{"id":171,"date":"2014-04-02T21:39:04","date_gmt":"2014-04-03T04:39:04","guid":{"rendered":"http:\/\/visualgdb.com\/w\/?p=171"},"modified":"2023-03-29T17:57:12","modified_gmt":"2023-03-30T00:57:12","slug":"visualizergettingstarted","status":"publish","type":"post","link":"https:\/\/visualgdb.com\/w\/tutorials\/visualizergettingstarted\/","title":{"rendered":"Getting started with VisualGDB Type Visualizers"},"content":{"rendered":"

Type visualizers are a powerful mechanism allowing you to display the variable values during debugging in a more user-friendly way than simply listing all members. This is extremely useful if your program contains custom STL-like containers or string classes.<\/p>\n

This tutorial shows the very basics of making a simple type visualizer and registering it with VisualGDB. It will simply make VisualGDB show “Hello, Visual Studio” instead of the actual value for a given C++ class.<\/p>\n

    \n
  1. Create a simple “Hello, World” application with VisualGDB. Although the type visualizers will work for all projects types, the most simple way to start is by creating a MinGW application (follow this tutorial<\/a>).<\/li>\n
  2. Replace the contents of the main C++ file with the following:\n
    #include<stdio.h>\r\n\r\ntemplate <class _Type> class VeryBasicArray\r\n{\r\nprivate:\r\n    size_t m_Count;\r\n    _Type *m_pData; \r\n};\r\n\r\nint main()\r\n{\r\n    VeryBasicArray<int> test;\r\n    return 0;\r\n}<\/pre>\n<\/li>\n
  3. Place a breakpoint at the “return 0” line and start debugging. When the breakpoint is hit, hover the mouse over “test” to see its value:\"01-expval\"<\/a><\/li>\n
  4. We will now make a VisualGDB plugin that will replace the value of test (“m_Count = 68, m_pData = …”<\/strong>) with a custom string. Please refer to the SDK reference<\/a> for more information about things that type visualizers can change.<\/li>\n
  5. Start Visual Studio as Administrator so that it can write to the VisualGDB installation directory inside Program Files. Go to FIle->New Project and select C# -> Class Library:\"02-csproj\"<\/a><\/li>\n
  6. Right-click on the newly created project, select “Add Reference”. Select “Browse” and point to the  VisualGDBExpressions.dll<\/strong> assembly inside the VisualGDB directory.<\/li>\n
  7. Right-click on the project and select “Properties”. Go to the Debug tab, select “Start External Program” and specify the path to your Visual Studio’s devenv.exe:\"03-debugsettings\"<\/a><\/strong><\/li>\n
  8. Go to the Build Events page and specify the following post-build command line:\n
    copy \/y $(TargetPath) \"C:\\Program Files (x86)\\Sysprogs\\VisualGDB\\TypeVisualizers<\/pre>\n
    Ensure that the VisualGDB installation directory is specified correctly.<\/li>\n
  9. Add a file called MyBasicFilter.cs<\/strong> with the following contents:\n
    using System;\r\nusing System.Collections.Generic;\r\nusing System.Linq;\r\nusing System.Text;\r\nusing System.Threading.Tasks;\r\nusing VisualGDBExpressions;\r\n \r\nnamespace MyTypeVisualizer\r\n{\r\n    class MyBasicFilter : TypeListBasedExpressionFilter\r\n    {\r\n        public MyBasicFilter()\r\n            : base(\"VeryBasicArray<\")\r\n        {\r\n        }\r\n\r\n        protected override IExpression DoAttach(\r\n             IExpression expr, \r\n             IExpressionEvaluator evaluator)\r\n        {\r\n            return new StaticExpressionFilter(expr) \r\n                 { \r\n                     ValueOverride = new ExpressionValue.Custom(\r\n                                         \"Hello, Visual Studio\")\r\n                 };\r\n        }\r\n    }\r\n }<\/pre>\n<\/li>\n
  10. Add a file called Factory.cs<\/strong> with the following contents:\n
    using System;\r\nusing System.Collections.Generic;\r\nusing System.Linq;\r\nusing System.Text;\r\nusing System.Threading.Tasks;\r\nusing VisualGDBExpressions;\r\n\r\nnamespace MyTypeVisualizer\r\n{\r\n    public class MyFilterFactory : IExpressionFilterFactory\r\n    {\r\n        public IEnumerable<ExpressionFilterRecord>\r\n             CreateExpressionFilters()\r\n        {\r\n            return new ExpressionFilterRecord[] \r\n            {\r\n                 new MyBasicFilter().Record\r\n            };\r\n        }\r\n    }\r\n}\r\n<\/pre>\n<\/li>\n
  11. Build the project. Ensure that your DLL has been copied to the TypeVisualizers<\/strong> directory inside the VisualGDB directory (the directory should already contain STLTypeVisualizer.dll<\/strong>).<\/li>\n
  12. Start debugging your project. Another instance of Visual Studio will be executed. Open your VisualGDB-based project using that Visual Studio. Put a breakpoint on the return statement and run the project.<\/li>\n
  13. Hover the mouse over “test” to see the modified value:\"04-hooked\"<\/a><\/li>\n
  14. Go back to the outer Visual Studio instance, set a breakpoint inside the DoAttach() function, go back to the inner Visual Studio and hover the mouse over test<\/strong> again. A breakpoint will be triggered.
    \nDo not evaluate the  IExpression<\/strong> members in the outer Visual Studio. This would require a cross-thread call that cannot be performed while your plugin is stopped at a breakpoint.<\/span><\/li>\n
  15. Use edit-and-continue to copy the value of expr.Type into a temporary variable. Run the newly created statement using the “Set next statement” and “Step” commands:\"05-enc\"<\/a><\/li>\n<\/ol>\n
    Now we are ready to make a meaningful expression visualizer. Follow the next tutorial<\/a> to make this visualizer display array contents in a structured way.<\/p>\n
    The explanation<\/h2>\n
    This section explains how the basic visualizer implemented above works.<\/p>\n
    When we inherited the TypeListBasedExpressionFilter<\/a> class and specified “VeryBasicArray<” in the constructor, we have created a simple filter that only attaches itself to instances of the VeryBasicArray class.<\/p>\n
    The DoAttach() method essentially allows replacing an expression (the original value) with another arbitrary expression returned by the method. However, instead of implementing the  IExpression<\/a> interface manually we have used the StaticExpressionFilter<\/a> class to make a clone of the original expression replacing the value with our string (represented as an instance of  ExpressionValue.Custom<\/a>).<\/p>\n
    Source code<\/h2>\n
    You can download the source code for the example in this tutorial here<\/a>. The code in the archive is provided under the BSD license.<\/p>\n
     <\/p>\n
     <\/p>\n","protected":false},"excerpt":{"rendered":"
    Type visualizers are a powerful mechanism allowing you to display the variable values during debugging in a more user-friendly way<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[26],"tags":[],"_links":{"self":[{"href":"https:\/\/visualgdb.com\/w\/wp-json\/wp\/v2\/posts\/171"}],"collection":[{"href":"https:\/\/visualgdb.com\/w\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/visualgdb.com\/w\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/visualgdb.com\/w\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/visualgdb.com\/w\/wp-json\/wp\/v2\/comments?post=171"}],"version-history":[{"count":11,"href":"https:\/\/visualgdb.com\/w\/wp-json\/wp\/v2\/posts\/171\/revisions"}],"predecessor-version":[{"id":8037,"href":"https:\/\/visualgdb.com\/w\/wp-json\/wp\/v2\/posts\/171\/revisions\/8037"}],"wp:attachment":[{"href":"https:\/\/visualgdb.com\/w\/wp-json\/wp\/v2\/media?parent=171"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/visualgdb.com\/w\/wp-json\/wp\/v2\/categories?post=171"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/visualgdb.com\/w\/wp-json\/wp\/v2\/tags?post=171"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}