[ENOMEM] Handle immutable buffer in shape_full()

Move the content_type changing to shape_plan_execute() where it belongs.
Skip setting if content type is UNKNOWN, which happens with empty buffers
only, including the immutable buffer.

Alternate fix to https://github.com/harfbuzz/harfbuzz/pull/2606
and https://github.com/harfbuzz/harfbuzz/pull/2625

src/hb-shape-plan.cc

@@ -355,26 +355,12 @@ hb_shape_plan_get_shaper (hb_shape_plan_t *shape_plan)
 }
 
 
-/**
- * hb_shape_plan_execute:
- * @shape_plan: a shape plan.
- * @font: a font.
- * @buffer: a buffer.
- * @features: (array length=num_features):
- * @num_features:
- *
- *
- *
- * Return value:
- *
- * Since: 0.9.7
- **/
-hb_bool_t
-hb_shape_plan_execute (hb_shape_plan_t    *shape_plan,
-		       hb_font_t          *font,
-		       hb_buffer_t        *buffer,
-		       const hb_feature_t *features,
-		       unsigned int        num_features)
+static bool
+_hb_shape_plan_execute_internal (hb_shape_plan_t    *shape_plan,
+				 hb_font_t          *font,
+				 hb_buffer_t        *buffer,
+				 const hb_feature_t *features,
+				 unsigned int        num_features)
 {
   DEBUG_MSG_FUNC (SHAPE_PLAN, shape_plan,
 		  "num_features=%d shaper_func=%p, shaper_name=%s",
@@ -412,6 +398,35 @@ hb_shape_plan_execute (hb_shape_plan_t    *shape_plan,
 
   return false;
 }
+/**
+ * hb_shape_plan_execute:
+ * @shape_plan: a shape plan.
+ * @font: a font.
+ * @buffer: a buffer.
+ * @features: (array length=num_features):
+ * @num_features:
+ *
+ *
+ *
+ * Return value:
+ *
+ * Since: 0.9.7
+ **/
+hb_bool_t
+hb_shape_plan_execute (hb_shape_plan_t    *shape_plan,
+		       hb_font_t          *font,
+		       hb_buffer_t        *buffer,
+		       const hb_feature_t *features,
+		       unsigned int        num_features)
+{
+  bool ret = _hb_shape_plan_execute_internal (shape_plan, font, buffer,
+					      features, num_features);
+
+  if (ret && buffer->content_type == HB_BUFFER_CONTENT_TYPE_UNICODE)
+    buffer->content_type = HB_BUFFER_CONTENT_TYPE_GLYPHS;
+
+  return ret;
+}
 
 
 /*

src/hb-shape.cc

@@ -132,8 +132,6 @@ hb_shape_full (hb_font_t          *font,
 	       unsigned int        num_features,
 	       const char * const *shaper_list)
 {
-  if (unlikely (hb_object_is_immutable (buffer))) return false;
-
   hb_shape_plan_t *shape_plan = hb_shape_plan_create_cached2 (font->face, &buffer->props,
 							      features, num_features,
 							      font->coords, font->num_coords,
@@ -141,8 +139,6 @@ hb_shape_full (hb_font_t          *font,
   hb_bool_t res = hb_shape_plan_execute (shape_plan, font, buffer, features, num_features);
   hb_shape_plan_destroy (shape_plan);
 
-  if (res)
-    buffer->content_type = HB_BUFFER_CONTENT_TYPE_GLYPHS;
   return res;
 }