Rename putchar() to plot_char() (#944)

Some old platforms (NetBSD, AIX) implement the common stdio "putchar()"
function as a global macro which poisons the global namespace, preventing
all C and C++ programs from using "putchar()" as a function or method.

There was a long thread about this in fltk.coredev during the period
Mar 25 2024 ~ Apr 4 2024, subject "RFC: Fl_Terminal::putchar() in public API"
as to why we have no choice but to not use putchar() as a method name.

FL/Fl_Terminal.H

@@ -144,7 +144,7 @@
   Single character output can be done with:
   \par
      - print_char() to print a single ASCII/UTF-8 char at the cursor
-     - putchar() to put single ASCII/UTF-8 char at an x,y position
+     - plot_char() to put single ASCII/UTF-8 char at an x,y position
   \par
 
   \subsection Fl_Terminal_Attributes Text Attributes
@@ -1017,8 +1017,8 @@ private:
   void utf8_cache_flush(void);
   // API: Character display output
 public:
-  void putchar(const char *text, int len, int drow, int dcol);
-  void putchar(char c, int drow, int dcol);
+  void plot_char(const char *text, int len, int drow, int dcol);
+  void plot_char(char c, int drow, int dcol);
   void print_char(const char *text, int len=-1);
   void print_char(char c);
   // API: String display output

src/Fl_Terminal.cxx

@@ -1902,10 +1902,10 @@ void Fl_Terminal::clear_sod(void) {
   for (int drow=0; drow <= cursor_.row(); drow++)
     if (drow == cursor_.row())
       for (int dcol=0; dcol<=cursor_.col(); dcol++)
-        putchar(' ', drow, dcol);
+        plot_char(' ', drow, dcol);
     else
       for (int dcol=0; dcol<disp_cols(); dcol++)
-        putchar(' ', drow, dcol);
+        plot_char(' ', drow, dcol);
   //TODO: Clear mouse selection?
 }
 
@@ -1914,10 +1914,10 @@ void Fl_Terminal::clear_eod(void) {
   for (int drow=cursor_.row(); drow<disp_rows(); drow++)
     if (drow == cursor_.row())
       for (int dcol=cursor_.col(); dcol<disp_cols(); dcol++)
-        putchar(' ', drow, dcol);
+        plot_char(' ', drow, dcol);
     else
       for (int dcol=0; dcol<disp_cols(); dcol++)
-        putchar(' ', drow, dcol);
+        plot_char(' ', drow, dcol);
   //TODO: Clear mouse selection?
 }
 
@@ -2977,7 +2977,7 @@ const Fl_Terminal::Utf8Char* Fl_Terminal::utf8_char_at_glob(int grow, int gcol)
 }
 
 /**
-  Print UTF-8 character \p text of length \p len at display position \p (drow,dcol).
+  Plot the UTF-8 character \p text of length \p len at display position \p (drow,dcol).
   The character is displayed using the current text color/attributes.
 
   This is a very low level method.
@@ -2987,12 +2987,12 @@ const Fl_Terminal::Utf8Char* Fl_Terminal::utf8_char_at_glob(int grow, int gcol)
   - \p dcol must be in range 0..(display_columns()-1)
 
   - Does not trigger redraws
-  - Does not handle ANSI or XTERM escape sequences
+  - Does not handle control codes, ANSI or XTERM escape sequences.
   - Invalid UTF-8 chars show the error character (¿) depending on show_unknown(bool).
 
   \see handle_unknown_char()
 */
-void Fl_Terminal::putchar(const char *text, int len, int drow, int dcol) {
+void Fl_Terminal::plot_char(const char *text, int len, int drow, int dcol) {
   Utf8Char *u8c = u8c_disp_row(drow) + dcol;
   // text_utf8() warns we must do invalid checks first
   if (!text || len<1 || len>u8c->max_utf8() || len!=fl_utf8len(*text))
@@ -3001,7 +3001,7 @@ void Fl_Terminal::putchar(const char *text, int len, int drow, int dcol) {
 }
 
 /**
-  Print the ASCII character \p c at the terminal's display position \p (drow,dcol).
+  Plot the ASCII character \p c at the terminal's display position \p (drow,dcol).
 
   The character MUST be printable (in range 0x20 - 0x7e), and is displayed
   using the current text color/attributes. Characters outside that range are either
@@ -3018,7 +3018,7 @@ void Fl_Terminal::putchar(const char *text, int len, int drow, int dcol) {
 
   \see show_unknown(bool), handle_unknown_char(), is_printable()
 */
-void Fl_Terminal::putchar(char c, int drow, int dcol) {
+void Fl_Terminal::plot_char(char c, int drow, int dcol) {
   if (!is_printable(c)) { handle_unknown_char(); return; }
   Utf8Char *u8c = u8c_disp_row(drow) + dcol;
   u8c->text_ascii(c, *current_style_);
@@ -3053,7 +3053,7 @@ void Fl_Terminal::print_char(const char *text, int len/*=-1*/) {
   } else if (escseq.parse_in_progress()) {     // ESC sequence in progress?
     handle_escseq(*text);
   } else {                                     // Handle printable char..
-    putchar(text, len, cursor_row(), cursor_col());
+    plot_char(text, len, cursor_row(), cursor_col());
     cursor_right(1, do_scroll);
   }
 }
@@ -3074,7 +3074,7 @@ void Fl_Terminal::print_char(char c) {
   } else if (escseq.parse_in_progress()) {     // ESC sequence in progress?
     handle_escseq(c);
   } else {                                     // Handle printable char..
-    putchar(c, cursor_row(), cursor_col());
+    plot_char(c, cursor_row(), cursor_col());
     cursor_right(1, do_scroll);
     return;
   }

test/terminal.fl

@@ -1282,7 +1282,7 @@ for (int i=0; i<50; i++ ) {
     for ( int col=0; col<cols; col++ ) {
       char c = ' ' + (rand() % 0x50);              // random ASCII characters
       G_tty->textfgcolor_xterm(rand() % 8);        // random fg uchar color for each char
-      G_tty->putchar(c, row, col);
+      G_tty->plot_char(c, row, col);
     }
   }
   G_tty->redraw();