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

include/ftxui/component/component.hpp

@@ -51,8 +51,9 @@ Component Checkbox(ConstStringRef label,
                    bool* checked,
                    Ref<CheckboxOption> option = CheckboxOption::Simple());
 
+Component Input(StringRef content, Ref<InputOption> option = {});
 Component Input(StringRef content,
-                ConstStringRef placeholder,
+                StringRef placeholder,
                 Ref<InputOption> option = {});
 
 Component Menu(ConstStringListRef entries,

include/ftxui/component/component_options.hpp

@@ -5,7 +5,7 @@
 #include <ftxui/component/animation.hpp>  // for Duration, QuadraticInOut, Function
 #include <ftxui/dom/direction.hpp>  // for Direction, Direction::Left, Direction::Right, Direction::Down
 #include <ftxui/dom/elements.hpp>  // for Element, separator
-#include <ftxui/util/ref.hpp>      // for Ref, ConstRef
+#include <ftxui/util/ref.hpp>      // for Ref, ConstRef, StringRef
 #include <functional>              // for function
 #include <optional>                // for optional
 #include <string>                  // for string
@@ -134,20 +134,42 @@ struct CheckboxOption {
   std::function<void()> on_change = [] {};
 };
 
+/// @brief Used to define style for the Input component.
+struct InputState {
+  Element element;
+  bool hovered;         /// < Whether the input is hovered by the mouse.
+  bool focused;         /// < Whether the input is focused by the user.
+  bool is_placeholder;  /// < Whether the input is empty and displaying the
+                        /// < placeholder.
+};
+
 /// @brief Option for the Input component.
 /// @ingroup component
 struct InputOption {
+  // A set of predefined styles:
+
+  /// @brief Create the default input style:
+  static InputOption Default();
+  /// @brief A white on black style with high margins:
+  static InputOption Spacious();
+  /// @brief A style with a border:
+  static InputOption Arthur();
+
+  /// The content of the input when it's empty.
+  StringRef placeholder = "";
+
+  // Style:
+  std::function<Element(InputState)> transform;
+  Ref<bool> password = false;  /// < Obscure the input content using '*'.
+  Ref<bool> multiline = true;  /// < Whether the input can be multiline.
+
   /// Called when the content changes.
   std::function<void()> on_change = [] {};
   /// Called when the user presses enter.
   std::function<void()> on_enter = [] {};
 
-  /// Obscure the input content using '*'.
-  Ref<bool> password = false;
-
-  /// When set different from -1, this attributes is used to store the cursor
-  /// position.
-  Ref<int> cursor_position = -1;
+  // The char position of the cursor:
+  Ref<int> cursor_position = 0;
 };
 
 /// @brief Option for the Radiobox component.

include/ftxui/component/receiver.hpp

@@ -1,7 +1,7 @@
 #ifndef FTXUI_COMPONENT_RECEIVER_HPP_
 #define FTXUI_COMPONENT_RECEIVER_HPP_
 
-#include <algorithm>           // for copy
+#include <algorithm>           // for copy, max
 #include <atomic>              // for atomic, __atomic_base
 #include <condition_variable>  // for condition_variable
 #include <functional>

include/ftxui/screen/string.hpp

@@ -15,44 +15,10 @@ std::wstring to_wstring(T s) {
 }
 
 int string_width(const std::string&);
+
 // Split the string into a its glyphs. An empty one is inserted ater fullwidth
 // ones.
 std::vector<std::string> Utf8ToGlyphs(const std::string& input);
-// If |input| was an array of glyphs, this returns the number of char to eat
-// before reaching the glyph at index |glyph_index|.
-int GlyphPosition(const std::string& input,
-                  size_t glyph_index,
-                  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);
 
 // Map every cells drawn by |input| to their corresponding Glyphs. Half-size
 // Glyphs takes one cell, full-size Glyphs take two cells.

include/ftxui/util/ref.hpp

@@ -48,6 +48,7 @@ class StringRef {
   StringRef(const wchar_t* ref) : StringRef(to_string(std::wstring(ref))) {}
   StringRef(const char* ref) : StringRef(std::string(ref)) {}
   std::string& operator*() { return address_ ? *address_ : owned_; }
+  std::string& operator()() { return address_ ? *address_ : owned_; }
   std::string* operator->() { return address_ ? address_ : &owned_; }
 
  private: