MapContext CoClass

The context in which geometric effects and marker placement work.

Product Availability

Extended Error Information

Use the ISupportErrorInfo method InterfaceSupportsErrorInfo to determine if the object supports extended error information. If the object supports extended error info, VC++ developers should use the OLE/COM IErrorInfo interface to access the ErrorInfo object. Visual Basic developers should use the global error object Err to retrieve this extended error information.

Interfaces

Remarks

There are three reference frames which are used for data translation between geographic, map and output display context. These frames are:

1. Geographic Reference Frame: A feature layer represents geographic data and may be re-projected prior to drawing the features onto a map.
2. Map Reference Frame: This is an intermediate frame introduced to define a clear context in which geometric effects and all on-the-fly processing works. This frame is similar to the map sheet frame which is used with a 72 dpi graphic resolution centered at the center of the geographic spatial reference. The advantage of having the map reference frame is to provide a stable context for geometric effects and marker placement properties as this is in a graphic frame but independent of zoom levels and pan positions. All linear attributes (distance/length) are relative to this frame. For example, a 12 point offset is a 12 unit displacement in MRF. Effects will store these attributes in MRF units and use them without any transformation.
3. Output Reference Frame: This consists of an output device, that displays the map with a zoom level which is not equal to the reference scale and a changed center position.

MapContext CoClass relates to the Map Reference Frame. IMapContext interface manages the map context object.