JVCL Help:IJvDataItemsRenderer
JVCL Help: IJvDataItemsRenderer Interface
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IJvDataItemsRenderer
TJvBaseDataItemsRenderer
run\JvDataProviderIntf.pas
Summary
Support interface for IJvDataItems that handles rendering and measuring of its items and their sub items.
Pascal
run\JvDataProviderIntf.pas
IJvDataItemsRenderer = interface;
Description
IJvDataItemsRenderer is an optional supporting interface for IJvDataItems that can handle the rendering and measuring of the items in the list.
The interface provides methods to:
- Draw an item given its index.
- Measure an item given its index.
- Draw the specified IJvDataItem instance.
- Measure the specified IJvDataItem instance.
- Determine the average item size.
Some implementations of this interface will first check if the item to render or measure supports the IJvDataItemRenderer interface; if it does, it will redirect the operation to that implementation instead of handling it itself.
Consumers generally handle rendering/measuring in the following way:
- Check if the item supports the IJvDataItemRenderer interface. If it does use it to perform the rendering/measuring.
- Check for the closest IJvDataItemsRenderer interface (the direct owning IJvDataItems list or anyof the lists in its parent chain). If it finds one use it to perform the rendering/measuring.
- Handle the rendering at the consumer side. This means all items are considered equal and usually only IJvDataItemText and optionally IJvDataItemImage (and the corresponding IJvDataItemsImages) are used. The entire rendering/measuring is then consumer (control) dependent and the provider tree may no longer look uniform in different consumers/clients.
See Also
IJvDataItemRenderer, IJvDataItems
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