handle tabs correctly when highlighting text

With the old solution I replaced tabs with four spaces and then did
some calculations to get the correct byte positions for a coordinate.
With the new solution (using FontMetric.horizontalAdvance) this is not
necessary anymore and we can use tha native tab.
But I cannot change the tab width. It is always 8 characters.
You can set tabStopDistance on horizontalAdvance(), but not on
elided_text() and I did not find a way to use it while rendering text.

.envrc

@@ -0,0 +1 @@
+PATH=$(pwd)/venv312/bin:$PATH

constants.py

@@ -1,6 +1,7 @@
 import os
 
 krow_icon = "icons" + os.sep + "krowlog.svg"
+qt_icon = "icons" + os.sep + "qt-logo.png"
 license_file = os.path.dirname(os.path.realpath(__file__)) + os.sep + "LICENSE"
 changelog_file = os.path.dirname(os.path.realpath(__file__)) + os.sep + "changelog.txt"
 

src/plugins/krowlog/about_qt_dialog.py

@@ -0,0 +1,79 @@
+import textwrap
+
+import PySide6
+from PySide6.QtCore import Qt
+from PySide6.QtGui import QFont, QPalette
+from PySide6.QtWidgets import *
+
+import constants
+
+import krowlog
+from src.ui.icon import Icon
+from src.ui.label import Label
+from src.ui.vbox import VBox
+from src.i18n import _
+
+
+class AboutQTDialog(QDialog):
+    """Dialog for showing info about KrowLog"""
+
+    def __init__(self, parent=None):
+        super(AboutQTDialog, self).__init__(parent)
+        self.setWindowTitle(_("About QT"))
+        self.setModal(True)
+        # self.setMinimumWidth(850)
+        # self.setFixedHeight(400)
+
+        self.layout = QVBoxLayout(self)
+
+        text = f"""
+               <b>About QT</b>
+               <p>This program uses QT version {PySide6.QtCore.__version__}.</p>
+               
+               <p>QT is a C++ toolkit for cross-platform application development.</p>
+               
+               <p>Qt provides single-source portability across all major desktop 
+               operating systems. It is also available for embedded Linux and other 
+               embedded and mobile operating systems.</p>
+               
+               <p>Qt is available under multiple licensing options designed to accommodate 
+               the needs of our various users.</p>
+               
+               <p>Qt licensed under our commercial license agreement is appropriate for 
+               development of proprietary/commercial software where you do not want to 
+               share any source code with third parties or otherwise cannot comply with 
+               the terms of GNU (L)GPL.</p>
+               
+               <p>Qt licensed under GNU (L)GPL is appropriate for the development of Qt
+               applications provided you can comply with the terms and conditions of the 
+               respective licenses.</p>
+               
+               Please see <a href="http://qt.io/licensing">qt.io/licensing</a> for an<
+               overview of Qt licensing.
+               
+               <p>Copyright (C) 2025 The Qt Company Ltd and other contributors.</p>
+               
+               <p>Qt and the Qt logo are trademarks of The Qt Company Ltd.</p>
+               
+               <p>Qt is The Qt Company Ltd product developed as an open source project.
+               See <a href="http://qt.io">qt.io</a> for more information.</p>
+               """
+        label = Label(text)
+        label.setWordWrap(True)
+
+        app_icon = QLabel()
+        app_icon.setPixmap(Icon(constants.qt_icon).pixmap(64, 64))
+        heading = QWidget(self)
+        hbox = QHBoxLayout(heading)
+        hbox.addWidget(app_icon)
+        hbox.addWidget(label)
+        hbox.addSpacerItem(QSpacerItem(1, 1, hData=QSizePolicy.Policy.Expanding))
+
+        heading.layout = hbox
+        self.layout.addWidget(heading)
+
+        buttons = QDialogButtonBox(self)
+        buttons.setStandardButtons(QDialogButtonBox.StandardButton.Close)
+        buttons.rejected.connect(self.close)
+        self.layout.addWidget(buttons)
+        self.setSizePolicy(QSizePolicy.Policy.MinimumExpanding, QSizePolicy.Policy.MinimumExpanding)

src/plugins/krowlogplugin.py

@@ -5,6 +5,7 @@ from PySide6.QtCore import Qt
 from PySide6.QtWidgets import QDockWidget, QMessageBox
 
 import constants
+from src.plugins.krowlog.about_qt_dialog import AboutQTDialog
 from src.plugins.krowlog.aboutdialog import AboutDialog
 from src.mainwindow import MainWindow
 from src.pluginbase import PluginBase
@@ -36,6 +37,7 @@ class KrowLogPlugin(PluginBase):
         return [
             MenuContribution("file", action=self._action_close(), action_id="close application", after="<last>"),
             MenuContribution("help", action=self._action_about(), action_id="open about dialog", after="<last>"),
+            MenuContribution("help", action=self._action_about_qt(), action_id="open about QT dialog", after="<last>"),
             MenuContribution("settings", menu=self._sub_menu_languages(), action_id="recent files menu"),
         ]
 
@@ -108,6 +110,14 @@ class KrowLogPlugin(PluginBase):
         )
         return about_action
 
+    def _action_about_qt(self) -> RAction:
+        action = RAction(
+            _("&About QT"),
+            action=lambda: AboutQTDialog().exec(),
+            icon_file=constants.qt_icon
+        )
+        return action
+
     def _action_close(self) -> RAction:
         icon = "close" if sys.platform == 'win32' or sys.platform == 'cygwin' else "exit"
         close_action = RAction(_("E&xit"), action=lambda: self.main_window.destruct(), shortcut='Ctrl+X',

src/ui/bigtext/line.py

@@ -15,7 +15,7 @@ class Line:
         self._cache_char_to_column()
 
     def get_width_in_px(self, font_metric: QFontMetrics):
-        return font_metric.horizontalAdvance(self._line)
+        return font_metric.horizontalAdvance(self.line_prepared_for_display())
 
     def byte_offset(self) -> int:
         return self._byte_offset
@@ -43,7 +43,8 @@ class Line:
         return len(prefix_chars)
 
     def line_prepared_for_display(self) -> str:
-        line = self._line_tabs_replaced()
+        # line = self._line_tabs_replaced()
+        line = self._line
         line = self._replace_control_chars_with_pictures(line)
         return line
 
@@ -108,7 +109,7 @@ class Line:
             if not result in self._column_to_char_cache:
                 self._column_to_char_cache[result] = i
             current_char = self._line[i]
-            if current_char == "\t":
+            if False and current_char == "\t":
                 result = result + constants.tab_width - result % constants.tab_width
             else:
                 result = result + 1

src/ui/bigtext/testline.py

@@ -78,20 +78,6 @@ class MyTestCase(unittest.TestCase):
         self.assertEqual(2, line.char_to_column(4))  # z̈
         self.assertEqual(2, line.char_to_column(5))  # z̈
 
-    def test_line_tabs_replaced(self):
-        byte_offset = 123
-        text = "\ta\tb"  # will be rendered as: ....abc  where . represents a whitespace column
-        expected = "    a   b"
-        line = Line(byte_offset=byte_offset, byte_end=byte_offset + len(text.encode("utf8")), line=text)
-        self.assertEqual(expected, line.line_prepared_for_display())
-
-    def test_line_tabs_replaced_performance(self):
-        byte_offset = 123
-        text = "a\t" * 10000
-        expected = "a   " * 10000
-        line = Line(byte_offset=byte_offset, byte_end=byte_offset + len(text.encode("utf8")), line=text)
-        self.assertEqual(expected, line.line_prepared_for_display())
-
     def test_byte_index_to_char_index(self):
         byte_offset = 123
         text = "x\u0308y\u0308z\u0308\t\u0308a"