feat: spellcheck input (#6446)

Reviewed-by: Mm2PL <mm2pl+gh@kotmisia.pl>
Reviewed-by: pajlada <rasmus.karlsson@pajlada.com>
Reviewed-by: fourtf <tf.four@gmail.com>

.github/workflows/build.yml

@@ -220,6 +220,7 @@ jobs:
               -DBUILD_WITH_CRASHPAD="$Env:C2_ENABLE_CRASHPAD" `
               -DCHATTERINO_LTO="$Env:C2_ENABLE_LTO" `
               -DFORCE_JSON_GENERATION=On `
+              -DCHATTERINO_SPELLCHECK=On `
               ..
           set cl=/MP
           nmake /S /NOLOGO
@@ -273,8 +274,8 @@ jobs:
       - name: Install dependencies (MacOS)
         if: startsWith(matrix.os, 'macos')
         run: |
-          # brew install openssl rapidjson p7zip create-dmg cmake tree boost
-          brew install openssl rapidjson p7zip create-dmg tree boost
+          # brew install openssl rapidjson p7zip create-dmg cmake tree boost hunspell
+          brew install openssl rapidjson p7zip create-dmg tree boost hunspell
         shell: bash
 
       - name: Build (MacOS)
@@ -289,6 +290,7 @@ jobs:
               -DUSE_PRECOMPILED_HEADERS=OFF \
               -DCHATTERINO_LTO="$C2_ENABLE_LTO" \
               -DFORCE_JSON_GENERATION=Off \
+              -DCHATTERINO_SPELLCHECK=On \
               ..
           make -j"$(sysctl -n hw.logicalcpu)"
         shell: bash

.github/workflows/test-macos.yml

@@ -45,8 +45,8 @@ jobs:
 
       - name: Install dependencies
         run: |
-          # brew install openssl rapidjson p7zip create-dmg cmake boost
-          brew install openssl rapidjson p7zip create-dmg boost
+          # brew install openssl rapidjson p7zip create-dmg cmake boost hunspell
+          brew install openssl rapidjson p7zip create-dmg boost hunspell
 
       - name: Install httpbox
         run: |
@@ -64,6 +64,7 @@ jobs:
               -DBUILD_TESTS=On \
               -DBUILD_APP=OFF \
               -DUSE_PRECOMPILED_HEADERS=OFF \
+              -DCHATTERINO_SPELLCHECK=On \
               ..
           make -j"$(sysctl -n hw.logicalcpu)"
 

.github/workflows/test-windows.yml

@@ -115,6 +115,7 @@ jobs:
               -DCMAKE_TOOLCHAIN_FILE="conan_toolchain.cmake" `
               -DUSE_PRECOMPILED_HEADERS=On `
               -DBUILD_WITH_CRASHPAD="$Env:C2_ENABLE_CRASHPAD" `
+              -DCHATTERINO_SPELLCHECK=On `
               ..
           set cl=/MP
           nmake /S /NOLOGO

CHANGELOG.md

@@ -74,6 +74,7 @@
 - Dev: Unwrapped `LimitedQueueSnapshot` to `std::vector`. (#6606)
 - Dev: Simplified uses of `getMessageSnapshot`. (#6607)
 - Dev: Disabled `llvm-prefer-static-over-anonymous-namespace` in clang-tidy. (#6610)
+- Dev: Started work on spell checking. (#6446)
 - Dev: Added Clazy linting in CI. (#6623)
 - Dev: Added custom clang-tidy module linting in CI. (#6626)
 - Dev: CMake option `USE_ALTERNATE_LINKER` now errors if the given linker can't be found. (#6692)

CMakeLists.txt

@@ -31,6 +31,7 @@ option(CHATTERINO_LTO "Enable LTO for all targets" OFF)
 option(CHATTERINO_PLUGINS "Enable ALPHA plugin support in Chatterino" ON)
 option(CHATTERINO_USE_GDI_FONTENGINE "Use the legacy GDI fontengine instead of the new DirectWrite one on Windows (Qt 6.8.0 and later)" ON)
 option(CHATTERINO_ALLOW_PRIVATE_QT_API "Allow uses of Qt's private API - when enabling this, Chatterino must use the EXACT Qt version it was compiled against" OFF)
+option(CHATTERINO_SPELLCHECK "Enable spellchecking in Chatterino (requires Hunspell)" OFF)
 
 option(CHATTERINO_SANITIZER_SUPPORT "Attempt to enable Sanitizer support on the test and app targets. Actual sanitizers can then be enabled with the SANITIZE_* options." OFF)
 mark_as_advanced(CHATTERINO_SANITIZER_SUPPORT)
@@ -151,6 +152,16 @@ find_package(OpenSSL REQUIRED)
 
 find_package(Threads REQUIRED)
 
+if(CHATTERINO_SPELLCHECK)
+    # Find from package manager
+    find_package(hunspell QUIET CONFIG)
+    if(NOT hunspell_FOUND)
+        find_package(PkgConfig REQUIRED)
+        pkg_check_modules(hunspell REQUIRED IMPORTED_TARGET hunspell)
+        add_library(hunspell::hunspell ALIAS PkgConfig::hunspell)
+    endif()
+endif()
+
 find_library(LIBRT rt)
 
 if (USE_SYSTEM_LIBCOMMUNI)

conanfile.py

@@ -6,13 +6,14 @@ from os import path
 
 class Chatterino(ConanFile):
     name = "Chatterino"
-    requires = "boost/1.86.0"
+    requires = "boost/1.86.0", "hunspell/1.7.2"
     settings = "os", "compiler", "build_type", "arch"
     default_options = {
         "with_benchmark": False,
         "with_openssl3": True,
         "openssl*:shared": True,
         "boost*:header_only": True,
+        "hunspell*:shared": False,
     }
     options = {
         "with_benchmark": [True, False],

mocks/include/mocks/EmptyApplication.hpp

@@ -208,6 +208,11 @@ public:
         return nullptr;
     }
 
+    SpellChecker *getSpellChecker() override
+    {
+        return nullptr;
+    }
+
 #ifdef CHATTERINO_HAVE_PLUGINS
     PluginController *getPlugins() override
     {

resources/licenses/hunspell.txt

@@ -0,0 +1,339 @@
+                    GNU GENERAL PUBLIC LICENSE
+                       Version 2, June 1991
+
+ Copyright (C) 1989, 1991 Free Software Foundation, Inc.,
+ 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+                            Preamble
+
+  The licenses for most software are designed to take away your
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+License is intended to guarantee your freedom to share and change free
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+General Public License applies to most of the Free Software
+Foundation's software and to any other program whose authors commit to
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+your programs, too.
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+price.  Our General Public Licenses are designed to make sure that you
+have the freedom to distribute copies of free software (and charge for
+this service if you wish), that you receive source code or can get it
+if you want it, that you can change the software or use pieces of it
+in new free programs; and that you know you can do these things.
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+anyone to deny you these rights or to ask you to surrender the rights.
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+
+  <signature of Ty Coon>, 1 April 1989
+  Ty Coon, President of Vice
+
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+proprietary programs.  If your program is a subroutine library, you may
+consider it more useful to permit linking proprietary applications with the
+library.  If this is what you want to do, use the GNU Lesser General
+Public License instead of this License.

src/Application.cpp

@@ -11,6 +11,7 @@
 #include "controllers/ignores/IgnoreController.hpp"
 #include "controllers/notifications/NotificationController.hpp"
 #include "controllers/sound/ISoundController.hpp"
+#include "controllers/spellcheck/SpellChecker.hpp"
 #include "providers/bttv/BttvBadges.hpp"
 #include "providers/bttv/BttvEmotes.hpp"
 #include "providers/ffz/FfzEmotes.hpp"
@@ -198,6 +199,7 @@ Application::Application(Settings &_settings, const Paths &paths,
     , streamerMode(new StreamerMode)
     , twitchUsers(new TwitchUsers)
     , pronouns(new pronouns::Pronouns)
+    , spellChecker(new SpellChecker)
 #ifdef CHATTERINO_HAVE_PLUGINS
     , plugins(new PluginController(paths))
 #endif
@@ -608,6 +610,14 @@ eventsub::IController *Application::getEventSub()
     return this->eventSub.get();
 }
 
+SpellChecker *Application::getSpellChecker()
+{
+    assertInGuiThread();
+    assert(this->spellChecker);
+
+    return this->spellChecker.get();
+}
+
 void Application::aboutToQuit()
 {
     ABOUT_TO_QUIT.store(true);
@@ -660,6 +670,7 @@ void Application::stop()
     this->logging.reset();
     this->fonts.reset();
     this->themes.reset();
+    this->spellChecker.reset();
 
     STOPPED.store(true);
 }

src/Application.hpp

@@ -59,6 +59,7 @@ class Pronouns;
 namespace eventsub {
 class IController;
 }  // namespace eventsub
+class SpellChecker;
 
 class IApplication
 {
@@ -113,6 +114,7 @@ public:
     virtual ITwitchUsers *getTwitchUsers() = 0;
     virtual pronouns::Pronouns *getPronouns() = 0;
     virtual eventsub::IController *getEventSub() = 0;
+    virtual SpellChecker *getSpellChecker() = 0;
 };
 
 class Application : public IApplication
@@ -181,6 +183,7 @@ private:
     std::unique_ptr<IStreamerMode> streamerMode;
     std::unique_ptr<ITwitchUsers> twitchUsers;
     std::unique_ptr<pronouns::Pronouns> pronouns;
+    std::unique_ptr<SpellChecker> spellChecker;
 #ifdef CHATTERINO_HAVE_PLUGINS
     std::unique_ptr<PluginController> plugins;
 #endif
@@ -234,6 +237,7 @@ public:
     ILinkResolver *getLinkResolver() override;
     IStreamerMode *getStreamerMode() override;
     ITwitchUsers *getTwitchUsers() override;
+    SpellChecker *getSpellChecker() override;
 
 private:
     void initNm(const Paths &paths);

src/CMakeLists.txt

@@ -292,6 +292,9 @@ set(SOURCE_FILES
         controllers/sound/NullBackend.cpp
         controllers/sound/NullBackend.hpp
 
+        controllers/spellcheck/SpellChecker.cpp
+        controllers/spellcheck/SpellChecker.hpp
+
         controllers/twitch/LiveController.cpp
         controllers/twitch/LiveController.hpp
 
@@ -825,6 +828,8 @@ set(SOURCE_FILES
         widgets/splits/InputCompletionItem.hpp
         widgets/splits/InputCompletionPopup.cpp
         widgets/splits/InputCompletionPopup.hpp
+        widgets/splits/InputHighlighter.cpp
+        widgets/splits/InputHighlighter.hpp
         widgets/splits/Split.cpp
         widgets/splits/Split.hpp
         widgets/splits/SplitCommon.hpp
@@ -931,6 +936,11 @@ if (CHATTERINO_PLUGINS)
     target_link_libraries(${LIBRARY_PROJECT} PUBLIC lua sol2::sol2)
 endif()
 
+if (CHATTERINO_SPELLCHECK)
+    target_compile_definitions(${LIBRARY_PROJECT} PUBLIC CHATTERINO_WITH_SPELLCHECK)
+    target_link_libraries(${LIBRARY_PROJECT} PRIVATE hunspell::hunspell)
+endif()
+
 if (CHATTERINO_ALLOW_PRIVATE_QT_API)
     target_link_libraries(${LIBRARY_PROJECT} PUBLIC Qt${MAJOR_QT_VERSION}::GuiPrivate)
     target_compile_definitions(${LIBRARY_PROJECT} PUBLIC 

src/common/QLogging.cpp

@@ -47,6 +47,7 @@ Q_LOGGING_CATEGORY(chatterinoSeventv, "chatterino.seventv", logThreshold);
 Q_LOGGING_CATEGORY(chatterinoSeventvEventAPI, "chatterino.seventv.eventapi",
                    logThreshold);
 Q_LOGGING_CATEGORY(chatterinoSound, "chatterino.sound", logThreshold);
+Q_LOGGING_CATEGORY(chatterinoSpellcheck, "chatterino.spellcheck", logThreshold);
 Q_LOGGING_CATEGORY(chatterinoStreamerMode, "chatterino.streamermode",
                    logThreshold);
 Q_LOGGING_CATEGORY(chatterinoStreamlink, "chatterino.streamlink", logThreshold);

src/common/QLogging.hpp

@@ -36,6 +36,7 @@ Q_DECLARE_LOGGING_CATEGORY(chatterinoSettings);
 Q_DECLARE_LOGGING_CATEGORY(chatterinoSeventv);
 Q_DECLARE_LOGGING_CATEGORY(chatterinoSeventvEventAPI);
 Q_DECLARE_LOGGING_CATEGORY(chatterinoSound);
+Q_DECLARE_LOGGING_CATEGORY(chatterinoSpellcheck);
 Q_DECLARE_LOGGING_CATEGORY(chatterinoStreamerMode);
 Q_DECLARE_LOGGING_CATEGORY(chatterinoStreamlink);
 Q_DECLARE_LOGGING_CATEGORY(chatterinoTheme);

src/common/WindowDescriptors.cpp

@@ -111,6 +111,12 @@ void SplitDescriptor::loadFromJSON(SplitDescriptor &descriptor,
         descriptor.channelName_ = data.value("name").toString();
     }
     descriptor.filters_ = loadFilters(root.value("filters"));
+
+    auto spellOverride = root["checkSpelling"];
+    if (spellOverride.isBool())
+    {
+        descriptor.spellCheckOverride = spellOverride.toBool();
+    }
 }
 
 TabDescriptor TabDescriptor::loadFromJSON(const QJsonObject &tabObj)

src/common/WindowDescriptors.hpp

@@ -44,6 +44,8 @@ struct SplitDescriptor {
     // Whether "Moderation Mode" (the sword icon) is enabled in this split or not
     bool moderationMode_{false};
 
+    std::optional<bool> spellCheckOverride;
+
     QList<QUuid> filters_;
 
     static void loadFromJSON(SplitDescriptor &descriptor,

src/controllers/spellcheck/SpellChecker.cpp

@@ -0,0 +1,120 @@
+#include "controllers/spellcheck/SpellChecker.hpp"
+
+#include "Application.hpp"
+#include "common/QLogging.hpp"
+#include "singletons/Paths.hpp"
+#include "util/FilesystemHelpers.hpp"
+
+#ifdef CHATTERINO_WITH_SPELLCHECK
+#    include <hunspell/hunspell.hxx>
+#endif
+
+namespace chatterino {
+
+#ifdef CHATTERINO_WITH_SPELLCHECK
+class SpellCheckerPrivate
+{
+public:
+    static std::unique_ptr<SpellCheckerPrivate> tryLoad();
+
+    Hunspell hunspell;
+
+private:
+    SpellCheckerPrivate(const char *affpath, const char *dpath);
+};
+
+std::unique_ptr<SpellCheckerPrivate> SpellCheckerPrivate::tryLoad()
+{
+    auto stdPath = qStringToStdPath(getApp()->getPaths().dictionariesDirectory);
+    auto aff = stdPath / "index.aff";
+    auto dic = stdPath / "index.dic";
+    if (!std::filesystem::exists(aff) || !std::filesystem::exists(dic))
+    {
+        qCInfo(chatterinoSpellcheck)
+            << "Failed to find index.aff or index.dic in 'Dictionaries'";
+        return nullptr;
+    }
+    std::error_code ec;
+    auto affCanonical = std::filesystem::weakly_canonical(aff, ec);
+    if (ec)
+    {
+        qCInfo(chatterinoSpellcheck)
+            << "Failed to canonicalize" << stdPathToQString(aff)
+            << "error:" << QUtf8StringView(ec.message());
+        return nullptr;
+    }
+    auto dicCanonical = std::filesystem::weakly_canonical(dic, ec);
+    if (ec)
+    {
+        qCInfo(chatterinoSpellcheck)
+            << "Failed to canonicalize" << stdPathToQString(dic)
+            << "error:" << QUtf8StringView(ec.message());
+        return nullptr;
+    }
+
+    return std::unique_ptr<SpellCheckerPrivate>{new SpellCheckerPrivate(
+        affCanonical.string().c_str(), dicCanonical.string().c_str())};
+}
+
+SpellCheckerPrivate::SpellCheckerPrivate(const char *affpath, const char *dpath)
+    : hunspell(affpath, dpath)
+{
+}
+
+SpellChecker::SpellChecker()
+    : private_(SpellCheckerPrivate::tryLoad())
+{
+}
+#else
+class SpellCheckerPrivate
+{
+};
+SpellChecker::SpellChecker() = default;
+#endif
+
+SpellChecker::~SpellChecker() = default;
+
+bool SpellChecker::isLoaded() const
+{
+    return this->private_ != nullptr;
+}
+
+// NOLINTNEXTLINE(readability-convert-member-functions-to-static)
+bool SpellChecker::check(const QString &word)
+{
+#ifdef CHATTERINO_WITH_SPELLCHECK
+    if (!this->private_)
+    {
+        return true;
+    }
+
+    return this->private_->hunspell.spell(word.toStdString());
+#else
+    (void)word;
+    return true;
+#endif
+}
+
+// NOLINTNEXTLINE(readability-convert-member-functions-to-static)
+std::vector<std::string> SpellChecker::suggestions(const QString &word)
+{
+#ifdef CHATTERINO_WITH_SPELLCHECK
+    if (!this->private_)
+    {
+        return {};
+    }
+
+    auto stdWord = word.toStdString();
+    if (this->private_->hunspell.spell(stdWord))
+    {
+        return {};
+    }
+
+    return this->private_->hunspell.suggest(stdWord);
+#else
+    (void)word;
+    return {};
+#endif
+}
+
+}  // namespace chatterino

src/controllers/spellcheck/SpellChecker.hpp

@@ -0,0 +1,30 @@
+#pragma once
+
+#include <QString>
+
+#include <memory>
+#include <string>
+#include <vector>
+
+namespace chatterino {
+
+class Channel;
+class TwitchChannel;
+
+class SpellCheckerPrivate;
+class SpellChecker
+{
+public:
+    SpellChecker();
+    ~SpellChecker();
+
+    bool isLoaded() const;
+
+    bool check(const QString &word);
+    std::vector<std::string> suggestions(const QString &word);
+
+private:
+    std::unique_ptr<SpellCheckerPrivate> private_;
+};
+
+}  // namespace chatterino

src/singletons/Paths.cpp

@@ -145,6 +145,7 @@ void Paths::initSubDirectories()
     this->pluginsDirectory = makePath("Plugins");
     this->themesDirectory = makePath("Themes");
     this->crashdumpDirectory = makePath("Crashes");
+    this->dictionariesDirectory = makePath("Dictionaries");
 #ifdef Q_OS_WIN
     this->ipcDirectory = makePath("IPC");
 #else

src/singletons/Paths.hpp

@@ -39,6 +39,9 @@ public:
     // Custom themes live here. <appDataDirectory>/Themes
     QString themesDirectory;
 
+    // Spell checking dictionaries <appDataDirectory>/Dictionaries
+    QString dictionariesDirectory;
+
     // Directory for shared memory files.
     // <appDataDirectory>/IPC   on Windows
     // /tmp                     elsewhere

src/singletons/Settings.hpp

@@ -353,6 +353,9 @@ public:
         false,
     };
 
+    BoolSetting enableSpellChecking = {"/behaviour/spellChecking/enabled",
+                                       false};
+
     FloatSetting pauseOnHoverDuration = {"/behaviour/pauseOnHoverDuration", 0};
     EnumSetting<Qt::KeyboardModifier> pauseChatModifier = {
         "/behaviour/pauseChatModifier", Qt::KeyboardModifier::NoModifier};

src/singletons/WindowManager.cpp

@@ -681,6 +681,12 @@ void WindowManager::encodeNodeRecursively(SplitNode *node, QJsonObject &obj)
             QJsonArray filters;
             WindowManager::encodeFilters(node->getSplit(), filters);
             obj.insert("filters", filters);
+
+            auto spellOverride = node->getSplit()->checkSpellingOverride();
+            if (spellOverride)
+            {
+                obj["checkSpelling"] = *spellOverride;
+            }
         }
         break;
         case SplitNode::Type::HorizontalContainer:

src/widgets/helper/ResizingTextEdit.cpp

@@ -5,6 +5,7 @@
 #include "controllers/completion/TabCompletionModel.hpp"
 #include "singletons/Settings.hpp"
 
+#include <QMenu>
 #include <QMimeData>
 #include <QMimeDatabase>
 #include <QObject>
@@ -337,4 +338,11 @@ void ResizingTextEdit::insertFromMimeData(const QMimeData *source)
     insertPlainText(source->text());
 }
 
+void ResizingTextEdit::contextMenuEvent(QContextMenuEvent *event)
+{
+    QObjectPtr<QMenu> menu{this->createStandardContextMenu(event->pos())};
+    this->contextMenuRequested.invoke(menu.get(), event->pos());
+    menu->exec(event->globalPos());
+}
+
 }  // namespace chatterino

src/widgets/helper/ResizingTextEdit.hpp

@@ -21,6 +21,7 @@ public:
     pajlada::Signals::NoArgSignal focused;
     pajlada::Signals::NoArgSignal focusLost;
     pajlada::Signals::Signal<const QMimeData *> imagePasted;
+    pajlada::Signals::Signal<QMenu *, QPoint> contextMenuRequested;
 
     void setCompleter(QCompleter *c);
     /**
@@ -39,6 +40,8 @@ protected:
     bool canInsertFromMimeData(const QMimeData *source) const override;
     void insertFromMimeData(const QMimeData *source) override;
 
+    void contextMenuEvent(QContextMenuEvent *event) override;
+
 private:
     // hadSpace is set to true in case the "textUnderCursor" word was after a
     // space

src/widgets/settingspages/AboutPage.cpp

@@ -146,6 +146,10 @@ AboutPage::AboutPage()
             addLicense(form.getElement(), "Unicode",
                        "https://www.unicode.org/copyright.html",
                        ":/licenses/unicode.txt");
+#ifdef CHATTERINO_WITH_SPELLCHECK
+            addLicense(form.getElement(), "Hunspell",
+                       "https://hunspell.github.io", ":/licenses/hunspell.txt");
+#endif
         }
 
         // Attributions

src/widgets/settingspages/GeneralPage.cpp

@@ -481,6 +481,21 @@ void GeneralPage::initLayout(GeneralPageView &layout)
             "yours is successfully sent in the matching channel.")
         ->addTo(layout);
 
+#ifdef CHATTERINO_WITH_SPELLCHECK
+    SettingWidget::checkbox("Check spelling by default (experimental)",
+                            s.enableSpellChecking)
+        ->setTooltip(
+            u"Check the spelling of words in the input box of all splits by "
+            "default. This can be overwritten per split in the context menu."
+            " Chatterino does not include dictionaries - they have to "
+            "be downloaded or created manually. Chatterino expects Hunspell "
+            "dictionaries in '" %
+            getApp()->getPaths().dictionariesDirectory %
+            u"'. The file index.aff has to contain the affixes and index.dic "
+            u"must contain the dictionary (subject to change).")
+        ->addTo(layout);
+#endif
+
     layout.addTitle("Messages");
 
     SettingWidget::checkbox("Separate with lines", s.separateMessages)

src/widgets/splits/InputHighlighter.cpp

@@ -0,0 +1,104 @@
+#include "widgets/splits/InputHighlighter.hpp"
+
+#include "Application.hpp"
+#include "common/Aliases.hpp"
+#include "controllers/accounts/AccountController.hpp"
+#include "controllers/spellcheck/SpellChecker.hpp"
+#include "messages/Emote.hpp"
+#include "providers/bttv/BttvEmotes.hpp"
+#include "providers/seventv/SeventvEmotes.hpp"
+#include "providers/twitch/TwitchAccount.hpp"
+#include "providers/twitch/TwitchChannel.hpp"
+
+#include <QTextCharFormat>
+#include <QTextDocument>
+
+namespace {
+
+using namespace chatterino;
+
+bool isIgnoredWord(TwitchChannel *twitch, const QString &word)
+{
+    EmoteName name{word};
+    if (twitch)
+    {
+        if (twitch->bttvEmote(name) || twitch->ffzEmote(name) ||
+            twitch->seventvEmote(name))
+        {
+            return true;
+        }
+        auto locals = twitch->localTwitchEmotes();
+        if (locals->contains(name))
+        {
+            return true;
+        }
+
+        if (twitch->accessChatters()->contains(word))
+        {
+            return true;
+        }
+    }
+    if (getApp()->getBttvEmotes()->emote(name) ||
+        getApp()->getFfzEmotes()->emote(name) ||
+        getApp()->getSeventvEmotes()->globalEmote(name))
+    {
+        return true;
+    }
+
+    return getApp()
+        ->getAccounts()
+        ->twitch.getCurrent()
+        ->twitchEmote(name)
+        .has_value();
+}
+
+}  // namespace
+
+namespace chatterino {
+
+InputHighlighter::InputHighlighter(SpellChecker &spellChecker, QObject *parent)
+    : QSyntaxHighlighter(parent)
+    , spellChecker(spellChecker)
+    // FIXME: this also matches URLs - this probably needs to be some function like Firefox' mozEnglishWordUtils::FindNextWord
+    , wordRegex(R"(\p{L}(?:\P{Z}+\p{L}+)*)",
+                QRegularExpression::PatternOption::UseUnicodePropertiesOption)
+{
+    this->spellFmt.setUnderlineStyle(QTextCharFormat::SpellCheckUnderline);
+    this->spellFmt.setUnderlineColor(Qt::red);
+}
+InputHighlighter::~InputHighlighter() = default;
+
+void InputHighlighter::setChannel(const std::shared_ptr<Channel> &channel)
+{
+    auto twitch = std::dynamic_pointer_cast<TwitchChannel>(channel);
+    this->channel = twitch;
+    this->rehighlight();
+}
+
+void InputHighlighter::highlightBlock(const QString &text)
+{
+    if (!this->spellChecker.isLoaded())
+    {
+        return;
+    }
+    auto *channel = this->channel.lock().get();
+
+    QStringView textView = text;
+#if QT_VERSION >= QT_VERSION_CHECK(6, 5, 0)
+    auto it = this->wordRegex.globalMatchView(textView);
+#else
+    auto it = this->wordRegex.globalMatch(textView);
+#endif
+    while (it.hasNext())
+    {
+        auto match = it.next();
+        auto text = match.captured();
+        if (!isIgnoredWord(channel, text) && !this->spellChecker.check(text))
+        {
+            this->setFormat(static_cast<int>(match.capturedStart()),
+                            static_cast<int>(text.size()), this->spellFmt);
+        }
+    }
+}
+
+}  // namespace chatterino

src/widgets/splits/InputHighlighter.hpp

@@ -0,0 +1,43 @@
+#pragma once
+
+#include <QRegularExpression>
+#include <QString>
+#include <QSyntaxHighlighter>
+
+#include <memory>
+
+class QTextDocument;
+
+namespace chatterino {
+
+class Channel;
+class TwitchChannel;
+class SpellChecker;
+
+/// This highlights the text in the split input.
+/// Currently, it only does spell checking.
+class InputHighlighter : public QSyntaxHighlighter
+{
+public:
+    InputHighlighter(SpellChecker &spellChecker, QObject *parent);
+    ~InputHighlighter() override;
+    InputHighlighter(const InputHighlighter &) = delete;
+    InputHighlighter(InputHighlighter &&) = delete;
+    InputHighlighter &operator=(const InputHighlighter &) = delete;
+    InputHighlighter &operator=(InputHighlighter &&) = delete;
+
+    void setChannel(const std::shared_ptr<Channel> &channel);
+
+protected:
+    void highlightBlock(const QString &text) override;
+
+private:
+    SpellChecker &spellChecker;
+    QTextCharFormat spellFmt;
+
+    std::weak_ptr<TwitchChannel> channel;
+
+    QRegularExpression wordRegex;
+};
+
+}  // namespace chatterino

src/widgets/splits/Split.cpp

@@ -894,6 +894,16 @@ bool Split::getModerationMode() const
     return this->moderationMode_;
 }
 
+std::optional<bool> Split::checkSpellingOverride() const
+{
+    return this->input_->checkSpellingOverride();
+}
+
+void Split::setCheckSpellingOverride(std::optional<bool> override)
+{
+    this->input_->setCheckSpellingOverride(override);
+}
+
 void Split::insertTextToInput(const QString &text)
 {
     this->input_->insertText(text);

src/widgets/splits/Split.hpp

@@ -62,6 +62,9 @@ public:
     void setModerationMode(bool value);
     bool getModerationMode() const;
 
+    std::optional<bool> checkSpellingOverride() const;
+    void setCheckSpellingOverride(std::optional<bool> override);
+
     void insertTextToInput(const QString &text);
 
     void showChangeChannelPopup(const char *dialogTitle, bool empty,

src/widgets/splits/SplitContainer.cpp

@@ -908,6 +908,7 @@ void SplitContainer::applyFromDescriptorRecursively(
         split->setChannel(WindowManager::decodeChannel(splitNode));
         split->setModerationMode(splitNode.moderationMode_);
         split->setFilters(splitNode.filters_);
+        split->setCheckSpellingOverride(splitNode.spellCheckOverride);
 
         this->insertSplit(split);
 
@@ -943,6 +944,7 @@ void SplitContainer::applyFromDescriptorRecursively(
                 split->setFilters(splitNode.filters_);
                 split->setChannel(WindowManager::decodeChannel(splitNode));
                 split->setModerationMode(splitNode.moderationMode_);
+                split->setCheckSpellingOverride(splitNode.spellCheckOverride);
 
                 auto node = std::make_shared<Node>();
                 node->parent_ = baseNode;

src/widgets/splits/SplitInput.cpp

@@ -5,6 +5,7 @@
 #include "common/QLogging.hpp"
 #include "controllers/commands/CommandController.hpp"
 #include "controllers/hotkeys/HotkeyController.hpp"
+#include "controllers/spellcheck/SpellChecker.hpp"
 #include "messages/Link.hpp"
 #include "messages/Message.hpp"
 #include "providers/twitch/TwitchChannel.hpp"
@@ -25,6 +26,7 @@
 #include "widgets/Notebook.hpp"
 #include "widgets/Scrollbar.hpp"
 #include "widgets/splits/InputCompletionPopup.hpp"
+#include "widgets/splits/InputHighlighter.hpp"
 #include "widgets/splits/Split.hpp"
 #include "widgets/splits/SplitContainer.hpp"
 
@@ -73,14 +75,26 @@ SplitInput::SplitInput(QWidget *parent, Split *_chatWidget,
         new QCompleter(this->split_->getChannel()->completionModel);
     this->ui_.textEdit->setCompleter(completer);
 
+    // NOLINTNEXTLINE(cppcoreguidelines-prefer-member-initializer)
+    auto *spellChecker = getApp()->getSpellChecker();
+    this->inputHighlighter = new InputHighlighter(*spellChecker, this);
+    this->inputHighlighter->setChannel(this->split_->getChannel());
+
     this->signalHolder_.managedConnect(this->split_->channelChanged, [this] {
         auto channel = this->split_->getChannel();
         auto *completer = new QCompleter(channel->completionModel);
         this->ui_.textEdit->setCompleter(completer);
+        this->inputHighlighter->setChannel(this->split_->getChannel());
     });
 
+    getSettings()->enableSpellChecking.connect(
+        [this] {
+            this->checkSpellingChanged();
+        },
+        this->signalHolder_);
+
     // misc
-    this->installKeyPressedEvent();
+    this->installTextEditEvents();
     this->addShortcuts();
     // The textEdit's signal will be destroyed before this SplitInput is
     // destroyed, so we can safely ignore this signal's connection.
@@ -720,7 +734,7 @@ bool SplitInput::eventFilter(QObject *obj, QEvent *event)
     return BaseWidget::eventFilter(obj, event);
 }
 
-void SplitInput::installKeyPressedEvent()
+void SplitInput::installTextEditEvents()
 {
     // We can safely ignore this signal's connection because SplitInput owns
     // the textEdit object, so it will always be deleted before SplitInput
@@ -752,10 +766,42 @@ void SplitInput::installKeyPressedEvent()
             }
         });
 
-#ifdef DEBUG
-    assert(this->keyPressedEventInstalled == false);
-    this->keyPressedEventInstalled = true;
+    std::ignore = this->ui_.textEdit->contextMenuRequested.connect(
+        [this](QMenu *menu, QPoint pos) {
+#ifdef CHATTERINO_WITH_SPELLCHECK
+            menu->addSeparator();
+            auto *spellcheckAction = new QAction("Check spelling", menu);
+            spellcheckAction->setCheckable(true);
+            spellcheckAction->setChecked(this->shouldCheckSpelling());
+            QObject::connect(spellcheckAction, &QAction::toggled, this,
+                             [this](bool enabled) {
+                                 this->checkSpellingOverride_ = enabled;
+                                 this->checkSpellingChanged();
+                             });
+            menu->addAction(spellcheckAction);
+
+            auto cursor = this->ui_.textEdit->cursorForPosition(pos);
+            cursor.select(QTextCursor::WordUnderCursor);
+            auto word = cursor.selectedText();
+            if (!word.isEmpty())
+            {
+                auto suggestions =
+                    getApp()->getSpellChecker()->suggestions(word);
+                for (const auto &sugg : suggestions)
+                {
+                    auto qSugg = QString::fromStdString(sugg);
+                    menu->addAction(qSugg, [this, qSugg, cursor]() mutable {
+                        cursor.insertText(qSugg);
+                        this->ui_.textEdit->setTextCursor(cursor);
+                    });
+                }
+            }
+#else
+            (void)menu;
+            (void)pos;
+            (void)this;
 #endif
+        });
 }
 
 void SplitInput::mousePressEvent(QMouseEvent *event)
@@ -1329,6 +1375,40 @@ void SplitInput::setBackgroundColor(QColor newColor)
     this->updateTextEditPalette();
 }
 
+std::optional<bool> SplitInput::checkSpellingOverride() const
+{
+    return this->checkSpellingOverride_;
+}
+
+void SplitInput::setCheckSpellingOverride(std::optional<bool> override)
+{
+    this->checkSpellingOverride_ = override;
+    this->checkSpellingChanged();
+}
+
+bool SplitInput::shouldCheckSpelling() const
+{
+    if (this->checkSpellingOverride_)
+    {
+        return *this->checkSpellingOverride_;
+    }
+    return getSettings()->enableSpellChecking;
+}
+
+void SplitInput::checkSpellingChanged()
+{
+    QTextDocument *target = nullptr;
+    if (this->shouldCheckSpelling())
+    {
+        target = this->ui_.textEdit->document();
+    }
+
+    if (this->inputHighlighter->document() != target)
+    {
+        this->inputHighlighter->setDocument(target);
+    }
+}
+
 void SplitInput::updateFonts()
 {
     auto *app = getApp();

src/widgets/splits/SplitInput.hpp

@@ -20,11 +20,13 @@ namespace chatterino {
 class Split;
 class EmotePopup;
 class InputCompletionPopup;
+class InputHighlighter;
 class MessageView;
 class LabelButton;
 class ResizingTextEdit;
 class ChannelView;
 class SvgButton;
+class SpellCheckHighlighter;
 enum class CompletionKind;
 
 class SplitInput : public BaseWidget
@@ -78,6 +80,9 @@ public:
 
     void triggerSelfMessageReceived();
 
+    std::optional<bool> checkSpellingOverride() const;
+    void setCheckSpellingOverride(std::optional<bool> override);
+
     pajlada::Signals::Signal<const QString &> textChanged;
     pajlada::Signals::NoArgSignal selectionChanged;
 
@@ -102,10 +107,7 @@ protected:
     void addShortcuts() override;
     void initLayout();
     bool eventFilter(QObject *obj, QEvent *event) override;
-#ifdef DEBUG
-    bool keyPressedEventInstalled{};
-#endif
-    void installKeyPressedEvent();
+    void installTextEditEvents();
     void onCursorPositionChanged();
     void onTextChanged();
     void updateEmoteButton();
@@ -188,6 +190,12 @@ protected:
 
     QPropertyAnimation backgroundColorAnimation;
 
+    std::optional<bool> checkSpellingOverride_;
+    bool shouldCheckSpelling() const;
+    void checkSpellingChanged();
+
+    InputHighlighter *inputHighlighter = nullptr;
+
     void updateFonts();
 
 private Q_SLOTS:

vcpkg.json

@@ -13,6 +13,7 @@
     "boost-json",
     "boost-signals2",
     "boost-variant",
+    "hunspell",
     {
       "name": "qtbase",
       "default-features": false,