gpu: add getProcAddress

Signed-off-by: Stephen Gutekanst <stephen@hexops.com>

gpu/TODO-webgpu.h

@@ -10,8 +10,6 @@ typedef void (*WGPUQueueWorkDoneCallback)(WGPUQueueWorkDoneStatus status, void *
 typedef void (*WGPURequestAdapterCallback)(WGPURequestAdapterStatus status, WGPUAdapter adapter, char const * message, void * userdata);
 typedef void (*WGPURequestDeviceCallback)(WGPURequestDeviceStatus status, WGPUDevice device, char const * message, void * userdata);
 
-WGPU_EXPORT WGPUProc wgpuGetProcAddress(WGPUDevice device, char const * procName);
-
 // Methods of Adapter
 WGPU_EXPORT WGPUDevice wgpuAdapterCreateDevice(WGPUAdapter adapter, WGPUDeviceDescriptor const * descriptor /* nullable */);
 WGPU_EXPORT size_t wgpuAdapterEnumerateFeatures(WGPUAdapter adapter, WGPUFeatureName * features);

gpu/src/interface.zig

@@ -1,9 +1,11 @@
 const Instance = @import("instance.zig").Instance;
 const InstanceDescriptor = @import("instance.zig").InstanceDescriptor;
+const gpu = @import("main.zig");
 
 /// Verifies that a gpu.Interface implementation exposes the expected function declarations.
 pub fn Interface(comptime Impl: type) type {
     assertDecl(Impl, "createInstance", fn (descriptor: *const InstanceDescriptor) callconv(.Inline) ?Instance);
+    assertDecl(Impl, "getProcAddress", fn (device: gpu.Device, proc_name: [*:0]const u8) callconv(.Inline) ?gpu.Proc);
     return Impl;
 }
 
@@ -21,6 +23,11 @@ pub fn Export(comptime Impl: type) type {
         export fn wgpuCreateInstance(descriptor: *const InstanceDescriptor) ?Instance {
             return Impl.createInstance(descriptor);
         }
+
+        // WGPU_EXPORT WGPUProc wgpuGetProcAddress(WGPUDevice device, char const * procName);
+        export fn getProcAddress(device: gpu.Device, proc_name: [*:0]const u8) ?gpu.Proc {
+            return Impl.getProcAddress(device, proc_name);
+        }
     };
 }
 
@@ -30,6 +37,12 @@ pub const NullInterface = Interface(struct {
         _ = descriptor;
         return null;
     }
+
+    pub inline fn getProcAddress(device: gpu.Device, proc_name: [*:0]const u8) ?gpu.Proc {
+        _ = device;
+        _ = proc_name;
+        return null;
+    }
 });
 
 test "null" {

gpu/src/main.zig

@@ -44,6 +44,10 @@ const query_set = @import("query_set.zig");
 const texture_view = @import("texture_view.zig");
 const surface = @import("surface.zig");
 
+/// Generic function pointer type, used for returning API function pointers. Must be
+/// cast to a `fn (...) callconv(.C) T` before use.
+pub const Proc = *anyopaque;
+
 pub const ComputePassTimestampWrite = extern struct {
     query_set: query_set.QuerySet,
     query_index: u32,