A bug in the kilo code

Step 85 begins dealing with moving the cursor around tab characters, and step 88 gives the implementation of editorRowCxToRx, which calculates where the cursor should be based on how many tabs it's passed over in the line:

int editorRowCxToRx(erow *row, int cx) {
  int rx = 0;
  int j;
  for (j = 0; j < cx; j++) {
    if (row->chars[j] == '\t')
      rx += (KILO_TAB_STOP - 1) - (rx % KILO_TAB_STOP);
    rx++;
  }
  return rx;
}

Here, the parameter cx is the index into the array of characters of the line text, and the return value row offset of where the cursor should be placed on the screen

The problem comes when moving between two lines. Let's say you've got two lines, something like this:

\t
123456789

Now suppose that the cursor is on the first line, to the right of the tab character. Normally, the cursor will be displayed directly above the '9' character on the second line. Now suppose you press the down arrow to move to the next line, where should the cursor be? Virtually every editor I've ever used will place the cursor on the '9' of the second line.

However, the cx value will still be 1, and so for kilo, the cursor will be placed on the 2.

Maybe this will be fixed later in the project. I'm not going to try to deal with it now (honestly, this whole method of dealing with tabs feels like a botch anyway). Perhaps once I finish working through my first pass over the code.