fix: double characters on international keyboards

1 files changed, 71 insertions, 17 deletions

diff --git a/todo.c b/todo.c
index 738d506..fd26604 100644
--- a/todo.c
+++ b/todo.c
@@ -84,6 +84,47 @@ static int is_editing(enum Mode mode)
     return mode == MODE_INSERT || mode == MODE_REPLACE;
 }
 
+/* utf-8 helpers: edit_pos is a byte offset, but the cursor and h/l/backspace
+ * work in whole characters. a continuation byte has its top two bits as 10. */
+static int utf8_width(const char* text, int bytes)
+{
+    int width = 0;
+
+    for (int i = 0; i < bytes && text[i] != '\0'; i++)
+        if (((unsigned char) text[i] & 0xC0) != 0x80)
+            width++;
+
+    return width;
+}
+
+static int utf8_left(const char* text, int pos)
+{
+    if (pos <= 0)
+        return 0;
+
+    pos--;
+
+    while (pos > 0 && ((unsigned char) text[pos] & 0xC0) == 0x80)
+        pos--;
+
+    return pos;
+}
+
+static int utf8_right(const char* text, int pos)
+{
+    int length = (int) strlen(text);
+
+    if (pos >= length)
+        return length;
+
+    pos++;
+
+    while (pos < length && ((unsigned char) text[pos] & 0xC0) == 0x80)
+        pos++;
+
+    return pos;
+}
+
 static void todo_path(char* buffer, size_t size)
 {
     const char* env_path = getenv("TODO_FILE");
@@ -830,12 +871,13 @@ static void render(const struct List* list, int cursor, int scroll, enum Mode mo
     else if (mode != MODE_CONFIRM && cursor >= 0 && cursor < list->count && cursor_row >= 0)
     {
         int cursor_column;
+        int caret = utf8_width(list->items[cursor].text, edit_pos);
 
         if (is_section(&list->items[cursor]))
         {
             int level = section_level(&list->items[cursor]);
             int section_indent = LEFT_MARGIN + (level - 1) * SECTION_INDENT;
-            cursor_column = is_editing(mode) ? section_indent + 1 + edit_pos : section_indent + 1;
+            cursor_column = is_editing(mode) ? section_indent + 1 + caret : section_indent + 1;
         }
         else
         {
@@ -856,7 +898,7 @@ static void render(const struct List* list, int cursor, int scroll, enum Mode mo
             else
                 text_start = base_indent + number_width + 7;
 
-            cursor_column = text_start + edit_pos;
+            cursor_column = text_start + caret;
         }
 
         const char* shape = mode == MODE_REPLACE ? "\x1b[4 q"
@@ -999,12 +1041,18 @@ static int normal_key(struct List* list, int* cursor, enum Mode* mode, int* edit
 
         case 'h':
         case KEY_LEFT:
-            *edit_pos -= count;
+            if (*cursor >= 0 && *cursor < list->count)
+                for (int repeat = 0; repeat < count; repeat++)
+                    *edit_pos = utf8_left(list->items[*cursor].text, *edit_pos);
+
             break;
 
         case 'l':
         case KEY_RIGHT:
-            *edit_pos += count;
+            if (*cursor >= 0 && *cursor < list->count)
+                for (int repeat = 0; repeat < count; repeat++)
+                    *edit_pos = utf8_right(list->items[*cursor].text, *edit_pos);
+
             break;
 
         case 'w':
@@ -1320,17 +1368,13 @@ static void insert_key(struct List* list, int* cursor, enum Mode* mode, int* edi
 
     if (key == KEY_LEFT)
     {
-        if (*edit_pos > 0)
-            (*edit_pos)--;
-
+        *edit_pos = utf8_left(item->text, *edit_pos);
         return;
     }
 
     if (key == KEY_RIGHT)
     {
-        if (*edit_pos < (int) length)
-            (*edit_pos)++;
-
+        *edit_pos = utf8_right(item->text, *edit_pos);
         return;
     }
 
@@ -1340,18 +1384,24 @@ static void insert_key(struct List* list, int* cursor, enum Mode* mode, int* edi
         {
             if (*edit_pos > replace_start)
             {
-                (*edit_pos)--;
+                int start = utf8_left(item->text, *edit_pos);
+                int original_length = (int) strlen(replace_original);
 
-                if (*edit_pos < (int) strlen(replace_original))
-                    item->text[*edit_pos] = replace_original[*edit_pos];
+                if (*edit_pos <= original_length)
+                    for (int i = start; i < *edit_pos; i++)
+                        item->text[i] = replace_original[i];
                 else
-                    item->text[*edit_pos] = '\0';
+                    memmove(&item->text[start], &item->text[*edit_pos],
+                            length - (size_t) *edit_pos + 1);
+
+                *edit_pos = start;
             }
         }
         else if (*edit_pos > 0)
         {
-            memmove(&item->text[*edit_pos - 1], &item->text[*edit_pos], length - (size_t) *edit_pos + 1);
-            (*edit_pos)--;
+            int start = utf8_left(item->text, *edit_pos);
+            memmove(&item->text[start], &item->text[*edit_pos], length - (size_t) *edit_pos + 1);
+            *edit_pos = start;
         }
 
         return;
@@ -1529,7 +1579,8 @@ static void run(struct List* list, const char* path)
 
         if (list->count > 0)
         {
-            int text_length = (int) strlen(list->items[cursor].text);
+            const char* text = list->items[cursor].text;
+            int text_length = (int) strlen(text);
             int caret_max = is_editing(mode) ? text_length : (text_length > 0 ? text_length - 1 : 0);
 
             if (edit_pos > caret_max)
@@ -1537,6 +1588,9 @@ static void run(struct List* list, const char* path)
 
             if (edit_pos < 0)
                 edit_pos = 0;
+
+            while (edit_pos > 0 && ((unsigned char) text[edit_pos] & 0xC0) == 0x80)
+                edit_pos--;
         }
 
         render(list, cursor, scroll, mode, edit_pos, command);