X11: More explicit warning when using rotated text w/o Xft.

The warning is issued to stderr only once (previously: every time rotated
text was used).



git-svn-id: file:///fltk/svn/fltk/branches/branch-1.3-porting@11978 ea41ed52-d2ee-0310-a9c1-e6b18d33e121

FL/fl_draw.H

@@ -3,7 +3,7 @@
 //
 // Portable drawing function header file for the Fast Light Tool Kit (FLTK).
 //
-// Copyright 1998-2011 by Bill Spitzak and others.
+// Copyright 1998-2016 by Bill Spitzak and others.
 //
 // This library is free software. Distribution and use rights are outlined in
 // the file "COPYING" which should have been included with this file.  If this
@@ -624,8 +624,8 @@ FL_EXPORT const char *fl_local_to_mac_roman(const char *t, int n=-1);
 */
 FL_EXPORT void fl_draw(const char* str, int x, int y);
 /**
-  Draws a nul-terminated UTF-8 string starting at the given \p x, \p y location and 
-  rotating \p angle degrees counter-clockwise.
+  Draws a nul-terminated UTF-8 string starting at the given \p x, \p y
+  location and rotating \p angle degrees counter-clockwise.
   This version of fl_draw provides direct access to the text drawing
   function of the underlying OS and is supported by Xft, Win32 and MacOS
   fltk subsets.
@@ -636,8 +636,13 @@ FL_EXPORT void fl_draw(int angle, const char* str, int x, int y);
 */
 inline void fl_draw(const char* str, int n, int x, int y) {fl_graphics_driver->draw(str,n,x,y); }
 /**
-  Draws at the given \p x, \p y location a UTF-8 string of length \p n bytes 
+  Draws at the given \p x, \p y location a UTF-8 string of length \p n bytes
   rotating \p angle degrees counter-clockwise.
+
+  \note When using X11 (Unix, Linux, Cygwin et al.) this needs Xft to work.
+	Under plain X11 (w/o Xft) rotated text is not supported by FLTK.
+	A warning will be issued to stderr at runtime (only once) if you
+	use this method with an angle other than 0.
 */
 inline void fl_draw(int angle, const char* str, int n, int x, int y) {fl_graphics_driver->draw(angle,str,n,x,y); }
 /**

src/drivers/Xlib/Fl_Xlib_Graphics_Driver_font_x.cxx

@@ -659,7 +659,13 @@ void Fl_Xlib_Graphics_Driver::draw(const char* c, int n, int x, int y) {
 }
 
 void Fl_Xlib_Graphics_Driver::draw(int angle, const char *str, int n, int x, int y) {
-  fprintf(stderr,"ROTATING TEXT NOT IMPLEMENTED\n");
+  static char warning = 0; // issue warning only once
+  if (!warning && angle != 0) {
+    warning = 1;
+    fprintf(stderr,
+	    "libfltk: rotated text not implemented by X backend.\n"
+	    "  You should use the Xft backend. Check USE_XFT in config.h.\n");
+  }
   this->draw(str, n, (int)x, (int)y);
 }