Export the guarded mutator

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+                    GNU AFFERO GENERAL PUBLIC LICENSE
+                       Version 3, 19 November 2007
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+USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
+DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
+PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS),
+EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
+SUCH DAMAGES.
+
+  17. Interpretation of Sections 15 and 16.
+
+  If the disclaimer of warranty and limitation of liability provided
+above cannot be given local legal effect according to their terms,
+reviewing courts shall apply local law that most closely approximates
+an absolute waiver of all civil liability in connection with the
+Program, unless a warranty or assumption of liability accompanies a
+copy of the Program in return for a fee.
+
+                     END OF TERMS AND CONDITIONS
+
+            How to Apply These Terms to Your New Programs
+
+  If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
+
+  To do so, attach the following notices to the program.  It is safest
+to attach them to the start of each source file to most effectively
+state the exclusion of warranty; and each file should have at least
+the "copyright" line and a pointer to where the full notice is found.
+
+    <one line to give the program's name and a brief idea of what it does.>
+    Copyright (C) <year>  <name of author>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Affero General Public License as published
+    by the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU Affero General Public License for more details.
+
+    You should have received a copy of the GNU Affero General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+Also add information on how to contact you by electronic and paper mail.
+
+  If your software can interact with users remotely through a computer
+network, you should also make sure that it provides a way for users to
+get its source.  For example, if your program is a web application, its
+interface could display a "Source" link that leads users to an archive
+of the code.  There are many ways you could offer source, and different
+solutions will be better for different programs; see section 13 for the
+specific requirements.
+
+  You should also get your employer (if you work as a programmer) or school,
+if any, to sign a "copyright disclaimer" for the program, if necessary.
+For more information on this, and how to apply and follow the GNU AGPL, see
+<https://www.gnu.org/licenses/>.

README.org

@@ -23,11 +23,10 @@ Components are SRFI-99 records which store data associated for a particular enti
 
 ** Systems
 Systems are functions which modify state and draw to the screen.
-Systems are stored in the ~systems~ list as a record containing a name (symbol), rendering (a symbol), a priority (integer), entity criteria (list of symbols), and the function itself.
+Systems are stored in the ~systems~ list as a record containing a name (symbol), a priority (integer), entity criteria (list of symbols), and the function itself.
 Each system specifies the components an entity (the entity criteria) must have for it to be processed by that system. The entities are then selected for the system from the ~component-sets~.
 Each system is applied to all entities which match its entity criteria.
 Systems have a priority which defaults to 0. Lower priority systems will be executed before higher priority systems. Systems within the same priority execute in order of addition to the ~systems~ list.
-If a system defines a rendering symbol of 3D, it will be wrapped in ~with-mode-3d~. If a system defines a rendering symbol of 2D, it will be wrapped in ~with-mode-2d~. All systems run in render loop, wrapped in ~with-drawing~, and can draw non-2D and non-3D elements arbitrarily. In this way ~with-mode-3d~ and ~with-mode-2d~ can be avoided in system function bodies, and non-3D/2D systems can draw in screen space.
 
 The ~systems~ list is sorted on each addition and removal of a system.
 Like entities, the addition of systems is queued for the beginning of each frame. This prevents the system list from being sorted multiple times per frame.
@@ -43,27 +42,149 @@ Systems can choose to either pop the event off the bus (removing it from further
 The symbol an event is associated by is essentially an "action". The event bus can have multiple events of the same type (for example, multiple different key presses can occur in a frame). Only one event of each name (for example, only 1 event can be called "jump", which might correspond to a space key press) is allowed in the bus at any one time.
 Custom event buses can be created and stored in the ~event-buses~ hash table. Systems can query a particular event bus within that list for a particular event.
 
+** Rendering
+Imugi maintains 3 render queues, with one each for screen, 2D and 3D drawing.
+New queues can be added by adding a new list to the ~render-queues~ hash table.
+Systems can push render objects to any of these queues, which are simply pairs of integers and a lambda thunk.
+The initial integer denotes a layer, while the lambda thunk contains the drawing function to evaluate.
+When drawing the next frame, the system iterates and executes every drawing thunk in order from the smallest to the largest layer.
+The 3D queue is executed first, followed by the 2D queue, followed by the screen queue.
+The order of execution can be changed by modifying the ~render-priority~ list.
+The render-priority list contains pairs where the first symbol in the pair is a reference to the render queue in the ~render-queues~ hash table, and the second symbol is either ~screen~, ~2d~, or ~3d~. The order of items in this list informs Imugi of the order in which to execute the queues, and the second symbol of each pair tells Imugi what draw mode to use for each thunk.
+For 2D and 3D drawing, systems can set the currently active camera object on the parameters ~*active-camera-2d*~ and ~*active-camera-3d*~. If a 3D or 2D render is queued but no corresponding camera for the mode is set, the render will not occur but the render queue will still be emptied.
+
 ** Resources
 When a resource, such as a font or texture, is loaded from the filesystem, the pointer is stored in an SRFI-69 hash table ~resources~ keyed by the path.
 When records are first loaded, a finalizer is set for them ensuring they are unloaded when collected by the GC.
 If the game attempts to load a resource which has already been loaded, it will use the pointer in the ~resources~ hash table instead.
 
-* Structure & Modules
+* Folder Structure & Module Documentation
 The ~engine~ folder contains core engine code, organised across the following modules:
-- ~(engine core)~ which contains core functionality including starting the window and game loop, and functions for adding/removing systems, entities, and event buses to/from the game state.
-- ~(engine components)~ which contains methods for creating and accessing components.
-- ~(engine systems)~ which contains functions for creating new systems.
-- ~(engine events)~ which contains functions for creating and interacting with event buses.
-- ~(engine resources)~ which contains functions for loading and using resources.
-- ~(engine utilities)~ which contains generic engine utility functions.
-- ~(engine debug)~ which contains parameters and functions for debugging and profiling.
-- ~(engine math)~ which contains utility math and randomness functions.
-
-The ~components~ folder contains pre-made components, entities, and systems for ease of use:
-- ~(components ui)~ contains building blocks for basic UI elements.
-- ~(components 2d)~ contains building blocks for basic 2D elements.
-
 The ~games~ folder contains various sample games made with Imugi.
+** ~(engine core)~
+~(engine core)~ contains the fundamental engine functions. Entire games can be made using just the core module, and all other modules simply extend this module.
+
+*** Game State
+~world~ is an SRFI-69 hash table, which contains all entity component lists keyed by their symbol name.
+
+~component-sets~ is an SRFI-69 hash table, which contains an SRFI-113 set for every component type in the ~world~. Each set contains a symbol referencing a ~world~ entity that has a component of that type.
+
+~systems~ is a list, which contains all lists to be executed on each frame.
+
+~event-buses~ is an SRFI-69 hash table, which contains hash tables keyed by the event bus name. Each hash table in ~event-buses~ keeps track of individual event records keyed by action names.
+
+~render-queues~ is an SRFI-69 hash table, which contains lists keyed by the render queue name. Each item in these lists is a pair, where the first element is the layer of the drawing and the second is a thunk that gets called during the render.
+
+~render-priority~ is an association list, where the first element of each pair is a render queue name from the ~render-queues~ hash table, and the second element is the drawing mode (a symbol which is either ~screen~, ~2d~, or ~3d~). The order of elements in the ~render-priority~ association list determines the order in which the render-queues are evaluated, with the first queue name in the list being the first queue to evaluate.
+*** Entities
+#+begin_src scheme
+  (create-named-entity id . components)
+  (create-entity . components)
+  (remove-entity id)
+  (get-entity id)
+  (clear-world)
+#+end_src
+Functions for creating, removing, and fetching entities. ~id~ must be a symbol, and each parameter passed in as ~components~ must be an SRFI-99 record.
+
+When entities are created or removed, the creation/deletion is added to an internal queue. Entity creation and removal to/from the ~world~ state from the queue is performed at the top of each frame, or when ~(resolve-queues)~ is executed.
+*** Systems
+#+begin_src scheme
+  (make-system name priority criteria process)
+  (system? record)
+  (system-name system)
+  (system-priority system)
+  (set-system-priority! system priority)
+  (system-mode system)
+  (system-criteria system)
+  (set-system-criteria! system criteria)
+  (system-process system)
+  (set-system-process! system process)
+#+end_src
+Functions for creating systems, which are SRFI-99 records. ~name~ must be a symbol, ~priority~ must be an integer, ~mode~ must be either ~entity~ or ~batch~, ~criteria~ must be a list of symbols, and ~process~ must be a single argument procedure (where the single argument is expected to be either a single entity matching all given criteria when the mode is ~entity~, or a list of entities matching the given criteria when the mode is ~batch~).
+
+#+begin_src scheme
+  (add-system system)
+  (remove-system name)
+  (clear-systems)
+#+end_src
+Functions for adding and removing systems from process. ~system~ must be an SRFI-99 record, and ~name~ must be a symbol (which is used to identify a ~system~ record in the ~systems~ list).
+
+When systems are created or removed, the creation/deletion is added to an internal queue. System creation and removal to/from the ~systems~ list from the queue is performed at the top of each frame, or when ~(resolve-queues)~ is executed.
+*** Event Buses
+#+begin_src scheme
+  (register-event-bus name)
+  (remove-event-bus name)
+  (fetch-event-bus name)
+#+end_src
+Functions for creating, removing, and retrieving event buses. ~name~ must be a symbol referencing the bus name in the ~event-buses~ hash table.
+
+Event buses are added and remove immediately, without queuing.
+
+#+begin_src scheme
+  (push-event bus action event)
+  (peek-event bus action)
+  (pop-event bus action)
+#+end_src
+Functions for creating and fetching events. ~bus~ must be a symbol referencing a bus name, ~action~ must be a symbol referencing the name of the action, and ~event~ must be a record.
+
+~peek-event~ returns the event record but keeps the event in the event bus. ~pop-event~ returns the event record and removes it from the event bus.
+*** Frame Generation, Render Queues, and Game Loop
+#+begin_src scheme
+  (register-render-queue queue-name drawing)
+#+end_src
+Create a new render queue in ~render-queues~, where ~queue-name~ is the queue name symbol and ~drawing~ is the drawing mode (either ~screen~, ~2d~, or ~3d~). Render queues created this way are automatically placed at the front of the ~render-priority~ assocation list.
+
+#+begin_src scheme
+  (push-render-object queue-name layer thunk)
+#+end_src
+Adds a thunk to the given render queue name at the given layer. ~queue-name~ must be a symbol, ~layer~ must be an integer, and ~thunk~ must be a zero-argument procedure. 
+
+#+begin_src scheme
+  *active-camera-2d*
+  *active-camera-3d*
+#+end_src
+Parameters which describe the currently active camera for 2D and 3D drawing.
+
+#+begin_src scheme
+  *clear-color*
+#+end_src
+~*clear-color*~ is a parameter which expects a u8vector corresponding to a Raylib color.
+
+#+begin_src scheme
+  (evaluate-render-queue queue-name mode)
+  (perform-render)
+#+end_src
+Functions for evaluating the render queues. ~evaluate-render-queue~ evaluates a single queue where ~queue-name~ is a symbol corresponding to a queue in the ~render-queues~, and ~mode~ is a drawing mode symbol (either ~screen~, ~2d~, or ~3d~). The given queue is cleared after evaluation, and each thunk in the render queue is evaluated with the appropriate mode, using the ~*active-camera-2d*~ and ~*active-camera-3d*~ for the ~2d~ and ~3d~ drawing modes.
+
+~perform-render~ clears the screen to the set ~*clear-color*~, then iterates the ~render-priority~ association list and calls ~evaluate-render-queue~ on each queue in order with the appropriate mode.
+
+#+begin_src scheme
+  (resolve-queues)
+#+end_src
+~(resolve-queues)~ causes all queues to immediately resolve pending actions to the true game state.
+
+#+begin_src scheme
+  (next-frame)
+#+end_src
+~(next-frame)~ is a frame generation function. When called, it resolves all queues, then executes all systems, then finally performs the render of the next frame.
+
+*** Window Functions
+#+begin_src
+  *window-size*
+  *window-title*
+  *target-fps*
+#+end_src
+~*window-size*~ is a parameter that expects a cons pair of two integers, where the first integer is the window width, and the second is the window height.
+
+~*window-title*~ is a parameter that expects a string, which is used for the window title.
+
+~*target-fps*~ is a parameter that expects an integer, which specifies the desired frames per second to run at.
+
+#+begin_src scheme
+  (create-window process: (next-frame) close-predicate: (window-should-close?))
+#+end_src
+~create-window~ creates a window using the window parameters described above, sets the target frames per second, then enters a loop which runs the ~process:~ function (~next-frame~ by default) on each frame, unless ~close-predicate:~ (Raylib's ~window-should-close~ function by default) returns true, in which case the window is closed.
+
 * Dependencies
 The following Chicken dependencies are required:
 - raylib
@@ -71,4 +192,8 @@ The following Chicken dependencies are required:
 - SRFI-113
 - SRFI-69
 - csm
+- SRFI-78
+  
+* Running
+From the ~build~ directory, run ~csm -program test.engine .. && ./test.engine~ to run engine tests.
 

all.options

@@ -0,0 +1 @@
+-static -L /usr/local/lib64/libraylib.a

engine/components.scm

@@ -0,0 +1,385 @@
+(module (engine components core) ()
+(import scheme
+	(chicken base)
+	(chicken module)
+	(srfi 1)
+	(srfi 99))
+
+;; Vector exports
+(export make-vector2 vector2? vector2-x
+	set-vector2-x! vector2-y set-vector2-y!)
+
+;; 2D Vector type
+;; TODO: this could be done with a macro to save some definitions
+(define-record-type <vector2>
+  (int:make-vector2 x y)
+  vector2?
+  (x vector2-x int:set-vector2-x!)
+  (y vector2-y int:set-vector2-y!))
+
+;; Type safe 2D vector constructor
+(define (make-vector2 x y)
+  (assert (number? x))
+  (assert (number? y))
+  (int:make-vector2 x y))
+
+;; Type safe 2D vector setter
+(define (set-vector2-x! vector2 x)
+  (assert (vector2? vector2))
+  (assert (number? x))
+  (int:set-vector2-x! vector2 x))
+
+;; Type safe 2D vector setter
+(define (set-vector2-y! vector2 y)
+  (assert (vector2? vector2))
+  (assert (number? y))
+  (int:set-vector2-y! vector2 y))
+
+;; Vector utility functions
+(define (vector-x component)
+  (assert (record? component))
+  ((rtd-accessor (record-rtd component) 'x) component))
+
+(define (set-vector-x! component x)
+  (assert (record? component))
+  (assert (number? x))
+  ((rtd-mutator (record-rtd component) 'x) component x))
+
+(define (vector-y component)
+  (assert (record? component))
+  ((rtd-accessor (record-rtd component) 'y) component))
+
+(define (set-vector-y! component y)
+  (assert (record? component))
+  (assert (number? y))
+  ((rtd-mutator (record-rtd component) 'y) component y))
+
+;; Export vector functions
+(export vector-= vector-+ vector-- vector-* vector-/
+	vector-magnitude vector-normalize vector-dot
+	vector-angle-between)
+
+;; TODO: make this function accept any number of vectors
+(define (vector-= vec1 vec2)
+  (assert (and (record? vec1)
+	       (record? vec2)))
+  (assert (eq? (rtd-name (record-rtd vec1))
+	       (rtd-name (record-rtd vec2))))
+  (assert ((disjoin vector2?) vec1))
+  (cond
+   ((vector2? vec1)
+    (and (= (vector-x vec1) (vector-x vec2))
+	 (= (vector-y vec1) (vector-y vec2))))))
+
+;; TODO: make this function accept any number of vectors
+(define (vector-+ vec1 vec2)
+  (assert (and (record? vec1)
+	       (record? vec2)))
+  (assert (eq? (rtd-name (record-rtd vec1))
+	       (rtd-name (record-rtd vec2))))
+  (assert ((disjoin vector2?) vec1))
+  (cond
+   ((vector2? vec1)
+    (make-vector2 (+ (vector-x vec1) (vector-x vec2))
+		  (+ (vector-y vec1) (vector-y vec2))))))
+
+;; TODO: make this function accept any number of vectors
+(define (vector-- vec1 vec2)
+  (assert (and (record? vec1)
+	       (record? vec2)))
+  (assert (eq? (rtd-name (record-rtd vec1))
+	       (rtd-name (record-rtd vec2))))
+  (assert ((disjoin vector2?) vec1))
+  (cond
+   ((vector2? vec1)
+    (make-vector2 (- (vector-x vec1) (vector-x vec2))
+		  (- (vector-y vec1) (vector-y vec2))))))
+
+;; TODO: make this function accept any number of vectors
+(define (vector-* vec1 vec2)
+  (assert (and (record? vec1)
+	       (record? vec2)))
+  (assert (eq? (rtd-name (record-rtd vec1))
+	       (rtd-name (record-rtd vec2))))
+  (assert ((disjoin vector2?) vec1))
+  (cond
+   ((vector2? vec1)
+    (make-vector2 (* (vector-x vec1) (vector-x vec2))
+		  (* (vector-y vec1) (vector-y vec2))))))
+
+;; TODO: make this function accept any number of vectors
+(define (vector-/ vec1 vec2)
+  (assert (and (record? vec1)
+	       (record? vec2)))
+  (assert (eq? (rtd-name (record-rtd vec1))
+	       (rtd-name (record-rtd vec2))))
+  (assert ((disjoin vector2?) vec1))
+  (cond
+   ((vector2? vec1)
+    (make-vector2 (/ (vector-x vec1) (vector-x vec2))
+		  (/ (vector-y vec1) (vector-y vec2))))))
+
+;; Magnitude
+(define (vector-magnitude vec)
+  (assert ((disjoin vector2?) vec))
+  (cond
+   ((vector2? vec)
+    (sqrt (+ (expt (vector-x vec) 2)
+	     (expt (vector-y vec) 2))))))
+
+(define (vector-dot vec1 vec2)
+  (assert (and (record? vec1)
+	       (record? vec2)))
+  (assert (eq? (rtd-name (record-rtd vec1))
+	       (rtd-name (record-rtd vec2))))
+  (assert ((disjoin vector2?) vec1))
+  (cond
+   ((vector2? vec1)
+    (+ (* (vector-x vec1) (vector-x vec2))
+       (* (vector-y vec1) (vector-y vec2))))))
+
+(define (vector-angle-between vec1 vec2)
+  (assert (and (record? vec1)
+	       (record? vec2)))
+  (assert (eq? (rtd-name (record-rtd vec1))
+	       (rtd-name (record-rtd vec2))))
+  (assert ((disjoin vector2?) vec1))
+  (cond
+   ((vector2? vec1)
+    (acos (/ (vector-dot vec1 vec2)
+	     (* (vector-magnitude vec1)
+		(vector-magnitude vec2)))))))
+
+;; Normalization
+(define (vector-normalize vec)
+  (assert ((disjoin vector2?) vec)) ;; TODO: This assertion should be moved out of here
+  (let ((magnitude (vector-magnitude vec)))
+    (cond
+     ((vector2? vec)
+      (make-vector2 (/ (vector-x vec)
+		       magnitude)
+		    (/ (vector-y vec)
+		       magnitude))))))
+
+;; Color exports
+(export make-color color-r color-g color-b color-a
+	set-color-r! set-color-g! set-color-b! set-color-a!)
+
+;; Color type
+(define-record-type <color>
+  (int:make-color r g b a)
+  color?
+  (r color-r int:set-color-r!)
+  (g color-g int:set-color-g!)
+  (b color-b int:set-color-b!)
+  (a color-a int:set-color-a!))
+
+;; Type safe color constructor
+(define (make-color r g b a)
+  (assert (and (number? r) (<= 0 r 1)))
+  (assert (and (number? g) (<= 0 g 1)))
+  (assert (and (number? b) (<= 0 b 1)))
+  (assert (and (number? a) (<= 0 a 1)))
+  (int:make-color r g b a))
+
+;; Type safe color setter
+(define (set-color-r! color r)
+  (assert (color? color))
+  (assert (and (number? r) (<= 0 r 1)))
+  (int:set-color-r! color r))
+
+;; Type safe color setter
+(define (set-color-g! color g)
+  (assert (color? color))
+  (assert (and (number? g) (<= 0 g 1)))
+  (int:set-color-g! color g))
+
+;; Type safe color setter
+(define (set-color-b! color b)
+  (assert (color? color))
+  (assert (and (number? b) (<= 0 b 1)))
+  (int:set-color-b! color b))
+
+;; Type safe color setter
+(define (set-color-a! color a)
+  (assert (color? color))
+  (assert (and (number? a) (<= 0 a 1)))
+  (int:set-color-a! color a))
+
+;; Screen transform record and exports
+(export make-screen-transform screen-transform?)
+
+;; The screen transform is for representing transformations in screen-space, that is
+;; in UI and not in 2D/3D
+(define-record-type <screen-transform>
+  (int:make-screen-transform position pivot rotation scale anchor parent)
+  screen-transform?
+  (position screen-transform-position int:set-screen-transform-position!)
+  (pivot screen-transform-pivot int:set-screen-transform-pivot!)
+  (rotation screen-transform-rotation int:set-screen-transform-rotation!)
+  (scale screen-transform-scale int:set-screen-transform-scale!)
+  (anchor screen-transform-anchor int:set-screen-transform-anchor!)
+  (parent screen-transform-parent int:set-screen-transform-parent!))
+
+;; Type safe constructor
+(define (make-screen-transform position rotation scale anchor parent)
+  (assert (vector2? position))
+  (assert (real? rotation))
+  (assert (vector2? scale))
+  (assert (and (symbol? anchor) (member anchor '(top-left top-middle top-right
+							  center-left center center-right
+							  bottom-left bottom-middle bottom-right))))
+  (assert (and (symbol? parent)))
+  (int:make-screen-transform position rotation scale anchor parent))
+
+;; Generic accessors and mutators for position, rotation, scale, anchor, and parent
+;; This allows us to abstract across different transform types - (position) will work for
+;; screen-transform and 2D-transform, with type checking
+(export position set-position! rotation set-rotation! scale set-scale!
+	anchor set-anchor! parent set-parent!)
+
+(define (position component)
+  (assert (record? component))
+  ((rtd-accessor (record-rtd component) 'position) component))
+
+(define (set-position! component position)
+  (assert (record? component))
+  (cond
+   ((screen-transform? component) (assert (vector2? position))))
+  ((rtd-mutator (record-rtd component) 'position) component position))
+
+(define (pivot component)
+  (assert (record? component))
+  ((rtd-accessor (record-rtd component) 'pivot) component))
+
+(define (set-pivot! component pivot)
+  (assert (record? component))
+  (cond
+   ((screen-transform? component) (assert (vector2? pivot))))
+  ((rtd-mutator (record-rtd component) 'pivot) component pivot))
+
+(define (rotation component)
+  (assert (record? component))
+  ((rtd-accessor (record-rtd component) 'rotation) component))
+
+(define (set-rotation! component rotation)
+  (assert (record? component))
+  (cond
+   ((screen-transform? component) (assert (real? rotation))))
+  ((rtd-mutator (record-rtd component) 'rotation) component rotation))
+
+(define (scale component)
+  (assert (record? component))
+  ((rtd-accessor (record-rtd component) 'scale) component))
+
+(define (set-scale! component scale)
+  (assert (record? component))
+  (cond
+   ((screen-transform? component) (assert (vector2? scale))))
+  ((rtd-mutator (record-rtd component) 'scale) component scale))
+
+(define (anchor component)
+  (assert (record? component))
+  ((rtd-accessor (record-rtd component) 'anchor) component))
+
+(define (set-anchor! component anchor)
+  (assert (record? component))
+  (cond
+   ((screen-transform? component)
+    (assert (and (symbol? anchor)
+		 (member anchor '(top-left top-middle top-right
+					   center-left center center-right
+					   bottom-left bottom-middle bottom-right))))))
+  ((rtd-mutator (record-rtd component) 'anchor) component anchor))
+
+(define (parent component)
+  (assert (record? component))
+  ((rtd-accessor (record-rtd component) 'parent) component))
+
+(define (set-parent! component parent)
+  (assert (record? component))
+  (cond
+   ((screen-transform? component)
+    (assert (symbol? anchor))))
+  ((rtd-mutator (record-rtd component) 'parent) component parent))
+
+;; Visuals
+;; Primitive shape visual types
+(define-record-type <pixel-2d>
+  (int:make-pixel-2d position)
+  pixel-2d?
+  (position pixel-2d-position int:set-pixel-2d-position!))
+
+(define (make-pixel-2d position)
+  (assert (vector2? position))
+  (int:make-pixel-2d position))
+
+(define set-pixel-2d-position!
+  (guarded-mutator pixel-2d? 'position vector2?))
+
+(define-record-type <line-2d>
+  (int:make-line-2d start-pos end-pos thickness)
+  line-2d?
+  (start-pos line-2d-start-pos int:set-line-2d-start-pos!)
+  (end-pos line-2d-end-pos int:set-line-2d-end-pos!)
+  (thickness line-2d-thickness int:set-line-2d-thickness!))
+
+(define (make-line-2d start-pos end-pos thickness)
+  (assert (vector2? start-pos))
+  (assert (vector2? end-pos))
+  (assert ((conjoin integer? positive?) thickness))
+  (int:make-line-2d start-pos end-pos thickness))
+
+(define set-line-2d-start-pos!
+  (guarded-mutator line-2d? 'start-pos vector2?))
+(define set-line-2d-end-pos!
+  (guarded-mutator line-2d? 'end-pos vector2?))
+(define set-line-2d-thickness!
+  (guarded-mutator line-2d? 'start-pos (conjoin integer? positive?)))
+
+(define-record-type <circle-2d>
+  (int:make-circle-2d center radius filled)
+  circle-2d?
+  (center circle-2d-center int:set-circle-2d-center!)
+  (radius circle-2d-radius int:set-circle-2d-radius!)
+  (filled circle-2d-filled? int:set-circle-2d-filled!))
+
+(define (make-circle-2d center radius filled)
+  (assert (vector2? center))
+  (assert ((conjoin integer? positive?) radius))
+  (assert (boolean? filled))
+  (int:make-circle-2d center radius filled))
+
+(define set-circle-2d-center!
+  (guarded-mutator circle-2d? 'center vector2?))
+(define set-circle-2d-radius!
+  (guarded-mutator circle-2d? 'radius ((conjoin integer? positive?) radius)))
+(define set-circle-2d-filled!
+  (guarded-mutator circle-2d? 'filled boolean?))
+
+;; TODO: might be nicer to have the origin and width/height inside a rect-2d type or similar
+(define-record-type <rectangle-2d>
+  (int:make-rectangle-2d origin width height filled thickness)
+  rectangle-2d?
+  (origin rectangle-2d-origin int:set-rectangle-2d-origin!)
+  (width rectangle-2d-width int:set-rectangle-2d-width!)
+  (height rectangle-2d-height int:set-rectangle-2d-height!)
+  (filled rectangle-2d-filled? int:set-rectangle-2d-filled!)
+  (thickness rectangle-2d-thickness int:set-rectangle-2d-thickness))
+
+(define-record-type <triangle-2d>
+  (int:make-triangle-2d vertex-1 vertex-2 vertex-3 filled)
+  triangle-2d?
+  (vertex-1 triangle-2d-vertex-1 int:set-triangle-2d-vertex-1!)
+  (vertex-2 triangle-2d-vertex-2 int:set-triangle-2d-vertex-2!)
+  (vertex-3 triangle-2d-vertex-3 int:set-triangle-2d-vertex-3!)
+  (filled triangle-2d-filled int:set-triangle-2d-filled!))
+
+;; Visual component
+(define-record-type <visual-2d>
+  (int:make-visual-2d draw color layer)
+  visual-2d?
+  (draw visual-2d-draw int:set-visual-2d-draw!) ;; NOTE: Typing here: pixel-2d, line-2d, circle-2d, rectangle-2d, triangle-2d etc
+  (color visual-2d-color int:set-visual-2d-color!)
+  (layer visual-2d-layer int:set-visual-2d-layer!))
+)

engine/core.scm

@@ -3,13 +3,20 @@
 	(chicken base)
 	(chicken module)
 	(chicken sort)
+	(engine guards)
 	raylib
 	(srfi 1)
+	(srfi 4)
 	(srfi 69)
 	(srfi 99)
 	(srfi 113)
 	(srfi 128))
 
+;; We export the world, component sets, systems, and event buses so that the core can be extended to
+;; include serialization functions across all.
+;; NOTE: direct read/write to these is undefined, and will cause problems.
+(export world component-sets systems event-buses render-queues render-priority)
+
 ;; The world hash table
 (define world (make-hash-table))
 ;; The component-sets hash table
@@ -33,7 +40,7 @@
 
 ;; Create an entity in the world immediately,
 ;; and add it to the requisite component-sets
-(define (create-entity id components)
+(define (create-entity-now id components)
   (hash-table-set! world id components)
   (for-each
    (lambda (component)
@@ -41,7 +48,7 @@
    components))
 
 ;; Remove a single matching item from a set
-(define (set-remove! set element)
+(define (remove-from-set! set element)
   (set-search! set element
 	       (lambda (insert ignore)
 		 (ignore #f))
@@ -50,11 +57,11 @@
 
 ;; Remove an entity from the world immediately,
 ;; as well as from all component sets.
-(define (remove-entity id)
+(define (remove-entity-now id)
   (hash-table-delete! world id)
   (for-each
    (lambda (set)
-     (set-remove! set id))
+     (remove-from-set! set id))
    (hash-table-values component-sets)))
 
 ;; Queues for entity creation and deletion
@@ -63,6 +70,7 @@
 
 ;; Add an entity to the incoming queue
 ;; TODO: append! doesn't work here and IDK why
+;; TODO: this could be done with cons anyway because we don't care about the order
 (define (queue-add-entity id components-lst)
   (set! add-entity-queue
     (append add-entity-queue (list (cons id components-lst)))))
@@ -78,7 +86,7 @@
    (lambda (entity)
      (let ((id (car entity))
 	   (components (cdr entity)))
-       (create-entity id components)))
+       (create-entity-now id components)))
    add-entity-queue)
   (set! add-entity-queue '()))
 
@@ -86,7 +94,7 @@
 (define (remove-queued-entities)
   (for-each
    (lambda (id)
-     (remove-entity id))
+     (remove-entity-now id))
    del-entity-queue)
   (set! del-entity-queue '()))
 
@@ -96,18 +104,24 @@
   (add-queued-entities))
 
 ;; Entity creation/removal interface
-(export add-named-entity add-entity remove-entity)
+(export create-named-entity create-entity remove-entity
+	get-entity clear-world)
+
+(define (get-entity id)
+  (assert (symbol? id))
+  (hash-table-ref world id))
 
 ;; Create an entity in the world and return it's ID
-(define (add-named-entity id . components)
+;; TODO: consider whether we want to use a hash-table for the entity list. I'm not sure yet how punishing O(n) lookup will be here, so it might be sometihng to look at once we start handling entity execution
+(define (create-named-entity id . components)
   (assert (symbol? id))
   (assert (every record? components))
   (queue-add-entity id components)
   id)
 
 ;; Shortcut for anonymous instancing
-(define (add-entity . components)
+(define (create-entity . components)
-  (apply add-named-entity (gensym) components))
+  (apply create-named-entity (gensym) components))
 
 ;; Remove an entity from the world
 (define (remove-entity id)
@@ -115,47 +129,53 @@
   (queue-del-entity id)
   id)
 
+;; Clear the entire world
+(define (clear-world)
+  (for-each
+   remove-entity
+   (hash-table-keys world)))
+
 ;; System record interface
-(export make-system system? system-name system-rendering
+(export make-system system? system-name
 	system-priority set-system-priority! system-criteria
 	set-system-criteria! system-process set-system-process!)
 
 ;; The system record
 (define-record-type <system>
-  (internal-make-system name rendering priority criteria process)
+  (int:make-system name priority mode criteria process)
   system?
   (name system-name)
-  (rendering system-rendering)
+  (priority system-priority int:set-system-priority!)
-  (priority system-priority internal-set-system-priority!)
+  (mode system-mode)
-  (criteria system-criteria internal-set-system-criteria!)
+  (criteria system-criteria int:set-system-criteria!)
-  (process system-process internal-set-system-process!))
+  (process system-process int:set-system-process!))
 
 ;; Type-checked system constructor wrapper
-(define (make-system name rendering priority criteria process)
+(define (make-system name priority mode criteria process)
   (assert (symbol? name))
-  (assert (and (symbol? rendering) (member rendering '(3d 2d screen none))))
   (assert (integer? priority))
+  (assert (member mode '(enity batch)))
   (assert (every symbol? criteria))
   (assert (procedure? process))
-  (internal-make-system name rendering priority criteria process))
+  (int:make-system name priority mode criteria process))
 
 ;; Type-checked system priority mutator
 (define (set-system-priority! system priority)
   (assert (system? system))
   (assert (integer? priority))
-  (internal-set-system-priority! system priority))
+  (int:set-system-priority! system priority))
 
 ;; Type-checked system criteria mutator
 (define (set-system-criteria! system criteria)
   (assert (system? system))
   (assert (every symbol? criteria))
-  (internal-set-system-criteria! system criteria))
+  (int:set-system-criteria! system criteria))
 
 ;; Type-checked system process mutator
 (define (set-system-process! system process)
   (assert (system? system))
   (assert (procedure? process))
-  (internal-set-system-process! system process))
+  (int:set-system-process! system process))
 
 ;; The systems list
 (define systems '())
@@ -216,7 +236,7 @@
   (sort-systems))
 
 ;; System creation/removal interface
-(export add-system remove-system)
+(export add-system remove-system clear-systems)
 
 ;; Add a system to the state processing and return its name
 (define (add-system system)
@@ -230,6 +250,11 @@
   (queue-del-system name)
   name)
 
+(define (clear-systems)
+  (for-each
+   remove-system
+   (map system-name systems)))
+
 ;; Execute a single system
 ;; TODO: Implement
 (define (execute-system system)
@@ -257,6 +282,8 @@
 	(hash-table-set! event-buses name (make-hash-table))
 	name)))
 
+(register-event-bus 'input)
+
 ;; Remove an event bus
 (define (remove-event-bus name)
   (assert (symbol? name))
@@ -307,12 +334,121 @@
 	  event)
 	#f)))
 
-;; Frame generation interface
+;; Render queue exports
-(export make-next-frame)
+(export register-render-queue push-render-object evaluate-render-queue)
-;; Generate the next frame, for use in the main game loop
+
-(define (make-next-frame)
+;; Render queues
+(define render-queues (make-hash-table))
+(define render-priority '())
+
+;; Register a new render queue
+(define (register-render-queue name drawing)
+  (assert (symbol? name))
+  (assert (and (symbol? drawing) (member drawing '(screen 2d 3d))))
+  (if (hash-table-exists? render-queues name)
+      #f
+      (begin
+	(hash-table-set! render-queues name '())
+	(set! render-priority (cons (cons name drawing) render-priority))
+	name)))
+
+;; Default render queues
+(register-render-queue '3d '3d)
+(register-render-queue '2d '2d)
+(register-render-queue 'screen 'screen)
+
+;; TODO: camera selection needs a better solution, ideally treating the camera
+;; as an entity.
+(define *active-camera-2d* (make-parameter '()))
+(define *active-camera-3d* (make-parameter '()))
+
+;; Push a render call to the queue
+(define (push-render-object queue-name layer thunk)
+  (assert (symbol? queue-name))
+  (assert (integer? layer))
+  (assert (procedure? thunk))
+  (hash-table-set! render-queues queue-name
+		   (cons (cons layer thunk) (hash-table-ref render-queues queue-name))))
+
+;; Evaluate a single render queue with a specific mode.
+;; Render objects are sorted by their layer
+(define (evaluate-render-queue queue-name mode)
+  (assert (symbol? queue-name))
+  (assert (symbol? mode) (member mode '(screen 2d 3d)))
+  (let ((queue (hash-table-ref render-queues queue-name)))
+    (when (or (eq? mode 'screen)
+	      (and (eq? mode '2d)
+		   (not (null? (*active-camera-2d*))))
+	      (and (eq? mode '3d)
+		   (not (null? (*active-camera-3d*)))))
+      (when (eq? mode '2d)
+	(begin-mode-2d (*active-camera-2d*)))
+      (when (eq? mode '3d)
+	(begin-mode-3d (*active-camera-3d*)))
+      (for-each
+       (lambda (render-obj) (cdr render-obj))
+       (sort queue
+	     (lambda (render-obj-a render-obj-b)
+	       (< (car render-obj-a)
+		  (car render-obj-b)))))
+      (when (eq? mode '2d)
+	(end-mode-2d))
+      (when (eq? mode '3d)
+	(end-mode-3d)))
+    (hash-table-set! render-queues queue-name '())))
+
+;; Frame generation and game loop
+(export resolve-queues next-frame *clear-color* perform-render)
+
+;; Resolve the entity and system queues. This is exported which allows breaking iteration
+(define (resolve-queues)
   (resolve-entity-queue)
-  (resolve-system-queue)
+  (resolve-system-queue))
-  (with-drawing
+
-   (execute-systems)))
+;; Clear color
+(define *clear-color* (guarded-parameter RAYWHITE u8vector?))
+
+;; Render all queues
+(define (perform-render)
+  (begin-drawing)
+  (clear-background (*clear-color*))
+  (for-each
+   (lambda (queue-spec)
+     (evaluate-render-queue (car queue-spec)
+			    (cdr queue-spec)))
+   render-priority)
+  (end-drawing))
+
+;; Generate the next frame, for use in the main game loop
+(define (next-frame)
+  (resolve-queues)
+  (perform-render))
+
+;; Window creation
+(export *window-size* *window-title* create-window)
+
+;; Window size to use
+(define *window-size* (guarded-parameter '(768 . 576)
+					 (lambda (x)
+					   (and (pair? x)
+						(integer? (car x))
+						(integer? (cdr x))))))
+
+;; Window title
+(define *window-title* (guarded-parameter "imugi"
+					  string?))
+
+;; Desired FPS count
+(define *target-fps* (guarded-parameter 60
+					integer?))
+
+;; Make a window with the above parameters and default processing and predicate
+(define (create-window #!key (process next-frame) (close-predicate window-should-close?))
+  (init-window (car (*window-size*)) (cdr (*window-size*)) (*window-title*))
+  (set-target-fps (*target-fps*))
+  (let loop ()
+    (process)
+    (unless (close-predicate)
+      (loop)))
+  (close-window))
 )

engine/guards.scm

@@ -0,0 +1,27 @@
+(module (engine guards) ()
+(import scheme
+	(chicken base)
+	(chicken module)
+	(srfi 99))
+
+;; Utility function for guarding parameter values
+(export guarded-parameter)
+(define (guarded-parameter default predicate)
+  (make-parameter default (lambda (val)
+			    (if (predicate val)
+				val
+				default))))
+
+;; Guarded record functions
+(export guarded-mutator)
+;; Shorthand for defining a guarded mutator for a record field
+(define (guarded-mutator record-type field predicate)
+  (lambda (rec val)
+    (assert (record-type rec))
+    (assert (predicate val))
+    ((rtd-mutator (record-rtd rec) field) rec val)))
+
+;; TODO: define a similar function here for record constructor
+
+;; TODO: define a similar function here for binary operations on records
+)

engine/math.scm

@@ -0,0 +1,27 @@
+(module (engine math) ()
+(import scheme
+	(chicken base)
+	(chicken module))
+
+(export PI PI/2)
+(define PI
+  3.141592653589793238462643383279502884197169399375105820974944592307816406286)
+
+(define PI/2
+  (/ PI 2))
+
+(export rad-to-deg deg-to-rad)
+;; Radians and degrees conversion
+(define (rad-to-deg rad)
+  (* rad
+     (/ 180 PI)))
+(define (deg-to-rad deg)
+  (* deg
+     (/ PI 180)))
+
+(export *float-precision* approx-=)
+(define *float-precision* (make-parameter 0.001))
+;; Approximately equal - for real number comparison
+(define (approx-= x y)
+  (< (abs (- x y)) (*float-precision*)))
+)

test/components.scm

@@ -0,0 +1,30 @@
+(module (test components) ()
+(import scheme
+	(chicken base)
+	(engine core)
+	(engine components core)
+	(engine math)
+	(srfi 78)
+	(srfi 99))
+
+(define v1 (make-vector2 0 0))
+(define v2 (make-vector2 10 10))
+
+(check (vector-= v2 (make-vector2 10 10)) => #t)
+(check (vector-= (make-vector2 20 20)
+		 (vector-+ v2 (make-vector2 10 10))) => #t)
+(check (vector-= v1
+		 (vector-- v2 (make-vector2 10 10))) => #t)
+(check (vector-= (make-vector2 100 100)
+		 (vector-* v2 (make-vector2 10 10))) => #t)
+(check (vector-= (make-vector2 1 1)
+		 (vector-/ v2 (make-vector2 10 10))) => #t)
+(check (vector-magnitude (make-vector2 100 0)) => 100)
+(check (vector-= (make-vector2 1 0)
+		 (vector-normalize (make-vector2 100 0))) => #t)
+(check (vector-dot (make-vector2 1 2)
+		   (make-vector2 3 4)) => 11)
+(check (rad-to-deg
+	(vector-angle-between (make-vector2 1 2)
+			      (make-vector2 3 4))) (=> approx-=) 10.305)
+)

test/engine.scm

@@ -0,0 +1,107 @@
+(module (test engine) ()
+(import scheme
+	(chicken base)
+	(engine core)
+	(srfi 69)
+	(srfi 78)
+	(srfi 99))
+
+(define-record-type <point> (make-point x y) point? (x point-x) (y point-y))
+
+;; Entity addition and world state modification
+(check (hash-table-size world) => 0) ;; World state starts empty
+(check (hash-table-size component-sets) => 0)
+
+(create-named-entity 'ball (make-point 1 1))
+(check (hash-table-size world) => 0) ;; World state empty before next frame
+(check (hash-table-size component-sets) => 0)
+
+(resolve-queues) ;; TODO: swap this for (next-frame) and remove (resolve-queues) once we have a full game loop setup
+(check (hash-table-size world) => 1) ;; World state updates after next frame
+(check (hash-table-size component-sets) => 1)
+(check (hash-table-exists? world 'ball) => #t)
+(check (hash-table-exists? component-sets '<point>) => #t)
+
+(check (point? (car (get-entity 'ball))) => #t) ;; Get entity retrieves the entity components
+
+(clear-world)
+(check (hash-table-size world) => 1) ;; World state does not immediately clear
+
+(resolve-queues)
+(check (hash-table-size world) => 0) ;; World state is empty after clear
+(check (hash-table-size component-sets) => 1) ;; Component-sets doesn't clear
+
+(create-named-entity 'ball (make-point 1 1))
+(resolve-queues)
+(remove-entity 'ball)
+(resolve-queues)
+(check (hash-table-size world) => 0) ;; Entity is properly removed
+
+;; System addition and state modification
+(check (length systems) => 0) ;; Systems list starts empty
+
+(define sys-1 (make-system 'foo 0 '() void))
+(define sys-2 (make-system 'bar 1 '() void))
+(add-system sys-1)
+(check (length systems) => 0) ;; Systems list is not immediately updated
+
+(resolve-queues)
+(check (length systems) => 1) ;; Systems list updates
+
+(add-system sys-2)
+(resolve-queues)
+(check (length systems) => 2) ;; Systems list updates
+(check (system-name (car systems)) => 'foo) ;; Foo is sorted before bar
+
+(set-system-priority! sys-1 2)
+(resolve-queues)
+(check (system-name (car systems)) => 'bar) ;; Bar is sorted earlier after a priority change
+
+(remove-system 'foo)
+(check (length systems) => 2) ;; Systems list does not automatically update
+
+(resolve-queues)
+(check (length systems) => 1) ;; Systems list updates after resolution
+
+(clear-systems)
+(resolve-queues)
+(check (length systems) => 0) ;; Systems list clears
+
+;; Event bus creation and events
+(check (hash-table-size event-buses) => 1) ;; Input bus already exists
+
+(remove-event-bus 'input)
+(check (hash-table-size event-buses) => 0) ;; Input bus is removed
+
+(register-event-bus 'foo)
+(check (hash-table-size event-buses) => 1) ;; Event bus registered
+
+(push-event 'foo 'bar (make-point 1 1))
+(check (hash-table-size (fetch-event-bus 'foo)) => 1) ;; Event is created
+
+(check (point-x (peek-event 'foo 'bar)) => 1) ;; Event is peaked
+(check (hash-table-size (fetch-event-bus 'foo)) => 1) ;; Event still exists
+
+(check (point-x (pop-event 'foo 'bar)) => 1) ;; Event is popped
+(check (hash-table-size (fetch-event-bus 'foo)) => 0) ;; Event is removed exists
+
+;; Render queue tests
+(check (hash-table-size render-queues) => 3)
+(check (length render-priority) => 3)
+
+(register-render-queue 'screen2 'screen)
+(check (hash-table-size render-queues) => 4)
+(check (length render-priority) => 4)
+
+(check (length (hash-table-ref render-queues 'screen)) => 0)
+
+(push-render-object 'screen 0 (lambda () #t))
+(check (length (hash-table-ref render-queues 'screen)) => 1)
+
+(evaluate-render-queue 'screen 'screen)
+(check (length (hash-table-ref render-queues 'screen)) => 0)
+
+(check-report)
+
+(create-window)
+)