switch to a more robust mechanism of looking for key release

ArduinoKeyboard.ino

@@ -17,12 +17,20 @@ static int rowPins[ROWS] = { A2, A3, A4, A5, 15 };
 
 byte matrixState[ROWS][COLS];
 
+// if we're sticking to boot protocol, these could all be 6 + mods
+// but *mumble*
+//
 
-long counter = 0;
-static const int LAYERS = 2;
 
+#define KEYS_HELD_BUFFER 12
+byte charsBeingReported[KEYS_HELD_BUFFER]; // A bit vector for the 256 keys we might conceivably be holding down
+byte charsReportedLastTime[KEYS_HELD_BUFFER]; // A bit vector for the 256 keys we might conceivably be holding down
+
+
+long reporting_counter = 0;
+static const int LAYERS = 2;
 int current_layer = 0;
-int previous_keymap = 0;
+
 
 static const Key keymaps[LAYERS][ROWS][COLS] = {
     {
@@ -44,6 +52,45 @@ static const Key keymaps[LAYERS][ROWS][COLS] = {
 };
 
 
+void release_keys_not_being_pressed() {
+
+    // we use charsReportedLastTime to figure out what we might not be holding anymore and can now release. this is destructive to charsReportedLastTime
+
+    for (int i=0; i<KEYS_HELD_BUFFER; i++) {
+        // for each key we were holding as of the end of the last cycle
+        // see if we're still holding it
+        // if we're not, call an explicit Release
+
+            if (charsReportedLastTime[i] != 0x00) {
+                // if there _was_ a character in this slot, go check the 
+                // currently held characters
+        for (int j=0; j<KEYS_HELD_BUFFER; j++) {
+            if (charsReportedLastTime[i] == charsBeingReported[j]) {
+                // if's still held, we don't need to do anything.
+                charsReportedLastTime[i] = 0x00;
+                break;
+            }
+            }
+
+        }
+    }
+    for (int i=0; i<KEYS_HELD_BUFFER; i++) {
+        if (charsReportedLastTime[i] != 0x00) {
+            Keyboard.release(charsReportedLastTime[i]);
+        }
+    }
+}
+
+void record_key_being_pressed(byte character) {
+    for (int i=0; i<KEYS_HELD_BUFFER; i++) {
+        // todo - deal with overflowing the 12 key buffer here
+        if (charsBeingReported[i] == 0x00) {
+            charsBeingReported[i] = character;
+            break;
+        }
+    }
+}
+
 boolean key_was_pressed (byte keyState) {
     if ( byte((keyState >> 4)) ^ B00001111 ) {
         return false;
@@ -109,6 +156,10 @@ void reset_matrix() {
             matrixState[row][col] <<= 1;
         }
     }
+    for (int i=0; i<KEYS_HELD_BUFFER; i++) {
+        charsReportedLastTime[i] = charsBeingReported[i];
+        charsBeingReported[i] = 0x00;
+    }
 }
 
 void send_key_events(int layer) {
@@ -145,19 +196,23 @@ void send_key_events(int layer) {
                 }
 
             } else {
-
+                if (key_is_pressed(switchState)) {
+                    record_key_being_pressed(mappedKey.rawKey);
                     if (key_toggled_on (switchState)) {
                         Keyboard.press(mappedKey.rawKey);
                     } 
+                }
                 else if (key_toggled_off (switchState)) {
                     Keyboard.release(mappedKey.rawKey);
                 }
             }
         }
     }
+    release_keys_not_being_pressed();
 }
 
 
+
 void setup_matrix() {
     //set up the row pins as outputs
     for (int row = 0; row < ROWS; row++) {
@@ -217,7 +272,7 @@ void scan_matrix() {
 
 
 void report_matrix() {
-    if (counter++ %100 == 0 ) {
+    if (reporting_counter++ %100 == 0 ) {
         for (int row = 0; row < ROWS; row++) {
             for (int col = 0; col < COLS; col++) {
                 Serial.print(matrixState[row][col],HEX);