ESC sequences can traverse append(), unicode support for backspace

This is basically a rewrite of the ESC handler, keeping state
in the class, so ESC sequences can continued between called
to append() (such as when reading data from a pipe in blocks).

New private class 'Fl_Escape_Seq' handles parsing and state info.
It also has careful bounds checking during parsing.

Backspace supports Unicode, and the unicode chars can straddle
across append() operations as well.

Private variables in Fl_Simple_Terminal renamed _xxx to xxx_
to improve CMP compliance.

FL/Fl_Simple_Terminal.H

@@ -123,21 +123,64 @@ protected:
   Fl_Text_Buffer *sbuf;     // style buffer
 
 private:
-  int history_lines_;       // max lines allowed in screen history
+  // Private class to handle parsing ESC sequences
+  //    Holds all state information for parsing esc sequences,
+  //    so sequences can span multiple block read(2) operations, etc.
+  //
+  class Fl_Escape_Seq {
+  public:
+    static const int maxbuf   = 80;
+    static const int maxvals  = 10;
+    // Return codes
+    static const int success   = 0;   // operation succeeded
+    static const int fail      = -1;  // operation failed
+    static const int completed = 1;   // multi-step operation completed successfully
+  private:
+    char  esc_mode_;        // escape parsing mode state
+    char  buf_[maxbuf];     // escape sequence being parsed
+    char *bufp_;            // parsing ptr into buf[]
+    char *bufendp_;         // end of buf[] (ptr to last valid buf char)
+    char *valbufp_;         // pointer to first char in buf of integer being parsed
+    int   vals_[maxvals];   // value array for parsing #'s in ESC[#;#;#..
+    int   vali_;            // parsing index into vals_[], 0 if none
+
+    int append_buf(char c);
+    int append_val();
+
+  public:
+    Fl_Escape_Seq();
+    void reset();
+    char esc_mode() const;
+    void esc_mode(char val);
+    int  total_vals() const;
+    int  val(int i) const;
+    bool parse_in_progress() const;
+    int parse(char c);
+  };
+
+private:
+  int  history_lines_;      // max lines allowed in screen history
   bool stay_at_bottom_;     // lets scroller chase last line in buffer
   bool ansi_;               // enables ANSI sequences
   // scroll management
-  int lines;                // #lines in buffer (optimization: Fl_Text_Buffer slow to calc this)
-  bool scrollaway;          // true when user changed vscroll away from bottom
-  bool scrolling;           // true while scroll callback active
+  int  lines_;              // #lines in buffer (optimization: Fl_Text_Buffer slow to calc this)
+  bool scrollaway_;         // true when user changed vscroll away from bottom
+  bool scrolling_;          // true while scroll callback active
   // Fl_Text_Display vscrollbar's callback+data
-  Fl_Callback *orig_vscroll_cb;
-  void *orig_vscroll_data;
+  Fl_Callback *orig_vscroll_cb_;
+  void *orig_vscroll_data_;
   // Style table
   const Fl_Text_Display::Style_Table_Entry *stable_;  // the active style table
-  int stable_size_;         // active style table size (in bytes)
-  int normal_style_index_;  // "normal" style used by "\033[0m" reset sequence
-  int current_style_index_; // current style used for drawing text
+  int  stable_size_;         // active style table size (in bytes)
+  int  normal_style_index_;  // "normal" style used by "\033[0m" reset sequence
+  int  current_style_index_; // current style used for drawing text
+  char current_style_;       // current 'style char' (e.g. 'A' = first style entry)
+  Fl_Escape_Seq escseq;      // escape sequence state handler
+  // String parsing vars initialized/used by append(), used by handle_backspace() etc.
+  char *ntm_;                // new text memory  (ntm) - malloc()ed by append() for output text
+  char *ntp_;                // new text ptr     (ntp) - points into ntm buffer
+  char *nsm_;                // new style memory (nsm) - malloc()ed by append() for output style
+  char *nsp_;                // new style ptr    (nsp) - points into nsm buffer
 
 public:
   Fl_Simple_Terminal(int X,int Y,int W,int H,const char *l=0);
@@ -157,6 +200,7 @@ public:
   int  normal_style_index() const;
   void current_style_index(int);
   int  current_style_index() const;
+  int  current_style() const;
 
   // Terminal text management
   void append(const char *s, int len=-1);
@@ -188,6 +232,8 @@ protected:
   void vscroll_cb2(Fl_Widget*, void*);
   static void vscroll_cb(Fl_Widget*, void*);
   void backspace_buffer(unsigned int count);
+  void handle_backspace();
+  void append_ansi(const char *s, int len);
 };
 
 #endif