fix(text): properly handle utf-8 chars

UTF-8 characters are now handled porperly. Also re-worked some helper
functions with UTF-8 in mind.

I secretly no real C developers will look at this. I might have to ask
for witness protection.

Closes #43

include/swappy.h

@@ -41,7 +41,7 @@ struct swappy_paint_text {
   double s;
   gchar *font;
   gchar *text;
-  size_t cursor;
+  glong cursor;
   struct swappy_point from;
   struct swappy_point to;
   enum swappy_text_mode mode;

include/util.h

@@ -3,6 +3,7 @@
 
 #include <glib.h>
 
-void string_remove_at(char *str, size_t pos);
-gchar *string_insert_chars_at(gchar *str, gchar *chars, size_t pos);
+glong string_get_nb_bytes_until(gchar *str, glong until);
+gchar *string_remove_at(char *str, glong pos);
+gchar *string_insert_chars_at(gchar *str, gchar *chars, glong pos);
 void pixel_data_print(guint32 pixel);

src/paint.c

@@ -11,7 +11,7 @@ static void cursor_move_backward(struct swappy_paint_text *text) {
 }
 
 static void cursor_move_forward(struct swappy_paint_text *text) {
-  if (text->cursor < strlen(text->text)) {
+  if (text->cursor < g_utf8_strlen(text->text, -1)) {
     text->cursor++;
   }
 }
@@ -194,6 +194,7 @@ void paint_update_temporary_text(struct swappy_state *state,
                                  GdkEventKey *event) {
   struct swappy_paint *paint = state->temp_paint;
   struct swappy_paint_text *text;
+  char *new_text;
   char buffer[32];
   guint32 unicode;
 
@@ -209,14 +210,18 @@ void paint_update_temporary_text(struct swappy_state *state,
       paint_commit_temporary(state);
       break;
     case GDK_KEY_BackSpace:
-      if (strlen(text->text) > 0) {
-        string_remove_at(text->text, text->cursor - 1);
+      if (g_utf8_strlen(text->text, -1) > 0) {
+        new_text = string_remove_at(text->text, text->cursor - 1);
+        g_free(text->text);
+        text->text = new_text;
         cursor_move_backward(text);
       }
       break;
     case GDK_KEY_Delete:
-      if (strlen(text->text) > 0) {
-        string_remove_at(text->text, text->cursor);
+      if (g_utf8_strlen(text->text, -1) > 0) {
+        new_text = string_remove_at(text->text, text->cursor);
+        g_free(text->text);
+        text->text = new_text;
       }
       break;
     case GDK_KEY_Left:
@@ -264,7 +269,7 @@ void paint_commit_temporary(struct swappy_state *state) {
 
   switch (paint->type) {
     case SWAPPY_PAINT_MODE_TEXT:
-      if (strlen(paint->content.text.text) == 0) {
+      if (g_utf8_strlen(paint->content.text.text, -1) == 0) {
         paint->can_draw = false;
       }
       paint->content.text.mode = SWAPPY_TEXT_MODE_DONE;

src/render.c

@@ -5,6 +5,7 @@
 
 #include "algebra.h"
 #include "swappy.h"
+#include "util.h"
 
 #define pango_layout_t PangoLayout
 #define pango_font_description_t PangoFontDescription
@@ -201,13 +202,13 @@ static void render_text(cairo_t *cr, struct swappy_paint_text text) {
 
   if (text.mode == SWAPPY_TEXT_MODE_EDIT) {
     pango_rectangle_t strong_pos;
-    pango_rectangle_t weak_pos;
     struct swappy_box cursor_box;
     cairo_set_source_rgba(cr, 0.5, 0.5, 0.5, 0.3);
     cairo_set_line_width(cr, 5);
     cairo_rectangle(cr, x, y, w, h);
     cairo_stroke(cr);
-    pango_layout_get_cursor_pos(layout, text.cursor, &strong_pos, &weak_pos);
+    glong bytes_til_cursor = string_get_nb_bytes_until(text.text, text.cursor);
+    pango_layout_get_cursor_pos(layout, bytes_til_cursor, &strong_pos, NULL);
     convert_pango_rectangle_to_swappy_box(strong_pos, &cursor_box);
     cairo_move_to(crt, cursor_box.x, cursor_box.y);
     cairo_set_source_rgba(crt, 0.3, 0.3, 0.3, 1);

src/util.c

@@ -3,40 +3,60 @@
 #include <glib.h>
 #include <string.h>
 
-void string_remove_at(gchar *str, size_t pos) {
-  if (str && strlen(str) > pos) {
-    memmove(&str[pos], &str[pos + 1], strlen(str) - pos);
+gchar *string_remove_at(gchar *str, glong pos) {
+  glong str_len = strlen(str);
+  gchar *new_str = g_new0(gchar, MAX(str_len, 1));
+  gchar *buffer_source = str;
+  gchar *buffer_copy = new_str;
+  glong i = 0;
+  gint bytes;
+  gunichar c;
+
+  if (pos <= str_len && g_utf8_validate(str, -1, NULL)) {
+    while (*buffer_source != '\0') {
+      c = g_utf8_get_char(buffer_source);
+      buffer_source = g_utf8_next_char(buffer_source);
+      if (i != pos) {
+        bytes = g_unichar_to_utf8(c, buffer_copy);
+        buffer_copy += bytes;
+      }
+      i++;
+    }
   }
+
+  return new_str;
 }
 
-gchar *string_insert_chars_at(gchar *str, gchar *chars, size_t pos) {
-  gchar *new_str;
+gchar *string_insert_chars_at(gchar *str, gchar *chars, glong pos) {
+  gchar *new_str = NULL;
 
-  if (str && chars) {
-    size_t n = strlen(str);
-    size_t m = strlen(chars);
-    size_t i = 0, j = 0;
+  if (g_utf8_validate(str, -1, NULL) && g_utf8_validate(chars, -1, NULL) &&
+      pos >= 0 && pos <= g_utf8_strlen(str, -1)) {
+    gchar *from = g_utf8_substring(str, 0, pos);
+    gchar *end = g_utf8_offset_to_pointer(str, pos);
 
-    new_str = g_new(gchar, n + m + 1);
+    new_str = g_strconcat(from, chars, end, NULL);
 
-    while (j < n + m) {
-      if (j == pos) {
-        for (size_t k = 0; k < m; k++) {
-          new_str[j++] = chars[k];
-        }
-      } else {
-        new_str[j++] = str[i++];
-      }
-    }
+    g_free(from);
 
-    new_str[j] = '\0';
   } else {
-    new_str = NULL;
+    new_str = g_new0(gchar, 1);
   }
 
   return new_str;
 }
 
+glong string_get_nb_bytes_until(gchar *str, glong until) {
+  glong ret = 0;
+  if (str) {
+    gchar *sub = g_utf8_substring(str, 0, until);
+    ret = strlen(sub);
+    g_free(sub);
+  }
+
+  return ret;
+}
+
 void pixel_data_print(guint32 pixel) {
   const guint32 r = pixel >> 24 & 0xff;
   const guint32 g = pixel >> 16 & 0xff;