From 5cf1da0cfebbf2760bb7cfbbda06854d5ea99241 Mon Sep 17 00:00:00 2001
From: Robert Csordas <xdever@gmail.com>
Date: Mon, 14 Nov 2016 22:09:33 +0100
Subject: [PATCH] Fixes the bug of additional characters when mod key is
 released before the other key

---
 right/src/keyboard_layout.c        |  3 +++
 right/src/keyboard_layout.h        | 22 ++++++++++++++++++++++
 right/src/usb_interface_keyboard.c |  1 +
 3 files changed, 26 insertions(+)
 create mode 100644 right/src/keyboard_layout.c

diff --git a/right/src/keyboard_layout.c b/right/src/keyboard_layout.c
new file mode 100644
index 0000000..915ccca
--- /dev/null
+++ b/right/src/keyboard_layout.c
@@ -0,0 +1,3 @@
+#include "keyboard_layout.h"
+
+uint8_t keyMasks[LAYOUT_KEY_COUNT];
diff --git a/right/src/keyboard_layout.h b/right/src/keyboard_layout.h
index 881ac0e..9b2e9ae 100644
--- a/right/src/keyboard_layout.h
+++ b/right/src/keyboard_layout.h
@@ -35,11 +35,20 @@
 #define MODIFIER_MOD_PRESSED 1
 #define MODIFIER_FN_PRESSED 2
 
+extern uint8_t keyMasks[LAYOUT_KEY_COUNT];
+
 
 static inline __attribute__((always_inline)) uint8_t getKeycode(KEYBOARD_LAYOUT(layout), uint8_t keyId, uint8_t modifierState)
 {
 	if (keyId<LAYOUT_KEY_COUNT) {
+		if (keyMasks[keyId]!=0 && keyMasks[keyId]!=modifierState){
+			//Mask out key presses after releasing modifier keys
+			return 0;
+		}
+
 		uint8_t k = layout[keyId][modifierState];
+		keyMasks[keyId] = modifierState;
+
 		if (k==0) {
 			k = layout[keyId][0];
 		}
@@ -62,4 +71,17 @@ static inline __attribute__((always_inline)) uint8_t getModifierState(const uint
 	return mod;
 }
 
+static inline __attribute__((always_inline)) void clearKeymasks(const uint8_t *leftKeyStates, const uint8_t *rightKeyStates){
+	int i;
+	for (i=0; i<KEY_STATE_COUNT; ++i){
+		if (rightKeyStates[i]==0){
+			keyMasks[i] = 0;
+		}
+
+		if (leftKeyStates[i]==0){
+			keyMasks[LAYOUT_LEFT_OFFSET+i] = 0;
+		}
+	}
+}
+
 #endif
diff --git a/right/src/usb_interface_keyboard.c b/right/src/usb_interface_keyboard.c
index a87745f..0de7b1c 100644
--- a/right/src/usb_interface_keyboard.c
+++ b/right/src/usb_interface_keyboard.c
@@ -101,6 +101,7 @@ void usbKeyboadTask(){
 	readLeftKeys(leftKeyStates);
 
 	uint8_t modifierState = getModifierState(leftKeyStates, keyMatrix.keyStates);
+	clearKeymasks(leftKeyStates, keyMatrix.keyStates);
 
 	int scancodeIdx = 0;
 	for (uint8_t keyId=0; keyId<KEYBOARD_MATRIX_COLS_NUM*KEYBOARD_MATRIX_ROWS_NUM; keyId++) {