boards: simulator: Add basic mute simulation

Currently the simulator shows redraw artifacts that are concealed
on the real device by using display on/off. We can improve this by
avoiding the refresh when the display is off. This does not match
the behaviour of the real hardware (which goes dark during transitions)
but does make the simulator feel much more comfortable to use.

Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>

wasp/boards/simulator/display.py

@@ -13,6 +13,8 @@ import numpy as np
 from PIL import Image
 import wasp
 
+DISPOFF = 0x28
+DISPON = 0x29
 CASET = 0x2a
 RASET = 0x2b
 RAMWR = 0x2c
@@ -35,6 +37,7 @@ class ST7789Sim(object):
         self.colclip = [0, WIDTH-1]
         self.rowclip = [0, HEIGHT-1]
         self.cmd = 0
+        self.mute = False
 
     def write(self, data):
         # Converting data to a memoryview ensures we act more like spi.write()
@@ -46,7 +49,14 @@ class ST7789Sim(object):
             # Assume if we get a byte at a time then it is command.
             # This is a simplification do we don't have to track
             # the D/C pin from within the simulator.
-            self.cmd = data[0]
+            cmd = data[0]
+            if cmd == DISPOFF:
+                self.mute = True
+            elif cmd == DISPON:
+                self.mute = False
+                window.refresh()
+            else:
+                self.cmd = data[0]
 
         elif self.cmd == CASET:
             self.colclip[0] = (data[0] << 8) + data[1]
@@ -91,7 +101,8 @@ class ST7789Sim(object):
             
             # Forcibly release the surface to ensure it is unlocked
             del pixelview
-            window.refresh()
+            if not self.mute:
+                window.refresh()
 
 class CST816SSim():
     def __init__(self):
@@ -268,4 +279,3 @@ def tick(pins):
         else:
             #print(event)
             pass
-    window.refresh()