PyQt5 - QSyntaxHighlighter not working properly

[Patitotective]

I'm using QSyntaxHighlighter to highlight a QTextEdit but it doesn't work if the QTextEdit has a text at start. It highlights all with a same color. If I instead of adding the whole text at once I add each character by character it works.
So not sure of which is the proper way to use a QSyntaxHighlighter.

Take a look at this minimal example:
Do uncomment 81, 93 and 84 lines and comment 80 line to see how it should look like.

import sys
import re
from PyQt5.QtGui import QBrush, QSyntaxHighlighter, QTextCharFormat, QColor, QPalette, QFont, QTextCursor, QTextLayout
from PyQt5.QtCore import Qt
from PyQt5.QtWidgets import QTextEdit, QMainWindow, QApplication

class MarkdownHighlighter(QSyntaxHighlighter):

    MARKDOWN_KEYS_REGEX = {
        'HeaderAtx': re.compile(u'(?u)^\#{1,6}(.*?)\#*(\n|$)'), # ## Header
    }

    def __init__(self, parent):
        super().__init__(parent)
        self.parent = parent
        parent.setTabStopWidth(parent.fontMetrics().width(' ') * 6)

        self.defaultTheme =  {
            "background-color":"#3e3d32", 
            "color":"#ffffff", 
            "header": {
                "color":"#fd971f", 
                "font-weight":"bold", 
                "font-style":"normal"
            }
        }
        
        self.setTheme(self.defaultTheme)

    def setTheme(self, theme):
        self.theme = theme
        self.MARKDOWN_KWS_FORMAT = {}

        pal = self.parent.palette()
        pal.setColor(QPalette.Base, QColor(theme['background-color']))
        self.parent.setPalette(pal)
        self.parent.setTextColor(QColor(theme['color']))

        text_char_format = QTextCharFormat()
        text_char_format.setForeground(QBrush(QColor(theme['header']['color'])))
        text_char_format.setFontWeight(QFont.Bold if theme['header']['font-weight']=='bold' else QFont.Normal)
        text_char_format.setFontItalic(True if theme['header']['font-style']=='italic' else False)
        self.MARKDOWN_KWS_FORMAT['HeaderAtx'] = text_char_format

        self.rehighlight()

    def highlightBlock(self, text):
        text = str(text)
        self.highlightMarkdown(text,0)

    def highlightMarkdown(self, text, strt):
        cursor = QTextCursor(self.document())
        bf = cursor.blockFormat()
        self.setFormat(0, len(text), QColor(self.theme['color']))

        if self.highlightAtxHeader(text, cursor, bf, strt):
            return

    def highlightEmptyLine(self, text, cursor, bf, strt):
        textAscii = str(text.replace(u'\u2029','\n'))
        if textAscii.strip():
            return False
        else:
            return True

    def highlightAtxHeader(self, text, cursor, bf, strt):
        found = False
        for mo in re.finditer(self.MARKDOWN_KEYS_REGEX['HeaderAtx'],text):
            #bf.setBackground(QBrush(QColor(7,54,65)))
            #cursor.movePosition(QTextCursor.End)
            #cursor.mergeBlockFormat(bf)
            self.setFormat(mo.start()+strt, mo.end() - mo.start(), self.MARKDOWN_KWS_FORMAT['HeaderAtx'])
            found = True
        return found

class MainWindow(QMainWindow):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

        text_edit = QTextEdit("## Some header<br>Some paragraph")
        # text_edit = QTextEdit("")

        # for char in "## Some header\nSome paragraph":
            # add_text_to_text_edit(text_edit, char)

        syntax_highlighter = MarkdownHighlighter(text_edit)

        self.setCentralWidget(text_edit)

        self.show()

def add_text_to_text_edit(text_edit: QTextEdit, text: str) -> None:
    current_text = text_edit.toPlainText()
    new_text = current_text + text

    text_edit.setPlainText(new_text)

if __name__ == "__main__":
    app = QApplication(sys.argv)
    
    main_window = MainWindow()

    sys.exit(app.exec_())

[eyllanesc]

@Patitotective Don't combine plain text not html. I think that in the first case it is happening that QTextEdit considers it to be plain text as opposed to the second that you explicitly consider to be plain text.

[SGaist]

Hi,

Did you already check the Syntax Highlighter Example ?

I think it provides a pretty good base that you can base your code on.

[eyllanesc]

@Patitotective Don't combine plain text not html. I think that in the first case it is happening that QTextEdit considers it to be plain text as opposed to the second that you explicitly consider to be plain text.

[Patitotective]

@SGaist I'll take a look at it, thanks 🙃

[Patitotective]

@eyllanesc Thanks, you were right 🙃
I did:

text_edit = QTextEdit()
text_edit.setPlainText(text)

Instead of:

text_edit = QTextEdit(text)

And it worked.