Fix double click to select full words (#5243)

Co-authored-by: Rasmus Karlsson <rasmus.karlsson@pajlada.com>

tests/src/MessageLayout.cpp

@@ -0,0 +1,90 @@
+#include "messages/layouts/MessageLayout.hpp"
+
+#include "Application.hpp"
+#include "controllers/accounts/AccountController.hpp"
+#include "messages/MessageBuilder.hpp"
+#include "messages/MessageElement.hpp"
+#include "mocks/EmptyApplication.hpp"
+#include "singletons/Emotes.hpp"
+#include "singletons/Fonts.hpp"
+#include "singletons/Settings.hpp"
+#include "singletons/Theme.hpp"
+#include "singletons/WindowManager.hpp"
+
+#include <gtest/gtest.h>
+#include <QDebug>
+#include <QString>
+
+#include <memory>
+
+using namespace chatterino;
+
+namespace {
+
+class MockApplication : mock::EmptyApplication
+{
+public:
+    MockApplication()
+        : settings(this->settingsDir.filePath("settings.json"))
+        , fonts(this->settings)
+        , windowManager(this->paths_)
+    {
+    }
+    Theme *getThemes() override
+    {
+        return &this->theme;
+    }
+
+    Fonts *getFonts() override
+    {
+        return &this->fonts;
+    }
+
+    WindowManager *getWindows() override
+    {
+        return &this->windowManager;
+    }
+
+    Settings settings;
+    Theme theme;
+    Fonts fonts;
+    WindowManager windowManager;
+};
+
+constexpr int WIDTH = 300;
+
+class MessageLayoutTest
+{
+public:
+    // "aaaaaaaa bbbbbbbb cccccccc"
+    MessageLayoutTest(const QString &text)
+    {
+        MessageBuilder builder;
+        builder.append(
+            std::make_unique<TextElement>(text, MessageElementFlag::Text));
+        this->layout = std::make_unique<MessageLayout>(builder.release());
+        this->layout->layout(WIDTH, 1, MessageElementFlag::Text, false);
+    }
+
+    MockApplication mockApplication;
+    std::unique_ptr<MessageLayout> layout;
+};
+
+}  // namespace
+
+TEST(TextElement, BasicCase)
+{
+    auto test = MessageLayoutTest("abc");
+
+    // Simulate we are clicking on the first word
+    auto point = QPoint(WIDTH / 20, test.layout->getHeight() / 2);
+
+    const auto *hoveredElement = test.layout->getElementAt(point);
+    ASSERT_NE(hoveredElement, nullptr);
+
+    const auto [wordStart, wordEnd] =
+        test.layout->getWordBounds(hoveredElement, point);
+
+    EXPECT_EQ(wordStart, 0);
+    EXPECT_EQ(wordEnd, 3);
+}