fix(steami_screen): Improve gauge reactivity and readability.

lib/steami_screen/examples/gauge_demo.py

@@ -1,35 +1,88 @@
-"""
-Displays VL53L1X time-of-flight distance with an arc gauge.
+"""Gauge demo example using VL53L1X distance sensor and SSD1327 OLED.
+
+Displays time-of-flight distance as an arc gauge on the round screen.
+The gauge color and arc width change dynamically based on the measured
+distance, providing a clear visual proximity indicator.
+
+Color zones:
+    WHITE  → object very close  (< 150 mm)
+    YELLOW → object at medium range (< 350 mm)
+    LIGHT  → object far away   (>= 350 mm)
+
+Arc width:
+    Thicker arc when close, thinner when far.
+
+Reactivity:
+    The sensor is polled every 10 ms but the display is only redrawn
+    when the distance changes by more than REDRAW_THRESHOLD mm,
+    avoiding unnecessary SPI transfers and keeping the gauge fluid.
 """
 
 from time import sleep_ms
 
+import micropython
 import ssd1327
 from machine import I2C, SPI, Pin
-from steami_screen import BLACK, Screen, SSD1327Display
+from steami_screen import LIGHT, WHITE, YELLOW, Screen, SSD1327Display
 from vl53l1x import VL53L1X
 
-# --- Display setup ---
+# === Display setup ===
 spi = SPI(1)
 dc = Pin("DATA_COMMAND_DISPLAY")
 res = Pin("RST_DISPLAY")
 cs = Pin("CS_DISPLAY")
-
-raw_display = ssd1327.WS_OLED_128X128_SPI(spi, dc, res, cs)
-display = SSD1327Display(raw_display)
+display = SSD1327Display(ssd1327.WS_OLED_128X128_SPI(spi, dc, res, cs))
 screen = Screen(display)
 
-# --- Sensor setup ---
+# === Sensor setup ===
 i2c = I2C(1)
 sensor = VL53L1X(i2c)
 
-# --- Main loop ---
-while True:
-    dist = sensor.read()
+# === Constants ===
+MAX_DIST = 500
+REDRAW_THRESHOLD = 10  # mm — minimum change to trigger a redraw
+
+
+def dist_to_color(dist):
+    """Return gauge color based on measured distance."""
+    if dist < 150:
+        return WHITE
+    elif dist < 350:
+        return YELLOW
+    else:
+        return LIGHT
 
+
+def dist_to_arc_width(dist):
+    """Return arc width based on distance — thicker when closer."""
+    ratio = 1.0 - max(0.0, min(1.0, dist / MAX_DIST))
+    return int(5 + ratio * 12)
+
+
+@micropython.native
+def redraw(dist):
+    """Redraw the full gauge screen."""
+    color = dist_to_color(dist)
+    arc_w = dist_to_arc_width(dist)
     screen.clear()
-    screen.gauge(dist, min_val=0, max_val=500, color=BLACK)
-    screen.value(dist, label="Distance", unit="mm")
+    screen.gauge(dist, min_val=0, max_val=MAX_DIST, color=color, arc_width=arc_w)
+    screen.text(f"{dist} mm", at="CENTER")
+    screen.subtitle("Distance")
     screen.show()
 
-    sleep_ms(10)
+
+# === Main loop ===
+last_dist = -1
+
+try:
+    while True:
+        dist = sensor.read()
+        if abs(dist - last_dist) >= REDRAW_THRESHOLD:
+            last_dist = dist
+            redraw(dist)
+        sleep_ms(10)
+except KeyboardInterrupt:
+    pass
+finally:
+    screen.clear()
+    screen.show()