Way to save QTextEdit scroll state?

[Rivridis]

Is there any way the scroll state of QTextEdit be saved to a local file or within code itself? I tried taking scrollbar position, but it gets reset while switching between files. I set up a QTextEdit to load a EPUB file's content when a element in QTreeview is doubleclicked. It works once and stops working after a while.
Or, is there any alternate way to load EPUB files that will make it easier?

from PySide6.QtWidgets import QApplication, QDialog, QVBoxLayout,QMessageBox,QLineEdit,QPushButton,QMainWindow,QSplashScreen,QFileDialog,QTreeView,QFileSystemModel,QTextBrowser,QTextEdit
from PySide6.QtGui import QPixmap,QTextCharFormat,QFont,QTextCursor,QColor
from PySide6.QtCore import Qt
from PySide6.QtUiTools import QUiLoader
import sys
from ebooklib import epub
from bs4 import BeautifulSoup
import qdarktheme
import hashlib
import time
scroll_positions = {}
qss = """
        QScrollBar::sub-page:horizontal {
        background: rgba(255, 255, 255, 0)
    }

    QScrollBar::add-page:horizontal {
        background: rgba(255, 255, 255, 0)
    }
    QScrollBar::sub-page:vertical {
        background: rgba(255, 255, 255, 0)
    }

    QScrollBar::add-page:vertical {
        background: rgba(255, 255, 255, 0)
    }
    QScrollBar::handle
    {
        background : rgba(138,124,171,1);
        min-height: 40px;
    }
    QScrollBar::handle:vertical
    {
        background : rgba(138,124,171,1);
        min-height: 40px;
    }
    QScrollBar::handle::pressed
    {
    background : rgba(138,124,171,1); 
    }
    QScrollBar::handle::hover
    {
    background : rgba(138,124,171,1);
    }
    QScrollBar::add-line,
    QScrollBar::sub-line {
        width: 0;
        subcontrol-position: right;
        subcontrol-origin: margin;
    }


    """

def show_splash_screen():
    splash_pix = QPixmap('assets\splash.jpg')
    splash_pix = splash_pix.scaled(550, 450, Qt.KeepAspectRatio,Qt.SmoothTransformation)
    splash = QSplashScreen(splash_pix, Qt.WindowStaysOnTopHint)
    splash.setMask(splash_pix.mask())
    splash.show()

    return splash

def main():
    app = QApplication(sys.argv)
    qdarktheme.setup_theme(additional_qss=qss,custom_colors={
        "[dark]": {
            "primary": "#D0BCFF",
            "border": "#00000000",
            "treeSectionHeader.background":"#8a7cab"
        }
    })

    # Create and show splash screen
    splash = show_splash_screen()
    main_window = Main()
    splash.close()

    main_window.children()[1].show()

    sys.exit(app.exec())

class Main(QMainWindow):
    def __init__(self):
        super().__init__()
        self.current_file_hash = None
        loader = QUiLoader()
        ui_file = "assets/main.ui" 
        ui = loader.load(ui_file, self)

        self.directory = ui.findChild(QPushButton,"direct")
        self.directory.clicked.connect(self.dirpop)

        self.tree = ui.findChild(QTreeView,"tree") 

        self.model = QFileSystemModel()
        self.model.setRootPath("/")
        self.tree.setModel(self.model)
        self.tree.setRootIndex(self.model.index("/"))

        self.tree.doubleClicked.connect(self.choose)

        self.text = ui.findChild(QTextEdit,'text')
        self.text.setReadOnly(True)
        self.scroll_bar = self.text.verticalScrollBar()


    def dirpop(self):
        options = QFileDialog.Options()
        directory = QFileDialog.getExistingDirectory(self, "Select Directory", "", options=options)

        if directory:
            self.tree.setRootIndex(self.model.index(directory))
    
    def generate_file_hash(self, content):
        sha256 = hashlib.sha256()
        sha256.update(content.encode('utf-8'))
        return sha256.hexdigest()
    
    def choose(self, index):
        file_path = self.model.filePath(index)
        if ".epub" in file_path:
            # Save the current scroll position
            if self.current_file_hash:
                scroll_positions[self.current_file_hash] = self.text.verticalScrollBar().value()

            book = epub.read_epub(file_path)
            content = ""
            for item in book.items:
                if isinstance(item, epub.EpubHtml):
                    content += item.content.decode('utf-8')
            styled_content = f"""
            <html>
                <head>
                    <style>
                        body 
                        {{
                            color: rgb(255, 255, 255);
                            font-size: 16px;
                            background-color: rgba(26, 26, 29, 1);
                        }}
                    </style>
                </head>
                <body>
                    {content}
                </body>
            </html>
            """
            self.text.setHtml(styled_content)

            # Generate a unique hash for the current file
            self.current_file_hash = self.generate_file_hash(content)

            # Restore the scroll position if available
            if self.current_file_hash in scroll_positions:
                self.text.verticalScrollBar().setValue(scroll_positions[self.current_file_hash])
            print(scroll_positions)
        else:
            QMessageBox.information(self, "Invalid filetype","Please choose another file")

if __name__ == "__main__":
    main()

[JonB]

@Rivridis said in Way to save QTextEdit scroll state?:

And for the files that does not work, the position gets shifted to around 1000 everytime

If it were me, I would try moving the

self.text.verticalScrollBar().setValue(scroll_positions[self.current_file_hash])

into a single shot QTimer with 0 or small delay after you have done the self.text.setHtml(styled_content).

[JonB]

@Rivridis said in Way to save QTextEdit scroll state?:

I tried taking scrollbar position, but it gets reset while switching between files.

Aren't you supposed to restore it after loading the file then?

[Rivridis]

@JonB That's what I did, as seen from the code, the thing is, it works for one fixed file and does not work for the others.

[JonB]

@Rivridis
Then I would guess you might have some issue in your "hash lookup" of each file? Use a debugger or more print() statements. For all the files where "it does not work", what is the saved scroll position, what are you restoring and where does to fail to work?

[Rivridis]

@JonB The hash function is not the issue, as I checked the printed dictionary value. And for the files that does not work, the position gets shifted to around 1000 everytime

[SGaist]

Did you try to update the position in reaction to textChanged rather than directly after setting the new content ?

[Rivridis]

@SGaist Yup, tried that, its not working either. I have now switched to textcursor methods but now the problem is of setting the textcursor to bottom of QTextEdit viewport.

[JonB]

@Rivridis said in Way to save QTextEdit scroll state?:

And for the files that does not work, the position gets shifted to around 1000 everytime

If it were me, I would try moving the

self.text.verticalScrollBar().setValue(scroll_positions[self.current_file_hash])

into a single shot QTimer with 0 or small delay after you have done the self.text.setHtml(styled_content).

[Rivridis]

@JonB Damn it works, thanks a lot. I had been trying to solve this for a day straight :/ Just needed 100 as time delay, small values did not work

[JonB]

@Rivridis
Anything "visual" like scroll position, size, cursor position, focus you need to leave it to draw itself once after e.g. setHtml(), because they get reset or need recalculating.