Spell-Checking-with-Hunspell-and-Qt

Qt 5/6 + hunspell example code

Put to git from here: https://wiki.qt.io/Spell-Checking-with-Hunspell

To ease the compilation and testing. Additionally, the following improvements had been added:

• Replacement of deprecated Hunspell functions
• Replacement of deprecated QRegExp with QRegularExpressions
• Replacement of old style signal/slot connects
• Add compatibility for Qt 6
• Implementation of "Replace all"
• Minor fixes and Cpplint/Clang-Tidy/Clazy