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Fix: unconditionally rewriting contentScaleFactor/drawableSize every layout pass caused a feedback loop under iOS 26 Smart Display Zoom (#4251)

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This commit is contained in:
Maarten Zonneveld
2026-04-27 11:39:07 +02:00
committed by GitHub
parent 2489914ec2
commit 5bf484bae4
2 changed files with 28 additions and 9 deletions
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2
platform/darwin/src/headless_backend_eagl.mm
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@@ -7,7 +7,7 @@
namespace mbgl {
namespace gl {
class EAGLBackendImpl : public HeadlessBackend::Impl {
class EAGLBackendImpl final : public HeadlessBackend::Impl {
public:
EAGLBackendImpl() {
glContext = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES3];

35
platform/ios/src/MLNMapView+Metal.mm
View File

@@ -106,6 +106,11 @@ public:
id<MTLCommandQueue> commandQueue;
bool presentsWithTransaction = false;
// Cached last-applied values comparing against MTKView's reflected state round-trips
// through UIKit and can defeat the no-op guard under non-integer scale factors.
CGFloat lastAppliedScaleFactor = 0;
CGSize lastAppliedDrawableSize = CGSizeZero;
// We count how often the context was activated/deactivated so that we can truly deactivate it
// after the activation count drops to 0.
NSUInteger activationCount = 0;
@@ -161,6 +166,9 @@ void MLNMapViewMetalImpl::createView() {
resource.mtlView.delegate = resource.delegate;
resource.mtlView.autoresizingMask =
UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
// We own drawable sizing in layoutChanged(); disable MTKView's automatic recompute so
// setting contentScaleFactor cannot race with explicit drawableSize assignment.
resource.mtlView.autoResizeDrawable = NO;
resource.mtlView.contentScaleFactor = scaleFactor;
resource.mtlView.contentMode = UIViewContentModeCenter;
resource.mtlView.colorPixelFormat = MTLPixelFormatBGRA8Unorm;
@@ -215,17 +223,28 @@ UIImage* MLNMapViewMetalImpl::snapshot() {
}
void MLNMapViewMetalImpl::layoutChanged() {
const auto scaleFactor = MLNEffectiveScaleFactorForView(mapView);
const auto screenSize = mapView.bounds.size;
// Fix: unconditionally rewriting contentScaleFactor/drawableSize every
// layout pass caused a feedback loop under iOS 26 Smart Display Zoom (non-integer scale).
// Also skip pre-layout/detached passes — MLNEffectiveScaleFactorForView falls back to
// mainScreen without a window, wrong for CarPlay.
auto& resource = getResource<MLNMapViewMetalRenderableResource>();
const auto viewSize = mapView.bounds.size;
if (!resource.mtlView || viewSize.width <= 0 || viewSize.height <= 0 || !mapView.window) {
return;
}
resource.mtlView.contentScaleFactor = scaleFactor;
resource.mtlView.drawableSize =
CGSizeMake(screenSize.width * scaleFactor, screenSize.height * scaleFactor);
const auto scaleFactor = MLNEffectiveScaleFactorForView(mapView);
const CGSize target = CGSizeMake(std::round(viewSize.width * scaleFactor),
std::round(viewSize.height * scaleFactor));
size = {static_cast<uint32_t>(resource.mtlView.drawableSize.width),
static_cast<uint32_t>(resource.mtlView.drawableSize.height)};
if (scaleFactor != resource.lastAppliedScaleFactor) {
resource.mtlView.contentScaleFactor = resource.lastAppliedScaleFactor = scaleFactor;
}
if (!CGSizeEqualToSize(target, resource.lastAppliedDrawableSize)) {
resource.mtlView.drawableSize = resource.lastAppliedDrawableSize = target;
}
size = {static_cast<uint32_t>(target.width), static_cast<uint32_t>(target.height)};
}
MLNBackendResource* MLNMapViewMetalImpl::getObject() {