How can one register a Direct2D custom effect that has variable numbers of inputs? - directx

Question

I am making custom effects with Direct2D, based on Microsoft Learn page. The problem is that, I wanted to make a Direct2D effect which support a variable input count, like Direct2D Composite Effect, while the XML registration string used for ID2D1Factory1::RegisterEffectFromString seemed to take fixed <Input> properties. What should be done in XML registration string?
My XML is almost the same as one from Microsoft Learn page. Still I will provide mine.
auto xml_AxisRotation = XML(
<?xml version='1.0'?>
<Effect>
<!--System Properties-->
<Property name='DisplayName' type='string' value='MultiInput Effect'/>
<Property name='Author' type='string' value='Nan_ok'/>
<Property name='Category' type='string' value='None'/>
<Property name='Description' type='string' value='asdfasdfasdf'/>
<Inputs>
<Input name='Source1'/>
<Input name='Source2'/>
//...?
</Inputs>
<!--Custom Properties go here-->
<Property name='Mode' type='int32'>
<Property name='DisplayName' type='string' value='Mode'/>
<Property name='Default' type='int32' value='1'/>
</Property>
</Effect>
);
I once deliberately omitted the whole <Input> part, but it failed to perform; E_INVALIDARG has been returned.

Answer 1

The XML registration and actual Direct2D effect's input taking worked differently. By proper implementing ID2D1EffectImpl::SetGraph and calling ID2D1Effect::SetInputCount, I was able to set variable numbers of target.
It seemed ok to leave <Inputs> with no <Input> property. here is my XML example.
auto xml_AxisRotation = XML(
<?xml version='1.0'?>
<Effect>
<!--System Properties-->
<Property name='DisplayName' type='string' value='MultiInput Effect'/>
<Property name='Author' type='string' value='Nan_o'/>
<Property name='Category' type='string' value='None'/>
<Property name='Description' type='string' value='asdfasdfasdf'/>
<Inputs> </Inputs> <!--Leaving like this is ok-->
<!--Custom Properties go here-->
<Property name='Mode' type='int32'>
<Property name='DisplayName' type='string' value='Mode'/>
<Property name='Default' type='int32' value='1'/>
</Property>
</Effect>
);