macOS: Introduce QMacKeyValueObserver and use in theme and style

Change-Id: I2d21c883628933543ae5a66b694ff7503119bc4a
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
 
 

2 files changed, 86 insertions, 0 deletions

diff --git a/src/corelib/kernel/qcore_mac_objc.mm b/src/corelib/kernel/qcore_mac_objc.mm
index 4550891e2a..9139b372a8 100644
--- a/src/corelib/kernel/qcore_mac_objc.mm
+++ b/src/corelib/kernel/qcore_mac_objc.mm
@@ -514,5 +514,36 @@ Q_CONSTRUCTOR_FUNCTION(qt_apple_check_os_version);
 
 // -------------------------------------------------------------------------
 
+void QMacKeyValueObserver::addObserver()
+{
+    [object addObserver:observer forKeyPath:keyPath
+        options:NSKeyValueObservingOptionNew context:callback.get()];
+}
+
+void QMacKeyValueObserver::removeObserver() {
+    if (object)
+        [object removeObserver:observer forKeyPath:keyPath context:callback.get()];
+    object = nil;
+}
+
+KeyValueObserver *QMacKeyValueObserver::observer = [[KeyValueObserver alloc] init];
+
+QT_END_NAMESPACE
+@implementation KeyValueObserver
+- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object
+        change:(NSDictionary<NSKeyValueChangeKey, id> *)change context:(void *)context
+{
+    Q_UNUSED(keyPath);
+    Q_UNUSED(object);
+    Q_UNUSED(change);
+
+    (*reinterpret_cast<QMacKeyValueObserver::Callback*>(context))();
+}
+@end
+QT_BEGIN_NAMESPACE
+
+// -------------------------------------------------------------------------
+
+
 QT_END_NAMESPACE
 
diff --git a/src/corelib/kernel/qcore_mac_p.h b/src/corelib/kernel/qcore_mac_p.h
index 2428faed15..8f4c96bbd6 100644
--- a/src/corelib/kernel/qcore_mac_p.h
+++ b/src/corelib/kernel/qcore_mac_p.h
@@ -67,6 +67,7 @@
 
 #ifdef __OBJC__
 #include <Foundation/Foundation.h>
+#include <functional>
 #endif
 
 #include "qstring.h"
@@ -334,6 +335,60 @@ public:
 private:
     id observer = nil;
 };
+
+QT_END_NAMESPACE
+@interface QT_MANGLE_NAMESPACE(KeyValueObserver) : NSObject
+@end
+QT_NAMESPACE_ALIAS_OBJC_CLASS(KeyValueObserver);
+QT_BEGIN_NAMESPACE
+
+class Q_CORE_EXPORT QMacKeyValueObserver
+{
+public:
+    using Callback = std::function<void()>;
+
+    QMacKeyValueObserver() {}
+
+    // Note: QMacKeyValueObserver must not outlive the object observed!
+    QMacKeyValueObserver(id object, NSString *keyPath, Callback callback)
+        : object(object), keyPath(keyPath), callback(new Callback(callback)) { addObserver(); }
+
+    QMacKeyValueObserver(const QMacKeyValueObserver &other)
+         : QMacKeyValueObserver(other.object, other.keyPath, *other.callback.get()) {}
+
+    QMacKeyValueObserver(QMacKeyValueObserver &&other) { swap(other, *this); }
+
+    ~QMacKeyValueObserver() { removeObserver(); }
+
+    QMacKeyValueObserver &operator=(const QMacKeyValueObserver &other) {
+        QMacKeyValueObserver tmp(other);
+        swap(tmp, *this);
+        return *this;
+    }
+
+    QMacKeyValueObserver &operator=(QMacKeyValueObserver &&other) {
+        QMacKeyValueObserver tmp(std::move(other));
+        swap(tmp, *this);
+        return *this;
+    }
+
+    void removeObserver();
+
+private:
+    void swap(QMacKeyValueObserver &first, QMacKeyValueObserver &second) {
+        std::swap(first.object, second.object);
+        std::swap(first.keyPath, second.keyPath);
+        std::swap(first.callback, second.callback);
+    }
+
+    void addObserver();
+
+    id object = nil;
+    NSString *keyPath = nullptr;
+    std::unique_ptr<Callback> callback;
+
+    static KeyValueObserver *observer;
+};
 #endif
 
 // -------------------------------------------------------------------------