Add better async support for wgpu-native (#609)

* Add proper async support for wgpu-native (to the extend that native supports it)

* fix codegen

* Apply for improved codegen

codegen/apipatcher.py

@@ -648,12 +648,17 @@ def apply(self, code):
                 # Test that a matching check is done
                 unchecked = method_structs.difference(checked)
                 unchecked = list(sorted(unchecked.difference(ignore_structs)))
-                if (
-                    methodname.endswith("_async")
-                    and f"return self.{methodname[:-7]}" in code
-                ):
-                    pass
-                elif unchecked:
+                # Must we check, or does this method defer to another
+                defer_func_name = "_" + methodname
+                defer_line_starts = (
+                    f"return self.{defer_func_name[:-7]}",
+                    f"awaitable = self.{defer_func_name[:-7]}",
+                )
+                this_method_defers = any(
+                    line.strip().startswith(defer_line_starts)
+                    for line in code.splitlines()
+                )
+                if not this_method_defers and unchecked:
                     msg = f"missing check_struct in {methodname}: {unchecked}"
                     self.insert_line(j1, f"# FIXME: {msg}")
                     print(f"ERROR: {msg}")

wgpu/_classes.py

@@ -90,7 +90,11 @@ class GPU:
     # IDL: Promise<GPUAdapter?> requestAdapter(optional GPURequestAdapterOptions options = {}); -> GPUPowerPreference powerPreference, boolean forceFallbackAdapter = false
     @apidiff.change("arguments include canvas")
     def request_adapter_sync(
-        self, *, power_preference=None, force_fallback_adapter=False, canvas=None
+        self,
+        *,
+        power_preference: enums.GPUPowerPreference = None,
+        force_fallback_adapter: bool = False,
+        canvas=None,
     ):
         """Sync version of `request_adapter_async()`.
 
@@ -108,7 +112,11 @@ def request_adapter_sync(
     # IDL: Promise<GPUAdapter?> requestAdapter(optional GPURequestAdapterOptions options = {}); -> GPUPowerPreference powerPreference, boolean forceFallbackAdapter = false
     @apidiff.change("arguments include canvas")
     async def request_adapter_async(
-        self, *, power_preference=None, force_fallback_adapter=False, canvas=None
+        self,
+        *,
+        power_preference: enums.GPUPowerPreference = None,
+        force_fallback_adapter: bool = False,
+        canvas=None,
     ):
         """Create a `GPUAdapter`, the object that represents an abstract wgpu
         implementation, from which one can request a `GPUDevice`.
@@ -117,8 +125,8 @@ async def request_adapter_async(
             power_preference (PowerPreference): "high-performance" or "low-power".
             force_fallback_adapter (bool): whether to use a (probably CPU-based)
                 fallback adapter.
-            canvas (WgpuCanvasInterface): The canvas that the adapter should
-                be able to render to. This can typically be left to None.
+            canvas : The canvas that the adapter should be able to render to. This can typically
+                 be left to None. If given, the object must implement ``WgpuCanvasInterface``.
         """
         # If this method gets called, no backend has been loaded yet, let's do that now!
         from .backends.auto import gpu