Welcome back to the Hooray! series — in this episode, which is right on the heels of the previous one, we actually cover three patches: numbers 5, 6, and 7. Up until now, the patches have had a uniform additive flavor — lots of adjacent “+” in the left-hand column — that indicate self-contained subsections not requiring much integration w/ the rest of the code. Today, we venture into new territory: (a) Patch 5, in addition to adding functionality, modifies functionality of existing code as well. (b) Patches 6 and 7 do the same, but with even more vigor and purpose! All in all, this should be a fun 10 minutes. Let's get started...
1 commit 08d8fe55c21d7db8e2f4491970f682fb8d2fe805
2 Author: Thien-Thi Nguyen <ttn@gnuvola.org>
3 Date: 2022-01-23 01:12:34 -0500
4
5 Add scenery
6
7 * hooray.scm (FAR): New data structure.
8 (refresh-scenery!): New proc.
9 (smokin): Call ‘refresh-scenery!’.
10 ---
11 hooray.scm | 31 +++++++++++++++++++++++++++++++
12 1 file changed, 31 insertions(+)
13
14 diff --git a/hooray.scm b/hooray.scm
15 index 0f8f0bd..b10c834 100644
16 --- a/hooray.scm
17 +++ b/hooray.scm
18 @@ -73,6 +73,35 @@ (SDL:set-video-mode (* 5 TILE-EDGE-LENGTH)
19 (* 5 TILE-EDGE-LENGTH)
20 32)
21
22 +(define FAR #2((window window window window window)
23 + (window cell cell cell window)
24 + (window cell cell cell window)
25 + (window cell cell cell window)
26 + (window window window window window)))
27 +
28 +(define refresh-scenery!
29 + (let ((rect (apply make-array #f (array-shape FAR))))
30 +
31 + (define (place-tile! name rect)
32 + (SDL:blit-surface (hashq-ref HT name) #f #f rect)
33 + rect)
34 +
35 + ;; initialize ‘rect’
36 + (array-index-map! rect (lambda (r c)
37 + ;; note order change: r c => c r => x y
38 + (SDL:make-rect
39 + (* TILE-EDGE-LENGTH c)
40 + (* TILE-EDGE-LENGTH r)
41 + TILE-EDGE-LENGTH
42 + TILE-EDGE-LENGTH)))
43 +
44 + ;; refresh-scenery!
45 + (lambda ()
46 + ;; far ground
47 + (array-map! rect place-tile! FAR rect)
48 + ;; mid ground
49 + (place-tile! 'rec-1 (array-ref rect 2 2)))))
50 +
51 (define smokin
52 (let ((keys (list->vector (hash-fold (lambda (k v acc)
53 (cons k acc))
54 @@ -94,6 +123,8 @@ (define smokin
55 (lambda (millisecs)
56 (do ((i 0 (1+ i)))
57 ((= 420 i))
58 + (and (zero? (modulo i 42))
59 + (refresh-scenery!))
60 (let ((tile (random-tile)))
61 (SDL:rect:set-x! rect (random-coord))
62 (SDL:rect:set-y! rect (random-coord))For this project, we define “scenery” as “stuff that goes behind the animation”, and divide it into the far ground and the mid ground.
Patch 5 starts by laying out, quite graphically, the far ground (lines 22-26).
That ‘#2(...)’ is syntax for a two-dimensional array, in this case, of symbols.
The symbols are the names of tiles (see ‘load-theme’).
We only use ‘window’ and ‘cell’ for now.
The main new stuff is procedure ‘refresh-scenery!’ (starts at line 28).
It has internal procedure ‘place-tile!’ (lines 31-33) which is responsible for blitting one tile.
Lines 29 and 36-42 set up an array (of the same shape as ‘FAR’) of rectangles for the blit, to be configured once and then never changed again.
The body of ‘refresh-scenery!’ is line 47, which handles the far ground, and line 49, which handles the mid ground (currently, just one tile — ‘rec-1’ — in the center).
Remember “modifies functionality of existing code” in the lead paragraph?
Well, that's what the second hunk of patch 5 (lines 54-62) does.
It adds a call to ‘refresh-scenery!’ to ‘smokin’.
The effect is to periodically (every 42 iterations) refresh the scenery.
Here's what I see when I run “guile -s hooray.scm Linux.png”:
1 commit 6b4537afb60b479b7b91f5bb306f92d474591656
2 Author: Thien-Thi Nguyen <ttn@gnuvola.org>
3 Date: 2022-01-23 01:21:51 -0500
4
5 Add abstraction: surf
6
7 * hooray.scm (surf): New proc.
8 (refresh-scenery! place-tile!): Use ‘surf’.
9 (smokin random-tile): Likewise.
10 ---
11 hooray.scm | 7 +++++--
12 1 file changed, 5 insertions(+), 2 deletions(-)
13
14 diff --git a/hooray.scm b/hooray.scm
15 index b10c834..7b7c24f 100644
16 --- a/hooray.scm
17 +++ b/hooray.scm
18 @@ -69,6 +69,9 @@ (define (load-theme filename) ; => hash table
19
20 (define HT (load-theme (cadr (command-line))))
21
22 +(define (surf name)
23 + (hashq-ref HT name))
24 +
25 (SDL:set-video-mode (* 5 TILE-EDGE-LENGTH)
26 (* 5 TILE-EDGE-LENGTH)
27 32)
28 @@ -83,7 +86,7 @@ (define refresh-scenery!
29 (let ((rect (apply make-array #f (array-shape FAR))))
30
31 (define (place-tile! name rect)
32 - (SDL:blit-surface (hashq-ref HT name) #f #f rect)
33 + (SDL:blit-surface (surf name) #f #f rect)
34 rect)
35
36 ;; initialize ‘rect’
37 @@ -117,7 +120,7 @@ (define smokin
38 (let ((name (vector-ref keys (random (vector-length keys)))))
39 (display " ")
40 (display name)
41 - (hashq-ref HT name)))
42 + (surf name)))
43
44 ;; smokin
45 (lambda (millisecs)In contrast to previous patches, patch 6 has very little additive nature, and what it does add is not a user-visible feature, but an “abstraction”.
In fact, the only real addition is procedure ‘surf’ (lines 22-23) in hunk 1.
Hunks 2 and 3 simply show ‘surf’ being used to replace existing code in two other places.
This is the first time we see “-” in the left-hand column, but it won't be the last.
1 commit a2dd73f5ab85c7de1b60d1d95549d66785ddeef1
2 Author: Thien-Thi Nguyen <ttn@gnuvola.org>
3 Date: 2022-01-23 01:29:31 -0500
4
5 Add abstraction: make-tile-rect
6
7 * hooray.scm (make-tile-rect): New proc.
8 (load-theme): Use ‘make-tile-rect’.
9 (refresh-scenery!): Likewise.
10 (smokin): Likewise.
11 ---
12 hooray.scm | 23 ++++++++++-------------
13 1 file changed, 10 insertions(+), 13 deletions(-)
14
15 diff --git a/hooray.scm b/hooray.scm
16 index 7b7c24f..ef226b2 100644
17 --- a/hooray.scm
18 +++ b/hooray.scm
19 @@ -37,6 +37,13 @@ (let-values (((cap mem fmt) (SDL:video-cmf)))
20
21 (define TILE-EDGE-LENGTH 64)
22
23 +(define (make-tile-rect r c)
24 + ;; note order change: r c => c r => x y
25 + (SDL:make-rect (* TILE-EDGE-LENGTH c)
26 + (* TILE-EDGE-LENGTH r)
27 + TILE-EDGE-LENGTH
28 + TILE-EDGE-LENGTH))
29 +
30 (define (load-theme filename) ; => hash table
31
32 (define (proper surface)
33 @@ -47,9 +54,7 @@ (define (load-theme filename) ; => hash table
34
35 (let* ((theme (proper (SDL:load-image filename)))
36 (ht (make-hash-table))
37 - (rect (SDL:make-rect 0 0
38 - TILE-EDGE-LENGTH
39 - TILE-EDGE-LENGTH)))
40 + (rect (make-tile-rect 0 0)))
41
42 (define (read-row! row tile-names)
43 (SDL:rect:set-y! rect (* TILE-EDGE-LENGTH row))
44 @@ -90,13 +95,7 @@ (define refresh-scenery!
45 rect)
46
47 ;; initialize ‘rect’
48 - (array-index-map! rect (lambda (r c)
49 - ;; note order change: r c => c r => x y
50 - (SDL:make-rect
51 - (* TILE-EDGE-LENGTH c)
52 - (* TILE-EDGE-LENGTH r)
53 - TILE-EDGE-LENGTH
54 - TILE-EDGE-LENGTH)))
55 + (array-index-map! rect make-tile-rect)
56
57 ;; refresh-scenery!
58 (lambda ()
59 @@ -109,9 +108,7 @@ (define smokin
60 (let ((keys (list->vector (hash-fold (lambda (k v acc)
61 (cons k acc))
62 '() HT)))
63 - (rect (SDL:make-rect 0 0
64 - TILE-EDGE-LENGTH
65 - TILE-EDGE-LENGTH)))
66 + (rect (make-tile-rect 0 0)))
67
68 (define (random-coord)
69 (* TILE-EDGE-LENGTH (random 5)))Like patch 6, patch 7 adds an abstraction.
This time, it's the procedure ‘make-tile-rect’ (lines 23-28), which is then used in three other places (hunks 2, 3, 4).
The result is a very satisfying negative delta — 10 insertions and 13 deletions (line 13) means the net change is 3 deletions — the code is smaller!
OK, see you next time.
Copyright (C) 2022 Thien-Thi Nguyen