Start work on allowing unlimited codepoints per cell

This is needed to properly support zero-width joiner based emoji
sequences.

kitty/data-types.h

@@ -224,6 +224,14 @@ typedef struct {
 } GPUCell;
 static_assert(sizeof(GPUCell) == 20, "Fix the ordering of GPUCell");
 
+typedef union CharOrIndex {
+    struct {
+        char_type ch_is_index: 1;
+        char_type ch: sizeof(char_type) - 1;
+    };
+    char_type val;
+} CharOrIndex;
+
 typedef struct {
     char_type ch;
     hyperlink_id_type hyperlink_id;

kitty/text-cache.c

@@ -0,0 +1,116 @@
+/*
+ * text-cache.c
+ * Copyright (C) 2024 Kovid Goyal <kovid at kovidgoyal.net>
+ *
+ * Distributed under terms of the GPL3 license.
+ */
+
+#include "data-types.h"
+typedef struct Chars {
+    size_t count;
+    const char_type *chars;
+} Chars;
+
+#define NAME chars_map
+#define KEY_TY Chars
+#define VAL_TY CharOrIndex
+static uint64_t hash_chars(Chars k);
+static bool cmpr_chars(Chars a, Chars b);
+#define HASH_FN hash_chars
+#define CMPR_FN cmpr_chars
+#include "kitty-verstable.h"
+
+typedef struct TextCache {
+    struct { Chars *items; size_t count, capacity; } array;
+    chars_map map;
+    unsigned refcnt;
+} TextCache;
+static uint64_t hash_chars(Chars k) { return vt_hash_bytes(k.chars, sizeof(k.chars[0]) * k.count); }
+static bool cmpr_chars(Chars a, Chars b) { return a.count == b.count && memcmp(a.chars, b.chars, sizeof(a.chars[0]) * a.count) == 0; }
+
+#define TEXT_CACHE_IMPLEMENTATION
+#include "text-cache.h"
+
+TextCache*
+tc_alloc(void) {
+    TextCache *ans = calloc(1, sizeof(TextCache));
+    if (!ans) return NULL;
+    ans->array.capacity = 256;
+    ans->array.items = malloc(ans->array.capacity * sizeof(ans->array.items[0]));
+    if (!ans->array.items) { free(ans); ans = NULL; return ans; }
+    vt_init(&ans->map);
+    ans->refcnt = 1;
+    return ans;
+}
+
+void
+tc_clear(TextCache *ans) {
+    ans->array.count = 0;
+    vt_cleanup(&ans->map);
+}
+
+static void
+free_text_cache(TextCache *self) {
+    vt_cleanup(&self->map);
+    for (size_t i = 0; i < self->array.count; i++) free((char_type*)self->array.items[i].chars);
+    free(self->array.items);
+    free(self);
+}
+
+TextCache*
+tc_incref(TextCache *self) { if (self) { self->refcnt++; } return self; }
+
+TextCache*
+tc_decref(TextCache *self) {
+    if (self) {
+        if (self->refcnt < 2) free_text_cache(self);
+        else self->refcnt--;
+    }
+    return NULL;
+}
+
+void
+tc_chars_at_index(const TextCache *self, CharOrIndex idx, ListOfChars *ans) {
+    if (idx.ch_is_index) {
+        if (self->array.count > idx.ch) {
+            ans->count = self->array.items[idx.ch].count;
+            ensure_space_for(ans, chars, char_type, ans->count, capacity, 8, false);
+            memcpy(ans->chars, self->array.items[idx.ch].chars, sizeof(ans->chars[0]) * ans->count);
+        } else {
+            ans->count = 0;
+        }
+    } else {
+        ans->count = 1;
+        ensure_space_for(ans, chars, char_type, 1, capacity, 8, false);
+        ans->chars[0] = idx.ch;
+    }
+}
+
+static CharOrIndex
+copy_and_insert(TextCache *self, const Chars key) {
+    if (self->array.count >= (1llu << (8*sizeof(char_type) - 1)) - 1) fatal("Too many items in TextCache");
+    ensure_space_for(&(self->array), items, Chars, self->array.count + 1, capacity, 256, false);
+    char_type *copy = malloc(key.count * sizeof(key.chars[0]));
+    if (!copy) fatal("Out of memory");
+    memcpy(copy, key.chars, key.count * sizeof(key.chars[0]));
+    CharOrIndex ans;
+    ans.ch_is_index = 1; ans.ch = self->array.count;
+    Chars *k = self->array.items + self->array.count++;
+    k->count = key.count; k->chars = copy;
+    chars_map_itr i = vt_insert(&self->map, *k, ans);
+    if (vt_is_end(i)) fatal("Out of memory");
+    return ans;
+}
+
+CharOrIndex
+tc_get_or_insert_chars(TextCache *self, const ListOfChars *chars) {
+    if (chars->count == 1) {
+        CharOrIndex ans = {0};
+        ans.ch = chars->chars[0];
+        return ans;
+    }
+    Chars key = {.count=chars->count, .chars=chars->chars};
+    chars_map_itr i = vt_get(&self->map, key);
+    if (vt_is_end(i)) return copy_and_insert(self, key);
+    return i.data->val;
+}

kitty/text-cache.h

@@ -0,0 +1,26 @@
+/*
+ * text-cache.h
+ * Copyright (C) 2024 Kovid Goyal <kovid at kovidgoyal.net>
+ *
+ * Distributed under terms of the GPL3 license.
+ */
+
+#pragma once
+
+#include "data-types.h"
+
+typedef struct ListOfChars {
+    char_type *chars;
+    size_t count, capacity;
+} ListOfChars;
+
+#ifndef TEXT_CACHE_IMPLEMENTATION
+typedef struct {int x; } *TextCache;
+#endif
+
+TextCache* tc_alloc(void);
+TextCache* tc_incref(TextCache *self);
+TextCache* tc_decref(TextCache *self);
+void tc_clear(TextCache *ans);
+void tc_chars_at_index(const TextCache *self, CharOrIndex idx, ListOfChars *ans);
+CharOrIndex tc_get_or_insert_chars(TextCache *self, const ListOfChars *chars);