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Create views of OpenCASCADE objects in the Debugger

eryar@163.com

Abstract.The Visual Studio Natvis framework lets you customize the way Visual Studio displays native types in debugger variable windows such as the Watch, Locals and Data Tips windows. It supersedes the autoexp.dat file that has been used in earlier versions of Visual Studio and offers XML syntax, better diagnostics, versioning, and multiple file support. The container in OpenCASCADE is difficult for debugging, such as TColStd_Array1OfInteger in the TColStd package, .etc. Use the natvis framework to create views of these objects will make it easy for developers to inspect them during debugging and so accelerate the debug process.

Key Words.Visual Studio Natvis, OpenCASCADE

1. Introduction

因为OpenCASCADE早期使用C开发，所以自定义了一些容器类，如包TColStd中的类，TColGeom包及包TopTools中的类等，这些类在C++中都可以使用STL来替代了。这些类在Debug过程中，很难查看其中的值，如TColStd_Array1OfInteger，这个类相当于 std::vector<int>，但是Debug时只能看到数据的指针，不容易查看容器中每个元素的值，如下图1.1所示：

Create views of OpenCASCADE objects in the Debugger

Figure 1.1 View of TColStd_Array1OfInteger in Locals Window

由上图1.1可知，对于这个类的对象，Debug时只能看到数据的起始指针。为了方便自定义类型调试，Visual Studio在2012版本以后，引入了Natvis框架，用来替代原来的autoexp.dat来为自定义类型定义调试时的数据显示。Natvis使用了XML文件，可读性更好，易于实现。

本文使用Visual Studio的Natvis框架，来对OpenCASCADE中的一些容器类数据进行可视化，方便开发者对OpenCASCADE的调试。

2.For Array Container

对于OpenCASCADE的包TColStd中的数组类，定义其natvis如下所示：

<Type Name="TColStd_Array1OfInteger">  <DisplayString Condition="isAllocated != 1">empty</DisplayString>   <DisplayString>{{size = {myUpperBound - myLowerBound + 1}}}</DisplayString>  <Expand>   <Item Condition="isAllocated == 1" Name="[size]">myUpperBound - myLowerBound + 1</Item>   <ArrayItems Condition="isAllocated == 1">    <Size>myUpperBound - myLowerBound + 1</Size>    <ValuePointer>(Standard_Integer*)(myStart) + myLowerBound</ValuePointer>   </ArrayItems>  </Expand> </Type>

调试时数据显示如下图2.1所示：

Create views of OpenCASCADE objects in the Debugger

Figure 2.1 OpenCASCADE array in Locals Windows

同理，可对此包中其他一维数组使用同样的规则，即可对其中的数据可视化，与std::vector显示的效果一样，方便调试。

3.For List Container

对于OpenCASCADE的包TColStd中的链表类，定义其natvis如下所示：

<Type Name="TColStd_ListNodeOfListOfInteger">  <DisplayString>{{current = {myValue}}}</DisplayString>  <Expand>   <LinkedListItems>    <HeadPointer>this</HeadPointer>    <NextPointer>(TColStd_ListNodeOfListOfInteger*)myNext</NextPointer>    <ValueNode>this->myValue</ValueNode>   </LinkedListItems>  </Expand> </Type> <Type Name="TColStd_ListOfInteger">  <DisplayString Condition="myFirst == 0">empty</DisplayString>  <Expand>   <Item Name="first">(TColStd_ListNodeOfListOfInteger*)myFirst</Item>  </Expand> </Type>