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Providing a User Interface

DSP plug-ins can provide a property page to create a user interface. To do this, the plug-in must include a property page object that provides an implementation of an IPropertyPage interface. The DSP plug-in object must implement ISpecifyPropertyPages::GetPages, which allows Windows Media Player to locate and identify the correct property page for the plug-in.

Displaying a Status Graphic

DSP plug-ins can display a small graphic, or series of graphics, in the Windows Media Player status area to notify the user that a plug-in is active. To support this feature, the plug-in must implement the IPropertyBag interface. Windows Media Player calls IPropertyBag::Read, providing a pointer to the requested property name "IconStreams", which is case-sensitive, and a pointer to a VARIANT structure that receives the data for the graphic. The plug-in creates an IStream object (or a SAFEARRAY of IStream objects if there are multiple graphics), then loads the graphic data, including header information, into the stream, and then returns a pointer to the IStream object using the punkVal member of the VARIANT structure. If the plug-in supplies only one graphic, it specifies the vt member of the VARIANT structure as VT_UNKNOWN. If the plug-in supplies multiple graphic IStream objects using a SAFEARRAY, it specifies the vt member of the VARIANT structure as VT_ARRAY.

Graphics can be stored in a variety of file formats, including:

BMP

Microsoft Windows Bitmap images are uncompressed.

JPEG

Compressed image format commonly used for webpages. JPEG format files usually have .jpg file name extensions.

GIF

Compressed image format commonly used for webpages.

PNG

Compressed image format commonly used for webpages.

The maximum dimensions for DSP plug-in graphics are 38 pixels wide and 14 pixels high.

The IStream byte stream containing the status graphic must include header information. Without header information, Windows Media Player cannot properly identify the type of graphic and therefore will not load the image.

Related topics

DSP Plug-in Developer Overview

 

 

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