For adding an area feature in the mode of drawing it is necessary to turn on the mode Adding new feature (the button 
), select the necessary layer and feature type on page “Input” of the window “Editor control”, and then click all polygon vertices of the outer boundary of the feature being added successively. After a double click the operation of adding a feature is completed. The system remains in the adding mode so that every new series of clicks will add one more area feature of the same type.
At figure 17-10 page “Input” of the window “Editor control” with selected area feature type is shown.
Figure 17-10. Window “Editor control”, adding an area feature
If the box Fix edge angle is checked, when polygon vertices are added the system will round the value of the angle between the neighboring edges to the value multiple of the one specified (in degrees) in the field Step.
If the box Fix by completion is checked the system will try to round the value of the angle between the last and first edges with the same step upon completing polygon vertices input.
If the box Inverse input of vertices is checked, the system considers that the polygon vertices are added in the reverse order starting from the last and ending with the first vertex. As it was pointed out above, the order of vertices is important if the line type used for displaying boundaries of the present feature is not symmetrical.
Upon completing the operation of adding an outer boundary of the feature the system checks correctness of this boundary and in case of an error displays a dialog box with the message “The operation will make the feature incorrect “ describing the incorrectness (figure 17-11).
Figure 17-11. Message about incorrectness of the edited feature
The possible user reaction to the message about incorrectness is determined by selection of one of three buttons:
Continue input – resumes performing of the operation of adding a boundary.
Cancel input – the operation of adding a boundary is canceled, the new feature is not created.
Details – a dialog box is extended and more detailed information about the reasons for incorrectness is displayed (for example, sequence numbers and intersection of edges with coordinates). The user should still push one of the first two buttons to close the dialog box.
If it is necessary to specify an inner boundary of the area feature the mode Adding inner boundary should be turned on. After switching to this mode the system does not react to mouse clicks made in the points which do not belong to any area feature. The first click on the area feature selects this feature for editing (if it was not selected before), the next click starts adding a polygon of the inner boundary. On completing adding of inner boundary (by a double click) the system checks its correctness and in case of detecting incorrectness displays a dialog box “The operation will make the feature incorrect“ which was described above.
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