add dialog to manage highlighters

- no support for "no color"
- settings not saved to disk

colorbutton.py

@@ -0,0 +1,47 @@
+import re
+
+from PyQt6.QtGui import QColor
+from PyQt6.QtWidgets import QWidget, QHBoxLayout, QPushButton, QColorDialog, QSizePolicy
+
+
+class ColorButton(QPushButton):
+    def __init__(self, color: str):
+        super(QPushButton, self).__init__()
+        self.color = color
+        self.setStyleSheet("background-color: #%s" % color)
+        self.pressed.connect(self._update_color)
+        self.setSizePolicy(QSizePolicy(QSizePolicy.Policy.Fixed, QSizePolicy.Policy.Fixed))
+
+    def set_color(self, color: str):
+        if self._is_hex_color(color):
+            self.setStyleSheet("background-color: #%s" % color)
+            self.setText(color)
+            self.color = color
+        else:
+            self.setStyleSheet("background-color: none")
+            self.setText(self.tr("not set"))
+            self.color = "None"
+
+    def _update_color(self):
+        new_color = QColorDialog.getColor(self._to_qcolor(self.color))
+        if new_color.isValid():
+            color = self._to_hex(new_color)
+            self.set_color(color)
+
+    @staticmethod
+    def _is_hex_color(color: str):
+        return re.match("[0-9a-f]{6}", color, flags=re.IGNORECASE)
+
+    def _to_qcolor(self, color: str):
+        if self._is_hex_color(color):
+            red = int(color[0:2], 16)
+            green = int(color[2:4], 16)
+            blue = int(color[4:6], 16)
+            return QColor(red, green, blue)
+        return QColor(255, 255, 255)
+
+    def _to_hex(self, color: QColor) -> str:
+        red = "{0:0{1}x}".format(color.red(), 2)
+        green = "{0:0{1}x}".format(color.green(), 2)
+        blue = "{0:0{1}x}".format(color.blue(), 2)
+        return red + green + blue