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Designer initialization and metadata configuration

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Manipulation of the metadata and filter attributes associated with a designer or designer component provides a mechanism for applications to define which tools are used by a particular designer to handle different Type objects (such as data structures, classes, or graphical entities), when the designer is available, and how the Visual Studio IDE is configured to support the designer (for instance which Toolbox category or tab is available).

The Visual Studio SDK provides several mechanisms to facilitate the control of a designer's or designer component's initialization and the manipulation of its metadata by a VSPackage.

Initialize metadata and configuration information

Because they are loaded on demand, VSPackages may not have been loaded by the Visual Studio environment prior to the instantiation of a designer. Therefore, VSPackages cannot use the standard mechanism for configuring a designer or designer component on creation, which is to handle a DesignerCreated event. Instead, a VSPackage implements an instance of the DesignSurfaceExtension interface and registers itself to provide customizations, referred to as design surface extensions.

Customize initialization

Customizing a designer, a component, or a designer surface, involves:

  1. Modifying the designer metadata and effectively changing how a certain Type is accessed or converted.

    This is typically done through the UITypeEditor or TypeConverter mechanisms.

    For example, when System.Windows.Forms-based designers are initialized, the Visual Studio environment modifies the UITypeEditor for Image objects used with the designer to use the resource manager to obtain bitmaps rather than the file system.

  2. Integrating with the environment, for example, by subscribing to events or obtaining project configuration information. You can obtain project configuration information and subscribe to events by obtaining the ITypeResolutionService interface.

  3. Modification of the user environment by activating appropriate Toolbox categories or by restricting the designer's applicability by applying an instance of the ToolboxItemFilterAttribute class to the designer.

Designer initialization by a VSPackage

A VSPackage should handle designer initialization by:

  1. Creating an object implementing the DesignSurfaceExtension class.

    Note

    The DesignSurfaceExtension class should never be implemented on the same object as the Package class.

  2. Registering the class that implements DesignSurfaceExtension as providing support for the VSPackage's designer extensions. Register the class by applying instances of DesignSurfaceExtensionAttribute, ProvideObjectAttribute, and ProvideServiceAttribute to the class that provides the VSPackage's implementation of Package.

Whenever a designer or designer component is created, the Visual Studio environment:

  • Accesses each registered design surface extension provider.

  • Instantiates and initializes an instance of each design surface extension provider's DesignSurfaceExtension object.

  • Calls each design surface extension provider's OnDesignerCreated method or OnComponentCreated method (as appropriate).

When implementing the DesignSurfaceExtension object as a member of a VSPackage, it is important to understand that:

  • The Visual Studio environment does not provide any control over what metadata or other configuration settings a particular DesignSurfaceExtension provider's modifies. It is possible for two or more DesignSurfaceExtension providers modifying the same designer feature in conflicting ways, with the final modification being definitive. It is indeterminate which modification is last applied.

  • It's possible to explicitly restrict an implementation of the DesignSurfaceExtension object to specific designers by applying instances of ToolboxItemFilterAttribute to that implementation. For more information on Toolbox item filtering, see the ToolboxItemFilterAttribute and ToolboxItemFilterType.

Additional metadata provisioning

A VSPackage can change the configuration of a designer or designer component other than at design time.

The ProvideDesignerMetadataAttribute class can be used programmatically or applied to a VSPackage that provides a designer.

An instance of the ProvideDesignerMetadataAttribute class is used to modify the metadata of components created on a design surface. For example, one could replace a default property browser used by CommonDialog objects with a custom property browser.

Modifications provided by an instance of ProvideDesignerMetadataAttribute applied to a VSPackage's implementation of Package can have one of two scopes:

  • Global -- for all new instances of a given component

  • Local -- pertaining only to instance of the component created on a design surface provided by the current VSPackage.

The IsGlobal property of the ProvideDesignerMetadataAttribute instance applied to a VSPackage's implementation of Package determines this scope.

Applying the attribute to an implementation of Package with the IsGlobal property of the ProvideDesignerMetadataAttribute object set to true, as below, changes the browser for the entire Visual Studio environment:

[ProvideDesignerMetadata(typeof(Color), typeof(CustomBrowser), IsGlobal=true )]

internal class MyPackage : Package {}

If the global flag was set to false, then the metadata change is local to the current designer supported by the current VSPackage:

[ProvideDesignerMetadata(typeof(Color), typeof(CustomBrowser), IsGlobal=false )]

internal class MyPackage : Package {}

Note

The design surface only supports creating components, and therefore only components can have local metadata. In the example above, we were attempting to modify a property, such as the Color property of an object. If false was passed in for the global flag, CustomBrowser would never appear because the designer never actually creates an instance of Color. Setting the global flag to false is useful for components, such as controls, timers, and dialog boxes.

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