Setting "Program Files" as a default installation directory in the Qt Installer Framework

In the Qt Installer Framework, all of the demos have TargetDir specification that (for Windows) place the application in, e.g., C:\InstallationDirectory. How can I have it default to Program Files?

<?xml version="1.0" encoding="UTF-8"?>
<Installer>
    <Name>Your application</Name>
    <Version>1.2.3</Version>
    <Title>Your application Installer</Title>
    <Publisher>Your vendor</Publisher>
    <StartMenuDir>Super App</StartMenuDir>
    <TargetDir>@RootDir@InstallationDirectory</TargetDir>
</Installer>

There is no option for this, but you can create use the Component Scripting interface to set the installation directory, as described here.

First, in your packages/com.myorg.myapp/meta/package.xml file, include this reference to the script file.

<?xml version="1.0" encoding="UTF-8"?>
<Package>
    ...
    <Script>installscript.qs</Script>
</Package>

The installscript.qs file, which should be in the same directory as package.xml, should be the following:

function Component()
{
     var programFiles = installer.environmentVariable("ProgramFiles");
     if (programFiles != "")
         installer.setValue("TargetDir", programFiles + "/MyPath");
}

Now the installer framework will suggest C:\Program Files\MyPath or C:\Program Files (x86)\MyPath, as needed.

Finally, if you want to allow installation paths with spaces (like C:\Program Files\MyPath), you need to enable that specifically in config/config.xml by adding this line:

<?xml version="1.0" encoding="UTF-8"?>
<Installer>
     ...
     <AllowSpaceInPath>true</AllowSpaceInPath>
</Installer>