Port cef_simple_mac.mm to cefsimple in this project

[dotmrjosh]

Right clicking anywhere in the page triggers a crash.

Info:

• Checkout: 0a4a701e1e08c8b2f2cae53a24edc1ad32ce5034
• Uname: Darwin xxxxx.local 23.5.0 Darwin Kernel Version 23.5.0: Wed May 1 20:16:51 PDT 2024; root:xnu-10063.121.3~5/RELEASE_ARM64_T8103 arm64
• Version: 135.0.20

Log output:

launch browser process
[0421/003350.706042:WARNING:resource_util.cc(83)] Please customize CefSettings.root_cache_path for your application. Use of the default value may lead to unintende
d process singleton behavior.
[11844:5647513:0421/003352.933582:ERROR:keychain_password_mac.mm(103)] Keychain lookup failed: Error Domain=NSOSStatusErrorDomain Code=-128 "userCanceledErr" (-128
)
[11844:5647590:0421/003353.031218:ERROR:login_database_async_helper.cc(114)] Encryption is not available.
[11844:5647600:0421/003353.031228:ERROR:login_database_async_helper.cc(114)] Encryption is not available.
cef context intiialized
*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSApplication isHandlingSendEvent]: unrecognized selector sent to instance 0
x118000e1200'
*** First throw call stack:
(
        0   CoreFoundation                      0x00000001876d32ec __exceptionPreprocess + 176
        1   libobjc.A.dylib                     0x00000001871ba788 objc_exception_throw + 60
        2   CoreFoundation                      0x000000018778556c -[NSObject(NSObject) __retain_OA] + 0
        3   CoreFoundation                      0x000000018763cf3c ___forwarding___ + 1580
        4   CoreFoundation                      0x000000018763c850 _CF_forwarding_prep_0 + 96
        5   Chromium Embedded Framework         0x0000000111005e38 ChromeWebAppShortcutCopierMain + 5528552
        6   Chromium Embedded Framework         0x0000000112700f44 rust_png$cxxbridge1$ResultOfWriter$operator$sizeof + 831772
        7   Chromium Embedded Framework         0x0000000115d35970 fontations_ffi$cxxbridge1$BridgeNormalizedCoords$operator$sizeof + 56686880
        8   Chromium Embedded Framework         0x0000000115d35e38 fontations_ffi$cxxbridge1$BridgeNormalizedCoords$operator$sizeof + 56688104
        9   Chromium Embedded Framework         0x000000010d00db84 cxxbridge1$rust_vec$u8$set_len + 54412
        10  Chromium Embedded Framework         0x000000010f909328 fontations_ffi$cxxbridge1$has_any_color_table + 24428300
        11  Chromium Embedded Framework         0x000000010f776b48 fontations_ffi$cxxbridge1$has_any_color_table + 22779692
        12  Chromium Embedded Framework         0x000000010de0fcf4 fontations_ffi$cxxbridge1$BridgeMappingIndex$operator$sizeof + 4578388
        13  Chromium Embedded Framework         0x00000001111357a8 ChromeWebAppShortcutCopierMain + 6772056
        14  Chromium Embedded Framework         0x000000011113ac28 ChromeWebAppShortcutCopierMain + 6793688
        15  Chromium Embedded Framework         0x0000000111137090 ChromeWebAppShortcutCopierMain + 6778432
        16  Chromium Embedded Framework         0x00000001116cba90 ChromeWebAppShortcutCopierMain + 12630080
        17  Chromium Embedded Framework         0x0000000110f8ac3c ChromeWebAppShortcutCopierMain + 5024236
        18  Chromium Embedded Framework         0x0000000110faadb8 ChromeWebAppShortcutCopierMain + 5155688
        19  Chromium Embedded Framework         0x0000000110ff61dc ChromeWebAppShortcutCopierMain + 5463948
        20  Chromium Embedded Framework         0x000000010cdbce18 Chromium Embedded Framework + 2100760
        21  Chromium Embedded Framework         0x0000000110ff5138 ChromeWebAppShortcutCopierMain + 5459688
        22  CoreFoundation                      0x000000018765e4d8 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 28
        23  CoreFoundation                      0x000000018765e46c __CFRunLoopDoSource0 + 176
        24  CoreFoundation                      0x000000018765e1dc __CFRunLoopDoSources0 + 244
        25  CoreFoundation                      0x000000018765cdc8 __CFRunLoopRun + 828
        26  CoreFoundation                      0x000000018765c434 CFRunLoopRunSpecific + 608
        27  HIToolbox                           0x0000000191e0019c RunCurrentEventLoopInMode + 292
        28  HIToolbox                           0x0000000191dfffd8 ReceiveNextEventCommon + 648
        29  HIToolbox                           0x0000000191dffd30 _BlockUntilNextEventMatchingListInModeWithFilter + 76
        30  AppKit                              0x000000018aebbd68 _DPSNextEvent + 660
        31  AppKit                              0x000000018b6b1808 -[NSApplication(NSEventRouting) _nextEventMatchingEventMask:untilDate:inMode:dequeue:] + 700
        32  AppKit                              0x000000018aeaf09c -[NSApplication run] + 476
        33  Chromium Embedded Framework         0x0000000110ff706c ChromeWebAppShortcutCopierMain + 5467676
        34  Chromium Embedded Framework         0x0000000110ff4af4 ChromeWebAppShortcutCopierMain + 5458084
        35  Chromium Embedded Framework         0x0000000110fab634 ChromeWebAppShortcutCopierMain + 5157860
        36  Chromium Embedded Framework         0x0000000110f6f17c ChromeWebAppShortcutCopierMain + 4910892
        37  Chromium Embedded Framework         0x000000010cf54fd4 blink$cxxbridge1$crash_in_rust_with_overflow + 281592
        38  cefsimple                           0x0000000100d7f97c _ZN3cef8bindings20aarch64_apple_darwin16run_message_loop17hb1871c31b5591355E + 16
        39  cefsimple                           0x0000000100d6bd4c _ZN9cefsimple4main17hd71f81c236a3f2a9E + 1512
        40  cefsimple                           0x0000000100d71e3c _ZN4core3ops8function6FnOnce9call_once17hdceb88c7d2a8d9d3E + 20
        41  cefsimple                           0x0000000100d694c4 _ZN3std3sys9backtrace28__rust_begin_short_backtrace17h8af2fafe553f31b1E + 24
        42  cefsimple                           0x0000000100d7180c _ZN3std2rt10lang_start28_$u7b$$u7b$closure$u7d$$u7d$17h10db5ec3802a203eE + 28
        43  cefsimple                           0x0000000100dc2f98 _ZN3std2rt19lang_start_internal17h95cf27b851151b9cE + 888
        44  cefsimple                           0x0000000100d717e4 _ZN3std2rt10lang_start17hed2feeb4880f1160E + 84
        45  cefsimple                           0x0000000100d6bf00 main + 36
        46  dyld                                0x00000001871f60e0 start + 2360
)
zsh: trace trap  ./target/debug/examples/cefsimple.app/Contents/MacOS/cefsimple

[wravery]

Looks like this is just a bug in this version of "cefsimple," we don't have the equivalent of the SimpleApplication/NSApplication defined in cefsimple_mac.mm.

This should be fixed as part of rewriting cefsimple to be a full port of the C++ version in CEF itself, whenever we get around to it. I'm tempted to make this the tracking bug for that work.

[Q1zin]

The error sounds like Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSApplication isHandlingSendEvent]: unrecognized selector sent to instance ...'

As @wravery already said, the problem is that it is not fully implemented cefsimple_mac.mm, namely the isHandlingSendEvent method (you will also need set_handling_send_event), it can be added manually

The solution to this problem is (run the extend_nswindow_class function as early as possible in your code):

extern "C" fn set_handling_send_event(_this: *mut AnyObject, _cmd: Sel, _handling_send_event: Bool) {}

extern "C" fn is_handling_send_event(_this: *mut AnyObject, _cmd: Sel) -> Bool {
    Bool::YES
}

unsafe fn extend_nswindow_class() {
    let ns_window = class!(NSApplication);

    let encoding_get = std::ffi::CStr::from_bytes_with_nul(b"B@:\0").unwrap();
    let encoding_set = std::ffi::CStr::from_bytes_with_nul(b"v@:B\0").unwrap();

    let _ = objc2::ffi::class_addMethod(
        ns_window as *const _ as *mut _,
        sel!(isHandlingSendEvent),
        std::mem::transmute(is_handling_send_event as *const ()),
        encoding_get.as_ptr(),
    );

    let _ = objc2::ffi::class_addMethod(
        ns_window as *const _ as *mut _,
        sel!(setHandlingSendEvent:),
        std::mem::transmute(set_handling_send_event as *const ()),
        encoding_set.as_ptr(),
    );
}

ps. If you have a similar problem, but here is [NSApplication isHandlingSendEvent], not NSApplication, but something else, then replace the corresponding class name in the code above let ns_window = class!(NSApplication);

[tasuren]

Hi, I've done some investigation into this issue and would like to propose a path forward for porting cefsimple_mac.mm.

As has been discussed, the root cause of the right-click crash is that our cefsimple example lacks an NSApplication subclass that correctly handles events required by Chromium. The official cefsimple solves this with a SimpleApplication class that conforms to the CefAppProtocol.

I agree that the best solution is to create a proper port of this SimpleApplication. A key first step is to create Rust bindings for the CefAppProtocol and its parent protocols. This can be done cleanly using the objc2 crate like so:

extern_protocol!(
    pub unsafe trait CrAppProtocol {
        #[unsafe(method(isHandlingSendEvent))]
        unsafe fn is_handling_send_event(&self) -> Bool;
    }
);

extern_protocol!(
    pub unsafe trait CrAppControlProtocol: CrAppProtocol {
        #[unsafe(method(setHandlingSendEvent:))]
        unsafe fn set_handling_send_event(&self, handling_send_event: Bool);
    }
);

extern_protocol!(
    pub unsafe trait CefAppProtocol: CrAppControlProtocol {}
);

With these bindings, we can define an NSApplication subclass in Rust that properly conforms to the protocol, which I've confirmed locally resolves the crash.

Additionally, @Q1zin's workaround of manually adding methods with class_addMethod fixes the crash in release builds of CEF but wouldn't pass the DCHECK in debug builds. But we can use this workaround as a patch in release builds until porting cefsimple_mac.mm is over.

[71702:370561:0817/132939.582378:FATAL:base/mac/scoped_sending_event.mm:13] DCHECK failed: [app_ conformsToProtocol:@protocol(CrAppControlProtocol)]. 

---

The Key Decision Needed

This brings us to one key decision before moving forward with an implementation:

Where should these protocol bindings live?

Since CefAppProtocol is part of the CEF framework (include/cef_application_mac.h), we could add these bindings to the core cef-rs crate itself. On the other hand, since they are macOS-specific, we could simply implement them within the cefsimple example as a demonstration.

My personal opinion is that providing the bindings in cef-rs would be helpful for any user targeting macOS, but I'm open to discussion. Instead of using the objc2 crate, We can also create the SimpleApplication via Objective-C code and link it with Rust code.

What are your thoughts? Deciding on this will give us a clear path to finally fixing this issue.

To provide a concrete example, I've implemented the protocol bindings in the cef_dll_sys crate in my fork and partially ported SimpleApplication to the cefsimple example. Please feel free to use it as a reference:

• CefAppProtocol ported from here
• SimpleApplication ported from here
• SimpleApplication usage ported from here

[wravery]

Where should these protocol bindings live?

Since CefAppProtocol is part of the CEF framework (include/cef_application_mac.h), we could add these bindings to the core cef-rs crate itself. On the other hand, since they are macOS-specific, we could simply implement them within the cefsimple example as a demonstration.

My personal opinion is that providing the bindings in cef-rs would be helpful for any user targeting macOS, but I'm open to discussion. Instead of using the objc2 crate, We can also create the SimpleApplication via Objective-C code and link it with Rust code.

What are your thoughts? Deciding on this will give us a clear path to finally fixing this issue.

To provide a concrete example, I've implemented the protocol bindings in the cef_dll_sys crate in my fork and partially ported SimpleApplication to the cefsimple example. Please feel free to use it as a reference:

I agree, it would be good to include these in the crate itself, although I recommend putting them in the cef crate rather than the underlying cef-dll-sys crate. There are already precedents there for Mac-only modules like cef::library_loader and cef::sandbox which do similar things.

I think even having a concrete implementation of SimpleApplication with safe defaults makes sense, perhaps with doc comments matching the original cefsimple sample implementation to explain when/why a consumer might want to implement their own. Most of the time, I think users should be fine with SimpleApplication, unless they're integrating with another app that already has an app delegate that they need to extend with these protocols.

[tasuren]

Hi all,

Apologies for the delay in my reply.

I've done porting the SimpleApplication to Rust, which resolves the original right-click crash on macOS. Following our discussion, I've added protocol bindings and a default SimpleApplication implementation to cef::application_mac in my fork. This approach is similar to existing platform-specific modules like cef::library_loader.

The complete implementation is available on my branch for you to review:
https://github.com/tasuren/cef-rs/blob/5d2f45910f7fddf9704f1ecfdb2f4a0a2a348691/cef/src/application_mac.rs

And it can be used without Objective-C knowledge:

// Call it at beginning of application main function.
#[cfg(target_os = "macos")]
cef::application_mac::SimpleApplication::init().unwrap();

Please let me know your thoughts on this approach. If everything looks good, I can open a Pull Request.

[wravery]

That looks good, please go ahead with the PR. 👍🏼