source: project/wiki/eggref/4/doodle @ 25832

[[tags: egg]]

== doodle - A minimal game 'framework'.

[[toc:]]

=== Description

A minimal game 'framework' inspired by [[http://love2d.org/|löve]].

'''This is still a work in progress and subject to change!'''

=== Author

[[/users/christian-kellermann|Christian Kellermann]]

=== Requirements

Requires the [[miscmacros]], [[cairo]] and [[sdl]] extensions.

=== General program flow of a doodle

A program creates a window, called a 'doodle' here and registers for
any of these three events: world-inits, world-ends and
world-changes. world-inits is called upon the first iteration of the
event loop, world-ends last and world-changes for every iteration.

world-inits and world-ends are thunks, whereas world-changes has the
following signature:

<procedure>(world-changes (lambda (event dt escape-continuation) ...)</procedure>

; event : holds the occured event of this loop iteration
; dt : holds the time delta between the last and this iteration
; escape-continuation : holds the continuation that will exit the loop

Please see below for a detailed list of supported {{event}} symbols.

{{dt}} is a flonum which can be used to adjust speed of animations for
example.

The game loop is started with the {{(run-event-loop)}} procedure.
Usually the game loop will run as fast as it can unless the keyword
parameter {{minimum-wait}} has been given which adds that minimum
delay between iterations.

=== API Documentation

This egg is still under development; the API might change a bit in
future versions.

==== Event loop
===== Procedures
<procedure>(run-event-loop #!key (run-in-background #f) (minimum-wait 0))</procedure>

Starts the event loop and runs {{world-inits}}. If
{{run-in-background}} is #t a new thread is started. Within the event
loop the procedure given with {{world-changes}} is called with the
time delta of the last call and the events that occured. If
{{minimum-wait}} is given and the delta is smaller than
{{minimum-wait}} the thread will sleep for the remaining
time. {{minimum-wait}} takes a value in milliseconds.

===== Parameters
<parameter>(world-inits (lambda () ...))</parameter>

A thunk that is called once when the event loop is started.

<parameter>(world-ends (lambda () ...))</parameter>

A thunk that is called once when the even loop is exited.

<parameter>(world-changes (lambda (event dt exit-continuation) ...))</parameter>

A procedure that gets called every iteration of the event loop. The
{{event}} parameter holds the event, {{dt}} is the time difference in
milliseconds between the last and current
iteration. {{exit-continuation}} can be used to jump out of the
event-loop.

===== Events

One event is a list containing information about the individual
event. There are currently 3 types of handled events:

; quit : The quit event has the following form {{(quit)}}.
; key events : The first element of the list is either the symbol {{pressed}} or {{released}} followed by either the integer for the key code or the symbols {{up}}, {{down}}, {{left}} or {{right}} representing cursor keys.
; unknown : This will list all other events. The list contains the symbol {{unknown}} and the SDL event type. See the SDL egg documentation for hints on what this may be.

==== Drawing
===== Colors

Colors in doodle are represented as simple lists representing RGBA
values one number each. Currently there are two predefined colors:

; solid-black : {{(0 0 0 1)}}
; solid-white : {{(1 1 1 1)}}

===== Procedures

<procedure>(new-doodle #!key (width 680) (height 460) (title "Doodle") (background solid-black) (fullscreen #f))</procedure>

Initialises the internal state and createas a window with the given
dimensions and title.

<procedure>(show!)</procedure>

Causes a redraw of the window.

<procedure>(clear-screen!)</procedure>

Fills the screen with the {{current-background}} color.

<procedure>(rectangle x y width height color)</procedure>

Draws a rectangle at the given coordinates {{(x, y)}} with the
dimensions {{width}} and {{height}}. The border is drawn in {{color}}.

<procedure>(filled-rectangle x y width height color)</procedure>

Draws a rectangle at the given coordinates {{(x, y)}} with the
dimensions {{width}} and {{height}}. The border is drawn in
{{color}}. The rectangle also is filled with {{color}}.

<procedure>(circle x y diameter color)</procedure>

Draws a circle at the point defined by {{(x,y)}} with the given
{{diameter}} and {{color}}. The border is drawn in {{color}}.

<procedure>(filled-circle x y diameter color)</procedure>

Draws a circle at the point defined by {{(x,y)}} with the given
{{diameter}} and {{color}}. The border is drawn in {{color}}. The
circle is filled in {{color}} too.

<procedure>(draw-line x1 y1 x2 y2 #!key (color solid-white) (style #:solid))</procedure>

Draw a line between the two points {{(x1,y1)}} and {{(x2,y2)}} in the
given style. Valid {{style}}s are either {{#:solid}} (the default) or
{{#:dashed}} for dashed lines. The line is drawn in {{color}}.

<procedure>(set-font! font size color)</procedure>

Sets the font to {{font}}, given {{size}} and {{color}}. {{font}} is a
string representing the font's name. Every X11 TTF font is applicable.

<procedure>(text x y text #!key (align #:left))</procedure>

Print the given text in one line starting on point
{{(x,y)}}. Alignment can be changed with the {{align}}
parameter. Supported alignment values are {{#:left}}, {{#:center}} and
{{#:right}}.

<procedure>(save-screenshot filename)</procedure>

Saves the current screen content to a file called {{filename}} as a
portable network graphics (PNG). It is up to the user to provide an
appropriate extension to the filename.

===== Parameters

<parameter>(font-color)</parameter>

Holds the current font color.

<parameter>(font-size)</parameter>

Holds the current font-size.

<parameter>(current-background)</parameter>

Holds the current background color.

==== Collision detection

*sprites*

<procedure>add-sprite!</procedure>

<procedure>check-for-collisions</procedure>

<procedure>make-sprite</procedure>

<procedure>remove-sprite!</procedure>

<procedure>update-sprite!</procedure>

==== Example

<enscript highlight="scheme">
</enscript>

=== Changelog

; 0.1 : Initial version

=== License

  Copyright (c) 2012, Christian Kellermann
  All rights reserved.

  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions
  are met:

      Redistributions of source code must retain the above copyright
      notice, this list of conditions and the following disclaimer.
 
      Redistributions in binary form must reproduce the above
      copyright notice, this list of conditions and the following
      disclaimer in the documentation and/or other materials provided
      with the distribution.
 
  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
  COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
  INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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