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== 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!'''

=== Code repository

The source code for doodle is hosted on [[https://bitbucket.org/ckeen/doodle|bitbucket]].

You can grab it with git:

''git clone https://bitbucket.org/ckeen/doodle.git''

=== Author

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

=== Requirements

Requires the [[clojurian]], [[cairo]] and [[sdl-base]] 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 (events dt escape-continuation) ...))</procedure>

; event : holds the occured list of events 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 *minimum-wait*))</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 seconds.

<procedure>(world-inits (lambda () ...))</procedure>

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

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

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

<procedure>(world-changes (lambda (events dt exit-continuation) ...))</procedure>

A procedure that gets called every iteration of the event loop. The
{{events}} parameter holds the list of events, {{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.

<parameter>(world-update-delay flonum)</parameter>

The minimum delay between updates. Aka, the minimum-wait property in 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 the symbol {{key}} followed by 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.
; mouse events: The first element of this list is the symbol {{mouse}}. There are three types of events: {{pressed}}, {{released}} and {{moved}}. The first two are followed by three values {{x}} {{y}} and {{button}}, representing the coordinates of the pointer and the button number being pressed or released. Mouse buttons are numbered 1-5, with 4,5 being rotations of the mouse wheel. {{moved}} events have the coordinates as their only arguments.
; 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. If background is a string it will be interpreted as a filename pointing to a PNG file which will be loaded as background.

The background parameter can either be a doodle RGBA color list or a
string pointing to a PNG file.

<procedure>(show!)</procedure>

Causes a redraw of the window.

<procedure>(clear-screen #!optional (color (current-background)))</procedure>

Fills the screen with the {{current-background}} color. Color can
also be given as a string representing a filename to a PNG image which
will be loaded instead.

<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>(text-width text)</procedure>

Returns multiple values: The ''width'' and ''height'' in pixels of the
given ''text'' when rendered with the current font settings. ''text''
is assumed to be a string.

<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.

===== Exported values

{{doodle-width}} and {{doodle-height}} hold the width and height of
the window, that has been given on a call to {{(new-doodle)}}.

===== Changing Settings

The following can be used to get or set the current values.

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

Holds the current font color. Default is black.

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

Holds the current font-size. Default is 12.

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

Holds the current background color. Default is black.

<procedure>(line-width)</procedure>

Holds the line width used for drawing. Default is 2.0.

<procedure>(world-update-delay)</procedure>

Amount of milliseconds that should pass at minimum before calling the
world-changes procedure again.

==== Images

Since version 0.4 doodle supports blitting images in. The initial form
is {{define-resource}}. This registers an image and makes it available
through the given symbol ''name'' to all procedures that take a
resource argument below.

<procedure>(define-resource name type filename . data )</procedure>

Registers a resource under the name ''name''. The resource is read
from a file specified with ''filename''. The ''type'' argument is a
keyword and specifies how the ''data'' argument is handled and which
form is expected.

The following types are handled:

 * #:image

A single image from a single file. It takes optional argumens
''x-offset'', ''y-offset'' and ''scale-factor'' to take just a
fraction out of the given image file and to be able to scale it.

The following example does this several times:

<enscript language="scheme">
(define-resource 'water #:image "Water Block.png" *terrain-xoffset* *terrain-yoffset*)
(define-resource 'stone #:image "Stone Block.png" *terrain-xoffset* *terrain-yoffset*)
(define-resource 'princess #:image "Character Princess Girl.png" 0 -80)
(define-resource 'bubble #:image "SpeechBubble.png" -15 -120)
(define-resource 'bug #:image "Enemy Bug.png" 0 -80)
(define-resource 'tree #:image "Tree Tall.png" 0 -80 )
(define-resource 'heart #:image "Heart.png" 0 0 0.5)
</enscript>

 * #:tileset

This assumes the image to consist of one or more square tiles. Then
several images are referenced out of a single image file. The ''data''
argument is expected to be a list of two elements: the tile-size and a
list consisting of (name number) pairs (proper lists). The following
examples makes three tiles accessible through their names: wall, floor
and hero. They can be drawn with the {{blit-image}} procedure.

<enscript language="scheme">
(define-resource 'tiles
                  #:tileset
                   "../roguelike/tile.png"
                    32
                    '((wall 2)
                      (floor 30)
                      (hero 486)))
</enscript>

<procedure>(blit-image name x y rotation: angle )</procedure>

Blits in the image ''name'' at position (x, y). If angle is given the
image is rotated. The angle has to be given in degrees, negative
values indicate counter-clockwise rotation.

==== Example

The following example will show a little circle painting program. It
requires the [[matchable]] egg.

<enscript highlight="scheme">
(use matchable doodle)

(define *paint* #f)

(define red '(1 0 0 0.3))

(world-inits
 (lambda ()
   (clear-screen)
   (set-font! "Vollkorn" 18 red)
   (text (/ doodle-width 2)
         (/ doodle-height 2) '("Welcome to doodle!"
                               "Click the left mouse button to draw circles"
                               "Press ESC to leave")
         align: #:center)))

(world-changes
 (lambda (events dt exit)
   (for-each
    (lambda (e)
      (match e
       (('mouse 'pressed x y 1)
        (set! *paint* #t)
        (filled-circle x y 10 red))
       (('mouse 'released x y 1)
        (set! *paint* #f))
       (('mouse 'moved x y)
        (when *paint*
          (filled-circle x y 10 red)))
       (('key 'pressed #\esc)
        (exit #t))
       (else (void))))
    events)))

(new-doodle title: "Doodle paint" background: solid-white)
(run-event-loop)

</enscript>

=== Changelog

; 0.1 : Initial version
; 0.2 : bogus tag, sorry
; 0.3 : Fixed event handling, added mouse events, background images possible
; 0.4 : blit-image and define-resources added, text-width and line-width are exported
; 0.5-0.6 : Yours truly messing up the meta data, please ignore
; 0.7 : Correct dependencies to cairo and sdl
; 0.8 : Fixed text procedure, closed path on circles
; 0.9 : Changed dependency from sdl egg to sdl-base
; 0.10-0.12 : Fiddling with meta files
; 0.13 : callbacks are wrapped in exception handlers, parameters are no longer used, added world-update-delay
=== 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,
  STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
  OF THE POSSIBILITY OF SUCH DAMAGE.