1 files changed, 92 insertions, 0 deletions
diff --git a/layer.c b/layer.c
new file mode 100644
index 0000000000..5b9b591fe0
--- /dev/null
+++ b/layer.c
@@ -0,0 +1,92 @@
+#include "keymap_skel.h"
+#include "usb_keyboard.h"
+#include "debug.h"
+#include "timer.h"
+#include "layer.h"
+
+/*
+ * LAYER_ENTER_DELAY: prevent from moving new layer
+ *                     press                release
+ * Fn key sate     ____|~~~~~~~~~~~~~~~~~~~|_______________
+ * 
+ * enter_delay         |======|
+ *                              new layer
+ * Layer sw        ___________|~~~~~~~~~~~~|_______________
+ */ 
+#define LAYER_ENTER_DELAY 10
+
+/*
+ * LAYER_SEND_FN_TERM: send keycode if release key in this term
+ *                     press          release(send)
+ * Fn key state    ____|~~~~~~~~~~~~~|_______________
+ *                     press         |       release(not send)
+ * Fn key state    ____|~~~~~~~~~~~~~|~~~~~~|__________
+ *                                   |      |
+ * send_fn_term        |=============o==|   x
+ */
+#define LAYER_SEND_FN_TERM 30
+
+
+static uint8_t current_layer = 0;
+static bool layer_used = false;
+
+
+uint8_t layer_get_keycode(uint8_t row, uint8_t col)
+{
+    uint8_t code = keymap_get_keycode(current_layer, row, col);
+    // normal key or mouse key
+    if ((IS_KEY(code) || IS_MOUSE(code)))
+        layer_used = true;
+    return code;
+}
+
+void layer_switching(uint8_t fn_bits)
+{
+    // layer switching
+    static uint8_t last_bits = 0;
+    static uint8_t last_mod = 0;
+    static uint16_t last_timer = 0; 
+
+    //uint16_t now_timer;
+
+    if (fn_bits == last_bits) {
+        // switch layer when specific time elapsed
+        if (current_layer != keymap_fn_layer(fn_bits) &&
+                timer_elapsed(last_timer) > LAYER_ENTER_DELAY) {
+            current_layer = keymap_fn_layer(fn_bits);
+            debug("time_elapsed: "); debug_hex16(timer_elapsed(last_timer)); debug("\n"); 
+            debug("switch layer: "); debug_hex(current_layer); debug("\n");
+        }
+    } else if (fn_bits == 0) {
+        // send key when Fn key is released without using the layer and within specific time
+        if ((!layer_used || current_layer != keymap_fn_layer(last_bits)) &&
+                timer_elapsed(last_timer) < LAYER_SEND_FN_TERM) {
+            uint8_t code = keymap_fn_keycode(last_bits);
+            if (code != KB_NO) {
+                if (IS_MOD(code)) {
+                    keyboard_modifier_keys = last_mod | MOD_BIT(code);
+                } else {
+                    keyboard_keys[0] = code;
+                    keyboard_modifier_keys = last_mod;
+                }
+                usb_keyboard_send();
+                usb_keyboard_print();
+                usb_keyboard_clear();
+            }
+        }
+        last_bits = 0;
+        last_mod = 0;
+        layer_used = false;
+        current_layer = 0; // default layer
+    } else if ((fn_bits & (fn_bits - 1)) == 0) {
+        // switch layer when just one Fn Key is pressed
+        if (!usb_keyboard_has_key()) {
+            last_bits = fn_bits;
+            last_mod = keyboard_modifier_keys;
+            last_timer = timer_read();
+            debug("last_bits: "); debug_bin(last_bits); debug("\n");
+            debug("last_mod: "); debug_hex(last_mod); debug("\n");
+            debug("last_timer: "); debug_hex16(last_timer); debug("\n");
+        }
+    }
+}