Introduce ViewGuard: A weak ptr to View

src/CMakeLists.txt

@@ -98,6 +98,8 @@ set(DOCKSLIBS_SRCS
     controllers/TabBar.h
     View.cpp
     View.h
+    ViewGuard.cpp
+    ViewGuard.h
     ViewWrapper.cpp
     ViewWrapper.h
     Controller.cpp

src/ViewGuard.cpp

@@ -0,0 +1,57 @@
+#include "ViewGuard.h"
+#include "View.h"
+
+using namespace KDDockWidgets;
+
+ViewGuard::ViewGuard(View *view)
+    : v(view && view->inDtor() ? nullptr : view)
+{
+    if (v) {
+        m_onDestroy = v->beingDestroyed.connect([this] {
+            v = nullptr;
+        });
+    }
+}
+
+ViewGuard::operator bool() const
+{
+    return !isNull();
+}
+
+bool ViewGuard::isNull() const
+{
+    return v == nullptr;
+}
+
+View *ViewGuard::operator->()
+{
+    return v;
+}
+
+void ViewGuard::clear()
+{
+    v = nullptr;
+}
+
+View *ViewGuard::view() const
+{
+    return v;
+}
+
+ViewGuard& ViewGuard::operator=(View *view)
+{
+    if (view == v) {
+        return *this;
+    }
+
+    // Remove the pervious connection
+    if (m_onDestroy.isActive())
+        m_onDestroy.disconnect();
+
+    v = view;
+
+    m_onDestroy = v->beingDestroyed.connect([this] {
+        v = nullptr;
+    });
+    return *this;
+}

src/ViewGuard.h

@@ -0,0 +1,33 @@
+#ifndef KDDW_VIEW_GUARD_H
+#define KDDW_VIEW_GUARD_H
+
+#include "docks_export.h"
+
+#include "kdbindings/signal.h"
+
+namespace KDDockWidgets {
+class View;
+
+/// @brief This class provides a weak reference to a view
+/// i.e., it becomes null automatically once a View is destroyed
+class DOCKS_EXPORT ViewGuard
+{
+public:
+    ViewGuard(View *v);
+
+    operator bool() const;
+    View *operator->();
+    void clear();
+    bool isNull() const;
+    View *view() const;
+
+    ViewGuard& operator=(View *);
+
+private:
+    View *v = nullptr;
+    KDBindings::ConnectionHandle m_onDestroy;
+};
+
+}
+
+#endif

tests/CMakeLists.txt

@@ -49,3 +49,6 @@ endif()
 # tests_launcher
 add_executable(tests_launcher tests_launcher.cpp)
 target_link_libraries(tests_launcher Qt${Qt_VERSION_MAJOR}::Core)
+
+add_executable(tst_viewguard tst_viewguard.cpp)
+target_link_libraries(tst_viewguard kddockwidgets)

tests/tst_viewguard.cpp

@@ -0,0 +1,29 @@
+#include <cstdio>
+
+#include <ViewGuard.h>
+#include <qtwidgets/views/ViewWrapper_qtwidgets.h>
+
+using namespace KDDockWidgets;
+
+void test(bool cond, const char *stmt, int line)
+{
+    if (!cond) {
+        printf("[FAILED] %s line; %d\n", stmt, line);
+        exit(1);
+    }
+}
+#define TEST(cond) test(cond, #cond, __LINE__)
+
+int main()
+{
+    ViewGuard g(nullptr);
+    TEST(g.isNull());
+
+    {
+        Views::ViewWrapper_qtwidgets wv(static_cast<QWidget*>(nullptr));
+        g = &wv;
+        TEST(!g.isNull());
+    }
+
+    TEST(g.isNull());
+}