Platform-specific guides » Windows

Tips and tricks for Windows platforms.

HiDPI support

Windows supports two approaches to advertising HiDPI support. The recommended way is via a so-called manifest file added to an executable, but it's also possible to it programatically through the SetProcessDpiAwareness() family of APIs. Note there's three different levels of DPI awareness setup for Windows Vista and newer, Windows 8.1 and newer and Windows 10, and for best support may want to support all three.

When using MSVC, the manifest file can be added directly via CMake. Advertising application-wide per-monitor support can look like in the following snippet, together with fallbacks for older systems:

<assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0"
          xmlns:asmv3="urn:schemas-microsoft-com:asm.v3">
<asmv3:application>
  <asmv3:windowsSettings>
    <dpiAware xmlns="http://schemas.microsoft.com/SMI/2005/WindowsSettings">
      true/pm
    </dpiAware> <!-- legacy -->
    <dpiAwareness xmlns="http://schemas.microsoft.com/SMI/2016/WindowsSettings">
      permonitorv2,permonitor
    </dpiAwareness> <!-- falls back to pm if pmv2 is not available -->
  </asmv3:windowsSettings>
</asmv3:application>
</assembly>

Then, the manifest file can be supplied directly in the sources list for add_executable(), via a variable, or you can add it conditionally later using target_sources(). For example:

add_executable(my-application MyApplication.cpp)
if(CORRADE_TARGET_WINDOWS)
    target_sources(my-application PRIVATE WindowsHiDPI.manifest)
endif()

Some toolkits (such as GLFW in Platform::GlfwApplication) are advertising HiDPI support implicitly programatically. In that case the manifest file doesn't need to be supplied, but there may be some disadvantages compared to supplying the manifest. See the MSDN documentation about DPI awareness for more information.

Unicode support

Windows is the only major platform that forces developers into UTF-16. This presents several challenges, however Magnum tries to shield users from this as much as possible:

Colored terminal output

There's two options for colored terminal output — either using the classic Windows API (which is the default), or making use of the ANSI color escape codes compatible with all Unix systems. The former has a restriction that it works only when printing directly to the terminal (so your colors will get lost if you redirect to a file). The latter is available only in Windows 10, has to be explicitly enabled using CORRADE_UTILITY_USE_ANSI_COLORS when building Corrade and additionally requires an explicit setup during application startup. This setup is done when you link to the Corrade::Main library, see its documentation for more information.

Hiding console window

By default, CMake compiles GUI applications with a potentially unwanted console window lurking in the background. This can be fixed by creating your executable with add_executable(... WIN32 ...) and linking to the Corrade::Main library. See its documentation for more information.

Windows RT

Windows RT is a restricted subset of Windows API, used for UWP / "Metro" / Windows Store apps. The major difference is lack of access to APIs that are common in Win32 world, such as memory-mapped files, DLLs or environment variables.

In particular, Windows RT doesn't provide a direct access to OpenGL, the only possibility to use it is through ANGLE. See Building for ANGLE on Windows and ANGLE for more information.

For Windows RT you need to provide logo images and splash screen, all referenced from the *.appxmanifest file. The file is slightly different for different targets, template for Windows Store and MSVC 2013 is below, others are in the SDL2 bootstrap application.

<?xml version="1.0" encoding="utf-8"?>
<Package xmlns="http://schemas.microsoft.com/appx/2010/manifest"
         xmlns:m2="http://schemas.microsoft.com/appx/2013/manifest">
  <Identity Name="MyApplication" Publisher="CN=A Publisher" Version="1.1.0.0" />
  <Properties>
    <DisplayName>My Application</DisplayName>
    <PublisherDisplayName>A Publisher</PublisherDisplayName>
    <Logo>assets/logo-store.png</Logo>
  </Properties>
  <Resources>
    <Resource Language="x-generate" />
  </Resources>
  <Applications>
    <Application Id="App" Executable="$targetnametoken$.exe"
                 EntryPoint="MyApplication.App">
      <m2:VisualElements
        DisplayName="Magnum Windows Store Application"
        Description="My Application"
        BackgroundColor="#202020"
        ForegroundText="light"
        Square150x150Logo="assets/logo.png"
        Square30x30Logo="assets/logo-small.png">
        <m2:SplashScreen Image="assets/splash.png" />
      </m2:VisualElements>
    </Application>
  </Applications>
</Package>

The assets are referenced also from the main CMakeLists.txt file. You have to mark all non-source files (except for the *.pfx key) with VS_DEPLOYMENT_CONTENT property and optionally set their location with VS_DEPLOYMENT_LOCATION. If you are using *.resw files, these need to have the VS_TOOL_OVERRIDE property set to PRIResource.

MSVC version mapping

MSVC and Visual Studio use three, er, four different versioning schemes. CMake exposes compiler version equivalent to the _MSC_VER macro, see this handy Wikipedia table for mapping to Visual Studio versions. For example, a check for MSVC 2017 would look like this:

if(CMAKE_CXX_COMPILER_ID STREQUAL "MSVC" AND NOT
   CMAKE_CXX_COMPILER_VERSION VERSION_LESS "19.10")
    # Code requiring MSVC 2017
endif()

Troubleshooting

Ninja spams the output with tons of include file notices

This happens when you have a non-English locale of Visual Studio installed and apart from the spammy output it will probably cause incremental builds to not correctly rebuild files after a header change. A workaround is to uninstall the current locale and install the English one instead, additionally you have to recreate your build directory. See ninja-build/ninja#613 for more information.

Code page warnings with MSVC

On some Windows systems with non-English locales, a warning similar to the following might come up, emitted for practically any Magnum header:

src\Corrade/Utility/Debug.h : warning C4819: The file contains a character that cannot be represented in the current code page (949). Save the file in Unicode format to prevent data loss

This is due to Visual Studio expecting header files in your system locale. All Magnum headers are deliberately containing UTF-8 characters (usually at least the © character in the license block) in order to prevent encoding errors in 3rd party contributions. Solution is to convert your source files to UTF-8 as well, and, if the warning doesn't go away, add /utf-8 to CMAKE_CXX_FLAGS — either on the command line / via CMake GUI, or by directly adding the flag to your project's CMakeLists (useful if your whole team suffers from this problem). See https://stackoverflow.com/a/37872393 for more information.

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /utf-8")

The ALL_BUILD project can't be executed

When CMake generates Visual Studio projects, it will set ALL_BUILD as a default project. This can be annoying since the ALL_BUILD can be only built but not executed, and thus pressing Build & Run will fail with an error. A workaround is to right-click the actual executable target (such as MyApplication) and select Set as Startup Project. With CMake 3.6 and newer, this can be also changed by setting the VS_STARTUP_PROJECT property for the project directory:

add_executable(MyApplication ...)
set_property(DIRECTORY ${PROJECT_SOURCE_DIR} PROPERTY VS_STARTUP_PROJECT MyApplication)

The Magnum bootstrap projects set this automatically.