[ios, macos] Refcount view activations (#7208)

This adds a ref count to guard against calling activate after it has
already been called. This can happen when a layer is added during
certain map lifecycle methods like MapChangeWillStartRenderingFrame
that also triggers activation. This also protects against issues
related to a deactivation of the context happening in an inner scope
while an outer scope is still expecting to be able to use the context.

1 files changed, 11 insertions, 0 deletions

diff --git a/platform/macos/src/MGLMapView.mm b/platform/macos/src/MGLMapView.mm
index 50b77bc814..ba07048262 100644
--- a/platform/macos/src/MGLMapView.mm
+++ b/platform/macos/src/MGLMapView.mm
@@ -2611,11 +2611,19 @@ public:
     }
 
     void activate() override {
+        if (activationCount++) {
+            return;
+        }
+
         MGLOpenGLLayer *layer = (MGLOpenGLLayer *)nativeView.layer;
         [layer.openGLContext makeCurrentContext];
     }
 
     void deactivate() override {
+        if (--activationCount) {
+            return;
+        }
+
         [NSOpenGLContext clearCurrentContext];
     }
 
@@ -2661,6 +2669,9 @@ private:
 
     /// The current framebuffer of the NSOpenGLLayer we are painting to.
     GLint fbo = 0;
+
+    /// The reference counted count of activation calls
+    NSUInteger activationCount = 0;
 };
 
 @end