Custom utf8 conversion replaces unconvertable chars with ? instead of blanks, #154

src/screen.cpp

@@ -499,6 +499,9 @@ void Screen::setup()
     // Store a pointer to Screen so we can get to it from static functions.
     ui.getUiState()->userData = this;
 
+    // Set the utf8 conversion function
+    dispdev.setFontTableLookupFunction(customFontTableLookup);
+
     // Add frames.
     static FrameCallback bootFrames[] = {drawBootScreen};
     static const int bootFrameCount = sizeof(bootFrames) / sizeof(bootFrames[0]);

src/screen.h

@@ -149,6 +149,29 @@ class Screen : public PeriodicTask
         }
     }
 
+    /// Overrides the default utf8 character conversion, to replace empty space with question marks
+    static char customFontTableLookup(const uint8_t ch) {
+        // UTF-8 to font table index converter
+        // Code form http://playground.arduino.cc/Main/Utf8ascii
+        static uint8_t LASTCHAR;
+
+        if (ch < 128) { // Standard ASCII-set 0..0x7F handling
+            LASTCHAR = 0;
+            return ch;
+        }
+
+        uint8_t last = LASTCHAR;   // get last char
+        LASTCHAR = ch;
+
+        switch (last) {    // conversion depnding on first UTF8-character
+            case 0xC2: return (uint8_t) ch;
+            case 0xC3: return (uint8_t) (ch | 0xC0);
+            case 0x82: if (ch == 0xAC) return (uint8_t) 0x80;    // special case Euro-symbol
+        }
+
+        return (uint8_t) '?'; // otherwise: return ?, if character can't be converted
+    }
+
     /// Returns a handle to the DebugInfo screen.
     //
     // Use this handle to set things like battery status, user count, GPS status, etc.