[libcalamares] Rename cPointerSetter

This class doesn't really set a pointer -- it is a scoped assignment
through a pointer, which **can** set a value on destruction (when
it leaves scope). Rename it.

While here, extend the API so that it can do an assignment to the
underlying object **now**, while also doing a scoped assignment
later when it leaves scope. This makes some code a bit easier
to read ("in this scope, X is now <v> and then it becomes <v'>")

src/libcalamares/PythonJobApi.cpp

@@ -244,7 +244,7 @@ gettext_path()
 {
     // Going to log informatively just once
     static bool first_time = true;
-    cPointerSetter( &first_time, false );
+    cScopedAssignment( &first_time, false );
 
     // TODO: distinguish between -d runs and normal runs
     // TODO: can we detect DESTDIR-installs?

src/libcalamares/utils/RAII.h

@@ -48,10 +48,11 @@ using cSignalBlocker = QSignalBlocker;
 /** @brief Writes a value on destruction to a pointed-to location.
  *
  * If the pointer is non-null, write the last-given-value if there
- * is one to the pointed-to object.
+ * is one to the pointed-to object. This is called the "then-value".
+ *
  */
 template < typename T >
-struct cPointerSetter
+struct cScopedAssignment
 {
     std::optional< T > m_value;
     T* m_pointer;
@@ -62,22 +63,36 @@ struct cPointerSetter
      * will do nothing on destruction, leaving the pointed-to
      * value unchanged.
      */
-    cPointerSetter( T* p )
+    cScopedAssignment( T* p )
         : m_pointer( p )
     {
     }
-    /** @brief Create a setter with a value already set
+    /** @brief Create a setter with a then-value already set
      *
      * This ensures that on destruction, the value @p v will be written;
      * it is equivalent to assigning @p v immediately. The pointed-to
      * value is **not** changed (until destruction).
      */
-    cPointerSetter( T* p, T v )
+    cScopedAssignment( T* p, T then )
-        : m_value( v )
+        : m_value( then )
         , m_pointer( p )
     {
     }
-    ~cPointerSetter()
+    /** @brief Create a setter with a then-value and assign a new value now
+     *
+     * As above, but also assign @p now to the thing pointed-to.
+     */
+    cScopedAssignment( T* p, T now, T then )
+        : m_value( then )
+        , m_pointer( p )
+    {
+        if ( p )
+        {
+            *p = now;
+        }
+    }
+
+    ~cScopedAssignment()
     {
         if ( m_pointer && m_value.has_value() )
         {
@@ -85,13 +100,13 @@ struct cPointerSetter
         }
     }
 
-    const T& operator=( const T& v )
+    const T& operator=( const T& then )
     {
-        m_value = v;
+        m_value = then;
-        return v;
+        return then;
     }
 };
 
 template < typename T >
-cPointerSetter( T p )->cPointerSetter< decltype( *p ) >;
+cScopedAssignment( T p )->cScopedAssignment< decltype( *p ) >;
 #endif

src/libcalamares/utils/Tests.cpp

@@ -346,35 +346,35 @@ LibCalamaresTests::testPointerSetter()
 
     QCOMPARE( special, 17 );
     {
-        cPointerSetter p( &special );
+        cScopedAssignment p( &special );
     }
     QCOMPARE( special, 17 );
     {
-        cPointerSetter p( &special );
+        cScopedAssignment p( &special );
         p = 18;
     }
     QCOMPARE( special, 18 );
     {
-        cPointerSetter p( &special );
+        cScopedAssignment p( &special );
         p = 20;
         p = 3;
     }
     QCOMPARE( special, 3 );
     {
-        cPointerSetter< int > p( nullptr );
+        cScopedAssignment< int > p( nullptr );
     }
     QCOMPARE( special, 3 );
     {
         // "don't do this" .. order of destructors is important
-        cPointerSetter p( &special );
+        cScopedAssignment p( &special );
-        cPointerSetter q( &special );
+        cScopedAssignment q( &special );
         p = 17;
     }
     QCOMPARE( special, 17 );
     {
         // "don't do this" .. order of destructors is important
-        cPointerSetter p( &special );
+        cScopedAssignment p( &special );
-        cPointerSetter q( &special );
+        cScopedAssignment q( &special );
         p = 34;
         q = 2;
         // q destroyed first, then p

src/modules/keyboard/Config.cpp

@@ -275,7 +275,7 @@ Config::detectCurrentKeyboardLayout()
     {
         return;
     }
-    cPointerSetter returnToIntial( &m_state, State::Initial );
+    cScopedAssignment returnToIntial( &m_state, State::Initial );
     m_state = State::Guessing;
 
     //### Detect current keyboard layout and variant
@@ -427,7 +427,7 @@ Config::guessLocaleKeyboardLayout()
     {
         return;
     }
-    cPointerSetter returnToIntial( &m_state, State::Initial );
+    cScopedAssignment returnToIntial( &m_state, State::Initial );
     m_state = State::Guessing;
 
     /* Guessing a keyboard layout based on the locale means

src/modules/locale/LocalePage.cpp

@@ -174,8 +174,7 @@ LocalePage::locationChanged( const CalamaresUtils::Locale::TimeZoneData* locatio
     {
         return;
     }
-    m_blockTzWidgetSet = true;  // Blocked until we go out of scope
+    cScopedAssignment b( &m_blockTzWidgetSet, true, false );
-    cPointerSetter b( &m_blockTzWidgetSet, false );
 
     // Set region index
     int index = m_regionCombo->findData( location->region() );

src/modules/partition/core/PartUtils.cpp

@@ -529,7 +529,7 @@ efiFilesystemMinimumSize()
 QString
 canonicalFilesystemName( const QString& fsName, FileSystem::Type* fsType )
 {
-    cPointerSetter type( fsType );
+    cScopedAssignment type( fsType );
     if ( fsName.isEmpty() )
     {
         type = FileSystem::Ext4;