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perf(ios): cache fontScale to avoid dispatch_sync on every measurement #495

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perf(ios): cache fontScale to avoid dispatch_sync on every measurement #495

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4b06dca
perf(ios): cache fontScale to avoid dispatch_sync on every measurement
hryhoriiK97 Jul 3, 2026
82e8c6f
fix(macos): guard UIContentSizeCategoryDidChangeNotification with !TA…
hryhoriiK97 Jul 3, 2026
c8a5365
fix: use external linkage for ENRMFontScaleForMeasurement
hryhoriiK97 Jul 3, 2026
2b7a4e9
fix: add missing includes for mutex and TargetConditionals
hryhoriiK97 Jul 3, 2026
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39 changes: 30 additions & 9 deletions packages/react-native-enriched-markdown/ios/internals/ShadowMeasurementUtils.h
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Original file line number Diff line number Diff line change
Expand Up @@ -3,8 +3,11 @@
#include "MeasurementCache.h"
#import <Foundation/Foundation.h>
#import <React/RCTUtils.h>
#include <TargetConditionals.h>
#include <algorithm>
#include <atomic>
#include <cmath>
#include <mutex>
#include <react/renderer/core/LayoutConstraints.h>
#include <react/utils/ManagedObjectWrapper.h>

Expand All @@ -15,22 +18,40 @@ namespace facebook::react {
// synchronously joins the layout queue from main. A synchronous
// layout flush from main would deadlock.

static inline CGFloat ENRMFontScaleForMeasurement(bool allowFontScaling)
inline CGFloat ENRMFontScaleForMeasurement(bool allowFontScaling)
{
if (!allowFontScaling) {
return 1.0;
}

__block CGFloat fontScale = 1.0;
void (^readFontScale)(void) = ^{ fontScale = RCTFontSizeMultiplier(); };
static std::atomic<double> cachedScale{0.0};
static std::once_flag flag;
Comment on lines +27 to +28

if ([NSThread isMainThread]) {
readFontScale();
} else {
dispatch_sync(dispatch_get_main_queue(), readFontScale);
}
std::call_once(flag, [] {
__block CGFloat scale = 1.0;
void (^readScale)(void) = ^{ scale = RCTFontSizeMultiplier(); };

return fontScale;
if ([NSThread isMainThread]) {
readScale();
} else {
dispatch_sync(dispatch_get_main_queue(), readScale);
}
cachedScale.store(scale, std::memory_order_relaxed);

#if !TARGET_OS_OSX
dispatch_async(dispatch_get_main_queue(), ^{
[[NSNotificationCenter defaultCenter]
addObserverForName:UIContentSizeCategoryDidChangeNotification
object:nil
queue:[NSOperationQueue mainQueue]
usingBlock:^(NSNotification *) {
cachedScale.store(RCTFontSizeMultiplier(), std::memory_order_relaxed);
}];
});
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#endif
Comment on lines +41 to +51
});

return cachedScale.load(std::memory_order_relaxed);
}

static inline Size ENRMClampMeasuredSize(CGSize size, const LayoutConstraints &layoutConstraints)
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