Getting Started (The Chickadee Game Toolkit)

From 0e699be281c8dea53e589e08a5831837e0eae7ea Mon Sep 17 00:00:00 2001 From: David Thompson Date: Thu, 7 Oct 2021 20:17:50 -0400 Subject: Updates for Chickadee 0.8.0 and Guile-SDL2 0.7.0. --- manuals/chickadee/Getting-Started.html | 177 +++++++++++++++++++++++++++++++++ 1 file changed, 177 insertions(+) create mode 100644 manuals/chickadee/Getting-Started.html (limited to 'manuals/chickadee/Getting-Started.html') diff --git a/manuals/chickadee/Getting-Started.html b/manuals/chickadee/Getting-Started.html new file mode 100644 index 0000000..7508ebe --- /dev/null +++ b/manuals/chickadee/Getting-Started.html @@ -0,0 +1,177 @@ + + + + + + +Getting Started (The Chickadee Game Toolkit) + + + + + + + + + + + + + + + + + + + + +

2 Getting Started

+ +

One of the simplest programs we can make with Chickadee is rendering +the text “Hello, world” on screen. Here’s what that looks like: +

(define (draw alpha)
+  (draw-text "Hello, world!" (vec2 64.0 240.0)))
+

+ +

The draw procedure is called frequently to draw the game scene. +For the sake of simplicity, we will ignore the alpha variable +in this tutorial. +

To run this program, we’ll use the chickadee play command: +

chickadee play hello.scm
+

+ +

This is a good start, but it’s boring. Let’s make the text move! +

(define position (vec2 0.0 240.0))
+
+(define (draw alpha)
+  (draw-text "Hello, world!" position))
+
+(define (update dt)
+  (set-vec2-x! position (+ (vec2-x position) (* 100.0 dt))))
+

+ +

The vec2 type is used to store 2D coordinates +(see Vectors.) A variable named position contains the +position where the text should be rendered. A new hook called +update has been added to handle the animation. This hook is +called frequently to update the state of the game. The variable +dt (short for “delta-time”) contains the amount of time that +has passed since the last update, in seconds. Putting it all +together, this update procedure is incrementing the x coordinate of +the position by 100 pixels per second. +

This is neat, but after a few seconds the text moves off the screen +completely, never to be seen again. It would be better if the text +bounced back and forth against the sides of the window. +

(define position (vec2 0.0 240.0))
+
+(define (draw alpha)
+  (draw-text "Hello, world!" position))
+
+(define (update dt)
+  (update-agenda dt))
+
+(define (update-x x)
+  (set-vec2-x! position x))
+
+(let ((start 0.0)
+      (end 536.0)
+      (duration 4.0))
+  (script
+   (while #t
+    (tween duration start end update-x)
+    (tween duration end start update-x))))
+

+ +

This final example uses Chickadee’s scripting features +(see Scripting) to bounce the text between the edges of the window +indefinitely using the handy tween procedure. The only thing +the update procedure needs to do now is advance the clock of +the “agenda” (the thing that runs scripts.) The script takes care +of the rest. +

This quick tutorial has hopefully given you a taste of what you can do +with Chickadee. The rest of this manual gets into all of the details +that were glossed over, and much more. Try rendering a sprite, +playing a sound effect, or handling keyboard input. But most +importantly: Have fun! +

+ + + + + + -- cgit v1.2.3