└── PSPDFUIKitMainThreadGuard.m


/PSPDFUIKitMainThreadGuard.m:
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 1 | // Taken from the commercial iOS PDF framework http://pspdfkit.com.
 2 | // Copyright (c) 2014 Peter Steinberger, PSPDFKit GmbH. All rights reserved.
 3 | // Licensed under MIT (http://opensource.org/licenses/MIT)
 4 | //
 5 | // You should only use this in debug builds. It doesn't use private API, but I wouldn't ship it.
 6 | 
 7 | #if DEBUG
 8 | 
 9 | @import Foundation;
10 | @import UIKit;
11 | #import <objc/runtime.h>
12 | #import <objc/message.h>
13 | 
14 | #define PROPERTY(propName) NSStringFromSelector(@selector(propName))
15 | 
16 | #define PSPDFAssert(expression, ...) \
17 | do { if(!(expression)) { \
18 | NSLog(@"%@", [NSString stringWithFormat: @"Assertion failure: %s in %s on line %s:%d. %@", #expression, __PRETTY_FUNCTION__, __FILE__, __LINE__, [NSString stringWithFormat:@"" __VA_ARGS__]]); \
19 | abort(); }} while(0)
20 | 
21 | // http://www.mikeash.com/pyblog/friday-qa-2010-01-29-method-replacement-for-fun-and-profit.html
22 | BOOL PSPDFReplaceMethodWithBlock(Class c, SEL origSEL, SEL newSEL, id block) {
23 |     PSPDFAssert(c && origSEL && newSEL && block);
24 |     if ([c instancesRespondToSelector:newSEL]) return YES; // Selector already implemented, skip silently.
25 | 
26 |     Method origMethod = class_getInstanceMethod(c, origSEL);
27 | 
28 |     // Add the new method.
29 |     IMP impl = imp_implementationWithBlock(block);
30 |     if (!class_addMethod(c, newSEL, impl, method_getTypeEncoding(origMethod))) {
31 |         NSLog(@"Failed to add method: %@ on %@", NSStringFromSelector(newSEL), c);
32 |         return NO;
33 |     }else {
34 |         Method newMethod = class_getInstanceMethod(c, newSEL);
35 | 
36 |         // If original doesn't implement the method we want to swizzle, create it.
37 |         if (class_addMethod(c, origSEL, method_getImplementation(newMethod), method_getTypeEncoding(origMethod))) {
38 |             class_replaceMethod(c, newSEL, method_getImplementation(origMethod), method_getTypeEncoding(newMethod));
39 |         }else {
40 |             method_exchangeImplementations(origMethod, newMethod);
41 |         }
42 |     }
43 |     return YES;
44 | }
45 | 
46 | SEL _PSPDFPrefixedSelector(SEL selector) {
47 |     return NSSelectorFromString([NSString stringWithFormat:@"pspdf_%@", NSStringFromSelector(selector)]);
48 | }
49 | 
50 | void PSPDFAssertIfNotMainThread(void) {
51 |     PSPDFAssert(NSThread.isMainThread, @"\nERROR: All calls to UIKit need to happen on the main thread. You have a bug in your code. Use dispatch_async(dispatch_get_main_queue(), ^{ ... }); if you're unsure what thread you're in.\n\nBreak on PSPDFAssertIfNotMainThread to find out where.\n\nStacktrace: %@", NSThread.callStackSymbols);
52 | }
53 | 
54 | __attribute__((constructor)) static void PSPDFUIKitMainThreadGuard(void) {
55 |     @autoreleasepool {
56 |         for (NSString *selStr in @[PROPERTY(setNeedsLayout), PROPERTY(setNeedsDisplay), PROPERTY(setNeedsDisplayInRect:)]) {
57 |             SEL selector = NSSelectorFromString(selStr);
58 |             SEL newSelector = NSSelectorFromString([NSString stringWithFormat:@"pspdf_%@", selStr]);
59 |             if ([selStr hasSuffix:@":"]) {
60 |                 PSPDFReplaceMethodWithBlock(UIView.class, selector, newSelector, ^(__unsafe_unretained UIView *_self, CGRect r) {
61 |                     // Check for window, since *some* UIKit methods are indeed thread safe.
62 |                     // https://developer.apple.com/library/ios/#releasenotes/General/WhatsNewIniPhoneOS/Articles/iPhoneOS4.html
63 |                     /*
64 |                      Drawing to a graphics context in UIKit is now thread-safe. Specifically:
65 | 
66 |                      The routines used to access and manipulate the graphics context can now correctly handle contexts residing on different threads.
67 | 
68 |                      String and image drawing is now thread-safe.
69 | 
70 |                      Using color and font objects in multiple threads is now safe to do.
71 |                      */
72 |                     if (_self.window) PSPDFAssertIfNotMainThread();
73 |                     ((void ( *)(id, SEL, CGRect))objc_msgSend)(_self, newSelector, r);
74 |                 });
75 |             }else {
76 |                 PSPDFReplaceMethodWithBlock(UIView.class, selector, newSelector, ^(__unsafe_unretained UIView *_self) {
77 |                     if (_self.window) {
78 |                         if (!NSThread.isMainThread) {
79 | #pragma clang diagnostic push
80 | #pragma clang diagnostic ignored "-Wdeprecated-declarations"
81 |                             dispatch_queue_t queue = dispatch_get_current_queue();
82 | #pragma clang diagnostic pop
83 |                             // iOS 8 layouts the MFMailComposeController in a background thread on an UIKit queue.
84 |                             // https://github.com/PSPDFKit/PSPDFKit/issues/1423
85 |                             if (!queue || !strstr(dispatch_queue_get_label(queue), "UIKit")) {
86 |                                 PSPDFAssertIfNotMainThread();
87 |                             }
88 |                         }
89 |                     }
90 |                     ((void ( *)(id, SEL))objc_msgSend)(_self, newSelector);
91 |                 });
92 |             }
93 |         }
94 |     }
95 | }
96 | 
97 | #endif


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