From 1e16b3e134a9e5453541ab22a36e204dcf0ee935 Mon Sep 17 00:00:00 2001
From: Scott Shawcroft <scott@tannewt.org>
Date: Tue, 12 Feb 2019 14:18:53 -0800
Subject: [PATCH] Tweaks based on dhalbert's feedback.

---
 shared-bindings/displayio/Group.c | 11 ++++++-----
 shared-module/displayio/Group.c   |  6 +++---
 2 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/shared-bindings/displayio/Group.c b/shared-bindings/displayio/Group.c
index f8013050d0..421dc1ae59 100644
--- a/shared-bindings/displayio/Group.c
+++ b/shared-bindings/displayio/Group.c
@@ -43,9 +43,11 @@
 //|
 //| .. class:: Group(*, max_size=4, scale=1)
 //|
-//|   Create a Group of a given size.
+//|   Create a Group of a given size and scale. Scale is in one dimension. For example, scale=2
+//|   leads to a layer's pixel being 2x2 pixels when in the group.
 //|
 //|   :param int max_size: The maximum group size.
+//|   :param int scale: Scale of layer pixels in one dimension.
 //|
 STATIC mp_obj_t displayio_group_make_new(const mp_obj_type_t *type, size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
     enum { ARG_max_size, ARG_scale };
@@ -58,12 +60,12 @@ STATIC mp_obj_t displayio_group_make_new(const mp_obj_type_t *type, size_t n_arg
 
     mp_int_t max_size = args[ARG_max_size].u_int;
     if (max_size < 1) {
-        mp_raise_ValueError_varg(translate("Group must have %q at least 1"), MP_QSTR_max_size);
+        mp_raise_ValueError_varg(translate("%q must be >= 1"), MP_QSTR_max_size);
     }
 
     mp_int_t scale = args[ARG_scale].u_int;
     if (scale < 1) {
-        mp_raise_ValueError_varg(translate("Group must have %q at least 1"), MP_QSTR_scale);
+        mp_raise_ValueError_varg(translate("%q must be >= 1"), MP_QSTR_scale);
     }
 
     displayio_group_t *self = m_new_obj(displayio_group_t);
@@ -76,7 +78,6 @@ STATIC mp_obj_t displayio_group_make_new(const mp_obj_type_t *type, size_t n_arg
 // Helper to ensure we have the native super class instead of a subclass.
 static displayio_group_t* native_group(mp_obj_t group_obj) {
     mp_obj_t native_group = mp_instance_cast_to_native_base(group_obj, &displayio_group_type);
-    assert(native_group == MP_OBJ_NULL);
     return MP_OBJ_TO_PTR(native_group);
 }
 
@@ -96,7 +97,7 @@ STATIC mp_obj_t displayio_group_obj_set_scale(mp_obj_t self_in, mp_obj_t scale_o
 
     mp_int_t scale = mp_obj_get_int(scale_obj);
     if (scale < 1) {
-        mp_raise_ValueError_varg(translate("Group must have %q at least 1"), MP_QSTR_scale);
+        mp_raise_ValueError_varg(translate("%q must be >= 1"), MP_QSTR_scale);
     }
     common_hal_displayio_group_set_scale(self, scale);
     return mp_const_none;
diff --git a/shared-module/displayio/Group.c b/shared-module/displayio/Group.c
index e40b5a7ea0..adaad15057 100644
--- a/shared-module/displayio/Group.c
+++ b/shared-module/displayio/Group.c
@@ -39,8 +39,8 @@ uint32_t common_hal_displayio_group_get_scale(displayio_group_t* self) {
 }
 
 void common_hal_displayio_group_set_scale(displayio_group_t* self, uint32_t scale) {
+    self->needs_refresh = self->scale != scale;
     self->scale = scale;
-    self->needs_refresh = true;
 }
 
 mp_int_t common_hal_displayio_group_get_x(displayio_group_t* self) {
@@ -48,8 +48,8 @@ mp_int_t common_hal_displayio_group_get_x(displayio_group_t* self) {
 }
 
 void common_hal_displayio_group_set_x(displayio_group_t* self, mp_int_t x) {
+    self->needs_refresh = self->x != x;
     self->x = x;
-    self->needs_refresh = true;
 }
 
 mp_int_t common_hal_displayio_group_get_y(displayio_group_t* self) {
@@ -57,8 +57,8 @@ mp_int_t common_hal_displayio_group_get_y(displayio_group_t* self) {
 }
 
 void common_hal_displayio_group_set_y(displayio_group_t* self, mp_int_t y) {
+    self->needs_refresh = self->y != y;
     self->y = y;
-    self->needs_refresh = true;
 }
 
 void common_hal_displayio_group_insert(displayio_group_t* self, size_t index, mp_obj_t layer) {