Improved(?) 32-bit CPU compatibility for fonts

Author: PaintYourDragon

Adafruit_GFX.cpp

@@ -31,17 +31,34 @@ ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 POSSIBILITY OF SUCH DAMAGE.
 */
 
-#include "Adafruit_GFX.h"
-#include "glcdfont.c"
 #ifdef __AVR__
  #include <avr/pgmspace.h>
- #define pgm_read_pointer(addr) ((void *)pgm_read_word(addr))
 #elif defined(ESP8266)
  #include <pgmspace.h>
- #define pgm_read_pointer(addr) ((void *)pgm_read_dword(addr))
-#else
+#endif
+#include "Adafruit_GFX.h"
+#include "glcdfont.c"
+
+// Many (but maybe not all) non-AVR board installs define macros
+// for compatibility with existing PROGMEM-reading AVR code.
+// Do our own checks and defines here for good measure...
+
+#ifndef pgm_read_byte
  #define pgm_read_byte(addr) (*(const unsigned char *)(addr))
+#endif
+#ifndef pgm_read_word
  #define pgm_read_word(addr) (*(const unsigned short *)(addr))
+#endif
+#ifndef pgm_read_dword
+ #define pgm_read_dword(addr) (*(const unsigned long *)(addr))
+#endif
+
+// Pointers are a peculiar case...typically 16-bit on AVR boards,
+// 32 bits elsewhere.  Try to accommodate both...
+
+#if !defined(__INT_MAX__) || (__INT_MAX__ > 0xFFFF)
+ #define pgm_read_pointer(addr) ((void *)pgm_read_dword(addr))
+#else
  #define pgm_read_pointer(addr) ((void *)pgm_read_word(addr))
 #endif