de1a9fd25e
`device.activeFormat.formatDescription` reports the device's
*selected* format, but on macOS the session-preset remap means the
data output sometimes delivers a different resolution than what
the active format claims. The mismatch surfaced as a stretched
preview on macOS: camera_thumb's SizedBox was sized for a 4:3
buffer, the FittedBox(cover) was given a 16:9 texture, so the
texture stretched to fill the wrongly-shaped box.
PreviewSink now snapshots `CVPixelBufferGet{Width,Height}` from
the first sample buffer that arrives and forwards it via a
callback. CameraInstance hooks the callback to emit the existing
`previewSizeChanged` event (same shape the Android backend uses).
The Dart controller writes it into `value.previewSize`,
camera_thumb's SizedBox snaps to the real buffer aspect, and
FittedBox(cover) crops cleanly without stretching.
Identical wire shape and event name as the Android equivalent —
no Dart changes needed.
89 lines
3.1 KiB
Swift
89 lines
3.1 KiB
Swift
import AVFoundation
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import CoreVideo
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#if canImport(UIKit)
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import Flutter
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#else
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import FlutterMacOS
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#endif
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/// Single-slot latest-pixel-buffer sink that feeds a `FlutterTexture`.
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///
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/// AVCaptureVideoDataOutput's sample-buffer delegate fires on
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/// `videoBufferQueue`; we extract the `CVPixelBuffer`, store it as
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/// `latestPixelBuffer`, and notify the texture registry on `main` so
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/// Flutter pulls the new frame via `copyPixelBuffer()` on the engine
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/// thread.
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///
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/// We retain *only the most recent* buffer — the previous one is
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/// released the moment a new sample arrives. This matches the
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/// `camera_avfoundation` lifetime invariant and bounds memory at one
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/// frame regardless of how fast we produce vs. consume.
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final class PreviewSink: NSObject, FlutterTexture {
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private weak var registry: FlutterTextureRegistry?
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private var textureId: Int64 = -1
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/// Serial queue for the `latestPixelBuffer` swap. Sample-buffer
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/// delegate writes; `copyPixelBuffer()` reads. Without this the
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/// pointer could be freed mid-read on a different thread.
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private let bufferQueue = DispatchQueue(
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label: "ux.camera.preview.buffer",
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qos: .userInitiated
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)
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private var latestPixelBuffer: CVPixelBuffer?
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/// Fires once after the first sample buffer arrives, carrying the
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/// buffer's actual `CVPixelBuffer` dimensions. The active-format
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/// dims reported by `device.activeFormat` aren't always what the
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/// data output actually delivers (notably on macOS where the
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/// session preset gets remapped). [CameraInstance] forwards this
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/// to Dart as a `previewSizeChanged` event so the camera_thumb's
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/// SizedBox aspect matches the texture's real aspect.
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var onFirstFrameSize: ((CGSize) -> Void)?
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private var emittedFirstSize = false
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func register(with registry: FlutterTextureRegistry) -> Int64 {
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self.registry = registry
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textureId = registry.register(self)
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return textureId
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}
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func unregister() {
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registry?.unregisterTexture(textureId)
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bufferQueue.sync { latestPixelBuffer = nil }
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}
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// MARK: - FlutterTexture
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func copyPixelBuffer() -> Unmanaged<CVPixelBuffer>? {
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var pb: CVPixelBuffer?
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bufferQueue.sync {
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pb = latestPixelBuffer
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latestPixelBuffer = nil
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}
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if let pb = pb { return Unmanaged.passRetained(pb) }
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return nil
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}
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/// Receives a new frame. Called from the
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/// `AVCaptureVideoDataOutputSampleBufferDelegate` on
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/// `videoBufferQueue`. Cheap — just swaps the pointer + notifies
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/// the registry.
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func receive(sampleBuffer: CMSampleBuffer) {
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guard let pb = CMSampleBufferGetImageBuffer(sampleBuffer) else {
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return
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}
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bufferQueue.sync { latestPixelBuffer = pb }
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if !emittedFirstSize {
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emittedFirstSize = true
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let size = CGSize(
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width: CGFloat(CVPixelBufferGetWidth(pb)),
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height: CGFloat(CVPixelBufferGetHeight(pb))
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)
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onFirstFrameSize?(size)
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}
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if let registry = registry {
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registry.textureFrameAvailable(textureId)
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}
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}
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}
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