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Teach the artwork tutorial the converted listing

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Chapter 18 still taught the machinery the listing lost when it moved onto
SOLID and the persistent drawing layer: the frame-boundary PACE routine, the
flattened live list, the SSHAPE pool accounting, and the sixty lines of
BALLBRICKS/TESTCELL that computed a minimum translation axis by hand.

Step 8 now registers each brick with SOLID, arms COLLISION 2 and reads the
contact back with RCOLLISION, including the point that costs an evening if it
is missed: the BUMP mask is by sprite, and the balls are sprites 5, 6 and 7,
so their bits are 16, 32 and 64. The FOR-with-equal-bounds rule that every
one-item case in the chapter depends on is now stated where it is first used
rather than referred to from a step that no longer exists.

The listing loses six declarations orphaned by the conversion and the comment
blocks that still described the captures.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EwxGB6TdoVvZ11KQQME9cL
This commit is contained in:
Andrew Kesterson
2026-08-02 13:13:51 -04:00
parent 39d1d0c80c
commit a01554d304
3 changed files with 248 additions and 369 deletions
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42
examples/breakout/sprites/breakout.bas
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@@ -145,9 +145,9 @@ DIM BRV#(6)
BRN# = 0
REM ------------------------------------------------------- shapes and dirt
REM SHN# counts the SSHAPE slots spent. There are sixteen, nothing gives
REM one back, and GRAPHIC 5 gives back all of them at once -- so the brick
REM stamps are thrown away and rebuilt every time the pool runs dry.
REM Eight of the sixteen SSHAPE slots, spent once in DRAWPROTOS and never
REM again: six brick stamps and the two erasers. Nothing captures per frame
REM any more, so the pool never runs dry and GRAPHIC 5 is never called.
REM One scalar per row colour, and scalars rather than an array because
REM SSHAPE and GSHAPE used to read the leaf they were handed without
REM applying its subscript -- a string array element always resolved to
@@ -160,8 +160,6 @@ S3$ = ""
S4$ = ""
S5$ = ""
Z$ = ""
REM 99 means the stamps are gone and have to be rebuilt before anything
REM can be drawn with them.
DHUD# = 1
DPLAY# = 1
BAN$ = ""
@@ -228,12 +226,6 @@ T3# = 0
T4# = 0
BX1# = 0
BY1# = 0
LFT# = 0
TOP# = 0
RGT# = 0
BOT# = 0
CC1# = 0
CC2# = 0
RR1# = 0
RR2# = 0
HIT# = 0
@@ -310,14 +302,10 @@ GOSUB TITLESCREEN
REM =====================================================================
REM The frame loop
REM
REM PACE first, because it is what puts the drawing at the top of a host
REM batch; then at most one capture, because a capture is the only thing
REM with a deadline; then the game, which may take as long as it likes.
REM At most one drawing job, then the game, which may take as long as it
REM likes. Nothing here has a deadline: a drawing that spans two host
REM batches simply arrives over two frames and the layer keeps both halves.
REM =====================================================================
REM No pacing. PACE spun on TI# until a batch boundary so that an SSHAPE
REM capture would not be cut in half by a present; nothing is captured now, so
REM a drawing that spans two batches simply arrives over two frames and the
REM layer keeps both halves.
LABEL FRAME
GOSUB DRAWJOB
GOSUB READKEYS
@@ -338,18 +326,17 @@ PRINT "FINAL SCORE " + SCORE# + " BEST " + HISCORE#
END
REM =====================================================================
REM One capture per frame, and only one
REM One drawing job per frame, and only one
REM
REM Rebuilding the brick stamps comes first, because everything else
REM draws with them and GRAPHIC 5 has just thrown them away.
REM The field is the expensive one -- sixty stamps and a border -- so it
REM never shares a frame with the HUD. Both are flagged rather than drawn
REM where the change happens, so a routine that changes three things costs
REM one drawing.
REM =====================================================================
REM Labels rather than BEGIN blocks here. When this was written it was not
REM a style choice -- a loop inside a block that was skipped left the
REM interpreter with no GOSUB to return from and stopped the program. That
REM is fixed; the shape is kept because it reads the same either way.
REM The stamps are built once now rather than counted and rebuilt. Nothing
REM captures per frame any more, so the sixteen SSHAPE slots are spent once and
REM stay spent -- eight of them -- and GRAPHIC 5 is never called.
LABEL DRAWJOB
LABEL DRAWJOB2
IF DPLAY# = 0 THEN GOTO DRAWJOB3
@@ -1002,10 +989,9 @@ FOR I# = 0 TO 59
BRK#(I#) = 0
NEXT I#
REM Retire the previous level's rectangles *before* laying this one out, not
REM after. This is where GOSUB BUILDLIVE used to sit, and it meant something
REM different: rebuild the list of what is standing. Left in place, the clear
REM ran after FILLROW had registered all sixty and threw them all away again --
REM which cost nothing visible and simply stopped the ball hitting anything.
REM after. Put after FILLROW it throws away all sixty rectangles that were
REM just registered, which costs nothing visible and simply stops the ball
REM hitting anything.
SOLID
FOR R# = 0 TO 5
IF R# < T3# THEN GOSUB FILLROW