Struct AVVideoPerformanceMetrics

Source

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

Available on crate feature AVVideoPerformanceMetrics only.

Expand description

[SPI] An instance of AVVideoPerformanceMetrics provides current performance metrics.

An instance of AVVideoPerformanceMetrics provides named properties for accessing the video playback quality metrics. Subclasses of this type that are used from Swift must fulfill the requirements of a Sendable type.

Implementations§

Source §

pub unsafe fn totalNumberOfFrames(&self) -> NSInteger

[SPI] The total number of frames that would have been displayed if no frames are dropped.

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pub unsafe fn numberOfDroppedFrames(&self) -> NSInteger

[SPI] The total number of frames dropped prior to decoding or dropped because a frame missed its display deadline.

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pub unsafe fn numberOfCorruptedFrames(&self) -> NSInteger

[SPI] The total number of corrupted frames that have been detected.

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pub unsafe fn numberOfFramesDisplayedUsingOptimizedCompositing( &self, ) -> NSInteger

[SPI] The total number of full screen frames that were rendered in a special power-efficient mode that didn’t require the frame to be composited with other UI elements.

Source

pub unsafe fn totalAccumulatedFrameDelay(&self) -> NSTimeInterval

[SPI] The accumulated amount of time between the prescribed presentation times of displayed video frames and the actual time at which they were displayed.

This delay is always greater than or equal to zero since frames must never be displayed before their presentation time. Non-zero delays are a sign of playback jitter and possible loss of A/V sync.

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pub unsafe fn totalNumberOfVideoFrames(&self) -> c_ulong

[SPI] The total number of frames that would have been displayed if no frames are dropped. Same as totalNumberOfFrames.

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pub unsafe fn numberOfDroppedVideoFrames(&self) -> c_ulong

[SPI] The total number of frames dropped prior to decoding or dropped because a frame missed its display deadline. Same as numberOfDroppedFrames.

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pub unsafe fn numberOfCorruptedVideoFrames(&self) -> c_ulong

[SPI] The total number of corrupted frames that have been detected. Same as numberOfCorruptedFrames.

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pub unsafe fn numberOfDisplayCompositedVideoFrames(&self) -> c_ulong

[SPI] The total number of frames that were composited in detached mode. Same as numberOfFramesDisplayedUsingOptimizedCompositing.

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pub unsafe fn numberOfNonDisplayCompositedVideoFrames(&self) -> c_ulong

[SPI] The total number of frames that were composited in undetached mode.

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pub unsafe fn totalFrameDelay(&self) -> c_double

[SPI] The accumulated amount of time, in microseconds, between the prescribed presentation times of displayed video frames and the actual time at which they were displayed.

This delay is always greater than or equal to zero since frames must never be displayed before their presentation time. Non-zero delays are a sign of playback jitter and possible loss of A/V sync. Same as totalAccumulatedFrameDelay.

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());

Source

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`
    }
}