How to manually load a native visualiser during debugging in Visual Studio 2022?

Question

I'm working with COM objects, which means I need to debug SAFEARRAY objects.

It looks as follows in the watch-window:

receivedData 0x007cc980 safearray of UI1, [rank]=1 _variant_t
 safearray 0x007cc980 safearray of UI1, [rank]=1 tagSAFEARRAY*
 [0] 55 '7' unsigned char
 [1] 48 '0' unsigned char
...

I would like it to look as follows:

receivedData 0x007cc980 safearray of UI1, [rank]=1 _variant_t
 safearray 0x007cc980 safearray. ILbound=0, cElements=19, array=[55 '7', 48 '0', ...] tagSAFEARRAY*

In order to achieve this, I have created a SAFEARRAY.natvis file, which looks as follows:

<?xml version="1.0" encoding="utf-8"?>
<AutoVisualizer xmlns="http://schemas.microsoft.com/vstudio/debugger/natvis/2010">
 <Type Name="tagSAFEARRAY">
 <DisplayString>
 0x{address} safearray. ILbound={ILbound[0]}, cElements={cElements}, array=[{Items}]
 </DisplayString>
 <Expand> <!-- Customize how each element is displayed -->
 <Item Name="Items">
 <ArrayItems> <!-- Assuming the array is of type UI1 (unsigned 8-bit integer) -->
 <ItemExpression>data[0]</ItemExpression>
 </ArrayItems>
 </Item>
 </Expand>
 <Expand>
 <Item Name="ILbound">
 <ArrayItems>
 <ItemExpression>rgsabound[0].lLbound</ItemExpression> <!-- Adjust if necessary -->
 </ArrayItems>
 </Item>
 </Expand>
 <Expand>
 <Item Name="cElements">
 <ArrayItems>
 <ItemExpression>cElements</ItemExpression>
 </ArrayItems>
 </Item>
 </Expand>
 </Type>
</AutoVisualizer>

Now I'd like to test this.

I have put the mentioned file in one of the required directories and I've launched .natvisreload. In my output window, I see the following error message:

Natvis: C:\Program Files\Microsoft Visual Studio2022円\Professional\Common7\
 Packages\Debugger\Visualizers\SAFEARRAY.natvis(10,21):
 Fatal error:
 Element '{http://schemas.microsoft.com/vstudio/debugger/natvis/2010}ArrayItems'
 is unexpected according to content model of parent element
 '{http://schemas.microsoft.com/vstudio/debugger/natvis/2010}Item'.

Where can I find a schema/DTD for creating native visualisers? I know it's embedded into the executable of Visual Studio but in a world of sharing knowledge, there must be a copy of this document somewhere. Can anybody show me such a schema/DTD?

• IInspectable: The schema is published here.
• IInspectable: Also consider studying windows.natvis (in the same folder you placed your visualizer). It provides a visualizer for SAFEARRAY/tagSAFEARRAY that can serve as a starting point for customization. I don't know how Visual Studio's debugger prioritizes which visualizer to use in case there is more than one for a particular type.

Answer 1

ArrayItems doesn't belong inside an Item. It should be at the same level (under Expand) as any Items you may have.

If you're trying to flatten the hierarchy, then I think you'll need ExpandedItem. If you're trying to create an extra level, see Synthetic.

The links above jump into the Microsoft reference for creating C++ visualizers. It seems a rather complete description of the XML scheme.

• SoronelHaetir: Also note that you can enable visualizer debugging under tools -> options, Debugging -> Output window. Errors in the visualizer schema will then be related as encountered.
• Dominique: Your answer, combined with the natvis schema link, provided by your colleague "stackoverflow.com/users/1889329/iinspectable" (iinspectabe), solves my question. Thanks.