2014 snapchat source code
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//
// SCBlackCameraPreviewDetector.m
// Snapchat
//
// Created by Derek Wang on 25/01/2018.
//
#import "SCBlackCameraPreviewDetector.h"
#import "SCBlackCameraReporter.h"
#import "SCMetalUtils.h"
#import <SCCrashLogger/SCCrashLogger.h>
#import <SCFoundation/SCQueuePerformer.h>
#import <SCFoundation/SCThreadHelpers.h>
#import <SCFoundation/SCZeroDependencyExperiments.h>
// Check whether preview is visible when AVCaptureSession is running
static CGFloat const kSCBlackCameraCheckingDelay = 0.5;
@interface SCBlackCameraPreviewDetector () {
BOOL _previewVisible;
dispatch_block_t _checkingBlock;
}
@property (nonatomic) SCQueuePerformer *queuePerformer;
@property (nonatomic) SCBlackCameraReporter *reporter;
@end
@implementation SCBlackCameraPreviewDetector
- (instancetype)initWithPerformer:(SCQueuePerformer *)performer reporter:(SCBlackCameraReporter *)reporter
{
self = [super init];
if (self) {
_queuePerformer = performer;
_reporter = reporter;
}
return self;
}
- (void)capturePreviewDidBecomeVisible:(BOOL)visible
{
[_queuePerformer perform:^{
_previewVisible = visible;
}];
}
- (void)sessionDidChangeIsRunning:(BOOL)running
{
if (running) {
[self _scheduleCheck];
} else {
[_queuePerformer perform:^{
if (_checkingBlock) {
dispatch_block_cancel(_checkingBlock);
_checkingBlock = nil;
}
}];
}
}
- (void)_scheduleCheck
{
[_queuePerformer perform:^{
@weakify(self);
_checkingBlock = dispatch_block_create(0, ^{
@strongify(self);
SC_GUARD_ELSE_RETURN(self);
self->_checkingBlock = nil;
[self _checkPreviewState];
});
[_queuePerformer perform:_checkingBlock after:kSCBlackCameraCheckingDelay];
}];
}
- (void)_checkPreviewState
{
if (!_previewVisible) {
runOnMainThreadAsynchronously(^{
// Make sure the app is in foreground
SC_GUARD_ELSE_RETURN([UIApplication sharedApplication].applicationState == UIApplicationStateActive);
SCBlackCameraCause cause =
SCDeviceSupportsMetal() ? SCBlackCameraRenderingPaused : SCBlackCameraPreviewIsHidden;
[_reporter reportBlackCameraWithCause:cause];
[_reporter fileShakeTicketWithCause:cause];
});
}
}
@end