Initial commit of Python gauge cluster implementation

py/hexagram/cluster.py

@@ -0,0 +1,46 @@
+import math
+import cairo
+
+CLUSTER_WIDTH  = 1280
+CLUSTER_HEIGHT =  480
+
+class Gauge():
+    __slots = 'x', 'y', 'radius',
+
+    BEZEL_WIDTH = 16
+
+    BEZEL_GRADIENT_STOPS = (
+        (0, 1.0, 0.4, 1.0, 1.0),
+        (1, 0.4, 0.0, 0.4, 0.0)
+    )
+
+    def __init__(self, x: float, y: float, radius: float):
+        self.x      = x
+        self.y      = y
+        self.radius = radius
+
+    def _gradient(self):
+        gradient = cairo.LinearGradient(0, 0, 2 * self.radius, 2 * self.radius)
+
+        for stop in self.BEZEL_GRADIENT_STOPS:
+            gradient.add_color_stop_rgba(*stop)
+
+        return gradient
+
+    def _draw_face(self, cr: cairo.Context):
+        arc = (self.radius,
+               self.radius,
+               self.radius - self.BEZEL_WIDTH,
+               0,
+               2.0 * math.pi)
+
+        # Gauge face
+        cr.set_source_rgba(0, 0, 0, 1)
+        cr.arc(*arc)
+        cr.fill()
+
+        # Gauge bezel
+        cr.set_source(self._gradient())
+        cr.set_line_width(self.BEZEL_WIDTH)
+        cr.arc(*arc)
+        cr.stroke()