Unregister deleted IContext objects automatically

Change-Id: I7b84c02c8fe1e7201431116e3d993792370fb942
Reviewed-by: hjk <hjk@qt.io>

doc/qtcreatordev/src/actionmanager.qdoc

@@ -124,8 +124,9 @@
     Core::ICore::addContextObject(contextObj);
     \endcode
 
-    You also have to unregister the IContext object with
-    Core::ICore::removeContextObject() when you do not need it anymore.
+    IContext instances are automatically unregistered when they are deleted.
+    Use Core::ICore::removeContextObject() if you need to unregister an IContext
+    instance manually.
 
     Some constructs in \QC automatically have an associated context, like
     Core::IEditor and Core::IMode.

src/plugins/coreplugin/icontext.cpp

@@ -179,8 +179,10 @@ QDebug operator<<(QDebug debug, const Core::Context &context)
     Core::ICore::addContextObject() to have an effect. For many subclasses of
     IContext, like Core::IEditor and Core::IMode, this is done automatically.
     But instances of IContext can be created manually to associate a context
-    and context help for an arbitrary widget, too. Mind that IContext instances
-    must be unregistered with Core::ICore::removeContextObject() as well.
+    and context help for an arbitrary widget, too. IContext instances are
+    automatically unregistered when they are deleted. Use
+    Core::ICore::removeContextObject() if you need to unregister an IContext
+    instance manually.
 
     Whenever the widget is part of the application wide focus widget's parent
     chain, the associated context list is made active. This makes actions active

src/plugins/coreplugin/icore.cpp

@@ -569,6 +569,7 @@ void ICore::addContextObject(IContext *context)
 
 /*!
     Unregisters a \a context object from the list of know contexts.
+    IContext instances are automatically removed when they are deleted.
 
     \sa addContextObject(), updateAdditionalContexts(), currentContextObject()
 */

src/plugins/coreplugin/mainwindow.cpp

@@ -917,9 +917,10 @@ void MainWindow::openFileWith()
     }
 }
 
-IContext *MainWindow::contextObject(QWidget *widget)
+IContext *MainWindow::contextObject(QWidget *widget) const
 {
-    return m_contextWidgets.value(widget);
+    const auto it = m_contextWidgets.find(widget);
+    return it == m_contextWidgets.end() ? nullptr : it->second;
 }
 
 void MainWindow::addContextObject(IContext *context)
@@ -927,10 +928,11 @@ void MainWindow::addContextObject(IContext *context)
     if (!context)
         return;
     QWidget *widget = context->widget();
-    if (m_contextWidgets.contains(widget))
+    if (m_contextWidgets.find(widget) != m_contextWidgets.end())
         return;
 
-    m_contextWidgets.insert(widget, context);
+    m_contextWidgets.insert(std::make_pair(widget, context));
+    connect(context, &QObject::destroyed, this, [this, context] { removeContextObject(context); });
 }
 
 void MainWindow::removeContextObject(IContext *context)
@@ -938,11 +940,17 @@ void MainWindow::removeContextObject(IContext *context)
     if (!context)
         return;
 
-    QWidget *widget = context->widget();
-    if (!m_contextWidgets.contains(widget))
+    disconnect(context, &QObject::destroyed, this, nullptr);
+
+    const auto it = std::find_if(m_contextWidgets.cbegin(),
+                                 m_contextWidgets.cend(),
+                                 [context](const std::pair<QWidget *, IContext *> &v) {
+                                     return v.second == context;
+                                 });
+    if (it == m_contextWidgets.cend())
         return;
 
-    m_contextWidgets.remove(widget);
+    m_contextWidgets.erase(it);
     if (m_activeContext.removeAll(context) > 0)
         updateContextObject(m_activeContext);
 }
@@ -959,7 +967,7 @@ void MainWindow::updateFocusWidget(QWidget *old, QWidget *now)
     if (QWidget *p = QApplication::focusWidget()) {
         IContext *context = nullptr;
         while (p) {
-            context = m_contextWidgets.value(p);
+            context = contextObject(p);
             if (context)
                 newContext.append(context);
             p = p->parentWidget();

src/plugins/coreplugin/mainwindow.h

@@ -31,10 +31,10 @@
 #include <utils/appmainwindow.h>
 #include <utils/dropsupport.h>
 
-#include <QMap>
 #include <QColor>
 
 #include <functional>
+#include <unordered_map>
 
 QT_BEGIN_NAMESPACE
 class QPrinter;
@@ -82,7 +82,7 @@ public:
     void extensionsInitialized();
     void aboutToShutdown();
 
-    IContext *contextObject(QWidget *widget);
+    IContext *contextObject(QWidget *widget) const;
     void addContextObject(IContext *context);
     void removeContextObject(IContext *context);
 
@@ -164,7 +164,7 @@ private:
 
     QList<IContext *> m_activeContext;
 
-    QMap<QWidget *, IContext *> m_contextWidgets;
+    std::unordered_map<QWidget *, IContext *> m_contextWidgets;
 
     GeneralSettings *m_generalSettings = nullptr;
     SystemSettings *m_systemSettings = nullptr;