[Effective WX] 理解wxWindow中增加和去除/销毁子窗口的过程

wxWindow中增加和去除/销毁子窗口的过程：

a) 增加一个子窗口

void wxWindowBase::AddChild(wxWindowBase *child)
{
wxCHECK_RET( child, wxT("can't add a NULL child") );

// this should never happen and it will lead to a crash later if it does
// because RemoveChild() will remove only one node from the children list
// and the other(s) one(s) will be left with dangling pointers in them
wxASSERT_MSG( !GetChildren().Find((wxWindow*)child), _T("AddChild() called twice") );

GetChildren().Append((wxWindow*)child);
child->SetParent(this);
}

b) 销毁所有的子窗口

bool wxWindowBase::DestroyChildren()
{
wxWindowList::compatibility_iterator node;
for ( ;; )
{
// we iterate until the list becomes empty
node = GetChildren().GetFirst();
if ( !node )
break;

wxWindow *child = node->GetData();

// note that we really want to call delete and not ->Destroy() here
// because we want to delete the child immediately, before we are
// deleted, and delayed deletion would result in problems as our (top
// level) child could outlive its parent
delete child;

wxASSERT_MSG( !GetChildren().Find(child),
wxT("child didn't remove itself using RemoveChild()") );
}

return true;
}

上面直接delete一个子窗口的指针。它会触发子窗口的析构。

// reset the dangling pointer our parent window may keep to us
if ( m_parent )
{
m_parent->RemoveChild(this);
}

析构过程中会调用父窗口的RemoveChild函数，用来去除该子窗口，从父窗口的子窗口链表中。

void wxWindowBase::RemoveChild(wxWindowBase *child)
{
wxCHECK_RET( child, wxT("can't remove a NULL child") );

GetChildren().DeleteObject((wxWindow *)child);
child->SetParent(NULL);
}

c) wxWindows的reparent

如果没有指定parent，那么就将这个窗口添加到全局的toplevel windows列表中。

bool wxWindowBase::Reparent(wxWindowBase *newParent)
{
wxWindow *oldParent = GetParent();
if ( newParent == oldParent )
{
// nothing done
return false;
}

// unlink this window from the existing parent.
if ( oldParent )
{
oldParent->RemoveChild(this);
}
else
{
wxTopLevelWindows.DeleteObject((wxWindow *)this);
}

// add it to the new one
if ( newParent )
{
newParent->AddChild(this);
}
else
{
wxTopLevelWindows.Append((wxWindow *)this);
}

return true;
}