While debugging you can view your variable's value. Visual Studio will try its best to show you relevant information, but there are times where being defining our own visualization rules would improve readability. This is where debugger visualizers come in.
For example, say we define a new type age (see strong typedefs):
struct age : tagged<int, age>, ordered<age> { using tagged::tagged; };
age a(5);When querying the value of a while debugging, Visual Studio
shows you { ... }. Hardly impressive. There is the
possibility to expand the view, which results in
a { ... }
tagged<int, age> { _value = 5 '\x5' }
ordered<age> { ... }
We'd prefer it if we didn't have to press the expand arrow
to find out what a's value is.
To define a debugger visualizer for values of type age,
start by adding a .natvis file to your project:
- Right click on the project
- Add
- New Item
- Under Utility, choose Debugger visualization file
Open this file. It should contain
<?xml version="1.0" encoding="utf-8"?>
<AutoVisualizer xmlns="http://schemas.microsoft.com/vstudio/debugger/natvis/2010">
</AutoVisualizer>Add the following rule for the type age:
<?xml version="1.0" encoding="utf-8"?>
<AutoVisualizer xmlns="http://schemas.microsoft.com/vstudio/debugger/natvis/2010">
+ <Type Name="age">
+ <DisplayString>{{age = {_value,d}}}</DisplayString>
+ </Type>
</AutoVisualizer>The DisplayString determines what is shown while debugging.
With the configuration above, viewing an age variable will reveal
a { age = 5 '\x5' }
which is more helpful that the old { ... }.