From 1181f74d19f6f9e881b539ed9fdb8cc17d03f7bf Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Ekl=C3=B6f?= <daniel@ekloef.se>
Date: Fri, 24 Jan 2025 09:52:57 +0100
Subject: [PATCH] composed: re-factor: break out key calculation from vt.c

---
 composed.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 composed.h |  3 +++
 vt.c       | 24 ++----------------------
 3 files changed, 51 insertions(+), 22 deletions(-)

diff --git a/composed.c b/composed.c
index 442325ea..7a36275e 100644
--- a/composed.c
+++ b/composed.c
@@ -4,6 +4,52 @@
 #include <stdbool.h>
 
 #include "debug.h"
+#include "terminal.h"
+
+uint32_t
+composed_key_from_chars(const uint32_t chars[], size_t count)
+{
+    if (count == 0)
+        return 0;
+
+    uint32_t key = chars[0];
+    for (size_t i = 1; i < count; i++)
+        key = composed_key_from_key(key, chars[i]);
+
+    return key;
+}
+
+uint32_t
+composed_key_from_key(uint32_t prev_key, uint32_t next_char)
+{
+    unsigned bits = 32 - __builtin_clz(CELL_COMB_CHARS_HI - CELL_COMB_CHARS_LO);
+
+    /* Rotate old key 8 bits */
+    uint32_t new_key = (prev_key << 8) | (prev_key >> (bits - 8));
+
+    /* xor with new char */
+    new_key ^= next_char;
+
+    /* Multiply with magic hash constant */
+    new_key *= 2654435761ul;
+
+    /* And mask, to ensure the new value is within range */
+    new_key &= CELL_COMB_CHARS_HI - CELL_COMB_CHARS_LO;
+    return new_key;
+}
+
+UNITTEST
+{
+    const char32_t chars[] = U"abcdef";
+
+    uint32_t k1 = composed_key_from_key(chars[0], chars[1]);
+    uint32_t k2 = composed_key_from_chars(chars, 2);
+    xassert(k1 == k2);
+
+    uint32_t k3 = composed_key_from_key(k2, chars[2]);
+    uint32_t k4 = composed_key_from_chars(chars, 3);
+    xassert(k3 == k4);
+}
 
 struct composed *
 composed_lookup(struct composed *root, uint32_t key)
diff --git a/composed.h b/composed.h
index 17158407..fcaf87d4 100644
--- a/composed.h
+++ b/composed.h
@@ -12,6 +12,9 @@ struct composed {
     uint8_t width;
 };
 
+uint32_t composed_key_from_chars(const uint32_t chars[], size_t count);
+uint32_t composed_key_from_key(uint32_t prev_key, uint32_t next_char);
+
 struct composed *composed_lookup(struct composed *root, uint32_t key);
 void composed_insert(struct composed **root, struct composed *node);
 
diff --git a/vt.c b/vt.c
index bd1cf4ca..8f5d27d9 100644
--- a/vt.c
+++ b/vt.c
@@ -647,26 +647,6 @@ action_put(struct terminal *term, uint8_t c)
     dcs_put(term, c);
 }
 
-static inline uint32_t
-chain_key(uint32_t old_key, uint32_t new_wc)
-{
-    unsigned bits = 32 - __builtin_clz(CELL_COMB_CHARS_HI - CELL_COMB_CHARS_LO);
-
-    /* Rotate old key 8 bits */
-    uint32_t new_key = (old_key << 8) | (old_key >> (bits - 8));
-
-    /* xor with new char */
-    new_key ^= new_wc;
-
-    /* Multiply with magic hash constant */
-    new_key *= 2654435761ul;
-
-    /* And mask, to ensure the new value is within range */
-    new_key &= CELL_COMB_CHARS_HI - CELL_COMB_CHARS_LO;
-
-    return new_key;
-}
-
 #if defined(FOOT_GRAPHEME_CLUSTERING)
 static int
 emoji_vs_compare(const void *_key, const void *_entry)
@@ -738,9 +718,9 @@ action_utf8_print(struct terminal *term, char32_t wc)
         if (composed != NULL) {
             base = composed->chars[0];
             last = composed->chars[composed->count - 1];
-            key = chain_key(composed->key, wc);
+            key = composed_key_from_key(composed->key, wc);
         } else
-            key = chain_key(base, wc);
+            key = composed_key_from_key(base, wc);
 
 #if defined(FOOT_GRAPHEME_CLUSTERING)
         if (grapheme_clustering) {