From 7f05e35622d9ed056261827b4f8dfa847a4f61b5 Mon Sep 17 00:00:00 2001
From: Phil Howard <phil@gadgetoid.com>
Date: Wed, 20 Jan 2021 23:46:13 +0000
Subject: [PATCH] Attempt to allocate a bytearray behind the sCenes

This rebuilds the crucial parts of MicroPython's bytearray creation and calls it quietly from inside the C-bindings, avoiding the need for a bytearray to be passed in by the user.

Whether this magically holds a reference and evades GC remains to be seen.
---
 micropython/modules/pico_display/pico_display.c  | 16 +++++++++++++++-
 .../modules/pico_display/pico_display.cpp        |  8 +++-----
 micropython/modules/pico_display/pico_display.h  |  4 +++-
 3 files changed, 21 insertions(+), 7 deletions(-)

diff --git a/micropython/modules/pico_display/pico_display.c b/micropython/modules/pico_display/pico_display.c
index 7678d78f..bae8e178 100755
--- a/micropython/modules/pico_display/pico_display.c
+++ b/micropython/modules/pico_display/pico_display.c
@@ -1,4 +1,6 @@
 #include "pico_display.h"
+#include "py/binary.h"
+#include "py/objarray.h"
 
 /***** Constants *****/
 enum buttons
@@ -9,13 +11,25 @@ enum buttons
     BUTTON_Y,
 };
 
+mp_obj_t alloc_new_bytearray(int len) {
+    int typecode_size = mp_binary_get_size('@', BYTEARRAY_TYPECODE, NULL);
+    mp_obj_array_t *o = m_new_obj(mp_obj_array_t);
+    o->base.type = &mp_type_bytearray;
+    o->typecode = BYTEARRAY_TYPECODE;
+    o->free = 0;
+    o->len = len;
+    o->items = m_new(byte, typecode_size * o->len);
+    memset(o->items, 0, len);
+    return MP_OBJ_FROM_PTR(o);
+}
+
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////
 // picodisplay Module
 ////////////////////////////////////////////////////////////////////////////////////////////////////
 
 /***** Module Functions *****/
-STATIC MP_DEFINE_CONST_FUN_OBJ_1(picodisplay_init_obj, picodisplay_init);
+STATIC MP_DEFINE_CONST_FUN_OBJ_0(picodisplay_init_obj, picodisplay_init);
 STATIC MP_DEFINE_CONST_FUN_OBJ_0(picodisplay_get_width_obj, picodisplay_get_width);
 STATIC MP_DEFINE_CONST_FUN_OBJ_0(picodisplay_get_height_obj, picodisplay_get_height);
 STATIC MP_DEFINE_CONST_FUN_OBJ_0(picodisplay_update_obj, picodisplay_update);
diff --git a/micropython/modules/pico_display/pico_display.cpp b/micropython/modules/pico_display/pico_display.cpp
index 43afdc51..69d0b96e 100644
--- a/micropython/modules/pico_display/pico_display.cpp
+++ b/micropython/modules/pico_display/pico_display.cpp
@@ -12,12 +12,10 @@ PicoDisplay *display;
 extern "C" {
 #include "pico_display.h"
 
-mp_obj_t buf_obj;
-
-mp_obj_t picodisplay_init(mp_obj_t buf) {
+mp_obj_t picodisplay_init() {
+    mp_obj_t ba = alloc_new_bytearray(PicoDisplay::WIDTH * PicoDisplay::HEIGHT * sizeof(uint16_t));
     mp_buffer_info_t bufinfo;
-    mp_get_buffer_raise(buf, &bufinfo, MP_BUFFER_RW);
-    buf_obj = buf;
+    mp_get_buffer_raise(ba, &bufinfo, MP_BUFFER_RW);
     display = new PicoDisplay((uint16_t *)bufinfo.buf);
     display->init();
     return mp_const_none;
diff --git a/micropython/modules/pico_display/pico_display.h b/micropython/modules/pico_display/pico_display.h
index 3201df89..cfb86716 100644
--- a/micropython/modules/pico_display/pico_display.h
+++ b/micropython/modules/pico_display/pico_display.h
@@ -2,8 +2,10 @@
 #include "py/runtime.h"
 #include "py/objstr.h"
 
+extern mp_obj_t alloc_new_bytearray(int len);
+
 // Declare the functions we'll make available in Python
-extern mp_obj_t picodisplay_init(mp_obj_t buf);
+extern mp_obj_t picodisplay_init();
 extern mp_obj_t picodisplay_get_width();
 extern mp_obj_t picodisplay_get_height();
 extern mp_obj_t picodisplay_set_backlight(mp_obj_t brightness_obj);