widgets: Introduce a slider widget

Currently the slider doesn't actually slide (because we process touch
events rather than swipe events) but we've called is a slider anyway.

1 files changed, 77 insertions, 0 deletions

diff --git a/wasp/widgets.py b/wasp/widgets.py
index 9271fe6..97410b0 100644
--- a/wasp/widgets.py
+++ b/wasp/widgets.py
@@ -10,6 +10,7 @@ shared between applications.
 
 import icons
 import watch
+from micropython import const
 
 class BatteryMeter(object):
     """Battery meter widget.
@@ -94,3 +95,79 @@ class ScrollIndicator():
             draw.rleblit(icons.up_arrow, pos=self._pos, fg=0x7bef)
         if self.down:
             draw.rleblit(icons.down_arrow, pos=(self._pos[0], self._pos[1] + 13), fg=0x7bef)
+
+_SLIDER_KNOB_DIAMETER = const(40)
+_SLIDER_KNOB_RADIUS = const(_SLIDER_KNOB_DIAMETER // 2)
+_SLIDER_WIDTH = const(220)
+_SLIDER_TRACK = const(_SLIDER_WIDTH - _SLIDER_KNOB_DIAMETER)
+_SLIDER_TRACK_HEIGHT = const(8)
+_SLIDER_TRACK_Y1 = const(_SLIDER_KNOB_RADIUS - (_SLIDER_TRACK_HEIGHT // 2))
+_SLIDER_TRACK_Y2 = const(_SLIDER_TRACK_Y1 + _SLIDER_TRACK_HEIGHT)
+
+class Slider():
+    """A slider to select values."""
+    def __init__(self, steps, x=10, y=90, color=0x39ff):
+        self.value = 0
+        self._steps = steps
+        self._stepsize = _SLIDER_TRACK / (steps-1)
+        self._x = x
+        self._y = y
+        self._color = color
+
+        # Automatically generate a lowlight color
+        if color < 0b10110_000000_00000:
+            color = (color | 0b10110_000000_00000) & 0b10110_111111_11111
+        if (color & 0b111111_00000) < 0b101100_00000:
+            color = (color | 0b101100_00000) & 0b11111_101100_11111
+        if (color & 0b11111) < 0b10110:
+            color = (color | 0b11000) & 0b11111_111111_10110
+        self._lowlight = color
+
+    def draw(self):
+        """Draw the slider."""
+        draw = watch.drawable
+        x = self._x
+        y = self._y
+        color = self._color
+        light = self._lowlight
+
+        knob_x = x + ((_SLIDER_TRACK * self.value) // (self._steps-1))
+        draw.blit(icons.knob2, knob_x, y, color)
+
+        w = knob_x - x
+        if w > 0:
+            draw.fill(0, x, y, w, _SLIDER_TRACK_Y1)
+            if w > _SLIDER_KNOB_RADIUS:
+                draw.fill(0, x, y+_SLIDER_TRACK_Y1,
+                          _SLIDER_KNOB_RADIUS, _SLIDER_TRACK_HEIGHT)
+                draw.fill(color, x+_SLIDER_KNOB_RADIUS, y+_SLIDER_TRACK_Y1,
+                          w-_SLIDER_KNOB_RADIUS, _SLIDER_TRACK_HEIGHT)
+            else:
+                draw.fill(0, x, y+_SLIDER_TRACK_Y1, w, _SLIDER_TRACK_HEIGHT)
+            draw.fill(0, x, y+_SLIDER_TRACK_Y2, w, _SLIDER_TRACK_Y1)
+
+        sx = knob_x + _SLIDER_KNOB_DIAMETER
+        w = _SLIDER_WIDTH - _SLIDER_KNOB_DIAMETER - w
+        if w > 0:
+            draw.fill(0, sx, y, w, _SLIDER_TRACK_Y1)
+            if w > _SLIDER_KNOB_RADIUS:
+                draw.fill(0, sx+w-_SLIDER_KNOB_RADIUS, y+_SLIDER_TRACK_Y1,
+                          _SLIDER_KNOB_RADIUS, _SLIDER_TRACK_HEIGHT)
+                draw.fill(light, sx, y+_SLIDER_TRACK_Y1,
+                          w-_SLIDER_KNOB_RADIUS, _SLIDER_TRACK_HEIGHT)
+            else:
+                draw.fill(0, sx, y+_SLIDER_TRACK_Y1, w, _SLIDER_TRACK_HEIGHT)
+            draw.fill(0, sx, y+_SLIDER_TRACK_Y2, w, _SLIDER_TRACK_Y1)
+
+    def update(self):
+        self.draw()
+
+    def touch(self, event):
+        tx = event[1]
+        threshold = self._x + 20 - (self._stepsize / 2)
+        v = int((tx - threshold) / self._stepsize)
+        if v < 0:
+            v = 0
+        elif v >= self._steps:
+            v = self._steps - 1
+        self.value = v