LSB: Extend the Qt API to be able to compile without Designer having to access private headers/classes

8.2.2008: Designer will not be the LSB test app. Still, a nice-to-have.

This whole task is about being able to compile Designer without private Qt headers to enable its
use as a LSB compliance test application.
The intention is make the missing API (that is currently accessed via private headers) public
without breaking BC.

Qt 4.4:
---------

QFontPrivate:

• Make the QFontPrivate::ResolveMask flag enum (QFontPrivate::Family....) accessible (potentially rename it)

QToolBar:

• Add accessor for the handleRect() area of QToolBarLayout. Also see item 2) for 4.5

Provide a way to validate (CSS) style sheets

QLayout:

• Make qSmartMinSize accessible
• We want a factory method hook for those places in which the QWidgetItems/QSpacerItems are created (by the layout) and and we need to invoke that method.
  Currently, this is:

class QLayoutPrivate {
typedef QWidgetItem * (*QWidgetItemFactoryMethod)(const QLayout *layout, QWidget *widget);
typedef QSpacerItem * (*QSpacerItemFactoryMethod)(const QLayout *layout, int w, int h, QSizePolicy::Policy hPolicy, QSizePolicy::Policy);
static QWidgetItem *createWidgetItem(const QLayout *layout, QWidget *widget);
static QSpacerItem *createSpacerItem(const QLayout *layout, int w, int h, QSizePolicy::Policy hPolicy = QSizePolicy::Minimum, QSizePolicy::Policy vPolicy = QSizePolicy::Minimum);
static QWidgetItemFactoryMethod widgetItemFactoryMethod;
static QSpacerItemFactoryMethod spacerItemFactoryMethod;

To make this very flexible, we could
enum QtHook

static SomeCentralClass::setHook(int enumValue, void *);
static void *SomeCentralClass::hook(int enumValue);
providing method ptrs can be reinterpret_casted to void* everywhere?

QObject:
To make some of the current d-ptr pains bearable, maybe
void *QObject::userData()
void QObject::setUserData(void *)
could be introduced (or maybe QVariant). But that is only a suggestion, we can of course hack with static maps.

Qt 4.5:
----------
1) Provide a widget post-painting hook: We want a widget painting hook that is invoked with its QPainter after the widget has painted to be able to paint grids , utility lines on top of it without [significant] loss of performance or [backing-store] caused artifacts

2) Introduce methods (QStyle?) to tell in what kind of subarea/subcontrol a given point is in a QWidget: We want a [computationally inexpensive] method to tell whether an area of a widget is a "Passive interactor" , that is, whether Designer should refrain from blocking events in that area (for example, a toolbar handle, scrollbar handle, etc). QUestion is, whether a simple bool is sufficient .. enumeration instead?