Tag Archives: XAML

Drawing a transparent image with OpenGL ES in a UWP XAML app

In my previous post Testing XAML App for OpenGL ES on Windows 10 Mobile Device I described the changes I made to UWP application based on “XAML App for OpenGL ES (Universal Windows)” template to demonstrate some strange effect related to the transparency of the image drawn with OpenGL ES in SwapChainPanel. But I did yet another experiment with this application and got some beautiful pictures that demonstrate what happens if I make the scene completely transparent with the following code:

void SimpleRenderer::Draw()
{
    glEnable(GL_DEPTH_TEST);
    glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    ...
}

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Testing XAML App for OpenGL ES on Windows 10 Mobile Device

Today I played a bit with a UWP application based on “XAML App for OpenGL ES (Universal Windows)” template and realized that there is some specific bug probably related to the interaction between SwapChainPanel and OpenGL surface. First, I made the cube transparent by changing two lines of code in the vertex shader:

const std::string vs = STRING
(
    uniform mat4 uModelMatrix;
    uniform mat4 uViewMatrix;
    uniform mat4 uProjMatrix;
    attribute vec4 aPosition;
    attribute vec3 aColor;
    varying vec4 vColor;
    void main()
    {
        gl_Position = uProjMatrix * uViewMatrix * uModelMatrix * aPosition;
        vColor = vec4(aColor, 0.1);
    }
);

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Initialization of UWP C++ XAML application

UWP C++ applications based on “DirectX 11 and XAML App” or “XAML App for OpenGL ES“ project templates have some partial App class defined in user code and in generated file App.g.h:

partial ref class App :  public ::Windows::UI::Xaml::Application,
    public ::Windows::UI::Xaml::Markup::IXamlMetadataProvider
{
public:
    void InitializeComponent();
    [Windows::Foundation::Metadata::DefaultOverload]
    virtual ::Windows::UI::Xaml::Markup::IXamlType^ GetXamlType(::Windows::UI::Xaml::Interop::TypeName type);
    virtual ::Windows::UI::Xaml::Markup::IXamlType^ GetXamlType(::Platform::String^ fullName);
    virtual ::Platform::Array<::Windows::UI::Xaml::Markup::XmlnsDefinition>^ GetXmlnsDefinitions();
private:
    ::XamlTypeInfo::InfoProvider::XamlTypeInfoProvider^ _provider;
    bool _contentLoaded;
};

the user code:

ref class App sealed
{
public:
    App();
    virtual void OnLaunched(Windows::ApplicationModel::Activation::LaunchActivatedEventArgs^ e) override;
    ...
};

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Combining OpenGL and XAML together in a Universal Windows App (UWP)

Visual Studio 2015 allows easily combine OpenGL graphics with XAML controls in a single window. To accomplish this task we can create a new project based on “XAML App for OpenGL ES (Universal Windows)” template:

XAML App for OpenGL ES (Universal Windows)

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How to multiply a value by a constant in WinRT XAML

The easiest way to accomplish this task is to use converter provided below. It is written in C++ but this convertor can be easily converted to C#:

[Windows::Foundation::Metadata::WebHostHidden]
public ref class MultiplicationConverter sealed : Windows::UI::Xaml::Data::IValueConverter
{
public:

    virtual Platform::Object^ Convert(Platform::Object^ value, Windows::UI::Xaml::Interop::TypeName targetType, Platform::Object^ parameter, Platform::String^ language);

    virtual Platform::Object^ ConvertBack(Platform::Object^ value, Windows::UI::Xaml::Interop::TypeName targetType, Platform::Object^ parameter, Platform::String^ language);

private:

    Platform::Object^ InternalConvert(Platform::Object^ value, Platform::Object^ parameter, bool forward);
};

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