Rujia Liu rujia.liu@gmail.com writes:

Hi!

I'd like to create an item group for a QGraphicsScene with this function:

QGraphicsItemGroup * QGraphicsScene::createItemGroup ( const QList<QGraphicsItem *> & items )

However, I don't know how to create a variable of type QList<QGraphicsItem*>. I even can't find the class:

• (qt:qapropos "QList")

; No debug variables for current frame: using EVAL instead of EVAL-IN-FRAME. Class QListView Class QListWidget Class QListWidgetItem Method QListView::QListView [7272] Method QListView::QListView [7342] Method QListView::~QListView [7356] Method QListWidget::QListWidget [7364] Method QListWidget::QListWidget [7422] Method QListWidget::~QListWidget [7426] Method QListWidgetItem::QListWidgetItem [7427] Method QListWidgetItem::QListWidgetItem [7428] Method QListWidgetItem::QListWidgetItem [7429] Method QListWidgetItem::QListWidgetItem [7430] Method QListWidgetItem::QListWidgetItem [7472] Method QListWidgetItem::QListWidgetItem [7473] Method QListWidgetItem::QListWidgetItem [7474] Method QListWidgetItem::QListWidgetItem [7475] Method QListWidgetItem::QListWidgetItem [7476] Method QListWidgetItem::QListWidgetItem [7477] Method QListWidgetItem::~QListWidgetItem [7480]

I tried to call canvas's items() and see what's inside. Then I see

(#<QGraphicsItem 0x01FEB0B8> #<QGraphicsItem 0x01FEABB8>)

That's the two items I created, before calling items(). So I see CommonQt does some magic to convert QList to a lisp list.

Then I tried to pass nil (here I mean empty list, not false) to createItemGroup, but I got the following: The value NIL is not of type SYSTEM-AREA-POINTER. I think that's because nil is not like a "C pointer", but I know almost nothing about CFFI or other low-level stuffs, so I'm stuck now.

There's something strange going on, I added a QList<QGraphicsItem*> marshaller, but when i try to use it with #_createItemGroup, it crashes hard with free(): invalid pointer: 0x00007ffff4375350.

You're probably better off for now with explicit item group functions, like (#_addToGroup QGraphicsItemGroup item)