From bb40a8782bafd0a3bb0aeb6f0aab9c3c1ef62607 Mon Sep 17 00:00:00 2001
From: Colin Okay <colin@cicadas.surf>
Date: Sat, 16 Jul 2022 10:32:07 -0500
Subject: [example ] mostly adding some docstrings to eg 10
---
examples/10-canvas-sneks.lisp | 25 ++++++++++++++++++++-----
1 file changed, 20 insertions(+), 5 deletions(-)
(limited to 'examples')
diff --git a/examples/10-canvas-sneks.lisp b/examples/10-canvas-sneks.lisp
index 453ef0e..a69b429 100644
--- a/examples/10-canvas-sneks.lisp
+++ b/examples/10-canvas-sneks.lisp
@@ -37,6 +37,11 @@
(setf (dy snek) (random-between -1 1))))
(defun advance-snek-pos (snek)
+ "Advance a snek's position. Check that the snek remains contained in
+its HOME. If it isn't, revert position and have the snek change its
+mind about where it wants to go. Finally, update the snek's BOD,
+ensuring that its BOD is no longer than LEN, truncating it when
+necessary."
(with-slots (x y dx dy home bod len) snek
(incf x dx)
(incf y dy)
@@ -46,10 +51,12 @@
(snek-change-mind snek))
(push y bod)
(push x bod)
- (when (< len (length bod))
+ (when (<= (* 2 len) (length bod))
(setf bod (nreverse (cddr (nreverse bod)))))))
(defun snek-thots (snek)
+ "A SNEK will decide to change direction the longer it has been
+moving in a particular direction."
(incf (brain snek) 0.01)
(when (< (random 1.0) (brain snek))
(setf (brain snek) 0.0)
@@ -59,15 +66,20 @@
(advance-snek-pos snek)
(snek-thots snek))
+(defvar *alpha-step* 10)
+
(defun draw-snek (snek canvas)
+ "Draws a snek to a canvas. The BOD of a snek is a list of recent
+positions that the snek's head had occupied. The body is drawn by
+reducing the alpha of the snek's COLOR by 10 for every point in the BOD."
(with-slots (bod color) snek
(destructuring-bind (red green blue) color
- (let ((alpha 255))
+ (let ((alpha (max 0 (- 255 (* *alpha-step* (/ (length bod) 2))))))
(loop
- for (x y . more) on bod by #'cddr
+ for (y x . more) on (reverse bod) by #'cddr
do (ww::with-pixel (r g b a) (ww::pixel canvas x y)
(setf r red g green b blue a alpha))
- (setf alpha (max 0 (- alpha 10))))))))
+ (setf alpha (min 255 (+ alpha *alpha-step*))))))))
(defun random-snek (&optional (boundx 100) (boundy 100))
(make-instance 'snek
@@ -81,6 +93,8 @@
(ww:defhandler sneks-a-go-go
(ww::on-perframe (app ticks)
+ "Clears cavnas. Moves gives each snek its turn. Draws each
+ snek. Updates the screen."
(with-slots (sneks snek-pit) app
(ww::clear-canvas snek-pit)
(dolist (snek sneks)
@@ -89,7 +103,8 @@
(ww::blit snek-pit))))
(defmethod ww::boot ((app sneking ))
- "Adds the intro text and sets up the start button handler."
+ "Sets up snek-pit, a canvas to which sneks are drawn. Creates random
+sneks. Adds the canvas to the app, and sets up the perframe handler."
(setf (snek-pit app)
(make-instance 'ww:canvas :pixel-width 100 :pixel-height 100)
(sneks app)
--
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