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Object Snap Control
The Object Snap Control is an ActiveX component that is designed for implementation in MapGuide applications
that require snapping capability. The control may be used in Redline applications that permit users to
add or modify objects, enabling the snapping of vertices to existing map objects. The Control provides
a set of public methods that enable the developer to:
- establish the snapping parameters, including:
- the vertices of an object to move: start node, end node, both endpoints, all vertices
- the types of locations to snap to: endpoint, vertex, intersection
- the maximum snap distance
- whether all layers or selected layers can be snapped to
- set the type of input and output coordinates: latitude/longitude or Mapping Coordinate System (MCS)
- pass an MGPoint or an MGCollection (of MGPoints) to the control,
- pause the MapGuide Viewer Control to avoid isBusy() conflicts.
When authoring maps, general or password access must be granted to the vertices of the layers which
are to be eligible for snapping; refer to the layer's Security tab. If password
access is granted, then the user will be prompted to enter the appropriate password when an object
from the layer is selected for evaluation.
The control appears as a clickable button:
The button may be sized through the BoxWidth and BoxHeight parameters while the label is set through the ButtonLabel
parameter. Clicking on the button pulls up the Snap Menu:
| Function |
Description |
| Move |
Defines the types of vertices in the object
passed to the control that are eligible to be relocated via snapping: None, Start Node Only, End Node Only, Both Endpoints,
All Vertices.
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| To |
The type of location that a vertex may
be snapped to: An Endpoint, Any Vertex, An Intersection. More than one option may be selected.
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| Distance |
The maximum distance that a vertex
can be moved, expressed in Mapping Coordinate System units.
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| On |
The vertex may be snapped to Any Object or
to an object on Selected Layers.
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| Layers |
A list of the layers in the map.
Check the box of those layers that a vertex may be snapped to; this list is ignored if the
vertex can be snapped to Any Object.
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The snap parameters may also be established through the control's public methods.
Loading the Control
Instructions for implementing the control on web pages are provided with the Toolkit documentation.
Parameters
| Name |
Description |
| Delim |
the delimiter used to separate items in a list, generally a forward slash (Default: "/")
(refer to SnapParamLayer).
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| PauseLen |
the length of time in seconds to
wait for the map prior to issuing an isBusy() call. Refer to the waitForMap() method. (Default: 2)
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| SnapParamMove |
Defines the types of vertices in the object passed to the control that are eligible to be relocated via snapping:
| 0 | | | None (default) |
| 1 | | | start node only |
| 2 | | | end node only |
| 3 | | | both endpoints |
| 4 | | | all vertices |
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| SnapParamTo |
Defines the type of location that a vertex may be snapped to:
| 1 | | | endpoint |
| 2 | | | vertex (but not an endpoint) |
| 4 | | | intersection of a perpendicular to a polyline or polygon object |
The values are additive: a value of 3 indicates that the new location can be an endpoint or a vertex of an existing object. The default value is 0.
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| SnapParamDistance |
The maximum distance that a vertex can be moved.
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| SnapParamObject |
Determines the layers that a vertex may be snapped to:
| 0 | | | Any object (default) |
| 1 | | | Objects on selected layers only |
If a value of one is passed, then the layer list must be established through SnapParamLayer.
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| SnapParamLayer |
A delimited list of the layers that
may be snapped to; the items in the list are separated by Delim.
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| InputCoordinates |
The type of coordinates that will be
passed to the control:
| 0 | | | latitude/longitude (default) |
| 1 | | | Mapping Coordinate System (MCS) |
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| OutputCoordinates |
The type of coordinates that will be
output by the control:
| 0 | | | latitude/longitude (default) |
| 1 | | | Mapping Coordinate System (MCS) |
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| ButtonLabel |
The label to appear on the button (Default: "Hgis Snap" )
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| BoxWidth |
The width of the control in Twips
(Default: 1500 Minimum: 200 )
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| BoxHeight |
The height of the control in Twips
(Default: 500 Minimum: 50 )
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Methods
A complete list of the public methods is provided with the Toolkit documentation.
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