add some matrix functions

matrix.fnl

@@ -0,0 +1,55 @@
+;; homogeneous matrix operations for 2d graphics
+
+(local identity
+       [
+        1 0 0
+        0 1 0
+        0 0 1
+        ])
+
+(fn multiply-matrix [a b]
+  [
+   (+ (* (. a 1) (. b 1))   (* (. a 2) (. b 4))   (* (. a 3) (. b 7)))
+   (+ (* (. a 1) (. b 2))   (* (. a 2) (. b 5))   (* (. a 3) (. b 8)))
+   (+ (* (. a 1) (. b 3))   (* (. a 2) (. b 6))   (* (. a 3) (. b 9)))
+
+   (+ (* (. a 4) (. b 1))   (* (. a 5) (. b 4))   (* (. a 6) (. b 7)))
+   (+ (* (. a 4) (. b 2))   (* (. a 5) (. b 5))   (* (. a 6) (. b 8)))
+   (+ (* (. a 4) (. b 3))   (* (. a 5) (. b 6))   (* (. a 6) (. b 9)))
+
+   (+ (* (. a 7) (. b 1))   (* (. a 8) (. b 4))   (* (. a 9) (. b 7)))
+   (+ (* (. a 7) (. b 2))   (* (. a 8) (. b 5))   (* (. a 9) (. b 8)))
+   (+ (* (. a 7) (. b 3))   (* (. a 8) (. b 6))   (* (. a 9) (. b 9)))
+   ])
+
+(fn scale [matrix x y]
+  (let [scale [
+               x 0 0
+               0 y 0
+               0 0 1]]
+    (multiply-matrix matrix scale)))
+
+(fn translate [matrix x y]
+  (let [translation [
+                     1 0 x
+                     0 1 y
+                     0 0 1]]
+    (multiply-matrix matrix translation)))
+
+(fn rotate [matrix rad]
+  (let [sin (math.sin rad)
+        cos (math.cos rad)
+        rotation [
+                  cos (- sin) 0
+                  sin  cos    0
+                  0     0     1
+                  ]]
+    (multiply-matrix matrix rotation)))
+
+
+{
+ : identity
+ : scale
+ : translate
+ : rotate
+ }

rc.fnl

@@ -1,6 +1,7 @@
 (local { : view } (require :fennel))
 
 (local texture (require :texture))
+(local matrix (require :matrix))
 (local socket-repl (require :socket-repl))
 
 (let [repl-socket-name
@@ -23,25 +24,23 @@
          spinner (texture.from-file r "carousel.png")]
      (output:on "render"
                 (fn [{: output : renderer}]
-                  (let [bar-height 40
+                  (let [bar-height 40]
-                        matrix [1 0 0
-                                0 1 0
-                                0 0 1]]
                     (renderer:draw_rect :#00000077
                                         0 (- 720 bar-height)
                                         690 360 bar-height)
                     (renderer:draw_texture
                      kill
-                     matrix
+                     matrix.identity
                      30 (- 720 bar-height)
                      0.7)
                     (renderer:draw_texture
-                     launch matrix
+                     launch
+                     matrix.identity
                      (- 180 (/ bar-height 2)) (- 720 bar-height)
                      0.7)
                     (renderer:draw_texture
                      spinner
-                     matrix
+                     matrix.identity
                      (- 360 30 bar-height) (- 720 bar-height)
                      0.7)))))))