Separate namespace for ANSI code sequences to avoid magic strings

Author: ianthomas23

CMakeLists.txt

@@ -58,6 +58,8 @@ set(GIT2CPP_SRC
     ${GIT2CPP_SOURCE_DIR}/subcommand/reset_subcommand.hpp
     ${GIT2CPP_SOURCE_DIR}/subcommand/status_subcommand.cpp
     ${GIT2CPP_SOURCE_DIR}/subcommand/status_subcommand.hpp
+    ${GIT2CPP_SOURCE_DIR}/utils/ansi_code.cpp
+    ${GIT2CPP_SOURCE_DIR}/utils/ansi_code.hpp
     ${GIT2CPP_SOURCE_DIR}/utils/common.cpp
     ${GIT2CPP_SOURCE_DIR}/utils/common.hpp
     ${GIT2CPP_SOURCE_DIR}/utils/git_exception.cpp

src/utils/ansi_code.cpp

@@ -0,0 +1,24 @@
+#include "ansi_code.hpp"
+
+namespace ansi_code
+{
+    std::string cursor_to_row(size_t row)
+    {
+        return "\e[" + std::to_string(row) + "H";
+    }
+
+    bool is_down_arrow(std::string str)
+    {
+        return str == "\e[B" || str == "\e[1B]";
+    }
+
+    bool is_escape_char(char ch)
+    {
+        return ch == '\e';
+    }
+
+    bool is_up_arrow(std::string str)
+    {
+        return str == "\e[A" || str == "\e[1A]";
+    }
+}

src/utils/ansi_code.hpp

@@ -0,0 +1,29 @@
+#pragma once
+
+#include <string>
+
+/**
+ * ANSI escape codes.
+ * Use `termcolor` for colours.
+ */
+namespace ansi_code
+{
+    // Constants.
+    const std::string bel = "\a";  // ASCII 7, used for audio/visual feedback.
+    const std::string cursor_to_top = "\e[H";
+    const std::string erase_screen = "\e[2J";
+
+    const std::string enable_alternative_buffer = "\e[?1049h";
+    const std::string disable_alternative_buffer = "\e[?1049l";
+
+    const std::string hide_cursor = "\e[?25l";
+    const std::string show_cursor = "\e[?25h";
+
+    // Functions.
+    std::string cursor_to_row(size_t row);
+
+    bool is_escape_char(char ch);
+
+    bool is_down_arrow(std::string str);
+    bool is_up_arrow(std::string str);
+}

src/utils/output.hpp

@@ -1,6 +1,7 @@
 #pragma once
 
 #include <iostream>
+#include "ansi_code.hpp"
 #include "common.hpp"
 
 // Scope object to hide the cursor. This avoids
@@ -10,11 +11,11 @@ struct cursor_hider : noncopyable_nonmovable
 {
     cursor_hider()
     {
-        std::cout << "\e[?25l";
+        std::cout << ansi_code::hide_cursor;
     }
 
     ~cursor_hider()
     {
-        std::cout << "\e[?25h";
+        std::cout << ansi_code::show_cursor;
     }
 };

src/utils/terminal_pager.cpp

@@ -10,6 +10,7 @@
 
 #include <termcolor/termcolor.hpp>
 
+#include "ansi_code.hpp"
 #include "terminal_pager.hpp"
 
 terminal_pager::terminal_pager()
@@ -31,7 +32,7 @@ std::string terminal_pager::get_input() const
     std::cin.get(ch);
     str += ch;
 
-    if (ch == '\e')  // Start of ANSI escape sequence.
+    if (ansi_code::is_escape_char(ch))  // Start of ANSI escape sequence.
     {
         do
         {
@@ -83,19 +84,19 @@ bool terminal_pager::process_input(std::string input)
             return false;
         case '\e':  // ANSI escape sequence.
             // Cannot switch on a std::string.
-            if (input == "\e[A" || input == "\e[1A]")  // Up arrow.
+            if (ansi_code::is_up_arrow(input))
             {
                 scroll(true, false);  // Up a line.
                 return false;
             }
-            else if (input == "\e[B" || input == "\e[1B]")  // Down arrow.
+            else if (ansi_code::is_down_arrow(input))
             {
                 scroll(false, false);  // Down a line.
                 return false;
             }
     }
 
-    std::cout << '\a';  // Emit BEL for visual feedback.
+    std::cout << ansi_code::bel;
     return false;
 }
 
@@ -108,8 +109,8 @@ void terminal_pager::render_terminal() const
 {
     auto end_row_index = m_start_row_index + m_rows - 1;
 
-    std::cout << "\e[2J";  // Erase screen.
-    std::cout << "\e[H";  // Cursor to top.
+    std::cout << ansi_code::erase_screen;
+    std::cout << ansi_code::cursor_to_top;
 
     for (size_t i = m_start_row_index; i < end_row_index; i++)
     {
@@ -120,7 +121,7 @@ void terminal_pager::render_terminal() const
         std::cout << m_lines[i] << std::endl;
     }
 
-    std::cout << "\e[" << m_rows << "H";  // Move cursor to bottom row of terminal.
+    std::cout << ansi_code::cursor_to_row(m_rows);  // Move cursor to bottom row of terminal.
     std::cout << ":";
 }
 
@@ -154,8 +155,7 @@ void terminal_pager::scroll(bool up, bool page)
 
     if (m_start_row_index == old_start_row_index)
     {
-        // No change, emit BEL for visual feedback.
-        std::cout << '\a';
+        std::cout << ansi_code::bel;
     }
     else
     {
@@ -188,7 +188,7 @@ void terminal_pager::show()
     new_termios.c_lflag &= (~ICANON & ~ECHO);
     tcsetattr(fileno(stdin), TCSANOW, &new_termios);
 
-    std::cout << "\e[?1049h";  // Enable alternative buffer.
+    std::cout << ansi_code::enable_alternative_buffer;
 
     m_start_row_index = 0;
     render_terminal();
@@ -199,7 +199,7 @@ void terminal_pager::show()
         stop = process_input(get_input());
     } while (!stop);
 
-    std::cout << "\e[?1049l";  // Disable alternative buffer.
+    std::cout << ansi_code::disable_alternative_buffer;
 
     // Restore original termios settings.
     tcsetattr(fileno(stdin), TCSANOW, &old_termios);