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| -rw-r--r-- | README.org | 180 |
1 files changed, 61 insertions, 119 deletions
@@ -22,77 +22,41 @@ #+BEGIN_SRC scheme (use-modules (2d game) - (2d scene) (2d sprite) - (2d vector2)) + (2d vector2) + (2d window)) - (define (make-demo-sprite) - (load-sprite "images/ghost.png" + (define sprite + (load-sprite "images/p1_front.png" #:position (vector2 320 240))) - (define simple-scene - (make-scene - "Simple" - #:init make-demo-sprite - #:draw draw-sprite)) + (add-hook! draw-hook (lambda (dt alpha) (draw-sprite sprite))) - (define simple-demo - (make-game - #:title "Simple Demo" - #:first-scene simple-scene)) - - (run-game simple-demo) + (with-window (make-window #:title "Simple Sprite Demo") + (run-game-loop)) #+END_SRC ** Features -*** Scenes - Game objects are used to define the basic aspects of a Guile-2D - game such as the window title, resolution, whether or not it - is fullscreen, and what the first scene is. +*** The Game Loop + Guile-2d's game loop doesn't tie drawing and updating + together. Instead, updates happen on a fixed timestep (60 ticks + per second by default) while drawing happens as many times as + possible. A framerate indepedent loop mitigates slow down that the + user might experience when updating the game takes longer than + drawing a frame at the desired rate. Instead of slowing to a + crawl, some frames are dropped and the loop tries to catch up on + updates. Additionally, a fixed timestep allows for a more + deterministic simulation than a variable timestep. + + To start up the game loop, simply call =(run-game-loop)=. It's a + good idea to set up the game window prior to starting the loop via + the =with-window= form. #+BEGIN_SRC scheme - (define my-game - (make-game - #:title "Simple Demo" - #:resolution (vector2 640 480) - #:fullscreen? #f - #:first-scene main-menu)) - #+END_SRC - - Games can be divided into several smaller pieces, called scenes. A - scene describes how a particular part of a game is initialized, - drawn, updated, etc. - - #+BEGIN_SRC scheme - (define main-menu - (make-scene - "Main Menu" - #:init create-menu - #:enter menu-enter - #:exit menu-exit - #:draw draw-menu - #:update update-menu - #:events `((key-down . ,menu-key-down)))) - #+END_SRC - - In addition to the essential callbacks (draw, update, enter, - exit), scenes can specify an alist of additional arbitrary event - handlers. Some events such as =key-down= are emitted by the game - loop when input events are received. - - Scenes live in a place called the stage. There can be many stages, - but only one is active at any given time. When a stage enters - focus, the scene's enter procedure is applied. When a stage loses - focus, the exit procedure is applied. Stages are stored in a - stack, and they can pushed and popped as needed. To change the - current scene, and thus the current stage, use =push-scene=, - =pop-scene=, or =replace-scene=. - - #+BEGIN_SRC scheme - (push-scene tetris-clone) - (pop-scene) - (replace-scene high-scores) + (with-window (make-window #:title "Best Game Ever" + #:resolution (vector2 640 480)) + (run-game-loop)) #+END_SRC *** Sprites @@ -110,9 +74,9 @@ #+BEGIN_SRC scheme (define sprite (load-sprite "cirno.png" - #:position #(0 0) + #:position (vector2 320 240) #:scale (1 1) - #:rotation (0) + #:rotation 45 #:color white #:anchor 'center)) #+END_SRC @@ -127,7 +91,7 @@ Position, scale, rotation, color, and anchor are mutable. #+BEGIN_SRC scheme - (set-sprite-position! sprite #(100 100)) + (set-sprite-position! sprite (vector2 100 100)) #+END_SRC Drawing a sprite is simple. @@ -154,6 +118,29 @@ (for-each draw-sprite sprites)) #+END_SRC +*** Keyboard and Mouse Input + There are hooks within the =(2d keyboard)= and =(2d mouse)= + modules that can be used to respond to user input. + + #+BEGIN_SRC scheme + (use-modules (2d keyboard) + (2d mouse)) + + ;; Quit when ESC is pressed. + (add-hook! key-press-hook + (lambda (key unicode) + (when (eq? key 'escape) + (quit-game)))) + + ;; Print coordinates when the mouse is moved. + (add-hook! mouse-move-hook + (lambda (x y) + (format #t "pos: (~d, ~d)\n" x y))) + #+END_SRC + + In the future, there will be more convenient ways to respond to + user input similar to how keymaps work in Emacs. + *** Coroutines and Agendas The ability to write scripts is very important for most games. A script for an RPG NPC could look like this: @@ -183,7 +170,7 @@ such that it does not halt further program execution. #+BEGIN_SRC scheme - (agenda-schedule + (schedule-next (colambda () (while #t (walk 'up) @@ -194,60 +181,15 @@ #+END_SRC =colambda= is a useful macro that is syntactic sugar for a lambda - expression executed as a coroutine. =agenda-schedule= accepts a + expression executed as a coroutine. =schedule-next= accepts a thunk (a procedure that takes 0 arguments) and schedules it to be - executed later. In this example we do not provide a second - argument to =agenda-schedule=, which means that the thunk will be - executed upon the next game update. + executed the next time the agenda is ticked. There are other ways + to schedule procedures such as =schedule=, =schedule-interval=, + and =schedule-every=. Since guile-2d enforces a fixed timestep and updates 60 times per - second, waiting for 60 updates means that the NPC will wait one - second in between each step. - -*** Actions - Actions encapsulate a procedure that operates over a certain - period of time. Action objects have two properties: an arbitrary - procedure and a duration in game ticks. Action procedures accept - one argument: a time delta in the range [0, 1]. Use actions in - combination with coroutines for things that are a function of - time, such as moving a sprite across the screen. - - #+BEGIN_SRC scheme - (schedule-action - ;; Move horizontally across the screen, starting at x=0 and moving to - ;; x=800, in 60 ticks. - (lerp (lambda (x) - (set-sprite-position! sprite (vector2 x (/ window-height 2)))) - 0 800 60)) - #+END_SRC - - =schedule-action= is used to schedule a coroutine that will - perform the given action in the current agenda. =lerp= is a type - of action, short for linear interpolation. =lerp= takes an - arbitrary procedure to apply at each tick, a start value, an end - value, and like all other actions, a duration. The code above - interpolates from 0 to 800 over 60 ticks. The result of this - action is a sprite moving across the screen from left to right. - - Actions can be combined to run in a sequence or in parallel. - - #+BEGIN_SRC scheme - (schedule-action - (action-parallel - (lerp (lambda (x) - (set-sprite-position! sprite (vector2 x (/ window-height 2)))) - 0 800 60) - ;; Rotate sprite 1080 degrees in 120 ticks. - (lerp (lambda (angle) - (set-sprite-rotation! sprite angle)) - 0 1080 120))) - #+END_SRC - - =action-parallel= will combine many actions into one action that - does everything at the same time. In the example above, the sprite - will still move across the screen from left to right, but while - it's doing so (and for 60 ticks after), it will be rotating from 0 - to 1080 degrees. + second by default, waiting for 60 updates means that the NPC will + wait one second in between each step. ** REPL Driven Development @@ -275,7 +217,7 @@ #+END_SRC ** Building - guile-2d uses the typical GNU build system. First run `autogen.sh` + Guile-2d uses the typical GNU build system. First run `autogen.sh` and then do the usual incantations. #+BEGIN_SRC sh @@ -295,8 +237,8 @@ guile simple.scm #+END_SRC - To run an example using the not-yet-installed files (useful when - developing): + To run an example using the modules in the source directory (useful + when developing): #+BEGIN_SRC sh cd examples @@ -305,7 +247,7 @@ To quit an example: - Close the window - - Press the =ESCAPE= or =Q= key + - Press the =ESCAPE= key ** Platforms |