From e19b6afb264deca6b24f2c6832ac71f961be7b86 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Minh=20Nguy=E1=BB=85n?= <mxn@1ec5.org>
Date: Tue, 14 Apr 2015 22:23:13 -0700
Subject: [PATCH] Leave GLKView in place, obscured by snapshot

Generate the snapshot using `-[UIView snapshotViewAfterScreenUpdates:]` and place it _over_ the `GLKView`. UIKit appears to be able to detect that the `GLKView` is completely obscured and avoids `-_display`ing it.
---
 platform/ios/MGLMapView.mm | 26 ++++++++++++--------------
 1 file changed, 12 insertions(+), 14 deletions(-)

diff --git a/platform/ios/MGLMapView.mm b/platform/ios/MGLMapView.mm
index afea8ae4f..d2ccd7396 100644
--- a/platform/ios/MGLMapView.mm
+++ b/platform/ios/MGLMapView.mm
@@ -67,8 +67,8 @@ static NSURL *MGLURLForBundledStyleNamed(NSString *styleName)
 
 @property (nonatomic) EAGLContext *context;
 @property (nonatomic) GLKView *glView;
-/** A static view to impersonate `glView` when the app is in the background. */
-@property (nonatomic) UIImageView *glImpersonatingView;
+/** A static view to simulate and obscure `glView` when the app is in the background. */
+@property (nonatomic) UIView *glSnapshotView;
 @property (nonatomic) NSOperationQueue *regionChangeDelegateQueue;
 @property (nonatomic) UIImageView *compass;
 @property (nonatomic) UIImageView *logoBug;
@@ -243,12 +243,6 @@ mbgl::DefaultFileSource *mbglFileSource = nullptr;
 
     _glView.contentMode = UIViewContentModeCenter;
     
-    // create GL impersonating view
-    //
-    _glImpersonatingView = [[UIImageView alloc] initWithFrame:_glView.frame];
-    _glImpersonatingView.autoresizingMask = _glView.autoresizingMask;
-    [self insertSubview:_glImpersonatingView belowSubview:_glView];
-    
     [self setBackgroundColor:[UIColor clearColor]];
 
     // load extensions
@@ -568,8 +562,11 @@ mbgl::DefaultFileSource *mbglFileSource = nullptr;
 // This is the delegate of the GLKView object's display call.
 - (void)glkView:(GLKView *)view drawInRect:(CGRect)rect
 {
-    mbglView->resize(rect.size.width, rect.size.height, view.contentScaleFactor, view.drawableWidth, view.drawableHeight);
-    mbglMap->renderSync();
+    if (!self.glSnapshotView)
+    {
+        mbglView->resize(rect.size.width, rect.size.height, view.contentScaleFactor, view.drawableWidth, view.drawableHeight);
+        mbglMap->renderSync();
+    }
 }
 
 // This gets called when the view dimension changes, e.g. because the device is being rotated.
@@ -592,9 +589,9 @@ mbgl::DefaultFileSource *mbglFileSource = nullptr;
 {
     [MGLMapboxEvents flush];
     
-    UIImage *snapshot = [self.glView snapshot];
-    self.glImpersonatingView.image = snapshot;
-    [self.glView removeFromSuperview];
+    self.glSnapshotView = [self.glView snapshotViewAfterScreenUpdates:YES];
+    self.glSnapshotView.autoresizingMask = self.glView.autoresizingMask;
+    [self insertSubview:self.glSnapshotView aboveSubview:self.glView];
     
     mbglMap->stop();
 
@@ -607,7 +604,8 @@ mbgl::DefaultFileSource *mbglFileSource = nullptr;
 
     mbglMap->start();
     
-    [self insertSubview:self.glView aboveSubview:self.glImpersonatingView];
+    [self.glSnapshotView removeFromSuperview];
+    self.glSnapshotView = nil;
 }
 
 - (void)tintColorDidChange