Struct MTKMeshBuffer

Source

#[repr(C)]
pub struct MTKMeshBuffer { /* private fields */ }

Available on crate feature MTKModel only.

Expand description

Mesh buffer created by MTKMeshBufferAllocator when Model I/O needs to memory for vertex or index data backing.

Memory backing these buffer are Metal buffers. Model I/O will load index and vertex data from from a model asset directly in to the Metal buffer.

Implementations§

Source §

impl MTKMeshBuffer

Source

pub unsafe fn init(this: Allocated<Self>) -> Retained<Self>

Only an MTKMeshBufferAllocator object can initilize a MTKMeshBuffer object

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pub unsafe fn length(&self) -> NSUInteger

Size in bytes of the buffer allocation.

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pub unsafe fn allocator(&self) -> Retained<MTKMeshBufferAllocator>

Allocator object used to create this buffer.

This allcoator is stored so that it can be used by Model I/O for copy and relayout operations (such as when a new vertex descriptor is applied to a vertex buffer).

Source

pub unsafe fn zone( &self, ) -> Option<Retained<ProtocolObject<dyn MDLMeshBufferZone>>>

Available on crate feature objc2-model-io only.

Zone from which this buffer was created (if it was created from a zone).

A single MetalBuffer is allocated for each zone. Each zone could have many MTKMeshBuffers, each with it’s own offset. If a MTKMeshBufferAllocator is used, Model I/O will attempt to load all vertex and index data of a single mesh into a single zone. This allows the GPU to achieve a higher cache hit rate when drawing the mesh. So although there maybe many MTKMeshBuffers for a model they will be backed with the same contigous MetalBuffer.

Source

pub unsafe fn buffer(&self) -> Retained<ProtocolObject<dyn MTLBuffer>>

Metal Buffer backing vertex/index data.

Many MTKMeshBuffers may reference the same buffer, but each with it’s own offset. (i.e. Many MTKMeshBuffers may be suballocated from a single buffer)

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pub unsafe fn offset(&self) -> NSUInteger

Byte offset of the data within the metal buffer.

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pub unsafe fn type(&self) -> MDLMeshBufferType

Available on crate feature objc2-model-io only.

the intended type of the buffer

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impl MTKMeshBuffer

Methods declared on superclass NSObject.

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pub unsafe fn new() -> Retained<Self>

Methods from Deref<Target = NSObject>§

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pub fn doesNotRecognizeSelector(&self, sel: Sel) -> !

Handle messages the object doesn’t recognize.

See Apple’s documentation for details.

Methods from Deref<Target = AnyObject>§

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pub fn class(&self) -> &'static AnyClass

Dynamically find the class of this object.

§Example

Check that an instance of NSObject has the precise class NSObject.

use objc2::ClassType;
use objc2::runtime::NSObject;

let obj = NSObject::new();
assert_eq!(obj.class(), NSObject::class());

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pub unsafe fn get_ivar<T>(&self, name: &str) -> &T
where T: Encode,

👎Deprecated: this is difficult to use correctly, use Ivar::load instead.

Use Ivar::load instead.

§Safety

The object must have an instance variable with the given name, and it must be of type T.

See Ivar::load_ptr for details surrounding this.

Source

pub fn downcast_ref<T>(&self) -> Option<&T>
where T: DowncastTarget,

Attempt to downcast the object to a class of type T.

This is the reference-variant. Use Retained::downcast if you want to convert a retained object to another type.

§Mutable classes

Some classes have immutable and mutable variants, such as NSString and NSMutableString.

When some Objective-C API signature says it gives you an immutable class, it generally expects you to not mutate that, even though it may technically be mutable “under the hood”.

So using this method to convert a NSString to a NSMutableString, while not unsound, is generally frowned upon unless you created the string yourself, or the API explicitly documents the string to be mutable.

See Apple’s documentation on mutability and on isKindOfClass: for more details.

§Generic classes

Objective-C generics are called “lightweight generics”, and that’s because they aren’t exposed in the runtime. This makes it impossible to safely downcast to generic collections, so this is disallowed by this method.

You can, however, safely downcast to generic collections where all the type-parameters are AnyObject.

§Panics

This works internally by calling isKindOfClass:. That means that the object must have the instance method of that name, and an exception will be thrown (if CoreFoundation is linked) or the process will abort if that is not the case. In the vast majority of cases, you don’t need to worry about this, since both root objects NSObject and NSProxy implement this method.

§Examples

Cast an NSString back and forth from NSObject.

use objc2::rc::Retained;
use objc2_foundation::{NSObject, NSString};

let obj: Retained<NSObject> = NSString::new().into_super();
let string = obj.downcast_ref::<NSString>().unwrap();
// Or with `downcast`, if we do not need the object afterwards
let string = obj.downcast::<NSString>().unwrap();

Try (and fail) to cast an NSObject to an NSString.

use objc2_foundation::{NSObject, NSString};

let obj = NSObject::new();
assert!(obj.downcast_ref::<NSString>().is_none());

Try to cast to an array of strings.

use objc2_foundation::{NSArray, NSObject, NSString};

let arr = NSArray::from_retained_slice(&[NSObject::new()]);
// This is invalid and doesn't type check.
let arr = arr.downcast_ref::<NSArray<NSString>>();

This fails to compile, since it would require enumerating over the array to ensure that each element is of the desired type, which is a performance pitfall.

Downcast when processing each element instead.

use objc2_foundation::{NSArray, NSObject, NSString};

let arr = NSArray::from_retained_slice(&[NSObject::new()]);

for elem in arr {
    if let Some(data) = elem.downcast_ref::<NSString>() {
        // handle `data`
    }
}