From 30c95635112836059f4b76d287913484631563b8 Mon Sep 17 00:00:00 2001
From: Ethan Wong <e1hanw0ng@gmail.com>
Date: Mon, 28 Mar 2022 20:17:53 +0800
Subject: [PATCH] Fix crash of accessing mainScreen from background thread on
 10.11.

---
 SDWebImage/Core/SDGraphicsImageRenderer.m | 16 ++++++++++++++--
 SDWebImage/Core/SDImageGraphics.m         | 16 ++++++++++++++--
 SDWebImage/Core/SDWebImageDefine.m        |  8 +++++++-
 SDWebImage/Private/SDImageAssetManager.m  |  8 +++++++-
 4 files changed, 42 insertions(+), 6 deletions(-)

diff --git a/SDWebImage/Core/SDGraphicsImageRenderer.m b/SDWebImage/Core/SDGraphicsImageRenderer.m
index 03aef3a5..aeda97b1 100644
--- a/SDWebImage/Core/SDGraphicsImageRenderer.m
+++ b/SDWebImage/Core/SDGraphicsImageRenderer.m
@@ -132,7 +132,13 @@
 #elif SD_UIKIT
             CGFloat screenScale = [UIScreen mainScreen].scale;
 #elif SD_MAC
-            CGFloat screenScale = [NSScreen mainScreen].backingScaleFactor;
+            NSScreen *mainScreen = nil;
+            if (@available(macOS 10.12, *)) {
+                mainScreen = [NSScreen mainScreen];
+            } else {
+                mainScreen = [NSScreen screens].firstObject;
+            }
+            CGFloat screenScale = mainScreen.backingScaleFactor ?: 1.0f;
 #endif
             self.scale = screenScale;
             self.opaque = NO;
@@ -166,7 +172,13 @@
 #elif SD_UIKIT
             CGFloat screenScale = [UIScreen mainScreen].scale;
 #elif SD_MAC
-            CGFloat screenScale = [NSScreen mainScreen].backingScaleFactor;
+            NSScreen *mainScreen = nil;
+            if (@available(macOS 10.12, *)) {
+                mainScreen = [NSScreen mainScreen];
+            } else {
+                mainScreen = [NSScreen screens].firstObject;
+            }
+            CGFloat screenScale = mainScreen.backingScaleFactor ?: 1.0f;
 #endif
             self.scale = screenScale;
             self.opaque = NO;
diff --git a/SDWebImage/Core/SDImageGraphics.m b/SDWebImage/Core/SDImageGraphics.m
index f6f89279..d1a1ca65 100644
--- a/SDWebImage/Core/SDImageGraphics.m
+++ b/SDWebImage/Core/SDImageGraphics.m
@@ -17,7 +17,13 @@ static void *kNSGraphicsContextScaleFactorKey;
 static CGContextRef SDCGContextCreateBitmapContext(CGSize size, BOOL opaque, CGFloat scale) {
     if (scale == 0) {
         // Match `UIGraphicsBeginImageContextWithOptions`, reset to the scale factor of the device’s main screen if scale is 0.
-        scale = [NSScreen mainScreen].backingScaleFactor;
+        NSScreen *mainScreen = nil;
+        if (@available(macOS 10.12, *)) {
+            mainScreen = [NSScreen mainScreen];
+        } else {
+            mainScreen = [NSScreen screens].firstObject;
+        }
+        scale = mainScreen.backingScaleFactor ?: 1.0f;
     }
     size_t width = ceil(size.width * scale);
     size_t height = ceil(size.height * scale);
@@ -106,7 +112,13 @@ UIImage * SDGraphicsGetImageFromCurrentImageContext(void) {
     }
     if (!scale) {
         // reset to the scale factor of the device’s main screen if scale is 0.
-        scale = [NSScreen mainScreen].backingScaleFactor;
+        NSScreen *mainScreen = nil;
+        if (@available(macOS 10.12, *)) {
+            mainScreen = [NSScreen mainScreen];
+        } else {
+            mainScreen = [NSScreen screens].firstObject;
+        }
+        scale = mainScreen.backingScaleFactor ?: 1.0f;
     }
     NSImage *image = [[NSImage alloc] initWithCGImage:imageRef scale:scale orientation:kCGImagePropertyOrientationUp];
     CGImageRelease(imageRef);
diff --git a/SDWebImage/Core/SDWebImageDefine.m b/SDWebImage/Core/SDWebImageDefine.m
index 845730f0..aee8ca4d 100644
--- a/SDWebImage/Core/SDWebImageDefine.m
+++ b/SDWebImage/Core/SDWebImageDefine.m
@@ -28,7 +28,13 @@ inline CGFloat SDImageScaleFactorForKey(NSString * _Nullable key) {
 #elif SD_UIKIT
     if ([[UIScreen mainScreen] respondsToSelector:@selector(scale)])
 #elif SD_MAC
-    if ([[NSScreen mainScreen] respondsToSelector:@selector(backingScaleFactor)])
+    NSScreen *mainScreen = nil;
+    if (@available(macOS 10.12, *)) {
+        mainScreen = [NSScreen mainScreen];
+    } else {
+        mainScreen = [NSScreen screens].firstObject;
+    }
+    if ([mainScreen respondsToSelector:@selector(backingScaleFactor)])
 #endif
     {
         // a@2x.png -> 8
diff --git a/SDWebImage/Private/SDImageAssetManager.m b/SDWebImage/Private/SDImageAssetManager.m
index 50a4da94..7bca347c 100644
--- a/SDWebImage/Private/SDImageAssetManager.m
+++ b/SDWebImage/Private/SDImageAssetManager.m
@@ -18,7 +18,13 @@ static NSArray *SDBundlePreferredScales() {
 #elif SD_UIKIT
         CGFloat screenScale = [UIScreen mainScreen].scale;
 #elif SD_MAC
-        CGFloat screenScale = [NSScreen mainScreen].backingScaleFactor;
+      NSScreen *mainScreen = nil;
+      if (@available(macOS 10.12, *)) {
+          mainScreen = [NSScreen mainScreen];
+      } else {
+          mainScreen = [NSScreen screens].firstObject;
+      }
+      CGFloat screenScale = mainScreen.backingScaleFactor ?: 1.0f;
 #endif
         if (screenScale <= 1) {
             scales = @[@1,@2,@3];