Added QWhatsThis to known issues.

Created sample workaround in `example/whatsthis.py`, showing how to
style the `QWhatsThis` widget using `QPalette`, and added a workaround
description to `ISSUES.md`.

Closes #59.

ISSUES.md

@@ -18,6 +18,8 @@ There are limitations to what can be styled with stylesheets, as well as rare bu
   - [Links](#links)
 - [QToolButton](#qtoolbutton)
   - [Menu Button Padding](#menu-button-padding)
+- [QWhatsThis]
+  - [Tooltip Colors](#tooltip-colors)
 - [QWidget]
   - [Standard Icons](#standard-icons)
 
@@ -220,6 +222,61 @@ def main():
 
 The default icon for `QCommandLinkButton` is platform-dependent, and depends on the standard icon `SP_CommandLink` (which cannot be specified in a stylesheet). See [Standard Icons](#standard-icons) for an explanation on how to override this standard icon.
 
+# QWhatsThis
+
+### Tooltip Colors
+
+QWhatsThis uses `QPalette::toolTipText` and `QPalette::toolTipBase` for its colors: unfortunately, these are not influenced by the stylesheet. To modify these, you can change the colors for `QPalette::ToolTipBase` and `QPalette::ToolTipText`. An example can be found in [whatsthis.py](/example/whatsthis.py).
+
+A simple example of modifying the tooltip palette for the `QWhatsThis` style is as follows:
+
+**C++**
+
+```cpp
+#include <QApplication>
+#include <QColor>
+#include <QPalette>
+
+int main(int argc, char* argv[])
+{
+    QApplication app(argc, argv);
+
+    auto palette = app.palette();
+    QColor green(0, 255, 0);
+    QColor blue(0, 0, 255);
+    palette.setColor(QPalette::ToolTipBase, green);
+    palette.setColor(QPalette::ToolTipText, blue);
+    app.setPalette(palette);
+
+    ...
+
+    return app.exec();
+}
+```
+
+**Python**
+
+```python
+import sys
+from PyQt6 import QtGui, QtWidgets
+
+ColorRole = QtGui.QPalette.ColorRole
+
+def main():
+    app = QtWidgets.QApplication(sys.argv)
+
+    palette = app.palette()
+    green = QtGui.QColor(0, 255, 0)
+    blue = QtGui.QColor(0, 0, 255)
+    palette.setColor(ColorRole.ToolTipBase, green)
+    palette.setColor(ColorRole.ToolTipText, blue)
+    app.setPalette(palette)
+
+    ...
+
+    return app.exec()
+```
+
 # QWidget
 
 ### Standard Icons

example/shared.py

@@ -233,6 +233,8 @@ def get_compat_definitions(args):
         ns.HoverMove = ns.EventType.HoverMove
         ns.HoverLeave = ns.EventType.HoverLeave
         ns.PlaceholderText = ns.ColorRole.PlaceholderText
+        ns.ToolTipBase = ns.ColorRole.ToolTipBase
+        ns.ToolTipText = ns.ColorRole.ToolTipText
         ns.NoTicks = ns.TickPosition.NoTicks
         ns.TicksAbove = ns.TickPosition.TicksAbove
         ns.TicksBelow = ns.TickPosition.TicksBelow
@@ -473,6 +475,8 @@ def get_compat_definitions(args):
         ns.HoverMove = QtCore.QEvent.HoverMove
         ns.HoverLeave = QtCore.QEvent.HoverLeave
         ns.PlaceholderText = QtGui.QPalette.PlaceholderText
+        ns.ToolTipBase = QtGui.QPalette.ToolTipBase
+        ns.ToolTipText = QtGui.QPalette.ToolTipText
         ns.NoTicks = QtWidgets.QSlider.NoTicks
         ns.TicksAbove = QtWidgets.QSlider.TicksAbove
         ns.TicksBelow = QtWidgets.QSlider.TicksBelow
@@ -642,6 +646,8 @@ def get_colors(args, compat):
     ns.Selected = compat.QtGui.QColor(61, 174, 233)
     ns.PlaceholderColor = compat.QtGui.QColor(255, 0, 0)
     ns.TickColor = compat.QtGui.QColor(255, 0, 0)
+    ns.ToolTipBase = compat.QtGui.QColor(0, 255, 0)
+    ns.ToolTipText = compat.QtGui.QColor(0, 0, 255)
     if 'dark' in args.stylesheet:
         ns.GrooveBackground = compat.QtGui.QColor(98, 101, 104)
         ns.GrooveBorder = compat.QtGui.QColor(49, 54, 59)
@@ -650,6 +656,8 @@ def get_colors(args, compat):
         ns.Notch = compat.QtGui.QColor(51, 78, 94)
         ns.PlaceholderColor = compat.QtGui.QColor(118, 121, 124)
         ns.TickColor = compat.QtGui.QColor(51, 78, 94)
+        ns.ToolTipBase = compat.QtGui.QColor(49, 54, 59)
+        ns.ToolTipText = compat.QtGui.QColor(239, 240, 241)
     elif 'light' in args.stylesheet:
         ns.GrooveBackground = compat.QtGui.QColor(106, 105, 105, 179)
         ns.GrooveBorder = compat.QtGui.QColor(239, 240, 241)
@@ -658,6 +666,8 @@ def get_colors(args, compat):
         ns.Notch = compat.QtGui.QColor(61, 173, 232, 51)
         ns.PlaceholderColor = compat.QtGui.QColor(186, 185, 184)
         ns.TickColor = compat.QtGui.QColor(61, 173, 232, 51)
+        ns.ToolTipBase = compat.QtGui.QColor(49, 54, 59)
+        ns.ToolTipText = compat.QtGui.QColor(239, 240, 241)
 
     return ns
 

example/whatsthis.py

@@ -0,0 +1,84 @@
+#!/usr/bin/env python
+#
+# The MIT License (MIT)
+#
+# Copyright (c) <2022-Present> <Alex Huszagh>
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the 'Software'), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+# THE SOFTWARE.
+
+'''
+    whatsthis
+    =========
+
+    Example showing how to style the tooltip base and text for QWhatsThis,
+    since it cannot be modified via stylesheets.
+'''
+
+import shared
+import sys
+
+parser = shared.create_parser()
+args, unknown = shared.parse_args(parser)
+QtCore, QtGui, QtWidgets = shared.import_qt(args)
+compat = shared.get_compat_definitions(args)
+colors = shared.get_colors(args, compat)
+
+
+class Ui:
+    '''Main class for the user interface.'''
+
+    def setup(self, MainWindow):
+        MainWindow.setObjectName('MainWindow')
+        MainWindow.resize(1068, 824)
+        self.centralwidget = QtWidgets.QWidget(MainWindow)
+        self.centralwidget.setObjectName('centralwidget')
+        self.layout = QtWidgets.QVBoxLayout(self.centralwidget)
+        self.layout.setObjectName('layout')
+        self.layout.setAlignment(compat.AlignHCenter)
+        MainWindow.setCentralWidget(self.centralwidget)
+
+        self.toolbar = QtWidgets.QToolBar('Toolbar')
+        self.toolbar.setOrientation(compat.Vertical)
+        self.action = compat.QAction('&Action 1', MainWindow)
+        self.action.setWhatsThis('Example action')
+        self.toolbar.addAction(self.action)
+        self.toolbar.addAction(QtWidgets.QWhatsThis.createAction(self.toolbar))
+        MainWindow.addToolBar(compat.TopToolBarArea, self.toolbar)
+
+
+def main():
+    'Application entry point'
+
+    app, window = shared.setup_app(args, unknown, compat)
+
+    palette = app.palette()
+    palette.setColor(compat.ToolTipBase, colors.ToolTipBase)
+    palette.setColor(compat.ToolTipText, colors.ToolTipText)
+    app.setPalette(palette)
+
+    # setup ui
+    ui = Ui()
+    ui.setup(window)
+    window.setWindowTitle('Stylized QWhatsThis.')
+
+    shared.set_stylesheet(args, app, compat)
+    return shared.exec_app(args, app, window, compat)
+
+if __name__ == '__main__':
+    sys.exit(main())