Implemented by clients to receive reports of buffer operation progress.
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OnOperationBegin | Called at the beginning of each buffer operation. For example, buffering a set of polygons and polylines, without dissolve, has two operations. |
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OnStageBegin | Called at the beginning of the next buffering stage within an operation. |
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OnStepCompleted | Called periodically to report number of steps completed in current stage. |
Remarks
ConstructBuffers , ConstructBuffersByDistances and ConstructBuffersByDistances2 can report progress, if desired, during lengthy operations. You can implement the IBufferProgress interface and specify it as the parameter to the BufferProgress property of a BufferConstruction object. You will then be notified of buffer progress events. You can also cancel a buffer operation in your implementation of the methods on this interface.
Buffer progress is measured in units of operations, stages and steps. An operation is either the action of buffering a group of geometries of the same dimension, or of dissolving together buffers generated from inputs of different dimensions. Each operation has one or more stages. Point buffering always has one stage. Polyline and polygon buffering may have multiple stages. Finally, each stage is divided into steps. There is one step for each buffer that is generated from each individual input.
Here are some examples.
1. Buffer 1000 points, without unioning the buffers. There is one operation, one stage and step progress will be reported for every point.
2. Buffer 1000 points with dissolve. There is 1 operation, 1 stage, and some number of steps, but in this case the steps correspond to progress made through both the buffering and dissolve operations, and thus do not correspond to individual points being buffered.
3. Buffer 500 points and 500 polygons, without dissolve. There are 2 operations. The polygon buffer operation may be subdivided into multiple stages depending on the buffer distance and complexity of the polygons encountered. Multiple stages mean that the buffers are grown incrementally. So for example, buffers at a distance of distance/3 are first generated, then those are rebuffered, etc. The number of stages may not be known in advance and could increase during the course of processing. There is one step per generated buffer.
4. 500 points and 500 polygons are buffered with dissolve. There are 3 operations, the final one being the dissolve operation. There may be multiple stages for the polygon buffering operation, depending on the buffer distance and how complicated the polygons are. If so, each stage would report 500 polygon buffering steps.