Allow graceful symbol degration to support iOS 15+ at runtime

platforms/ios/src/event.rs

@@ -11,15 +11,18 @@ use objc2_foundation::{
 };
 use objc2_ui_kit::{
     UIAccessibilityAnnouncementNotification, UIAccessibilityLayoutChangedNotification,
-    UIAccessibilityNotifications, UIAccessibilityPostNotification, UIAccessibilityPriority,
-    UIAccessibilityPriorityHigh, UIAccessibilityPriorityLow,
-    UIAccessibilityScreenChangedNotification, UIAccessibilitySpeechAttributeAnnouncementPriority,
-    UIAccessibilitySpeechAttributeQueueAnnouncement,
+    UIAccessibilityNotifications, UIAccessibilityPostNotification,
+    UIAccessibilityScreenChangedNotification, UIAccessibilitySpeechAttributeQueueAnnouncement,
 };
 use std::collections::VecDeque;
 use std::rc::Rc;
 
-use crate::{context::Context, filters::filter, node::PlatformNode};
+use crate::{
+    context::Context,
+    filters::filter,
+    node::PlatformNode,
+    util::{announcement_priority_high, announcement_priority_key, announcement_priority_low},
+};
 
 pub(crate) enum QueuedEvent {
     Generic {
@@ -29,19 +32,15 @@ pub(crate) enum QueuedEvent {
     NodeDestroyed(NodeId),
     Announcement {
         text: String,
-        priority: &'static UIAccessibilityPriority,
+        assertive: bool,
     },
 }
 
 impl QueuedEvent {
     fn live_region_announcement(text: String, priority: Live) -> Self {
         Self::Announcement {
             text,
-            priority: if priority == Live::Assertive {
-                unsafe { UIAccessibilityPriorityHigh }
-            } else {
-                unsafe { UIAccessibilityPriorityLow }
-            },
+            assertive: priority == Live::Assertive,
         }
     }
 
@@ -61,32 +60,46 @@ impl QueuedEvent {
             Self::NodeDestroyed(node_id) => {
                 context.remove_platform_node(node_id);
             }
-            Self::Announcement { text, priority } => {
-                Self::raise_announcement(&text, priority);
+            Self::Announcement { text, assertive } => {
+                Self::raise_announcement(&text, assertive);
             }
         }
     }
 
-    fn raise_announcement(text: &str, priority: &'static UIAccessibilityPriority) {
+    fn raise_announcement(text: &str, assertive: bool) {
         let text = NSString::from_str(text);
-        let mut attrs: objc2::rc::Retained<NSMutableDictionary<NSAttributedStringKey, AnyObject>> =
-            NSMutableDictionary::new();
-        unsafe {
-            attrs.setObject_forKey(
-                priority,
-                ProtocolObject::from_ref(UIAccessibilitySpeechAttributeAnnouncementPriority),
-            );
-            attrs.setObject_forKey(
-                &*NSNumber::new_bool(true),
-                ProtocolObject::from_ref(UIAccessibilitySpeechAttributeQueueAnnouncement),
-            );
-        }
-        let announcement = unsafe { NSAttributedString::new_with_attributes(&text, &attrs) };
-        unsafe {
-            UIAccessibilityPostNotification(
-                UIAccessibilityAnnouncementNotification,
-                Some(&announcement),
-            );
+        let priority = if assertive {
+            announcement_priority_high()
+        } else {
+            announcement_priority_low()
+        };
+        match (priority, announcement_priority_key()) {
+            (Some(priority), Some(priority_key)) => {
+                let mut attrs: objc2::rc::Retained<
+                    NSMutableDictionary<NSAttributedStringKey, AnyObject>,
+                > = NSMutableDictionary::new();
+                unsafe {
+                    attrs.setObject_forKey(priority, ProtocolObject::from_ref(priority_key));
+                    attrs.setObject_forKey(
+                        &*NSNumber::new_bool(true),
+                        ProtocolObject::from_ref(UIAccessibilitySpeechAttributeQueueAnnouncement),
+                    );
+                }
+                let announcement =
+                    unsafe { NSAttributedString::new_with_attributes(&text, &attrs) };
+                unsafe {
+                    UIAccessibilityPostNotification(
+                        UIAccessibilityAnnouncementNotification,
+                        Some(&announcement),
+                    );
+                }
+            }
+            _ => unsafe {
+                UIAccessibilityPostNotification(
+                    UIAccessibilityAnnouncementNotification,
+                    Some(&*text),
+                );
+            },
         }
     }
 }

platforms/ios/src/node.rs

@@ -23,14 +23,14 @@ use objc2_ui_kit::{
     UIAccessibilityTraitButton, UIAccessibilityTraitHeader, UIAccessibilityTraitImage,
     UIAccessibilityTraitLink, UIAccessibilityTraitNone, UIAccessibilityTraitNotEnabled,
     UIAccessibilityTraitSearchField, UIAccessibilityTraitSelected, UIAccessibilityTraitStaticText,
-    UIAccessibilityTraitToggleButton, UIAccessibilityTraitUpdatesFrequently, UIAccessibilityTraits,
+    UIAccessibilityTraitUpdatesFrequently, UIAccessibilityTraits,
 };
 use std::rc::{Rc, Weak};
 
 use crate::{
     context::Context,
     filters::{filter, filter_for_is_accessibility_element},
-    util::{UIAccessibilityExpandedStatus, to_cg_rect, to_screen_rect},
+    util::{UIAccessibilityExpandedStatus, to_cg_rect, to_screen_rect, toggle_button_trait},
 };
 
 #[derive(Debug, PartialEq)]
@@ -139,7 +139,7 @@ impl NodeWrapper<'_> {
         }
 
         if self.0.toggled().is_some() {
-            traits |= unsafe { UIAccessibilityTraitToggleButton };
+            traits |= toggle_button_trait();
         }
 
         if self.0.is_selected() == Some(true) {
@@ -710,7 +710,7 @@ mod tests {
         node.set_toggled(Toggled::False);
         let t = node_traits(&node);
         assert!(t & unsafe { UIAccessibilityTraitButton } != 0);
-        assert!(t & unsafe { UIAccessibilityTraitToggleButton } != 0);
+        assert!(t & toggle_button_trait() != 0);
     }
 
     #[test]
@@ -719,7 +719,7 @@ mod tests {
         node.set_toggled(Toggled::True);
         let t = node_traits(&node);
         assert!(t & unsafe { UIAccessibilityTraitButton } != 0);
-        assert!(t & unsafe { UIAccessibilityTraitToggleButton } != 0);
+        assert!(t & toggle_button_trait() != 0);
     }
 
     #[test]
@@ -745,7 +745,7 @@ mod tests {
             let mut node = NodeBuilder::new(Role::CheckBox);
             node.set_toggled(toggled);
             assert!(
-                node_traits(&node) & unsafe { UIAccessibilityTraitToggleButton } != 0,
+                node_traits(&node) & toggle_button_trait() != 0,
                 "toggled {toggled:?}",
             );
         }
@@ -821,7 +821,7 @@ mod tests {
         assert!(t & unsafe { UIAccessibilityTraitButton } != 0);
         assert!(t & unsafe { UIAccessibilityTraitNotEnabled } == 0);
         assert!(t & unsafe { UIAccessibilityTraitSelected } == 0);
-        assert!(t & unsafe { UIAccessibilityTraitToggleButton } == 0);
+        assert!(t & toggle_button_trait() == 0);
         assert!(t & unsafe { UIAccessibilityTraitUpdatesFrequently } == 0);
         assert!(t & unsafe { UIAccessibilityTraitAllowsDirectInteraction } == 0);
     }
@@ -864,7 +864,7 @@ mod tests {
         node.set_disabled();
         let t = node_traits(&node);
         assert!(t & unsafe { UIAccessibilityTraitButton } != 0);
-        assert!(t & unsafe { UIAccessibilityTraitToggleButton } != 0);
+        assert!(t & toggle_button_trait() != 0);
         assert!(t & unsafe { UIAccessibilityTraitNotEnabled } != 0);
     }
 

platforms/ios/src/util.rs

@@ -6,8 +6,13 @@
 use accesskit::Point;
 use accesskit_consumer::Node;
 use objc2::encode::{Encode, Encoding, RefEncode};
-use objc2_foundation::{CGPoint, CGRect, CGSize, NSInteger};
-use objc2_ui_kit::{UIAccessibilityConvertFrameToScreenCoordinates, UICoordinateSpace, UIView};
+use objc2_foundation::{CGPoint, CGRect, CGSize, NSAttributedStringKey, NSInteger, NSString};
+use objc2_ui_kit::{
+    UIAccessibilityConvertFrameToScreenCoordinates, UIAccessibilityPriority, UIAccessibilityTraits,
+    UICoordinateSpace, UIView,
+};
+use std::ffi::{c_char, c_void};
+use std::sync::OnceLock;
 
 // TODO: Remove once we update to objc2 0.6
 #[repr(transparent)]
@@ -56,3 +61,44 @@ pub(crate) fn to_cg_rect(view: &UIView, rect: accesskit::Rect) -> CGRect {
     };
     to_screen_rect(view, local_rect)
 }
+
+const RTLD_DEFAULT: *mut c_void = -2isize as *mut c_void;
+
+unsafe extern "C" {
+    fn dlsym(handle: *mut c_void, symbol: *const c_char) -> *mut c_void;
+}
+
+pub(crate) fn toggle_button_trait() -> UIAccessibilityTraits {
+    static TRAIT: OnceLock<UIAccessibilityTraits> = OnceLock::new();
+    *TRAIT.get_or_init(|| unsafe {
+        let symbol = dlsym(RTLD_DEFAULT, c"UIAccessibilityTraitToggleButton".as_ptr());
+        if symbol.is_null() {
+            0
+        } else {
+            *symbol.cast::<UIAccessibilityTraits>()
+        }
+    })
+}
+
+fn resolve_nsstring_const(symbol: *const c_char) -> Option<&'static NSString> {
+    unsafe {
+        let slot = dlsym(RTLD_DEFAULT, symbol);
+        if slot.is_null() {
+            None
+        } else {
+            (*slot.cast::<*const NSString>()).as_ref()
+        }
+    }
+}
+
+pub(crate) fn announcement_priority_high() -> Option<&'static UIAccessibilityPriority> {
+    resolve_nsstring_const(c"UIAccessibilityPriorityHigh".as_ptr())
+}
+
+pub(crate) fn announcement_priority_low() -> Option<&'static UIAccessibilityPriority> {
+    resolve_nsstring_const(c"UIAccessibilityPriorityLow".as_ptr())
+}
+
+pub(crate) fn announcement_priority_key() -> Option<&'static NSAttributedStringKey> {
+    resolve_nsstring_const(c"UIAccessibilitySpeechAttributeAnnouncementPriority".as_ptr())
+}