Type Hangul on the keyboard (두벌식)

Surfaces that read keys (the display, through evdev) had only a US
layout's letters. After the 한/영 key (Lang1, or AltRight standing for
it), letter keys now give jamo that compose syllables in the entry line
(surfaces/hangul.c): an initial, a vowel and an optional final, joined
vowels and finals, a final that moves on to a vowel after it (도깨비불),
Shift's doubled consonants, a lone jamo as its compatibility letter. The
syllable being composed shows after the entry line; Backspace takes it
back a jamo at a time before deleting what was typed; Enter, Tab, the
toggle or any key but a letter finishes it. The script language gains
hangul, letters HEX and back to drive it.

The check types ten cases through it (안녕하세요, 값을, 안자, 와원, 까원,
갑 after Backspace, 한글, ㅏ, 안ㅈ, 안녕 2) and follows the composing line
jamo by jamo; the messenger check has Alice type 안녕 on her display with
recorded keys, drawn on Bob's.

1 files changed, 19 insertions, 0 deletions

diff --git a/surfaces/vega.h b/surfaces/vega.h
index fd8780b..cd6b1ee 100644
--- a/surfaces/vega.h
+++ b/surfaces/vega.h
@@ -153,6 +153,25 @@ bool vega_display_show(VegaDisplay *);
 const uint32_t *vega_display_captured(const VegaDisplay *, size_t *stride);
 void vega_display_close(VegaDisplay *);
 
+/* Hangul typed on a US keyboard as the two-set layout (두벌식, hangul.c):
+ * letter keys give jamo that compose syllables as they come. type takes a
+ * letter (A-Z with Shift) and gives what it finished (UTF-8, at most one
+ * syllable) into done; false for a key that is not a letter. composing is
+ * the syllable being composed (0 bytes: none); back takes back its last jamo
+ * (false: none was being composed); finish ends it into out. */
+struct VegaJamo { signed char initial, vowel; unsigned char final; };
+typedef struct {
+    signed char initial, vowel; /* -1: none */
+    unsigned char final;        /* 0: none */
+    unsigned char steps;        /* what it was before each jamo, for Backspace */
+    struct VegaJamo before[8];
+} VegaHangul;
+void vega_hangul_reset(VegaHangul *);
+bool vega_hangul_type(VegaHangul *, char key, char done[4], size_t *done_length);
+size_t vega_hangul_composing(const VegaHangul *, char out[4]);
+bool vega_hangul_back(VegaHangul *);
+size_t vega_hangul_finish(VegaHangul *, char out[4]);
+
 /* Input from evdev: keyboards (key names and the text they type on a US
  * layout), mice and touch screens (presses at a pixel of a width x height
  * screen). With count paths, recorded events are read from those files