New keycode macro (XP) for shifted character pairs using UNICODEMAP + bug fixes and improvements (#4803)

* Expose unicode_saved_mods

* Add UNICODEMAP shift pair functionality and XS keycode

* Add XS to keycode reference documentation

* Pick pair index based on both Shift and Caps Lock state

* Add XS to Unicode feature docs

* Clean up process_unicode* headers

* Extract unicode_map index calculation into function

* Pick pair index as XOR rather than OR of Shift and Caps states

* unicode_input_start() has to be called before the unicode_map index is calculated

* Replace unicodemap_input_error() with more generic unicode_input_cancel()

* Replace register+tap+unregister with tap_code16(LCTL(LSFT(KC_U)))

* UNICODE_OSX_KEY → UNICODE_KEY_OSX, UNICODE_WINC_KEY → UNICODE_KEY_WINC

* Make keycode range checks more robust

* Fix keycode range checks for different input modes

* Add UNICODE_KEY_LNX, update docs

* QK_UNICODEMAP_SHIFT → QK_UNICODEMAP_PAIR

* XS → XP, update docs

* Tweak Unicode docs

* Use recently added MOD_MASK_SHIFT and IS_HOST_LED_ON helpers

* Update Unicode table in docs/keycodes.md

* Update Unicode docs per review comments

* Replace references to Mac OS X with macOS in Unicode docs

* As of v0.9.0, WinCompose supports all possible code points

* Expand descriptions in XP docs

* Update keycode table and cycling docs

* Further expand cycling docs

1 files changed, 9 insertions, 4 deletions

diff --git a/quantum/process_keycode/process_unicode_common.h b/quantum/process_keycode/process_unicode_common.h
index e608ab76be..7340800e56 100644
--- a/quantum/process_keycode/process_unicode_common.h
+++ b/quantum/process_keycode/process_unicode_common.h
@@ -23,11 +23,14 @@
 #endif
 
 // Keycodes used for starting Unicode input on different platforms
-#ifndef UNICODE_OSX_KEY
-  #define UNICODE_OSX_KEY  KC_LALT
+#ifndef UNICODE_KEY_OSX
+  #define UNICODE_KEY_OSX  KC_LALT
 #endif
-#ifndef UNICODE_WINC_KEY
-  #define UNICODE_WINC_KEY KC_RALT
+#ifndef UNICODE_KEY_LNX
+  #define UNICODE_KEY_LNX  LCTL(LSFT(KC_U))
+#endif
+#ifndef UNICODE_KEY_WINC
+  #define UNICODE_KEY_WINC KC_RALT
 #endif
 
 // Comma-delimited, ordered list of input modes selected for use (e.g. in cycle)
@@ -63,6 +66,7 @@ typedef union {
 } unicode_config_t;
 
 extern unicode_config_t unicode_config;
+extern uint8_t          unicode_saved_mods;
 
 void unicode_input_mode_init(void);
 uint8_t get_unicode_input_mode(void);
@@ -72,6 +76,7 @@ void persist_unicode_input_mode(void);
 
 void unicode_input_start(void);
 void unicode_input_finish(void);
+void unicode_input_cancel(void);
 
 void register_hex(uint16_t hex);
 void send_unicode_hex_string(const char *str);