From 585e062e87dbb227e73e2cb31d5041ff5520fb4d Mon Sep 17 00:00:00 2001
From: Pete Johanson <peter@peterjohanson.com>
Date: Mon, 18 May 2020 23:34:36 -0400
Subject: [PATCH] Initial basic modifiers support.

---
 include/dt-bindings/zmk/keys.h | 22 +++++++++++++++++-----
 include/zmk/hid.h              |  2 ++
 include/zmk/keys.h             |  1 +
 src/endpoints.c                |  1 +
 src/hid.c                      | 26 ++++++++++++++++++++++++++
 5 files changed, 47 insertions(+), 5 deletions(-)

diff --git a/include/dt-bindings/zmk/keys.h b/include/dt-bindings/zmk/keys.h
index 4c975dbe..5a2d97a2 100644
--- a/include/dt-bindings/zmk/keys.h
+++ b/include/dt-bindings/zmk/keys.h
@@ -60,13 +60,25 @@
 
 #define KC_APP 0x65
 
+#define KC_LCTL 0xE0
+#define KC_LSFT 0xE1
+#define KC_LALT 0xE2
+#define KC_LGUI 0xE3
+#define KC_RCTL 0xE4
+#define KC_RSFT 0xE5
+#define KC_RALT 0xE6
 #define KC_RGUI 0xE7
 
-#define MD_SHFT 0x01
-#define KC_ALT 0x02
-#define KC_CTRL 0x03
-
 #define ZC_TRNS 0xF0
 #define ZC_NOOP 0xF1
 
-#define ZC_CSTM(n) (0xFF + n)
\ No newline at end of file
+#define ZC_CSTM(n) (0xFF + n)
+
+#define MOD_LCTL 0x00
+#define MOD_LSFT 0x01
+#define MOD_LALT 0x02
+#define MOD_LGUI 0x03
+#define MOD_RCTL 0x04
+#define MOD_RSFT 0x05
+#define MOD_RALT 0x06
+#define MOD_RGUI 0x07
\ No newline at end of file
diff --git a/include/zmk/hid.h b/include/zmk/hid.h
index 9f0760ab..8fbcf4fd 100644
--- a/include/zmk/hid.h
+++ b/include/zmk/hid.h
@@ -101,6 +101,8 @@ struct zmk_hid_report
     u8_t keys[13];
 } __packed;
 
+int zmk_hid_register_mod(zmk_mod modifier);
+int zmk_hid_unregister_mod(zmk_mod modifier);
 int zmk_hid_press_key(zmk_key key);
 int zmk_hid_release_key(zmk_key key);
 
diff --git a/include/zmk/keys.h b/include/zmk/keys.h
index b61ef811..be057841 100644
--- a/include/zmk/keys.h
+++ b/include/zmk/keys.h
@@ -4,6 +4,7 @@
 #include <dt-bindings/zmk/keys.h>
 
 typedef u64_t zmk_key;
+typedef u8_t zmk_mod;
 
 struct zmk_key_event
 {
diff --git a/src/endpoints.c b/src/endpoints.c
index 6854370f..b73e7ed9 100644
--- a/src/endpoints.c
+++ b/src/endpoints.c
@@ -33,6 +33,7 @@ int zmk_endpoints_send_key_event(struct zmk_key_event key_event)
     struct zmk_hid_report *report;
     int err;
 
+
     if (key_event.pressed)
     {
         zmk_hid_press_key(key_event.key);
diff --git a/src/hid.c b/src/hid.c
index faf3cfc5..234c624f 100644
--- a/src/hid.c
+++ b/src/hid.c
@@ -4,6 +4,22 @@ static struct zmk_hid_report report = {
     .modifiers = 0,
     .keys = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}};
 
+#define _TOGGLE_MOD(mod, state) \
+    if (modifier > MOD_RGUI)    \
+    {                           \
+        return -EINVAL;         \
+    }                           \
+    WRITE_BIT(report.modifiers, mod, state);
+
+int zmk_hid_register_mod(zmk_mod modifier)
+{
+    _TOGGLE_MOD(modifier, true);
+}
+int zmk_hid_unregister_mod(zmk_mod modifier)
+{
+    _TOGGLE_MOD(modifier, false);
+}
+
 #define KEY_OFFSET 0x02
 #define MAX_KEYS 6
 
@@ -24,6 +40,11 @@ static struct zmk_hid_report report = {
 
 int zmk_hid_press_key(zmk_key code)
 {
+    if (code >= KC_LCTL && code <= KC_RGUI)
+    {
+        return zmk_hid_register_mod(code - KC_LCTL);
+    }
+
     if (code > ZMK_HID_MAX_KEYCODE)
     {
         return -EINVAL;
@@ -38,6 +59,11 @@ int zmk_hid_press_key(zmk_key code)
 
 int zmk_hid_release_key(zmk_key code)
 {
+    if (code >= KC_LCTL && code <= KC_RGUI)
+    {
+        return zmk_hid_unregister_mod(code - KC_LCTL);
+    }
+
     if (code > ZMK_HID_MAX_KEYCODE)
     {
         return -EINVAL;