[SOLVED] Saving/Loading of XML based dialogs

Automatically saving/loading of POD types is easy using the ATTRIBUTE macro inside RegisterObject(Context* context).

But what if I wanted to automatically save/load the changes of a Resource, in this case an XMLFile. I see there is a VAR_RESOURCEREF as part of the VariantType enum, but how would I use it with the ATTRIBUTE macro and my XMLFile?

The serialization system doesn’t readily extend into saving whole resources automatically. Normally attributes only refer to a resource, which the VAR_RESOURCEREF is for (think of model / material attributes in StaticModel)

However, there’s one workaround which is possibly a bit ugly. You can save a binary buffer inside a Variant. Look at how the NavigationMesh component stores its data.

By using the ACCESSOR_ATTRIBUTE macro you can define get and set functions for the attribute. In several cases those get/set functions are “fictional” -> they’re just used for the attribute serialization, not as actual user-callable getters & setters. For example in NavigationMesh, the functions GetNavigationDataAttr() & SetNavigationDataAttr() serialize the navigation mesh into a binary buffer variant. Or a slightly more normal example, GetModelAttr() & SetModelAttr() in StaticModel, which form a ResourceRef variant from the current model.

Another way is to just load and save your XMLFile into a separate, ordinary file. I’d actually recommend that. If you need that to happen automatically as a part of Serializable load / save, those functions are virtual so you can override them.

The thing is, I would like to have only a single save file, where everything is contained, including all the dialogs and also the scene itself. The problem is, I can’t successfully load the xml dialog(s) (saving is not a problem) because XMLFile::Load returns false here:

if (source.Read(buffer.Get(), dataSize) != dataSize)
return false;

It is assuming that the file only contains the xml dialog, but in my case it includes much more.

I tried doing it like in the StaticModel example you mentioned, but that doesn’t save the xml. I assume I would have to do it like in the NavigationMesh example (using a buffer) and traverse the whole xml file when implementing my own Get/SetDialogAttr methods.

In general resources always assume they’re the only thing being read from a Deserializer, because how else would an XML file know how big the actual data is? But you can work around like this:

  • Save XMLFile into a temporary buffer (VectorBuffer)
  • Get the size of the buffer after save
  • Write the size to your save file, followed by data. You can repeat this for as many data files as you wish.
  • When loading, read the data size from the file first, then read the data into another temporary VectorBuffer. Perform XML file load from the buffer, not from the file.

Ah, that’s a good idea. Ok, so I did this but now it can’t properly load the dialog components. It says “Component type 013F not known, creating UnknownComponent as placeholder”.

Am I overriding Load/Save correctly, or does it interfere with RegisterObject or something?

bool Dialog::Load(Deserializer& source, bool setInstanceDefault)
    unsigned size = source.ReadUInt();

    VectorBuffer temp;
    if (source.Read(temp.GetModifiableData(), size) != size)
        LOGERROR("Load might be corrupted");


    return Component::Load(source, setInstanceDefault);

bool Dialog::Save(Serializer& dest) const
    VectorBuffer temp;

    unsigned size = temp.GetSize();

    if (!dest.WriteUInt(size))
        LOGERROR("Save might be corrupted");
    if (dest.Write(temp.GetData(), size) != size)
        LOGERROR("Save might be corrupted");

    // Write attributes
    return Component::Save(dest);

Component loading expects the data stream to contain type & ID first, because those are actually loaded in Node’s code, so that it knows what component to create.

Getting closer. Now “source.Read(temp.GetModifiableData(), size” crashes, because GetModifiableData() seems to return null.

When I do this:

PODVector<unsigned char> buffer(size);
VectorBuffer temp(buffer);

it still crashes, and I don’t get any debug information (only show disassembly).

Perhaps in this case MemoryBuffer is actually more appropriate, for that one you can manually assign the data buffer to use.

The crash likely happens because you’re reading to a null size or not large enough buffer. Now that I look at it VectorBuffer doesn’t have a convenient function to resize the buffer at once, instead it’s usually written to in increments, ie. WriteInt() etc. so that it expands the buffer on demand. I will look into providing a VectorBuffer::Resize() or similar later.

Yay. I got it working now. The crash was actually unrelated to the buffer issue. As always, thanks for your help!

Nice that you got it working. Hm, VectorBuffer in fact already has Resize(). For some reason I didn’t spot it in the morning.