uctx: deprecated start_group and end_group

They seem to not work as documented in the ctx protocol, in the cases where it
seemed to work it was due to side effects of global alpha, existing code should
continue working after this commit. The API might return, it is not removed
from the ctx protocol - and can still be accessed through ctx.parse().

components/micropython/usermodule/mp_uctx.c

@@ -202,8 +202,12 @@ MP_CTX_COMMON_FUN_0(restore);
 MP_CTX_COMMON_FUN_0(start_frame);
 MP_CTX_COMMON_FUN_0(end_frame);
 
+#define UCTX_COMPOSITING_GROUPS 0
+
+#if UCTX_COMPOSITING_GROUPS
 MP_CTX_COMMON_FUN_0(start_group);
 MP_CTX_COMMON_FUN_0(end_group);
+#endif
 MP_CTX_COMMON_FUN_0(clip);
 MP_CTX_COMMON_FUN_1F(rotate);
 MP_CTX_COMMON_FUN_2F(scale);
@@ -804,6 +808,9 @@ STATIC void mp_ctx_attr(mp_obj_t obj, qstr attr, mp_obj_t *dest) {
 /* CTX class/type */
 
 static const mp_rom_map_elem_t mp_ctx_locals_dict_table[] = {
+    MP_CTX_METHOD(gray),
+    MP_CTX_METHOD(rgb),
+    MP_CTX_METHOD(rgba),
     MP_CTX_METHOD(line_to),
     MP_CTX_METHOD(move_to),
     MP_CTX_METHOD(curve_to),
@@ -823,6 +830,8 @@ static const mp_rom_map_elem_t mp_ctx_locals_dict_table[] = {
     MP_CTX_METHOD(fill),
     MP_CTX_METHOD(stroke),
     MP_CTX_METHOD(paint),
+    MP_CTX_METHOD(save),
+    MP_CTX_METHOD(restore),
     MP_CTX_METHOD(clip),
     MP_CTX_METHOD(text),
     MP_CTX_METHOD(text_width),
@@ -830,8 +839,13 @@ static const mp_rom_map_elem_t mp_ctx_locals_dict_table[] = {
     MP_CTX_METHOD(scale),
     MP_CTX_METHOD(translate),
     MP_CTX_METHOD(apply_transform),
+#if UCTX_COMPOSITING_GROUPS
     MP_CTX_METHOD(start_group),
     MP_CTX_METHOD(end_group),
+#else
+    { MP_ROM_QSTR(MP_QSTR_start_group), MP_ROM_PTR(&mp_ctx_save_obj) },
+    { MP_ROM_QSTR(MP_QSTR_end_group), MP_ROM_PTR(&mp_ctx_restore_obj) },
+#endif
     MP_CTX_METHOD(preserve),
     MP_CTX_METHOD(linear_gradient),
     MP_CTX_METHOD(radial_gradient),
@@ -839,15 +853,10 @@ static const mp_rom_map_elem_t mp_ctx_locals_dict_table[] = {
     MP_CTX_METHOD(line_dash),
     MP_CTX_METHOD(texture),
     MP_CTX_METHOD(image),
-    MP_CTX_METHOD(save),
-    MP_CTX_METHOD(restore),
     MP_CTX_METHOD(start_frame),
     MP_CTX_METHOD(end_frame),
     MP_CTX_METHOD(get_font_name),
 
-    MP_CTX_METHOD(gray),
-    MP_CTX_METHOD(rgb),
-    MP_CTX_METHOD(rgba),
 #if CTX_PARSER
     MP_CTX_METHOD(parse),
 #endif

python_payload/mypystubs/ctx.pyi

@@ -75,17 +75,6 @@ class Context(Protocol):
         should be balanced.
         """
         pass
-    def start_group(self) -> "Context":
-        """
-        Start a compositing group.
-        """
-        pass
-    def end_group(self) -> "Context":
-        """
-        End a compositing group, the global alpha, compositing mode and blend
-        mode set before this call is used to apply the group.
-        """
-        pass
     def clip(self) -> "Context":
         """
         Use the current path as a clipping mask, subsequent draw calls are

python_payload/st3m/about.py

@@ -189,7 +189,7 @@ class About(BaseView):
             ctx.translate(-240 * offs, 0)
 
             # Opaque circle
-            ctx.start_group()
+            ctx.save()
             ctx.global_alpha = 0.5
             ctx.rgb(0, 0, 0)
             ctx.arc(0, 0, 90, 0, tau, 0)
@@ -208,10 +208,10 @@ class About(BaseView):
                 ctx.font_size = 30
                 ctx.text_align = ctx.MIDDLE
                 ctx.text("\ue5c8")
-            ctx.end_group()
+            ctx.restore()
 
             # Text
-            ctx.start_group()
+            ctx.save()
             ctx.global_alpha = 1.0
             ctx.gray(1)
 
@@ -219,5 +219,5 @@ class About(BaseView):
 
             screen.draw(ctx)
 
-            ctx.end_group()
+            ctx.restore()
             ctx.restore()

sim/fakes/ctx.py

@@ -259,14 +259,6 @@ class Context:
         self._emit(f"stroke")
         return self
 
-    def start_group(self):
-        self._emit(f"start_group")
-        return self
-
-    def end_group(self):
-        self._emit(f"end_group")
-        return self
-
     def save(self):
         self._emit(f"save")
         return self