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""" Provides bracket matching for Q[Plain]TextEdit widgets.
"""
# System library imports
from qtpy import QtCore, QtGui, QtWidgets
class BracketMatcher(QtCore.QObject):
""" Matches square brackets, braces, and parentheses based on cursor
position.
"""
# Protected class variables.
_opening_map = { '(':')', '{':'}', '[':']' }
_closing_map = { ')':'(', '}':'{', ']':'[' }
#--------------------------------------------------------------------------
# 'QObject' interface
#--------------------------------------------------------------------------
def __init__(self, text_edit):
""" Create a call tip manager that is attached to the specified Qt
text edit widget.
"""
assert isinstance(text_edit, (QtWidgets.QTextEdit, QtWidgets.QPlainTextEdit))
super().__init__()
# The format to apply to matching brackets.
self.format = QtGui.QTextCharFormat()
self.format.setBackground(QtGui.QColor('silver'))
self._text_edit = text_edit
text_edit.cursorPositionChanged.connect(self._cursor_position_changed)
#--------------------------------------------------------------------------
# Protected interface
#--------------------------------------------------------------------------
def _find_match(self, position):
""" Given a valid position in the text document, try to find the
position of the matching bracket. Returns -1 if unsuccessful.
"""
# Decide what character to search for and what direction to search in.
document = self._text_edit.document()
start_char = document.characterAt(position)
search_char = self._opening_map.get(start_char)
if search_char:
increment = 1
else:
search_char = self._closing_map.get(start_char)
if search_char:
increment = -1
else:
return -1
# Search for the character.
char = start_char
depth = 0
while position >= 0 and position < document.characterCount():
if char == start_char:
depth += 1
elif char == search_char:
depth -= 1
if depth == 0:
break
position += increment
char = document.characterAt(position)
else:
position = -1
return position
def _selection_for_character(self, position):
""" Convenience method for selecting a character.
"""
selection = QtWidgets.QTextEdit.ExtraSelection()
cursor = self._text_edit.textCursor()
cursor.setPosition(position)
cursor.movePosition(QtGui.QTextCursor.NextCharacter,
QtGui.QTextCursor.KeepAnchor)
selection.cursor = cursor
selection.format = self.format
return selection
#------ Signal handlers ----------------------------------------------------
def _cursor_position_changed(self):
""" Updates the document formatting based on the new cursor position.
"""
# Clear out the old formatting.
self._text_edit.setExtraSelections([])
# Attempt to match a bracket for the new cursor position.
cursor = self._text_edit.textCursor()
if not cursor.hasSelection():
position = cursor.position() - 1
match_position = self._find_match(position)
if match_position != -1:
extra_selections = [ self._selection_for_character(pos)
for pos in (position, match_position) ]
self._text_edit.setExtraSelections(extra_selections)
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