iOS video frame render implementation.

Uses CVTextureCache, iOS only for now, OS-X code could be ported
but will need further work to support TEXTURE_RECTANGLE in the
QVideoNode classes.

When we can’t share a context, falls back to an offscreen window,
FBO rendering and grabbing a QImage.

Change-Id: I23b831fdcc63aeb1b67b7741d8d56779470240d3
Reviewed-by: Yoann Lopes <yoann.lopes@theqtcompany.com>

src/plugins/avfoundation/mediaplayer/avfdisplaylink.mm

@@ -46,8 +46,70 @@
 #include <QtCore/qdebug.h>
 #endif
 
+#if defined(Q_OS_IOS)
+#import <QuartzCore/CADisplayLink.h>
+#import <Foundation/NSRunLoop.h>
+#define _m_displayLink static_cast<DisplayLinkObserver*>(m_displayLink)
+#else
+#endif
+
 QT_USE_NAMESPACE
 
+#if defined(Q_OS_IOS)
+@interface DisplayLinkObserver : NSObject
+{
+    AVFDisplayLink *m_avfDisplayLink;
+    CADisplayLink *m_displayLink;
+}
+
+- (void)start;
+- (void)stop;
+- (void)displayLinkNotification:(CADisplayLink *)sender;
+
+@end
+
+@implementation DisplayLinkObserver
+
+- (id)initWithAVFDisplayLink:(AVFDisplayLink *)link
+{
+    self = [super init];
+
+    if (self) {
+        m_avfDisplayLink = link;
+        m_displayLink = [[CADisplayLink displayLinkWithTarget:self selector:@selector(displayLinkNotification:)] retain];
+    }
+
+    return self;
+}
+
+- (void) dealloc
+{
+    if (m_displayLink) {
+        [m_displayLink release];
+        m_displayLink = NULL;
+    }
+
+    [super dealloc];
+}
+
+- (void)start
+{
+    [m_displayLink addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
+}
+
+- (void)stop
+{
+    [m_displayLink removeFromRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
+}
+
+- (void)displayLinkNotification:(CADisplayLink *)sender
+{
+    Q_UNUSED(sender);
+    m_avfDisplayLink->displayLinkEvent(nullptr);
+}
+
+@end
+#else
 static CVReturn CVDisplayLinkCallback(CVDisplayLinkRef displayLink,
                                  const CVTimeStamp *inNow,
                                  const CVTimeStamp *inOutputTime,
@@ -65,12 +127,17 @@ static CVReturn CVDisplayLinkCallback(CVDisplayLinkRef displayLink,
     link->displayLinkEvent(inOutputTime);
     return kCVReturnSuccess;
 }
+#endif
 
 AVFDisplayLink::AVFDisplayLink(QObject *parent)
     : QObject(parent)
+    , m_displayLink(0)
     , m_pendingDisplayLinkEvent(false)
     , m_isActive(false)
 {
+#if defined(Q_OS_IOS)
+    m_displayLink = [[DisplayLinkObserver alloc] initWithAVFDisplayLink:this];
+#else
     // create display link for the main display
     CVDisplayLinkCreateWithCGDisplay(kCGDirectMainDisplay, &m_displayLink);
     if (m_displayLink) {
@@ -80,6 +147,7 @@ AVFDisplayLink::AVFDisplayLink(QObject *parent)
         // set the renderer output callback function
         CVDisplayLinkSetOutputCallback(m_displayLink, &CVDisplayLinkCallback, this);
     }
+#endif
 }
 
 AVFDisplayLink::~AVFDisplayLink()
@@ -89,8 +157,12 @@ AVFDisplayLink::~AVFDisplayLink()
 #endif
 
     if (m_displayLink) {
-        CVDisplayLinkStop(m_displayLink);
+        stop();
+#if defined(Q_OS_IOS)
+        [_m_displayLink release];
+#else
         CVDisplayLinkRelease(m_displayLink);
+#endif
         m_displayLink = NULL;
     }
 }
@@ -108,20 +180,27 @@ bool AVFDisplayLink::isActive() const
 void AVFDisplayLink::start()
 {
     if (m_displayLink && !m_isActive) {
-       CVDisplayLinkStart(m_displayLink);
-       m_isActive = true;
+#if defined(Q_OS_IOS)
+        [_m_displayLink start];
+#else
+        CVDisplayLinkStart(m_displayLink);
+#endif
+        m_isActive = true;
     }
 }
 
 void AVFDisplayLink::stop()
 {
     if (m_displayLink && m_isActive) {
+#if defined(Q_OS_IOS)
+        [_m_displayLink stop];
+#else
         CVDisplayLinkStop(m_displayLink);
+#endif
         m_isActive = false;
     }
 }
 
-
 void AVFDisplayLink::displayLinkEvent(const CVTimeStamp *ts)
 {
     // This function is called from a
@@ -131,7 +210,12 @@ void AVFDisplayLink::displayLinkEvent(const CVTimeStamp *ts)
     m_displayLinkMutex.lock();
     bool pending = m_pendingDisplayLinkEvent;
     m_pendingDisplayLinkEvent = true;
+#if defined(Q_OS_IOS)
+    Q_UNUSED(ts);
+    memset(&m_frameTimeStamp, 0, sizeof(CVTimeStamp));
+#else
     m_frameTimeStamp = *ts;
+#endif
     m_displayLinkMutex.unlock();
 
     if (!pending)