Syntax Highlighting

This example shows how to write a syntax-highlighted editor with Qt and Lark

Requirements:

PyQt5==5.15.8 QScintilla==2.13.4

import sys
import textwrap

from PyQt5.QtWidgets import QApplication
from PyQt5.QtGui import QColor, QFont, QFontMetrics

from PyQt5.Qsci import QsciScintilla
from PyQt5.Qsci import QsciLexerCustom

from lark import Lark


class LexerJson(QsciLexerCustom):

    def __init__(self, parent=None):
        super().__init__(parent)
        self.create_parser()
        self.create_styles()

    def create_styles(self):
        deeppink = QColor(249, 38, 114)
        khaki = QColor(230, 219, 116)
        mediumpurple = QColor(174, 129, 255)
        mediumturquoise = QColor(81, 217, 205)
        yellowgreen = QColor(166, 226, 46)
        lightcyan = QColor(213, 248, 232)
        darkslategrey = QColor(39, 40, 34)

        styles = {
            0: mediumturquoise,
            1: mediumpurple,
            2: yellowgreen,
            3: deeppink,
            4: khaki,
            5: lightcyan
        }

        for style, color in styles.items():
            self.setColor(color, style)
            self.setPaper(darkslategrey, style)
            self.setFont(self.parent().font(), style)

        self.token_styles = {
            "COLON": 5,
            "COMMA": 5,
            "LBRACE": 5,
            "LSQB": 5,
            "RBRACE": 5,
            "RSQB": 5,
            "FALSE": 0,
            "NULL": 0,
            "TRUE": 0,
            "STRING": 4,
            "NUMBER": 1,
        }

    def create_parser(self):
        grammar = '''
            anons: ":" "{" "}" "," "[" "]"
            TRUE: "true"
            FALSE: "false"
            NULL: "NULL"
            %import common.ESCAPED_STRING -> STRING
            %import common.SIGNED_NUMBER  -> NUMBER
            %import common.WS
            %ignore WS
        '''

        self.lark = Lark(grammar, parser=None, lexer='basic')
        # All tokens: print([t.name for t in self.lark.parser.lexer.tokens])

    def defaultPaper(self, style):
        return QColor(39, 40, 34)

    def language(self):
        return "Json"

    def description(self, style):
        return {v: k for k, v in self.token_styles.items()}.get(style, "")

    def styleText(self, start, end):
        self.startStyling(start)
        text = self.parent().text()[start:end]
        last_pos = 0

        try:
            for token in self.lark.lex(text):
                ws_len = token.start_pos - last_pos
                if ws_len:
                    self.setStyling(ws_len, 0)    # whitespace

                token_len = len(bytearray(token, "utf-8"))
                self.setStyling(
                    token_len, self.token_styles.get(token.type, 0))

                last_pos = token.start_pos + token_len
        except Exception as e:
            print(e)


class EditorAll(QsciScintilla):

    def __init__(self, parent=None):
        super().__init__(parent)

        # Set font defaults
        font = QFont()
        font.setFamily('Consolas')
        font.setFixedPitch(True)
        font.setPointSize(8)
        font.setBold(True)
        self.setFont(font)

        # Set margin defaults
        fontmetrics = QFontMetrics(font)
        self.setMarginsFont(font)
        self.setMarginWidth(0, fontmetrics.width("000") + 6)
        self.setMarginLineNumbers(0, True)
        self.setMarginsForegroundColor(QColor(128, 128, 128))
        self.setMarginsBackgroundColor(QColor(39, 40, 34))
        self.setMarginType(1, self.SymbolMargin)
        self.setMarginWidth(1, 12)

        # Set indentation defaults
        self.setIndentationsUseTabs(False)
        self.setIndentationWidth(4)
        self.setBackspaceUnindents(True)
        self.setIndentationGuides(True)

        # self.setFolding(QsciScintilla.CircledFoldStyle)

        # Set caret defaults
        self.setCaretForegroundColor(QColor(247, 247, 241))
        self.setCaretWidth(2)

        # Set selection color defaults
        self.setSelectionBackgroundColor(QColor(61, 61, 52))
        self.resetSelectionForegroundColor()

        # Set multiselection defaults
        self.SendScintilla(QsciScintilla.SCI_SETMULTIPLESELECTION, True)
        self.SendScintilla(QsciScintilla.SCI_SETMULTIPASTE, 1)
        self.SendScintilla(
            QsciScintilla.SCI_SETADDITIONALSELECTIONTYPING, True)

        lexer = LexerJson(self)
        self.setLexer(lexer)


EXAMPLE_TEXT = textwrap.dedent("""\
        {
            "_id": "5b05ffcbcf8e597939b3f5ca",
            "about": "Excepteur consequat commodo esse voluptate aute aliquip ad sint deserunt commodo eiusmod irure. Sint aliquip sit magna duis eu est culpa aliqua excepteur ut tempor nulla. Aliqua ex pariatur id labore sit. Quis sit ex aliqua veniam exercitation laboris anim adipisicing. Lorem nisi reprehenderit ullamco labore qui sit ut aliqua tempor consequat pariatur proident.",
            "address": "665 Malbone Street, Thornport, Louisiana, 243",
            "age": 23,
            "balance": "$3,216.91",
            "company": "BULLJUICE",
            "email": "elisekelley@bulljuice.com",
            "eyeColor": "brown",
            "gender": "female",
            "guid": "d3a6d865-0f64-4042-8a78-4f53de9b0707",
            "index": 0,
            "isActive": false,
            "isActive2": true,
            "latitude": -18.660714,
            "longitude": -85.378048,
            "name": "Elise Kelley",
            "phone": "+1 (808) 543-3966",
            "picture": "http://placehold.it/32x32",
            "registered": "2017-09-30T03:47:40 -02:00",
            "tags": [
                "et",
                "nostrud",
                "in",
                "fugiat",
                "incididunt",
                "labore",
                "nostrud"
            ]
        }\
    """)

def main():
    app = QApplication(sys.argv)
    ex = EditorAll()
    ex.setWindowTitle(__file__)
    ex.setText(EXAMPLE_TEXT)
    ex.resize(800, 600)
    ex.show()
    sys.exit(app.exec_())


if __name__ == "__main__":
    main()