Snake game inside a single PowerBuilder DataWindow

Hi everyone,

  I wanted to share a small weekend experiment: a fully playable Snake game where the entire playfield is a single DataWindow,
  with no external graphics, no images, and no third-party controls. This project was developed by Claude Code following my
  ideas and direction.

  The idea came from a Minesweeper clone I built a while ago using the same approach — dynamically generating shapes inside a
  DataWindow detail band via Modify() — and I wanted to see how far that technique could be pushed for something that needs to
  redraw several times per second.

  First version

  - A DataWindow object (dw_snake) with a single detail band as a black canvas.
  - A 31×21 logical grid stored in the window as two long arrays for the snake body coordinates plus an integer for the
  direction.
  - The window Timer event fires every 0.12s, computes the new head, handles wall wrap-around, self-collision and food.
  - wf_render() rebuilt the visible state by issuing dw_1.Modify("destroy rect_N") for every segment and then
  dw_1.Modify('create rectangle ...') to recreate them on each tick.
  - Keyboard handled in the window's Key event, with a guard against 180° reversals.

  It worked, but redrawing the whole snake by destroying and recreating every rectangle on each tick caused visible flicker and
  was wasteful.

  Borrowing from "Three Simple Games"

  I then found René Ullrich's Three Simple Games on Appeon CodeExchange
  (https://community.appeon.com/codeexchange/powerbuilder/114-three-simple-games), which contains another DataWindow-based
  Snake. His implementation is much smarter than mine in one key area: instead of destroying and recreating rectangles per tick,
   the cells are created once and their visibility/color is bound to a DataWindow expression that reads from a string column.

  I refactored my version to adopt that idea:

  - The DataWindow now has one row per game row, with a single char(40) column called cells. Each character encodes the state of
   one cell: 0 = empty, 1 = body, 2 = head, 9 = food.
  - At window open, wf_init_grid() creates once 31 rectangles cell_1..cell_31 in the detail band with expressions:
    - visible="0~tIf(long(mid(cells,N,1))>0,1,0)"
    - brush.color="65280~tCASE(long(mid(cells,N,1)) WHEN 2 THEN 65535 WHEN 9 THEN 255 ELSE 65280)"
  - Each tick now only issues 2-3 SetItem calls (new head, old head → body, old tail → empty). No Modify() per frame, no
  flicker.
  - I also added a small ib_intimer reentrancy guard, also inspired by his code, to avoid the timer event running into itself.

  Source

  Two files only — w_snake.srw and dw_snake.srd, around 280 lines total. PowerBuilder 2025 (release 25). Happy to share the
  source if anyone is interested, and big thanks to René for the elegant cell-binding trick — that one idea turned the project
  from a curiosity into something that actually feels smooth.

Stay Connected!

To be aware of what I publish you can follow my blog in Spanish:
rsrsystem.blogspot.com

Follow for more PowerBuilder tips, tricks, and modern integrations!