instanceOf now uses RTTI and checks its answer.

Next I'll just remove it, but this commit lets me
have something in history such that I can fall back to
check for bugs that might get introduced.

dw/oofawarewidget.cc

@@ -131,7 +131,7 @@ bool OOFAwareWidget::isOOFContainer (Widget *widget, int oofmIndex)
 
    switch (oofmIndex) {
    case OOFM_FLOATS:
-      return widget->instanceOf (OOFAwareWidget::CLASS_ID) &&
+      return widget->instanceOf <OOFAwareWidget>() &&
          (// For floats, only some OOF aware widgets are considered as
           // containers.
           ((OOFAwareWidget*)widget)->isPossibleOOFContainer (OOFM_FLOATS) &&
@@ -145,7 +145,7 @@ bool OOFAwareWidget::isOOFContainer (Widget *widget, int oofmIndex)
            // is also a text block, so possible float container)
            // within a table widget, which is not a suitable float
            // container parent).
-           !(widget->getParent()->instanceOf (OOFAwareWidget::CLASS_ID) &&
+           !(widget->getParent()->instanceOf <OOFAwareWidget>() &&
              ((OOFAwareWidget*)widget->getParent())
                  ->isPossibleOOFContainerParent (OOFM_FLOATS)) ||
            // Inline blocks are containing blocks, too.
@@ -163,7 +163,7 @@ bool OOFAwareWidget::isOOFContainer (Widget *widget, int oofmIndex)
       
    case OOFM_RELATIVE:
    case OOFM_ABSOLUTE:
-      return widget->instanceOf (OOFAwareWidget::CLASS_ID) &&
+      return widget->instanceOf <OOFAwareWidget>() &&
          (widget->getParent() == NULL ||
           OOFAwareWidget::testWidgetPositioned (widget));
 
@@ -192,7 +192,7 @@ void OOFAwareWidget::notifySetParent ()
            widget != NULL && oofContainer[oofmIndex] == NULL;
            widget = widget->getParent ())
          if (isOOFContainer (widget, oofmIndex)) {
-            assert (widget->instanceOf (OOFAwareWidget::CLASS_ID));
+            assert (widget->instanceOf <OOFAwareWidget>());
             oofContainer[oofmIndex] = (OOFAwareWidget*)widget;
          }
    

dw/oofposrelmgr.cc

@@ -66,7 +66,7 @@ void OOFPosRelMgr::calcWidgetRefSize (Widget *widget, Requisition *size)
    // (Notice also that Widget::sizeRequest has to be called in all
    // cases.)
 
-   if (widget->instanceOf (OOFAwareWidget::CLASS_ID))
+   if (widget->instanceOf <OOFAwareWidget>())
       *size = *((OOFAwareWidget*)widget)->getRequisitionWithoutOOF ();
 
    

dw/table.cc

@@ -607,7 +607,7 @@ AlignedTableCell *Table::getCellRef ()
       int n = curCol + row * numCols;
       if (childDefined (n)) {
          child = children->get(n)->cell.widget;
-         if (child->instanceOf (AlignedTableCell::CLASS_ID))
+         if (child->instanceOf <AlignedTableCell>())
             return (AlignedTableCell*)child;
       }
    }

dw/textblock.cc

@@ -2523,7 +2523,7 @@ void Textblock::addWidget (core::Widget *widget, core::style::Style *style)
       widget->setParent (this);
 
       // TODO Replace (perhaps) later "textblock" by "OOF aware widget".
-      if (widget->instanceOf (Textblock::CLASS_ID)) {
+      if (widget->instanceOf <Textblock>()) {
          for (int i = 0; i < NUM_OOFM; i++)
             searchOutOfFlowMgr(i)->addWidgetInFlow ((Textblock*)widget, this,
                                                     words->size ());
@@ -2765,7 +2765,7 @@ void Textblock::addParbreak (int space, core::style::Style *style)
          consider normal flow, no floats etc.) */
       for (Widget *widget = this;
            widget->getParent() != NULL &&
-              widget->getParent()->instanceOf (Textblock::CLASS_ID) &&
+              widget->getParent()->instanceOf <Textblock>() &&
               !isWidgetOOF (widget);
            widget = widget->getParent ()) {
          Textblock *textblock2 = (Textblock*)widget->getParent ();
@@ -2959,7 +2959,7 @@ void Textblock::handOverBreak (core::style::Style *style)
       Line *lastLine = lines->getRef (lines->size () - 1);
 
       if (lastLine->breakSpace != 0 && (parent = getParent()) &&
-          parent->instanceOf (Textblock::CLASS_ID) &&
+          parent->instanceOf <Textblock>() &&
           parent->getStyle()->display != core::style::DISPLAY_BLOCK) {
          Textblock *textblock2 = (Textblock*) parent;
          textblock2->addParbreak(lastLine->breakSpace, style);
@@ -3193,7 +3193,7 @@ int Textblock::getGeneratorWidth ()
          // We only examine instances of dw::Textblock, since they are relevant
          // for floats, for which this method is only called.
          if(word->content.type == core::Content::WIDGET_IN_FLOW &&
-            word->content.widget->instanceOf(Textblock::CLASS_ID)) {
+            word->content.widget->instanceOf<Textblock>()) {
             Textblock *tbChild = (Textblock*)word->content.widget;
             if(tbChild->findSizeRequestReference(this, &xRel, NULL))
                wChild = max(wChild, xRel + tbChild->getGeneratorWidth());
@@ -3291,7 +3291,7 @@ RegardingBorder *Textblock::getWidgetRegardingBorderForLine (int firstWord,
 
       if (word->content.type == core::Content::WIDGET_IN_FLOW) {
          Widget *widget = word->content.widget;
-         if (widget->instanceOf (RegardingBorder::CLASS_ID) &&
+         if (widget->instanceOf <RegardingBorder>() &&
              // Exclude cases where a textblock constitutes a new floats
              // container.
              !isOOFContainer (widget, OOFM_FLOATS))

lout/identity.cc

@@ -99,7 +99,7 @@ void IdentifiableObject::registerName (const char *className, const std::type_in
  * \brief Returns, whether this class is an instance of the class, given by
  *    \em otherClassId, or of a sub class of this class.
  */
-bool IdentifiableObject::instanceOf (std::intptr_t otherClassId)
+bool IdentifiableObject::instanceOf_impl (std::intptr_t otherClassId)
 {
    if (otherClassId == -1)
       // Other class has not been registered yet, while it should have been,

lout/identity.hh

@@ -3,6 +3,8 @@
 
 #include <memory>
 #include <typeindex>
+#include <exception>
+#include <stdexcept>
 #include <vector>
 #include <map>
 
@@ -143,7 +145,19 @@ public:
     */
    const char *getClassName() { return classesById.at( classId )->className; }
 
-   bool instanceOf (std::intptr_t otherClassId);
+   template< typename T >
+   [[deprecated]]
+   inline bool
+   instanceOf()
+   {
+      const bool expected= dynamic_cast< T * >( this );
+      const bool witness= instanceOf_impl( T::CLASS_ID );
+      if( witness != expected ) throw std::logic_error{ "RTTI based `instanceOf` disagrees with Dillo's lout:: impl." };
+	  return expected;
+   }
+
+  private:
+   bool instanceOf_impl (std::intptr_t otherClassId);
 };
 
 } // namespace identity

src/html.cc

@@ -798,7 +798,7 @@ bool DilloHtml::HtmlLinkReceiver::click (Widget *widget, int link, int img,
       /* Change the link color to "visited" as visual feedback */
       for (Widget *w = widget; w; w = w->getParent()) {
          _MSG("  ->%s\n", w->getClassName());
-         if (w->instanceOf(dw::Textblock::CLASS_ID)) {
+         if (w->instanceOf<dw::Textblock>()) {
             ((Textblock*)w)->changeLinkColor (link, html->visited_color);
             break;
          }