QGraphicsItem with QSizeGrip

[marcel]

Now, for MySizeGripQGraphicsItem, how can I detect dragging a portion of QGraphicsItem namely the corners via mouseEvent's?

You will just have to test if the user drags those corners. To see this is easy, because you know the position of your MySizeGripQGraphicsItem ( the resize handles are at the corners of the item ).
Then you can translate QMouseEvent:os() (from mouseMoveEvent ) to parent ( graphics scene ) coordinates and resize the items.

To know in mouseMoveEvent exactly what corner is dragged, you could use a convenience enum, like:

typedef enum EResizeHandle
{
    eNone,
    eHandleTopLeft,
    eHandleTop,
    eHandleTopRight,
    eHandleRight,
    eHandleBottomRight,
    ...
} EResizeHandle;

typedef enum EResizeHandle
{
    eNone,
    eHandleTopLeft,
    eHandleTop,
    eHandleTopRight,
    eHandleRight,
    eHandleBottomRight,
    ...
} EResizeHandle;

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Assuming you have a member of type EResizeHandle:

void Class::mousePressEvent( QMouseEvent *e )
{
    //
    // Look at e->pos() to establish which corner is dragged and assign a value to
    // mResizeHandle
    //
}
 
void Class::mouseMoveEvent( QMouseEvent *e )
{
    // if mResizeHandle is eNone then nothing is resized
    switch( mResizeHandle )
   {
    case eTopLeft:
    // code to resize the object
    break;
    ...
   }
}
 
void Class::mouseReleaseEvent( ... )
{
    mResizeHandle = eNone;
}

void Class::mousePressEvent( QMouseEvent *e )
{
    //
    // Look at e->pos() to establish which corner is dragged and assign a value to
    // mResizeHandle
    //
}

void Class::mouseMoveEvent( QMouseEvent *e )
{
    // if mResizeHandle is eNone then nothing is resized
    switch( mResizeHandle )
   {
    case eTopLeft:
    // code to resize the object
    break;
    ...
   }
}

void Class::mouseReleaseEvent( ... )
{
    mResizeHandle = eNone;
}

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