Extract XCUI text input controller to common layer

engine/include/XCEngine/UI/Text/UITextInputController.h

@@ -0,0 +1,39 @@
+#pragma once
+
+#include <XCEngine/UI/Types.h>
+
+#include <cstddef>
+#include <cstdint>
+#include <string>
+
+namespace XCEngine {
+namespace UI {
+namespace Text {
+
+struct UITextInputState {
+    std::string value = {};
+    std::size_t caret = 0u;
+};
+
+struct UITextInputOptions {
+    bool multiline = false;
+    std::size_t tabWidth = 4u;
+};
+
+struct UITextInputEditResult {
+    bool handled = false;
+    bool valueChanged = false;
+    bool submitRequested = false;
+};
+
+void ClampCaret(UITextInputState& state);
+bool InsertCharacter(UITextInputState& state, std::uint32_t character);
+UITextInputEditResult HandleKeyDown(
+    UITextInputState& state,
+    std::int32_t keyCode,
+    const UIInputModifiers& modifiers,
+    const UITextInputOptions& options = {});
+
+} // namespace Text
+} // namespace UI
+} // namespace XCEngine