Z80 Size Programming Challenge #5

Recently I issued the fifth Z80 challenge for the Sinclair Spectrum:

This time the challenge is to write a solid flood fill routine to fill a region of unset pixels, bounded in 4 directions (up, down, left, right) by set pixels or the screen edge. The routine should be called with the X and Y coordinates in a register. There’s no need to set the screen attributes.

Scoring is multi-objective: a routine will be judged by the code size and stack space required to fill a test image. Your routine will be awarded one point for each competing routine it is smaller *and* uses less stack space than. The routine(s) with the most points will be declared winner(s).

The deadline is Wednesday 22nd July, midday (GMT).

  1. The X and Y coordinates are in pixels with 0,0 at the top left.
  2. No memory other than the screen, stack and your routine can be written.
  3. If you call a ROM routine it’s size will be added to your code size.
  4. Programs must return. The RET instruction is included in the size.
  5. So everyone has a fair chance comment with the code size not code.
  6. There are no prizes, just the chance to show off your coding skills.

The test image is designed to check correct behaviour at the screen boundary and to be pathological — triggering suboptimal behaviour in some common flood fill algorithms:

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