.viewport().palette().color(QPalette.WindowText))
            
            painter.setBackgroundMode(Qt.TransparentMode)
            
            row = 0
            pxPosY = pxPosStartY
            while row <= self.__rowsShown:
                pxPosX = self.__pxPosHexX - pxOfsX
                pxPosAsciiX2 = self.__pxPosAsciiX - pxOfsX
                bPosLine = row * self.BYTES_PER_LINE
                
                colIdx = 0
                while (
                    bPosLine + colIdx < len(self.__dataShown) and
                    colIdx < self.BYTES_PER_LINE
                ):
                    c = self.viewport().palette().color(QPalette.Base)
                    painter.setPen(colStandard)
                    
                    posBa = self.__bPosFirst + bPosLine + colIdx
                    if (
                        self.getSelectionBegin() <= posBa and
                        self.getSelectionEnd() > posBa
                    ):
                        c = self.__selectionBrush.color()
                        painter.setPen(self.__selectionPen)
                    elif self.__highlighting:
                        if self.__markedShown and self.__markedShown[
                                posBa - self.__bPosFirst]:
                            c = self.__highlightingBrush.color()
                            painter.setPen(self.__highlightingPen)
                    
                    # render hex value
                    r = QRect()
                    if colIdx == 0:
                        r.setRect(
                            pxPosX,
                            pxPosY - self.__pxCharHeight +
                            self.__pxSelectionSub,
                            2 * self.__pxCharWidth,
                            self.__pxCharHeight)
                    else:
                        r.setRect(
                            pxPosX - self.__pxCharWidth,
                            pxPosY - self.__pxCharHeight +
                            self.__pxSelectionSub,
                            3 * self.__pxCharWidth,
                            self.__pxCharHeight)
                    painter.fillRect(r, c)
                    hexStr = (
                        chr(self.__hexDataShown[(bPosLine + colIdx) * 2]) +
                        chr(self.__hexDataShown[(bPosLine + colIdx) * 2 + 1])
                    )
                    painter.drawText(pxPosX, pxPosY, hexStr)
                    pxPosX += 3 * self.__pxCharWidth
                    
                    # render ascii value
                    if self.__asciiArea:
                        by = self.__dataShown[bPosLine + colIdx]
                        if by < 0x20 or (by > 0x7e and by < 0xa0):
                            ch = "."
                        else:
                            ch = chr(by)
                        r.setRect(
                            pxPosAsciiX2,
                            pxPosY - self.__pxCharHeight +
                            self.__pxSelectionSub,
                            self.__pxCharWidth,
                            self.__pxCharHeight)
                        painter.fillRect(r, c)
                        painter.drawText(pxPosAsciiX2, pxPosY, ch)
                        pxPosAsciiX2 += self.__pxCharWidth
                    
                    # increment loop variable
                    colIdx += 1
                
                # increment loop variables
                row += 1
                pxPosY += self.__pxCharHeight
        
        painter.setBackgroundMode(Qt.TransparentMode)
        painter.setPen(
            self.viewport().palette().color(QPalette.WindowText))
            
        # paint cursor
        if self.__blink and not self.__readOnly and self.isActiveWindow():
            painter.fillRect(
                self.__cursorRect, self.palette().color(QPalette.WindowText))
        else:
            if self.__hexDataShown:
                try:
                    c = chr(self.__hexDataShown[
                            self.__cursorPosition - self.__bPosFirst * 2])
                except IndexError:
                    c = ""
            else:
                c = ""
            painter.drawText(self.__pxCursorX, self.__pxCursorY, c)
        
        if self.__asciiArea:
            painter.drawRect(self.__cursorRectAscii)
        
        # emit event, if size has changed
        if self.__lastEventSize != self.__chunks.size():
            self.__lastEventSize = self.__chunks.size()
            self.currentSizeChanged.emit(self.__lastEventSize)
    
    def resizeEvent(self, evt):
        """
        Protected method to handle resize events.
        
        @param evt reference to the resize event
        @type QResizeEvent
        """
        self.__adjust()
    
    def __resetSelection(self, pos=None):
        """
        Private method to reset the selection.
        
        @param pos position to set selection start and end to
            (if this is None, selection end is set to selection start)
        @type int or None
        """
        if pos is None:
            self.__bSelectionBegin = self.__bSelectionInit
            self.__bSelectionEnd = self.__bSelectionInit
        else:
            if pos < 0:
                pos = 0
            pos = pos // 2
            self.__bSelectionInit = pos
            self.__bSelectionBegin = pos
            self.__bSelectionEnd = pos
        
        self.selectionAvailable.emit(False)
    
    def __setSelection(self, pos):
        """
        Private method to set the selection.
        
        @param pos position
        @type int
        """
        if pos < 0:
            pos = 0
        pos = pos // 2
        if pos >= self.__bSelectionInit:
            self.__bSelectionEnd = pos
            self.__bSelectionBegin = self.__bSelectionInit
        else:
            self.__bSelectionBegin = pos
            self.__bSelectionEnd = self.__bSelectionInit
        
        self.selectionAvailable.emit(True)
    
    def getSelectionBegin(self):
        """
        Public method to get the start of the selection.
        
        @return selection start
        @rtype int
        """
        return self.__bSelectionBegin
    
    def getSelectionEnd(self):
        """
        Public method to get the end of the selection.
        
        @return selection end
        @rtype int
        """
        return self.__bSelectionEnd
    
    def getSelectionLength(self):
        """
        Public method to get the length of the selection.
        
        @return selection length
        @rtype int
        """
        return self.__bSelectionEnd - self.__bSelectionBegin
    
    def hasSelection(self):
        """
        Public method to test for a selection.
        
        @return flag indicating the presence of a selection
        @rtype bool
        """
        return self.__bSelectionBegin != self.__bSelectionEnd
    
    def __initialize(self):
        """
        Private method to do some initialization.
        """
        self.__undoStack.clear()
        self.setAddressOffset(0)
        self.__resetSelection(0)
        self.setCursorPosition(0)
        self.verticalScrollBar().setValue(0)
        self.__modified = False
    
    def __readBuffers(self):
        """
        Private method to read the buffers.
        """
        self.__dataShown = self.__chunks.data(
            self.__bPosFirst,
            self.__bPosLast - self.__bPosFirst + self.BYTES_PER_LINE + 1,
            self.__markedShown
        )
        self.__hexDataShown = self.__toHex(self.__dataShown)
    
    def __toHex(self, byteArray):
        """
        Private method to convert the data of a Python bytearray to hex.
        
        @param byteArray byte array to be converted
        @type bytearray
        @return converted data
        @rtype bytearray
        """
        return bytearray(QByteArray(byteArray).toHex())
    
    def __fromHex(self, byteArray):
        """
        Private method to convert data of a Python bytearray from hex.
        
        @param byteArray byte array to be converted
        @type bytearray
        @return converted data
        @rtype bytearray
        """
        return bytearray(QByteArray.fromHex(byteArray))
        
    def __toReadable(self, byteArray):
        """
        Private method to convert some data into a readable format.
        
        @param byteArray data to be converted
        @type bytearray or QByteArray
        @return readable data
        @rtype str
        """
        byteArray = bytearray(byteArray)
        result = ""
        for i in range(0, len(byteArray), 16):
            addrStr = "{0:0{1}x}".format(self.__addressOffset + i,
                                         self.addressWidth())
            hexStr = ""
            ascStr = ""
            for j in range(16):
                if (i + j) < len(byteArray):
                    hexStr += " {0:02x}".format(byteArray[i + j])
                    by = byteArray[i + j]
                    if by < 0x20 or (by > 0x7e and by < 0xa0):
                        ch = "."
                    else:
                        ch = chr(by)
                    ascStr += ch
            result += "{0} {1:<48} {2:<17}\n".format(addrStr, hexStr, ascStr)
        return result
    
    @pyqtSlot()
    def __adjust(self):
        """
        Private slot to recalculate pixel positions.
        """
        # recalculate graphics
        if self.__addressArea:
            self.__addrDigits = self.addressWidth()
            self.__addrSeparators = self.__addrDigits // 4 - 1
            self.__pxPosHexX = (
                self.__pxGapAdr +
                (self.__addrDigits + self.__addrSeparators) *
                self.__pxCharWidth + self.__pxGapAdrHex)
        else:
            self.__pxPosHexX = self.__pxGapAdrHex
        self.__pxPosAdrX = self.__pxGapAdr
        self.__pxPosAsciiX = (
            self.__pxPosHexX +
            self.HEXCHARS_PER_LINE * self.__pxCharWidth +
            self.__pxGapHexAscii
        )
        
        # set horizontal scrollbar
        pxWidth = self.__pxPosAsciiX
        if self.__asciiArea:
            pxWidth += self.BYTES_PER_LINE * self.__pxCharWidth
        self.horizontalScrollBar().setRange(
            0, pxWidth - self.viewport().width())
        self.horizontalScrollBar().setPageStep(self.viewport().width())
        
        # set vertical scrollbar
        self.__rowsShown = (
            (self.viewport().height() - 4) // self.__pxCharHeight
        )
        lineCount = (self.__chunks.size() // self.BYTES_PER_LINE) + 1
        self.verticalScrollBar().setRange(0, lineCount - self.__rowsShown)
        self.verticalScrollBar().setPageStep(self.__rowsShown)
        
        # do the rest
        value = self.verticalScrollBar().value()
        self.__bPosFirst = value * self.BYTES_PER_LINE
        self.__bPosLast = (
            self.__bPosFirst + self.__rowsShown * self.BYTES_PER_LINE - 1
        )
        if self.__bPosLast >= self.__chunks.size():
            self.__bPosLast = self.__chunks.size() - 1
        self.__readBuffers()
        self.setCursorPosition(self.__cursorPosition)
    
    @pyqtSlot(int)
    def __dataChangedPrivate(self, idx=0):
        """
        Private slot to handle data changes.
        
        @param idx index
        @type int
        """
        self.__modified = (
            self.__undoStack.cleanIndex() == -1 or
            self.__undoStack.index() != self.__undoStack.cleanIndex())
        self.__adjust()
        self.dataChanged.emit(self.__modified)
    
    @pyqtSlot()
    def __refresh(self):
        """
        Private slot to refresh the display.
        """
        self.ensureVisible()
        self.__readBuffers()
    
    @pyqtSlot()
    def __updateCursor(self):
        """
        Private slot to update the blinking cursor.
        """
        self.__blink = not self.__blink
        self.viewport().update(self.__cursorRect)

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