Feature: Add multi-line input. (#630)

src/ftxui/screen/string_internal.hpp

@@ -0,0 +1,64 @@
+#ifndef FTXUI_SCREEN_STRING_INTERNAL_HPP
+#define FTXUI_SCREEN_STRING_INTERNAL_HPP
+
+namespace ftxui {
+
+bool EatCodePoint(const std::string& input,
+                  size_t start,
+                  size_t* end,
+                  uint32_t* ucs);
+bool EatCodePoint(const std::wstring& input,
+                  size_t start,
+                  size_t* end,
+                  uint32_t* ucs);
+
+bool IsCombining(uint32_t ucs);
+bool IsFullWidth(uint32_t ucs);
+bool IsControl(uint32_t ucs);
+
+size_t GlyphPrevious(const std::string& input, size_t start);
+size_t GlyphNext(const std::string& input, size_t start);
+
+// Return the index in the |input| string of the glyph at |glyph_offset|,
+// starting at |start|
+size_t GlyphIterate(const std::string& input,
+                    int glyph_offset,
+                    size_t start = 0);
+
+// Returns the number of glyphs in |input|.
+int GlyphCount(const std::string& input);
+
+// Properties from:
+// https://www.unicode.org/Public/UCD/latest/ucd/auxiliary/WordBreakProperty.txt
+enum class WordBreakProperty {
+  ALetter,
+  CR,
+  Double_Quote,
+  Extend,
+  ExtendNumLet,
+  Format,
+  Hebrew_Letter,
+  Katakana,
+  LF,
+  MidLetter,
+  MidNum,
+  MidNumLet,
+  Newline,
+  Numeric,
+  Regional_Indicator,
+  Single_Quote,
+  WSegSpace,
+  ZWJ,
+};
+WordBreakProperty CodepointToWordBreakProperty(uint32_t codepoint);
+std::vector<WordBreakProperty> Utf8ToWordBreakProperty(
+    const std::string& input);
+
+bool IsWordBreakingCharacter(const std::string& input, size_t glyph_index);
+}  // namespace ftxui
+
+#endif /* end of include guard: FTXUI_SCREEN_STRING_INTERNAL_HPP */
+
+// Copyright 2023 Arthur Sonzogni. All rights reserved.
+// Use of this source code is governed by the MIT license that can be found in
+// the LICENSE file.