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""" Provides bracket matching for Q[Plain]TextEdit widgets.
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"""
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# System library imports
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from PyQt4 import QtCore, QtGui
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class BracketMatcher(QtCore.QObject):
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""" Matches square brackets, braces, and parentheses based on cursor
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position.
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"""
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# Protected class variables.
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_opening_map = { '(':')', '{':'}', '[':']' }
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_closing_map = { ')':'(', '}':'{', ']':'[' }
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#--------------------------------------------------------------------------
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# 'QObject' interface
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#--------------------------------------------------------------------------
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def __init__(self, parent):
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""" Create a call tip manager that is attached to the specified Qt
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text edit widget.
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"""
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assert isinstance(parent, (QtGui.QTextEdit, QtGui.QPlainTextEdit))
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QtCore.QObject.__init__(self, parent)
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# The format to apply to matching brackets.
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self.format = QtGui.QTextCharFormat()
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self.format.setBackground(QtGui.QColor('silver'))
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parent.cursorPositionChanged.connect(self._cursor_position_changed)
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#--------------------------------------------------------------------------
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# Protected interface
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#--------------------------------------------------------------------------
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def _find_match(self, position):
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""" Given a valid position in the text document, try to find the
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position of the matching bracket. Returns -1 if unsuccessful.
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"""
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# Decide what character to search for and what direction to search in.
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document = self.parent().document()
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qchar = document.characterAt(position)
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start_char = qchar.toAscii()
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search_char = self._opening_map.get(start_char)
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if search_char:
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increment = 1
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else:
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search_char = self._closing_map.get(start_char)
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if search_char:
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increment = -1
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else:
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return -1
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# Search for the character.
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depth = 0
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while position >= 0 and position < document.characterCount():
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char = qchar.toAscii()
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if char == start_char:
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depth += 1
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elif char == search_char:
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depth -= 1
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if depth == 0:
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break
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position += increment
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qchar = document.characterAt(position)
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else:
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position = -1
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return position
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def _selection_for_character(self, position):
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""" Convenience method for selecting a character.
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"""
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selection = QtGui.QTextEdit.ExtraSelection()
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cursor = self.parent().textCursor()
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cursor.setPosition(position)
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cursor.movePosition(QtGui.QTextCursor.NextCharacter,
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QtGui.QTextCursor.KeepAnchor)
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selection.cursor = cursor
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selection.format = self.format
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return selection
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#------ Signal handlers ----------------------------------------------------
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def _cursor_position_changed(self):
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""" Updates the document formatting based on the new cursor position.
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"""
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# Clear out the old formatting.
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text_edit = self.parent()
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text_edit.setExtraSelections([])
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# Attempt to match a bracket for the new cursor position.
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cursor = text_edit.textCursor()
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if not cursor.hasSelection():
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position = cursor.position() - 1
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match_position = self._find_match(position)
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if match_position != -1:
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extra_selections = [ self._selection_for_character(pos)
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for pos in (position, match_position) ]
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text_edit.setExtraSelections(extra_selections)
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