New public static variable bool Fl_Image::register_images_done

Allows an app to detect whether fl_register_images() was called or not.

FL/Fl_Image.H

@@ -226,6 +226,7 @@ public:
   static void scaling_algorithm(Fl_RGB_Scaling algorithm) {scaling_algorithm_ = algorithm; }
   /** Gets what algorithm is used when resizing a source image to draw it. */
   static Fl_RGB_Scaling scaling_algorithm() {return scaling_algorithm_;}
+  static bool register_images_done;
 };
 
 

src/Fl_Image.cxx

@@ -297,6 +297,8 @@ int Fl_Image::draw_scaled(int X, int Y, int W, int H) {
   return 1;
 }
 
+/** True after fl_register_images() was called, false before */
+bool Fl_Image::register_images_done = false;
 
 //
 // RGB image class...

src/fl_images_core.cxx

@@ -57,6 +57,7 @@ static Fl_Image	*fl_check_images(const char *name, uchar *header, int headerlen)
 */
 void fl_register_images() {
   Fl_Shared_Image::add_handler(fl_check_images);
+  Fl_Image::register_images_done = true;
 }