Mostly fix problem of offset with cursor positioning when using mouse

In order to get right the cursor position on text on mouse clicks it is
needed to take into account text's subpixel positioning.

This fix mostly corrects the problem but cursor positioning is still
somewhat inaccurate for long lines due to repeated commands to draw a text
along a line. Repeated draw text calls make the subpixel information
lost and small errors will add-up.

src/rencache.c

@@ -130,10 +130,12 @@ void rencache_draw_rect(RenRect rect, RenColor color) {
 
 
 int rencache_draw_text(RenFont *font, const char *text, int x, int y, RenColor color) {
+  int subpixel_scale;
   RenRect rect;
   rect.x = x;
   rect.y = y;
-  rect.width = ren_get_font_width(font, text);
+  int w = ren_get_font_width(font, text, &subpixel_scale);
+  rect.width = ren_font_subpixel_round(w, subpixel_scale, 0);
   rect.height = ren_get_font_height(font);
 
   if (rects_overlap(screen_rect, rect)) {