wrapping goocanvas

[hyOzd]

Hi, I'm trying to create wrappers for GooCanvas library and I'm having some trouble that I hope you can help with.

Currently there is not much in my APILookupGooCanvas.txt file:

wrap: goocanvas
file: /usr/share/gir-1.0/GooCanvas-2.0.gir

addAliases: start
    public import gtkc.cairotypes;
    public import gtkc.gdkpixbuftypes;
    public import gtkc.gdktypes;
    public import gtkc.gtktypes;
addAliases: end

There are two interfaces defined in GooCanvas; CanvasItem and CanvasItemModel. When I run the wrapper as it is, it creates these modules for CanvasItem: CanvasItemModelT.d and CanvasItemModelIF.d . Both these modules have this import line that causes a compilation error because it doesn't exist!

private import goocanvas.CanvasItem;

The symbol CanvasItem is also referenced throughout the code, for ex. from CanvasItemIF.d file:

public CanvasItemIF getChild(int childNum)
{
    auto p = goo_canvas_item_get_child(getCanvasItemStruct(), childNum);

    if(p is null)
    {
        return null;
    }

    return ObjectG.getDObject!(CanvasItem, CanvasItemIF)(cast(GooCanvasItem*) p);
}

All usages of 'CanvasItem' for a ObjectG.getDObject call.

But there is no CanvasItem.d module created. I checked some interfaces used in Gtk, and as far as I understand they don't require any special attention in lookup.txt file.

What should I do in this case? Any help is appreciated.

[MikeWey]

You should provide an minimal implementation for CanvasItem.

You can do this by adding this to the APILookup file:

struct:
class: CanvasItem
extend: GObject.Object
implements: CanvasItem

[hyOzd]

Thanks a lot @MikeWey this seems to work.

Now I'm having problems with events (along with other problems that I haven't investigated yet). Specifically addEvents method. Here is the code generated for 'focus-in' event of CanvasItem:

    gulong addOnFocusIn(bool delegate(CanvasItemIF, Event, CanvasItemIF) dlg, ConnectFlags connectFlags=cast(ConnectFlags)0)
    {
        addEvents(EventMask.FOCUS_CHANGE_MASK);
        onFocusInListeners ~= new OnFocusInDelegateWrapper(dlg, 0, connectFlags);
        onFocusInListeners[onFocusInListeners.length - 1].handlerId = Signals.connectData(
            this,
            "focus-in-event",
            cast(GCallback)&callBackFocusIn,
            cast(void*)onFocusInListeners[onFocusInListeners.length - 1],
            cast(GClosureNotify)&callBackFocusInDestroy,
            connectFlags);
        return onFocusInListeners[onFocusInListeners.length - 1].handlerId;
    }

GooCanvas doesn't have a method named "add_events". My understanding from the gtk documentation is that this method is required because events that a gtk widget receives are filtered according to its event mask. To receive a certain event it has to be added to its event mask. As far as I can see GooCanvas doesn't have this functionality thus addEvents isn't required at all.

If I'm correct about removing addEvents where should this be done? Adding another exception here maybe?

[hyOzd]

Another problem that I couldn't figure out. CanvasItemT::getTransform method is created like this:

    public bool getTransform(out Matrix transform)
    {
        cairo_matrix_t* outtransform = gMalloc!cairo_matrix_t();

        auto p = goo_canvas_item_get_transform(getCanvasItemStruct(), outtransform) != 0;

        transform = new Matrix(outtransform, true); // ERROR HERE

        return p;
    }

Problem is cairo.Matrix doesn't have such a constructor?

[MikeWey]

Both cases should be fixed with the latest commit.

[hyOzd]

@MikeWey there is a typo here. One extra comma.

Now I have this error, but I haven't investigated this one myself yet:

src/goocanvas/CanvasWidgetAccessibleFactory.d(33): src/goocanvas/CanvasAccessibleFactory.d(33): Error: class goocanvas.CanvasAccessibleFactory.CanvasAccessibleFactory cannot implicitly generate a default ctor when base class atk.ObjectFactory.ObjectFactory is missing a default ctor
Error: class goocanvas.CanvasWidgetAccessibleFactory.CanvasWidgetAccessibleFactory cannot implicitly generate a default ctor when base class atk.ObjectFactory.ObjectFactory is missing a default ctor
src/goocanvas/CanvasItemAccessibleFactory.d(33): Error: class goocanvas.CanvasItemAccessibleFactory.CanvasItemAccessibleFactory cannot implicitly generate a default ctor when base class atk.ObjectFactory.ObjectFactory is missing a default ctor

[MikeWey]

Fixed in bac77c84043cf136aaa0559e3f8a952c18a04663

[hyOzd]

Finally got it working.

I think the last problem was caused by the GIR file. Because the library doesn't contain these classes: CanvasWidgetAccessibleFactory, CanvasWidgetAccessibleFactory, CanvasItemAccessibleFactory. At least the version distributed in mint doesn't. Adding 'noCode' for them in the lookup file solved the issue.

Now I have a question; I believe it's my responsibility to add missing constructors as member functions. For example for CanvasRect I added this constructor via API lookup file.

struct: CanvasRect
code: start
public this (CanvasItemIF parent, double x, double y, double width, double height)
{
    auto p = parent.getCanvasItemStruct();
    auto item = goo_canvas_rect_new(p, x, y, width, height);

    this (cast(GooCanvasRect*) item);
} 
code: end

Is this the correct approach? I want to be sure before moving on to others.

[hyOzd]

Here is another problem that I couldn't figure out. Actually I found a workaround for it but I'm not sure about it.

Below is the generated wrapper for goo_canvas_item_model_class_list_child_properties function:

    public static ParamSpec[] classListChildProperties(ObjectClass mclass)
    {
        uint nProperties;

        auto p = goo_canvas_item_model_class_list_child_properties((mclass is null) ? null : mclass.getObjectClassStruct(), &nProperties);

        if(p is null)
        {
            return null;
        }

        ParamSpec[] arr = new ParamSpec[nProperties];
        for(int i = 0; i < nProperties; i++)
        {
            arr[i] = ObjectG.getDObject!(ParamSpec)(cast(*) &p[i]); // ERROR HERE
        }

        return arr;
    }

Above code doesn't compile due to missing cast type. I checked other similar functions and it turns out there is a problem with the gir file entry of this function. Functions return value is missing the c:type field for GObject.ParamSpec. Here is the relevant section from gir file:

    <return-value transfer-ownership="container">
        <doc xml:space="preserve">
 a newly allocated array of #GParamSpec*. The array must be freed with g_free().</doc>
        <array length="1" zero-terminated="0" c:type="GParamSpec**">
          <type name="GObject.ParamSpec"/>
        </array>
      </return-value>

Other similar functions have it defined like this: <type name="GObject.ParamSpec" c:type="GParamSpec*"/> . So I changed above line and added tye c:type field in the GIR file and compilation succeeded.

My question is how can I solve this without hacking the GIR file?

[MikeWey]

For the constructors, on ArchLinux the definition in the gir file would be detected as an constructor.

There are two cases that are currently detected as a constructor: The function is defined with an constructor tag, or if its defined with an function tag and its name starts with "new".

For the missing cast, you can add:

structWrap: GParamSpec* ParamSpec

to the APILookup file. but the changes from commit 1c8a14bee4494298b5a5911d589e4b4dcdb0ca9f should also take care of this.

[hyOzd]

@MikeWey I don't understand, what is different in arch? I've checked the GIR file in this arch package and function is defined the same way with this tag:

      <function name="new"
                c:identifier="goo_canvas_rect_new"
                introspectable="0">

It is not defined with a constructor tag but its name is "new". Is it the introspectable="0"?

---

By the way the thanks for the fix. (workaround you suggested didn't work FYI)

In the mean time I've started to push my work here for anyone interested.

[hyOzd]

I've investigated other libraries a bit and it seems that other functions with similar signatures are generated just fine. For ex this one: pango_attr_font_desc_new .

[hyOzd]

I think it is skipped because it is variadic. Am I right?

[MikeWey]

That is correct, variadic functions are currently skipped.

[hyOzd]

That is correct, variadic functions are currently skipped.

In most cases variadic parameter is optional and used to pass property-value pairs to constructors. So it can be ignored. I was wondering if we could have another tag implemented in API lookup file that would instruct the wrapper to ignore variadic parameter of the function?

[hyOzd]

I went ahead, and added a new tag for API lookup file called noVariadic for ignoring (removing) variadic parameter of a function. Here. It worked. But then I noticed these runtime errors in running application:

(main:27620): GLib-GObject-WARNING **: g_object_set_valist: object class 'GooCanvasRect' has no property named '\xc0\xf6\x82'

Turns out goocanvas API expect variadic list to be ended with a null. So, variadic parameter is not entirely optional. I guess I will add constructors manually. There aren't that many after all.