From 6b41c8f3db1778826ec8556f8900878a8f32c87a Mon Sep 17 00:00:00 2001
From: Daniel Thompson <daniel@redfelineninja.org.uk>
Date: Sun, 17 Jan 2021 17:44:21 +0000
Subject: [PATCH] drivers: st7789: Pre-allocate a memoryview

Reduce the cost of slicing the linebuffer by pre-allocating a memoryview.

Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>
---
 wasp/apps/gameoflife.py |  4 ++--
 wasp/draw565.py         | 10 +++++-----
 wasp/drivers/st7789.py  |  4 ++--
 3 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/wasp/apps/gameoflife.py b/wasp/apps/gameoflife.py
index 109888c..7e2b518 100644
--- a/wasp/apps/gameoflife.py
+++ b/wasp/apps/gameoflife.py
@@ -223,7 +223,7 @@ class GameOfLifeApp():
 
         display = wasp.watch.display
         lb = display.linebuffer
-        alive = memoryview(lb)[0:2*16]
+        alive = lb[0:2*16]
         self._color = xorshift12(self._color)
         rgbhi = get_color(self._color)
         rgblo = rgbhi & 0xff
@@ -234,7 +234,7 @@ class GameOfLifeApp():
         for i in (0, 3,  12, 15):
             alive[i*2] = 0
             alive[i*2+1] = 0
-        dead = memoryview(lb)[2*16:4*16]
+        dead = lb[2*16:4*16]
         for i in range(len(dead)):
             dead[i] = 0
 
diff --git a/wasp/draw565.py b/wasp/draw565.py
index 5f61a6c..37e96b5 100644
--- a/wasp/draw565.py
+++ b/wasp/draw565.py
@@ -85,7 +85,7 @@ def _bounding_box(s, font):
 def _draw_glyph(display, glyph, x, y, bgfg):
     (px, h, w) = glyph
 
-    buf = memoryview(display.linebuffer)[0:2*(w+1)]
+    buf = display.linebuffer[0:2*(w+1)]
     buf[2*w] = 0
     buf[2*w + 1] = 0
     bytes_per_row = (w + 7) // 8
@@ -155,7 +155,7 @@ class Draw565(object):
 
         # Populate the line buffer
         buf = display.linebuffer
-        sz = len(display.linebuffer) // 2
+        sz = len(buf) // 2
         _fill(buf, bg, min(sz, remaining), 0)
 
         display.quick_start()
@@ -163,7 +163,7 @@ class Draw565(object):
             quick_write(buf)
             remaining -= sz
         if remaining:
-            quick_write(memoryview(display.linebuffer)[0:2*remaining])
+            quick_write(buf[0:2*remaining])
         display.quick_end()
 
     @micropython.native
@@ -195,7 +195,7 @@ class Draw565(object):
 
         display.set_window(pos[0], pos[1], sx, sy)
 
-        buf = memoryview(display.linebuffer)[0:2*sx]
+        buf = display.linebuffer[0:2*sx]
         bp = 0
         color = bg
 
@@ -233,7 +233,7 @@ class Draw565(object):
         palette = array.array('H', (0, c1, c2, fg))
         next_color = 1
         rl = 0
-        buf = memoryview(display.linebuffer)[0:2*sx]
+        buf = display.linebuffer[0:2*sx]
         bp = 0
 
         display.quick_start()
diff --git a/wasp/drivers/st7789.py b/wasp/drivers/st7789.py
index e689e4e..817c414 100644
--- a/wasp/drivers/st7789.py
+++ b/wasp/drivers/st7789.py
@@ -44,7 +44,7 @@ class ST7789(object):
         """
         self.width = width
         self.height = height
-        self.linebuffer = bytearray(2 * width)
+        self.linebuffer = memoryview(bytearray(2 * width))
         self.init_display()
 
     def init_display(self):
@@ -167,7 +167,7 @@ class ST7789(object):
         self.set_window(x, y, w, h)
 
         # Populate the line buffer
-        buf = memoryview(self.linebuffer)[0:2*w]
+        buf = self.linebuffer[0:2*w]
         for xi in range(0, 2*w, 2):
             buf[xi] = bg >> 8
             buf[xi+1] = bg & 0xff