Fix post call crash on iOS8

// FREEBIE

Signal/src/views/RemoteVideoView.m

@@ -3,16 +3,67 @@
 //
 
 #import "RemoteVideoView.h"
+#import "UIFont+OWS.h"
+#import "UIView+OWS.h"
 #import <MetalKit/MetalKit.h>
 #import <PureLayout/PureLayout.h>
 #import <WebRTC/RTCEAGLVideoView.h>
 #import <WebRTC/RTCMTLVideoView.h>
 #import <WebRTC/RTCVideoRenderer.h>
 
-@interface RTCMTLVideoView (MakePrivatePublic)
-+ (BOOL)isMetalAvailable;
+NS_ASSUME_NONNULL_BEGIN
+
+// As of RTC M61, iOS8 crashes when ending call while de-alloc'ing the EAGLVideoView
+// WebRTC doesn't seem to support iOS8 - e.g. their Podfile requires iOS9+
+// Until WebRTC supports iOS8, we show a "upgrade iOS to see remote video" view
+// to our few remaining iOS8 users
+@interface NullVideoRenderer : UIView <RTCVideoRenderer>
+
 @end
 
+@implementation NullVideoRenderer
+
+- (instancetype)initWithFrame:(CGRect)frame
+{
+    self = [super initWithFrame:frame];
+    if (!self) {
+        return self;
+    }
+
+    self.backgroundColor = UIColor.blackColor;
+
+    UILabel *label = [UILabel new];
+    label.numberOfLines = 0;
+    label.text
+        = NSLocalizedString(@"CALL_REMOTE_VIDEO_DISABLED", @"Text shown on call screen in place of remote video");
+    label.textAlignment = NSTextAlignmentCenter;
+    label.font = [UIFont ows_boldFontWithSize:ScaleFromIPhone5(20)];
+    label.textColor = UIColor.whiteColor;
+
+    [self addSubview:label];
+    [label autoVCenterInSuperview];
+    [label autoPinWidthToSuperviewWithMargin:ScaleFromIPhone5(16)];
+
+    return self;
+}
+
+#pragma mark - RTCVideoRenderer
+
+/** The size of the frame. */
+- (void)setSize:(CGSize)size
+{
+    // Do nothing.
+}
+
+/** The frame to be displayed. */
+- (void)renderFrame:(nullable RTCVideoFrame *)frame
+{
+    // Do nothing.
+}
+
+@end
+
+
 @interface RemoteVideoView () <RTCEAGLVideoViewDelegate>
 
 @property (nonatomic, readonly) __kindof UIView<RTCVideoRenderer> *videoRenderer;
@@ -28,6 +79,11 @@
         return self;
     }
 
+    if (!SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(9, 0)) {
+        _videoRenderer = [NullVideoRenderer new];
+    }
+
+    if (_videoRenderer == nil) {
 // This class is defined in objc in order to access this compile time macro
 // Currently RTC only supports metal on 64bit machines
 #if defined(RTC_SUPPORTS_METAL)
@@ -36,6 +92,8 @@
         _videoRenderer = [[RTCMTLVideoView alloc] initWithFrame:CGRectZero];
     }
 #endif
+    }
+
     if (_videoRenderer == nil) {
         RTCEAGLVideoView *eaglVideoView = [[RTCEAGLVideoView alloc] initWithFrame:CGRectZero];
         eaglVideoView.delegate = self;
@@ -86,3 +144,5 @@
 }
 
 @end
+
+NS_ASSUME_NONNULL_END

Signal/translations/en.lproj/Localizable.strings

@@ -208,6 +208,9 @@
 /* Accessibilty label for placing call button */
 "CALL_LABEL" = "Call";
 
+/* Text shown on call screen in place of remote video */
+"CALL_REMOTE_VIDEO_DISABLED" = "Please upgrade to iOS 9 or newer to see remote video.";
+
 /* Call setup status label after outgoing call times out */
 "CALL_SCREEN_STATUS_NO_ANSWER" = "No Answer.";
 
@@ -601,7 +604,7 @@
 /* A label for generic attachments. */
 "GENERIC_ATTACHMENT_LABEL" = "Attachment";
 
-/* Please enter your search. */
+/* Alert message shown when user tries to search for GIFs without entering any search terms. */
 "GIF_PICKER_VIEW_MISSING_QUERY" = "Please enter your search.";
 
 /* Title for the 'gif picker' dialog. */