Sketcher ConstrainCoincident/pt

Description
Affixes a point onto (coincident with) one or more other points. : It acts as a concentric constraint if two or more circles, arcs, ellipses or arcs of ellipses are selected.

Usage

 * 1) Do one of the following:
 * 2) * Select two or more points.
 * 3) * Select two or more edges of circles, arcs, ellipses or arcs of ellipses.
 * 4) There are several ways to invoke the command:
 * 5) * Press the button in the toolbar.
 * 6) * Use the keyboard shortcut.
 * 7) * Use the entry in the top menu.

Alternatives to Coincident constraint
The two constrained items of a Coincident constraint must be start point or end point vertices, or center points of arcs, circles or ellipses. Some combinations which are not possible with a coincident constraint can be emulated using other constraints:
 * The Sketcher_ConstrainSymmetric.svg Symmetric constraint can be used to place a start point, end point or center point on the midpoint of a straight line.
 * A midpoint-to-midpoint placement of two straight lines can be achieved by creating a new Sketcher_CreatePoint.svg Point and using two Sketcher_ConstrainSymmetric.svg Symmetric constraints so that it lies on the midpoint of both lines.
 * A vertex can be constrained to lie along an edge using a Sketcher_ConstrainPointOnObject.svgOnObject constraint. Note that with this constraint, the point can lie anywhere on the full extension of a segment or curve (i.e. also before the start point or beyond the end point).
 * A collinear placement of two straight lines can be obtained by applying a Sketcher_ConstrainTangent.svg Tangent constraint to them, or by combining a Sketcher_ConstrainPointOnObject.svg PointOnObject constraint and a Sketcher_ConstrainParallel.svg Parallel constraint.
 * Two edges can be made identical by using two Sketcher_ConstrainCoincident.svg Coincident constraints, one for each pair of extremities.
 * Two circles can be made identical by using a Sketcher_ConstrainCoincident.svg Coincident constraint to merge the centers, and applying an Sketcher_ConstrainEqual.svg Equal constraint to their edges. For arcs, this will ensure both arcs are part of the same circle, while allowing them to have different start and end points.

Scripting
The constraint can be created from macros and from the Python console by using the following command:

where :
 * is a sketch object
 * is the number of the line, that will not move by applying the constraint
 * indicates which vertex of has to fulfill the constraint
 * is the number of the line, that will move by applying the constraint
 * indicates which vertex of has to fulfill the constraint

As the names and  indicate, if both constrained vertices are free to move in any direction, the first one (first to be selected in the Gui) will remain fixed and the other one will move. In the presence of existing constraints, however, both edges may move.

The Sketcher scripting page explains the values which can be used for, , and , and contains further examples on how to create constraints from Python scripts.