Added support to resize canvas

Fixes #132

The width and height variables are updated everytime the canvas is resized.

p5/sketch/base.py

@@ -62,7 +62,7 @@ def __init__(self, setup_method, draw_method,
             title=builtins.title,
             size=(builtins.width, builtins.height),
             keys='interactive',
-            resizable=False,
+            resizable=True,
         )
 
         self.setup_method = setup_method
@@ -145,6 +145,9 @@ def on_draw(self, event):
         pass
 
     def on_resize(self, event):
+        builtins.width = int(self.size[0])
+        builtins.height = int(self.size[1])
+
         p5.renderer.reset_view()
         with p5.renderer.draw_loop():
             p5.renderer.clear()

test.py

@@ -0,0 +1,38 @@
+from p5 import *
+
+x = 0
+y = 0
+angle1 = 0.0
+angle2 = 0.0
+segLength = 100
+
+def setup():
+        size(640, 360)
+        stroke(255, 160)
+        stroke_weight(30)
+
+        global x, y
+        x = width * 0.3
+        y = height * 0.5
+
+def draw():
+        x = width * 0.3
+        y = height * 0.5
+
+        background(0)
+
+        angle1 = (mouse_x/width - 0.5) * -PI
+        angle2 = (mouse_y/height - 0.5) * PI
+
+        with push_matrix():
+                segment(x, y, angle1)
+                segment(segLength, 0, angle2)
+                pop_matrix()
+
+def segment(x, y, a):
+        translate(x, y)
+        rotate(a)
+        line((0, 0), (segLength, 0))
+
+if __name__ == '__main__':
+  run()