将Ptr（）转换为SourceCompletionProvider [英] Convert Ptr () to SourceCompletionProvider

问题描述

我已经部分解决了上一个问题。

现在我可以通过 bindings-gobject 注册 GObject 子类型（参见< hbase ）
我可以实现 SourceCompletionProvider 使用 a href =http://hackage.haskell.org/packages/archive/bindings-gobject/0.3/doc/html/Bindings-GObject-TypeInformation.html#v:c-39-g_type_add_interface_static =nofollow noreferrer > c'g_type_add_interface_static 函数（但尚未尝试过）。



唯一的问题是将 Ptr（） code> c'g_object_newv ，返回到 gtk2hs 数据类型 SourceCompletionProvider 。我该怎么做？任何提示？

SourceCompletionProvider 定义如下：

  newtype SourceCompletionProvider = SourceCompletionProvider（ForeignPtr（SourceCompletionProvider））
  

什么这个定义是否意味着？为什么它是递归的？ Provider是 ForeignPtr 提供者 - 看起来很奇怪。

谢谢。

解决方案：

  makeNewGObject mkGObject $ castPtr< $> c'g_object_newv myObType 0 nullPtr 
  

解决方案 < $ c> SourceCompletionProvider 是必需的，因为这是一个新类型，并且内部 SourceCompletionProvider 只是一个标记，用于区分这个外部指针和其他类型的指针。如果您查看定义 ptr a ，它是 data Ptr a = Ptr Addr＃ - a 是一个幻像类型，不会出现在右侧，因此定义实际上不是递归的。

可以将 Ptr（）到 ForeignPtr（）使用 newForeignPtr _ ，然后将它转换为 ForeignPtr SourceCompletionProvider 与 castForeignPtr 。

edit：在看了这些之后，我认为要做到这一点，您需要先将 Ptr 转换为 GObject w ith上述方法，然后使用 unsafeCastGObject 。不过未经测试。

I've solved the prev question partially.

Right now I'm able to register GObject subtype via bindings-gobject (see hpase) I can implement SourceCompletionProvider using c'g_type_add_interface_static function (but didn't tried yet).

The only issue is to convert Ptr (), returned by c'g_object_newv, to gtk2hs data type SourceCompletionProvider. How can I do it? Any hints?

SourceCompletionProvider is defined like:

newtype SourceCompletionProvider = SourceCompletionProvider (ForeignPtr (SourceCompletionProvider))

What does this definition means? Why it is recursive? Provider is a ForeignPtr to provider -- looks strange for me.

Thanks.

Solution:

makeNewGObject mkGObject $ castPtr <$> c'g_object_newv myObType 0 nullPtr

解决方案

The outer SourceCompletionProvider is required since this is a newtype, and the inner SourceCompletionProvider is just a marker to distinguish this foreign pointer from pointers to other types. If you look at the definition of Ptr a, it's data Ptr a = Ptr Addr# - a is a phantom type that doesn't appear on the right-hand side, so the definition is not actually recursive.

You can convert a Ptr () to ForeignPtr () using newForeignPtr_ and then cast it to ForeignPtr SourceCompletionProvider with castForeignPtr.

edit: After looking at this a bit more, I think that to make this work you'll need to first convert your Ptr to GObject with the method outlined above and then use unsafeCastGObject. Not tested, though.

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