Make default font tables overridable

Adafruit_LEDBackpack.cpp

@@ -51,6 +51,7 @@
   } ///< 16-bit var swap
 #endif
 
+#ifdef USE_DEFAULT_SEVENSEG_FONTTABLE
 static const PROGMEM uint8_t sevensegfonttable[] = {
 
     0b00000000, // (space)
@@ -150,7 +151,9 @@ static const PROGMEM uint8_t sevensegfonttable[] = {
     0b00000001, // ~
     0b00000000, // del
 };
+#endif
 
+#ifdef USE_DEFAULT_ALPHASEG_FONTTABLE
 static const PROGMEM uint16_t alphafonttable[] = {
 
     0b0000000000000001, 0b0000000000000010, 0b0000000000000100,
@@ -262,6 +265,7 @@ static const PROGMEM uint16_t alphafonttable[] = {
     0b0011111111111111,
 
 };
+#endif
 
 void Adafruit_LEDBackpack::setDisplayState(bool state) {
   uint8_t buffer;

Adafruit_LEDBackpack.h

@@ -50,6 +50,15 @@
 
 #define SEVENSEG_DIGITS 5 ///< # Digits in 7-seg displays, plus NUL end
 
+// You have to define ADAFRUIT_USER_DEFINED_FONT to override default font table and define the font table content
+#ifndef ADAFRUIT_USER_DEFINED_FONT
+#define USE_DEFAULT_SEVENSEG_FONTTABLE
+#define USE_DEFAULT_ALPHASEG_FONTTABLE
+#else
+extern const PROGMEM uint8_t sevensegfonttable[];
+extern const PROGMEM uint16_t alphafonttable[];
+#endif
+
 /*
 Segment names for 14-segment alphanumeric displays.
 See https://learn.adafruit.com/14-segment-alpha-numeric-led-featherwing/usage
@@ -473,6 +482,13 @@ class Adafruit_AlphaNum4 : public Adafruit_LEDBackpack {
   /*!
     @brief  Write single character of alphanumeric display as raw bits
             (not a general print function).
+              f-----------
+             a| 7\ 6| 5/ e|
+              9----  8----
+             b| 4/ 3| 2\ d|
+              c----------- 1.
+            The 16 bit digit you pass in for raw image has this mapping:
+            0(=0) 1 2 3 4 5 6 7 8 9 a b c d e f
     @param  n        Character index (0-3).
     @param  bitmask  Segment bitmask.
   */