From e6deb09e88ef02429e6b4c685c956aa975f5d5a8 Mon Sep 17 00:00:00 2001
From: Michael Richters <gedankenexperimenter@gmail.com>
Date: Thu, 17 Jun 2021 18:14:28 -0500
Subject: [PATCH] Add builtin modifier/layer-shift combo keys

Signed-off-by: Michael Richters <gedankenexperimenter@gmail.com>
---
 src/kaleidoscope/Runtime.cpp        | 13 ++++++++--
 src/kaleidoscope/key_defs.h         | 38 +++++++++++++++++++++++------
 src/kaleidoscope/key_defs/keymaps.h |  3 +++
 src/kaleidoscope/layers.cpp         |  5 ++++
 4 files changed, 50 insertions(+), 9 deletions(-)

diff --git a/src/kaleidoscope/Runtime.cpp b/src/kaleidoscope/Runtime.cpp
index 1a9bd414..08375ec5 100644
--- a/src/kaleidoscope/Runtime.cpp
+++ b/src/kaleidoscope/Runtime.cpp
@@ -157,9 +157,13 @@ void Runtime_::handleKeyEvent(KeyEvent event) {
       event.key == Key_Transparent)
     return;
 
-  // If it's a built-in Layer key, we handle it here, and skip sending report(s)
-  if (event.key.isLayerKey()) {
+  // Built-in layer change keys are handled by the Layer object.
+  if (event.key.isLayerKey() || event.key.isModLayerKey()) {
     Layer.handleLayerKeyEvent(event);
+  }
+  // If the event is for a layer change key, there's no need to send a HID
+  // report, so we return early.
+  if (event.key.isLayerKey()) {
     return;
   }
 
@@ -226,6 +230,11 @@ void Runtime_::addToReport(Key key) {
   if (result == EventHandlerResult::ABORT)
     return;
 
+  if (key.isModLayerKey()) {
+    uint8_t mod = key.getKeyCode() % 8;
+    key         = Key(Key_LeftControl.getRaw() + mod);
+  }
+
   if (key.isKeyboardKey()) {
     // The only incidental Keyboard modifiers that are allowed are the ones on
     // the key that generated the event, so we strip any others before adding
diff --git a/src/kaleidoscope/key_defs.h b/src/kaleidoscope/key_defs.h
index 8f5801ee..14a07b50 100644
--- a/src/kaleidoscope/key_defs.h
+++ b/src/kaleidoscope/key_defs.h
@@ -53,6 +53,12 @@
 #define SWITCH_TO_KEYMAP 0b00000100
 #define IS_CONSUMER      0b00001000
 
+// consumer: 01..1...
+// sysctl:   01..0001
+// layer:    01000100
+// modlayer: 01000110
+// macros:   01100000
+
 // HID Usage Types: Because these constants, like the ones above, are
 // used in the flags byte of the Key class, they can't overlap any of
 // the above bits. Nor can we use `SYNTHETIC` and `RESERVED` to encode
@@ -180,6 +186,9 @@ class Key {
   constexpr bool isLayerKey() const {
     return (flags_ == (SYNTHETIC | SWITCH_TO_KEYMAP));
   }
+  constexpr bool isModLayerKey() const {
+    return (flags_ == (SYNTHETIC | SWITCH_TO_KEYMAP | IS_INTERNAL));
+  }
 
   // ---------------------------------------------------------------------------
   // Additional utility functions for builtin `Key` variants
@@ -206,19 +215,26 @@ class Key {
   // used in a conceptually different way: to get a different symbol in the
   // output. We don't normally think "type `shift`+`1`"; we think "type `!`".
   constexpr bool isKeyboardShift() const {
-    return (isKeyboardModifier() &&
-            ((keyCode_ == HID_KEYBOARD_LEFT_SHIFT ||
-              keyCode_ == HID_KEYBOARD_RIGHT_SHIFT) ||
-             ((flags_ & SHIFT_HELD) != 0)));
+    return ((isKeyboardModifier() &&
+             ((keyCode_ == HID_KEYBOARD_LEFT_SHIFT ||
+               keyCode_ == HID_KEYBOARD_RIGHT_SHIFT) ||
+              ((flags_ & SHIFT_HELD) != 0))) ||
+            (isModLayerKey() &&
+             (keyCode_ % 8) % 4 == 1));
   }
   // Layer shift keys are conceptually similar to Keyboard modifier keys in that
   // they are used chorded to change the result of typing those other
   // keys. They're even more similar to `shift` keys. For both reasons, it's
   // worth singling them out.
   constexpr bool __attribute__((always_inline)) isLayerShift() const {
-    return (isLayerKey() &&
-            keyCode_ >= LAYER_SHIFT_OFFSET &&
-            keyCode_ < LAYER_MOVE_OFFSET);
+    return ((isLayerKey() &&
+             keyCode_ >= LAYER_SHIFT_OFFSET &&
+             keyCode_ < LAYER_MOVE_OFFSET) ||
+            isModLayerKey());
+  }
+
+  constexpr bool isMomentary() const {
+    return (isKeyboardModifier() || isLayerShift() || isModLayerKey());
   }
 
  private:
@@ -254,6 +270,14 @@ constexpr Key addFlags(Key k, uint8_t add_flags) {
   return Key(k.getKeyCode(), k.getFlags() | add_flags);
 }
 
+// =============================================================================
+/// Generate a ModLayer key (unchecked)
+constexpr Key modLayerKey(Key modifier, uint8_t layer) {
+  uint8_t mod  = modifier.getRaw() - Key_LeftControl.getRaw();
+  uint8_t code = mod + (layer * 8);
+  return Key(code, SYNTHETIC | SWITCH_TO_KEYMAP | IS_INTERNAL);
+}
+
 }  // namespace kaleidoscope
 
 // Redefine this macro to enable using alternative char-string to Key
diff --git a/src/kaleidoscope/key_defs/keymaps.h b/src/kaleidoscope/key_defs/keymaps.h
index 9039607c..5c29a63e 100644
--- a/src/kaleidoscope/key_defs/keymaps.h
+++ b/src/kaleidoscope/key_defs/keymaps.h
@@ -80,3 +80,6 @@ static const uint8_t LAYER_MOVE_OFFSET  = LAYER_SHIFT_OFFSET + LAYER_OP_OFFSET;
  * this is a one-way operation.
  */
 #define MoveToLayer(n) Key(n + LAYER_MOVE_OFFSET, KEY_FLAGS | SYNTHETIC | SWITCH_TO_KEYMAP)
+
+// Shorthand for keymap entry (e.g. `ML(LeftAlt, 3)`)
+#define ML(mod, layer) kaleidoscope::modLayerKey(Key_##mod, layer)
diff --git a/src/kaleidoscope/layers.cpp b/src/kaleidoscope/layers.cpp
index 9a98fd85..38f3a69c 100644
--- a/src/kaleidoscope/layers.cpp
+++ b/src/kaleidoscope/layers.cpp
@@ -62,6 +62,11 @@ void Layer_::handleLayerKeyEvent(const KeyEvent &event) {
   // The caller is responsible for checking that this is a Layer `Key`, so we
   // skip checking for it here.
   uint8_t key_code = event.key.getKeyCode();
+
+  // If this is a ModLayer key, we need to convert it into a layer shift first.
+  if (event.key.isModLayerKey())
+    key_code = (key_code / 8) + LAYER_SHIFT_OFFSET;
+
   uint8_t target_layer;
 
   if (key_code >= LAYER_MOVE_OFFSET) {