import sys
from PyQt4.QtCore import *
from PyQt4.QtGui import *

BYTES_PER_LINE, GAP = 8, 12

def clamp(minimum, x, maximum):
   return max(minimum, min(x, maximum))

def asciiChar(v):
   if v < 0x20 or v > 0x7e:
      return '.'
   else:
      return chr(v)

class BinViewer(QWidget):
   """ The view has an address, hex byte and ascii column """
   def __init__(self, scrollArea):
      super().__init__(scrollArea)
      self.scrollArea = scrollArea
      self.setFont(QFont('Courier', 18))
      self.setFocusPolicy(Qt.StrongFocus)
      self.blinkcursor = False
      self.cursorX = self.cursorY = 0
      self.scrollArea = scrollArea
      self.Data = bytearray()
      self.Offset = 0
      t = QTimer(self)
      t.timeout.connect(self.updateCursor)
      t.setInterval(500)
      t.start()
   def updateCursor(self):
      self.blinkcursor = not self.blinkcursor
      self.update(self.cursorX, self.cursorY, self.charWidth, self.charHeight)
   def setCursorPosition(self, position):
      position = clamp(0, int(position), len(self.Data) * 2 - 1)
      self.cursorPosition = position
      x = position % (2 * BYTES_PER_LINE)
      x = x + int(x / 2) # Create a gap between hex values
      self.cursorX = self.xposHex + x * self.charWidth
      y = int(position / (2 * BYTES_PER_LINE))
      self.cursorY = y * self.charHeight + 2
      self.blinkcursor = True
      self.update()
   def getCursorPosition(self):
      return self.cursorPosition
   CursorPosition = property(getCursorPosition, setCursorPosition)
   def setOffset(self, off):
      self.offset = off
      self.update()
   Offset = property(lambda self: self.offset, setOffset)
   def paintEvent(self, event):
      # Helper variables:
      er = event.rect()
      chw, chh = self.charWidth, self.charHeight
      painter = QPainter(self)
      # Background:
      painter.fillRect(er, self.palette().color(QPalette.Base))
      painter.fillRect(QRect(self.xposAddr, er.top(), 8 * chw, er.bottom() + 1), Qt.gray)
      painter.setPen(Qt.gray)
      x = self.xposAscii - (GAP / 2)
      painter.drawLine(x, er.top(), x, er.bottom())
      x = self.xposEnd - (GAP / 2)
      painter.drawLine(x, er.top(), x, er.bottom())
      # first and last index
      firstIndex = max((int(er.top() / chh) - chh) * BYTES_PER_LINE, 0)
      lastIndex = max((int(er.bottom() / chh) + chh) * BYTES_PER_LINE, 0)
      yposStart = int(firstIndex / BYTES_PER_LINE) * chh + chh
      # Draw contents:
      painter.setPen(Qt.black)
      ypos = yposStart
      for index in range(firstIndex, lastIndex, BYTES_PER_LINE):
         painter.drawText(self.xposAddr, ypos, '{0:08X}'.format(index + self.Offset))
         xpos = self.xposHex
         xposAscii = self.xposAscii
         for colIndex in range(BYTES_PER_LINE):
            if index + colIndex < len(self.Data):
               b = self.Data[index + colIndex]
               painter.drawText(xpos, ypos, '{0:02X}'.format(b))
               painter.drawText(xposAscii, ypos, asciiChar(b))
               xpos += 3 * chw
               xposAscii += chw
         ypos += chh
      # cursor
      if self.blinkcursor:
         painter.fillRect(self.cursorX, self.cursorY + chh - 2, chw, 2, Qt.black)
   def keyPressEvent(self, event):
      if event.matches(QKeySequence.MoveToNextChar):
         self.CursorPosition += 1
      if event.matches(QKeySequence.MoveToPreviousChar):
         self.CursorPosition -= 1
      if event.matches(QKeySequence.MoveToNextLine):
         self.CursorPosition += 2 * BYTES_PER_LINE
      if event.matches(QKeySequence.MoveToPreviousLine):
         self.CursorPosition -= 2 * BYTES_PER_LINE
      if event.matches(QKeySequence.MoveToNextPage):
         rows = int(self.scrollArea.viewport().height() / self.charHeight)
         self.CursorPosition += (rows - 1) * 2 * BYTES_PER_LINE
      if event.matches(QKeySequence.MoveToPreviousPage):
         rows = int(self.scrollArea.viewport().height() / self.charHeight)
         self.CursorPosition -= (rows - 1) * 2 * BYTES_PER_LINE
      char = event.text().lower()
      if char and char in '0123456789abcdef':
         i = int(self.CursorPosition / 2)
         hb = self.CursorPosition % 2
         v = int(char, 16)
         if hb == 0:
            # high half byte
            self.data[i] = (self.data[i] & 0xF) | (v << 4)
         else:
            self.data[i] = (self.data[i] & 0xF0) | v
         self.CursorPosition += 1
      self.scrollArea.ensureVisible(self.cursorX, self.cursorY + self.charHeight / 2, 4, self.charHeight / 2 + 4)
      self.update()
   def setCursorPositionAt(self, pos):
      """ Calculate cursor position at a certain point """
      if pos.x() > self.xposHex and pos.x() < self.xposAscii:
         x = round((2 * (pos.x() - self.xposHex)) / (self.charWidth * 3))
         y = int(pos.y() / self.charHeight) * 2 * BYTES_PER_LINE
         self.setCursorPosition(x + y)
   def mousePressEvent(self, event):
      self.setCursorPositionAt(event.pos())
   def adjust(self):
      self.charHeight = self.fontMetrics().height()
      self.charWidth = self.fontMetrics().width('x')
      self.xposAddr = GAP
      self.xposHex = self.xposAddr + 8 * self.charWidth + GAP
      self.xposAscii = self.xposHex + (BYTES_PER_LINE * 3 - 1) * self.charWidth + GAP
      self.xposEnd = self.xposAscii + self.charWidth * BYTES_PER_LINE + GAP
      self.setMinimumWidth(self.xposEnd)
      sbw = self.scrollArea.verticalScrollBar().width()
      self.scrollArea.setMinimumWidth(self.xposEnd + sbw + 5)
      r = len(self.Data) % BYTES_PER_LINE
      r = 1 if r > 0 else 0
      self.setMinimumHeight((int(len(self.Data) / BYTES_PER_LINE) + r) * self.charHeight + 4)
      self.scrollArea.setMinimumHeight(self.charHeight * 8)
      self.update()
   def setData(self, d):
      self.data = d
      self.adjust()
      self.setCursorPosition(0)
   Data = property(lambda self: self.data, setData)

class HexEdit(QScrollArea):
   def __init__(self):
      super().__init__()
      self.bv = BinViewer(self)
      self.setWidget(self.bv)
      self.setWidgetResizable(True)
      self.setVerticalScrollBarPolicy(Qt.ScrollBarAlwaysOn)
      self.setFocusPolicy(Qt.NoFocus)

if __name__ == '__main__':
   app = QApplication(sys.argv)
   he = HexEdit()
   he.show()
   he.bv.Data = bytearray(range(100)) * 8 + b'x'
   app.exec()