Home

Awesome

NAME

WebGPU::Direct - Direct access to the WebGPU native APIs.

SYNOPSIS

use WebGPU::Direct;
my $wgpu = WebGPU::Direct->new;

my $adapter = $wgpu->RequestAdapter;
my $device  = $adapter->RequestDevice;

DESCRIPTION

WebGPU::Direct is a thin, perl-ish coating over the WebGPU native APIs. While it provides some helper functions, much of the work is still left up to the developer to provide and know.

EXPERIMENTAL STATUS

This module is currently extremely experimental, including the documentation. This includes but is not limited to the following.

FUNCTIONS

new

my $wgpu = WebGPU::Direct->new;

Create a new WebGPU::Direct instance. This inherits from WebGPU::Direct::Instance, but also provides easy access to Constants and Types.

new_window

$wgpu->CreateSurface( { nextInChain => WebGPU::Direct->new_window( $width, $height ) } );

Constructs a WebGPU::Direct::SurfaceDescriptorFrom* object, usable for passing to CreateSurface. These are crude and simplistic windows suitable for testing WebGPU with, but there are no options and doesn't come with any way to interact or configure the window.

Currently the supported windowing systems are:

WebGPU::Direct::XS::HAS_<FOO>

Constant indicating if FOO support is compiled in. This only indicates that WebGPU::Direct detected and compiled FOO was available when installed, making "new_window" available. FOO windows can still be used if you manually construct the WebGPU::Direct::SurfaceDescriptorFrom* object.

METHODS

TYPES

There are two basic segments of types: Structs and Opaque. The struct types have members that can manipulated and modified. The opaque types are implementation specific to WebGPU so they have no fields that can be directly accessed, but they do have functions made available to them.

The struct types can be instantiated by calling new on the class; opaque types can only be returned by functions.

Struct type classes can be access in a few different ways: with the class name directly or as a class method on WebGPU::Direct. Struct types can also be instantiated with the new<TypeName> functions on WebGPU::Direct.

WebGPU::Direct::Color()->new({});
WebGPU::Direct->Color->new;
$wgpu->Color->new;
WebGPU::Direct->newColor;
$wgpu->newColor();

Often these type members and functions require other types. If these are given a plain hash, those hashes will be coerced into the correct type.

Functions on all struct types

new

my $color = $wgpu->Color->new({ r => 0.0, g => 1.0, b => 0.2, a => 0.9 });

Create a new object of the requested type. It accepts either a hash or a single hashref parameters. This will automatically call pack with the defaults and provided values. There is an associated C level struct stored in memory along side the object.

pack

$color->pack;

Take all of the members and copies the values from the perl level down to the C level struct in memory. Any references to other objects will be copied appropriately; in most cases this will copy a pointer to the referenced object. In some cases the entire struct will be copied into the object, in which case a new object will appear pointing directly to the new struct.

If you decide to manually manipulate the blessed hashref instead of using the mutator functions, you must call pack to propagate those changes down to the C level.

unpack

$color->unpack;

This is the opposite of "pack"; this will take the values in the C level struct and ensure the perl level values match.

bytes

my $binary = $color->bytes;

Returns the underlying, raw memory bytes of the struct. This includes direct pointers to other structures and the like. There is no way to save any changes to the returned string back to the C level memory. Caveat emptor.

Callbacks

In some places in the WebGPU API are callbacks; functions that are passed a function and userdata. The calls are adjusted so that regular perl subs can be passed along with arbitrary perl data. The calling parameters are dependant on the callback in question, but the last parameter will always be passed userdata.

Arrays

Some types have arrays of data, represented at the C level as a pointer field and a count field. These are translated from perl arrayrefs into the appropriate types. If a single hashref is passed instead, it will be coerced into an array automatically.

Enums

A value saved to an enum member will get coerced into the corresponding enum constant.

CONSTANTS

All of the WebGPU enum constant sets can be accessed in a few different ways: from the package directly, as class functions on WebGPU::Direct, and as exports from WebGPU::Direct. All three methods return the enum package for the set. Each of the following calls will produce the same results.

use WebGPU::Direct qw/:all/;
TextureFormat->RGBA8Uint;
WebGPU::Direct::TextureFormat->RGBA8Uint;
WebGPU::Direct->TextureFormat->RGBA8Uint;
$wgpu->TextureFormat->RGBA8Uint;

Enums are implemented as dualvars, so the numerical value will be the integer value that WebGPU expects, but the string value will match WebGPU's enum name. In the example above, RGBA8Uint will have a value of 0x00000015 as well as WGPUTextureFormat_RGBA8Uint. Note that the enum name preserves both the WGPU and the enum set prefixes.

ADDITIONAL WEBGPU INFORMATION

Force32

All of the enums have a Force32 value. These are not valid values, but are simply there to ensure that the underlying enum is a 32bit integer. WebGPU::Direct does not include them.

SwapChain

There are older tutorials or code examples around the internet that use a SwapChain type, both for WebGPU native and JavaScript. Later revisions of WebGPU eliminated that type and moved its functionality onto Surface.

WebGPU errors

The default operation of RequestDevice will install an error handler using SetUncapturedErrorCallback if a device is acquired. This means any errors not handled (generally using PushErrorScope/PopErrorScope) will be thrown as Error objects. If you override how RequestDevice searches for devices, you will need to install your own error handler.

BE WARNED that WebGPU is still young and experimental, and as such WebGPU native is more so as it lags behind the WebGPU JavaScript API. This means that not all errors will be passed to SetUncapturedErrorCallback, any may even abort instead, and may vary wildly between implementations and versions.

Error Diagnostics

invalid vertex shader module for vertex state

This is when the Buffer's step mode is invalid. Check the buffer objects in VertexState to ensure the sizes are correct and align with what data you are expecting to pack into a buffer.

invalid vertex shader module for vertex state

This is when a vertex state does not include a valid ShaderModuleDescriptor.

invalid bind group entry for bind group descriptor

In JavaScript examples, you may see a BindGroupEntry have a resource entry that points to a buffer, sampler or textureView. In WeGPU native, there is not that extra resource layer. So instead of resource => { buffer => $x }, simply use buffer => $x.

(left == right), Texture[1] is no longer alive

There appears to be an issue with ColorAttachment inside of RenderPassDescriptor, where just setting $renderPassDescriptor->{colorAttachments}->[0]->{view} on each frame causes this issue. This issue is likely inside of WebGPU::Direct. Generating a new ColorAttachment object should help while the fix is outstanding.

Error reflecting bind group 0: Validation Error / Invalid group index 0

When a RenderPipeline is being ran with an auto layout, that layout is not defined in the RenderPipelineDescriptor passed to $device->CreateRenderPipeline, WebGPU will auto analyze the WGSL to determine the group bindings. If a group binding is not used, the layout for it will not be included in the layout. You will need to either use the group binding in the shaders, or manually create and use a layout definition.

Surface image is already acquired

The WebGPU JavaScript API and the WebGPU Native API differ slightly in how you interact with the hardware. In JavaScript, the GPUCanvasContext is used, and with the native it is a Surface. The core functions are in both, but the Native API has several extra that the JavaScript API does not have, most notably Present, which informs the system that rendering is complete. Because of this, this you cannot acquire a TextureView twice in a single frame via the CreateView function before calls to Present. Tryig to get it a second time will will throw this error.

Because the JavaScript WebGPU API does not have a Present function, examples will not include it; it happens implictly after each frame function. That means you must remember to call it at the end of each frame loop when the render is ready to go.

AUTHOR

Jon Gentle cpan@atrodo.org

COPYRIGHT

Copyright 2023- Jon Gentle

LICENSE

This is free software. You may redistribute copies of it under the terms of the Artistic License 2 as published by The Perl Foundation.

SEE ALSO