Allow setting RGBW pixels with RGB tuples

adafruit_pypixelbuf.py

@@ -227,31 +227,39 @@ def _parse_color(self, value):
             g = (value >> 8) & 0xFF
             b = value & 0xFF
             w = 0
-            # If all components are the same and we have a white pixel then use it
-            # instead of the individual components.
-            if self._bpp == 4 and self._has_white and r == g and g == b:
+
+            if self._dotstar_mode:
+                w = 1.0
+        else:
+            if len(value) < 3 or len(value) > 4:
+                raise ValueError(
+                    "Expected tuple of length {}, got {}".format(self._bpp, len(value))
+                )
+            if len(value) == self._bpp:
+                if self._bpp == 3:
+                    r, g, b = value
+                else:
+                    r, g, b, w = value
+            elif len(value) == 3:
+                r, g, b = value
+                if self._dotstar_mode:
+                    w = 1.0
+
+        if self._bpp == 4:
+            if self._dotstar_mode:
+                # LED startframe is three "1" bits, followed by 5 brightness bits
+                # then 8 bits for each of R, G, and B. The order of those 3 are configurable and
+                # vary based on hardware
+                # same as math.ceil(brightness * 31) & 0b00011111
+                # Idea from https://www.codeproject.com/Tips/700780/Fast-floor-ceiling-functions
+                w = (32 - int(32 - w * 31) & 0b00011111) | DOTSTAR_LED_START
+            elif self._has_white and r == g and g == b:
+                # If all components are the same and we have a white pixel then use it
+                # instead of the individual components.
                 w = r
                 r = 0
                 g = 0
                 b = 0
-            elif self._dotstar_mode:
-                w = 1.0
-        elif len(value) == self._bpp:
-            if self._bpp == 3:
-                r, g, b = value
-            else:
-                r, g, b, w = value
-        elif len(value) == 3 and self._dotstar_mode:
-            r, g, b = value
-            w = 1.0
-
-        if self._bpp == 4 and self._dotstar_mode:
-            # LED startframe is three "1" bits, followed by 5 brightness bits
-            # then 8 bits for each of R, G, and B. The order of those 3 are configurable and
-            # vary based on hardware
-            # same as math.ceil(brightness * 31) & 0b00011111
-            # Idea from https://www.codeproject.com/Tips/700780/Fast-floor-ceiling-functions
-            w = (32 - int(32 - w * 31) & 0b00011111) | DOTSTAR_LED_START
 
         return (r, g, b, w)
 

examples/pypixelbuf_simpletest.py

@@ -4,12 +4,18 @@
 class TestBuf(adafruit_pypixelbuf.PixelBuf):
     called = False
 
-    def _transmit(self, buffer):
+    @property
+    def n(self):
+        return len(self)
+
+    def _transmit(self, buffer):  # pylint: disable=unused-argument
         self.called = True
 
 
-buf = TestBuf(20, "RGB", 1.0, auto_write=True)
+buf = TestBuf(20, "RGBW", 1.0, auto_write=True)
 buf[0] = (1, 2, 3)
+buf[1] = (1, 2, 3, 4)
+buf[2] = (2, 2, 2)
 
 print(buf[0])
 print(buf[0:2])