When a feature is selected for editing, handles – small squares or circles, the form and color of which depend on the current editing variant, are displayed in some characteristic points of this feature. The purpose of handles is the following: cursor positioning on a handle holding down the left mouse button permits the user to perform some operation connected with the present handle type – change feature size, move vertices, perform rotation, etc. The exception is only the mode of editing a point feature as a whole, when there are no handles.
Different handle types are shown at figure 17-1.
a) resizing handles b) handles of rotating a feature
and rotation center
c) handles of moving vertices d) a handle of rotating a vertex
(one vertex is marked) and rotation center
Figure 17-1. Handles of editing modes
Resizing handles (figure 17-1, a) are white squares located in the corners and in the middle of sides of the bounding box of a feature or group of features. These handles are used in the mode of editing a feature as a whole. It is possible to drag the handle to another position while holding down the left mouse button. The width and height of the bounding box are changed, the sizes of edited features are changed proportionally.
Handles of rotating a feature (figure 17-1, b) look like green circles in the corners of the bounding box. They are displayed in the mode of rotating a feature, the rotation center – a dark gray encircled point, is also displayed. The user can move the rotation center to the necessary point, and then rotate a feature or a group of features around this center moving any rotation handle along the circular arc.
Handles of moving vertices (figure 17-1, c) are white squares located in all vertices of the line or area feature being edited. They are displayed in the mode of editing feature vertices. Moving an individual handle, the user changes the feature form.
It is possible to mark one or several handles of vertices for performing operations with a group of feature vertices. After clicking a vertex it becomes a marked one. Marked vertices are displayed as handles of black color. A click keeping the key Ctrl pressed adds a mark, a click while holding down the key Alt removes the mark. Additional methods of marking vertices will be described below when speaking about operations of editing features.
A group of marked vertices can be moved as a whole and it is also possible to remove it by pressing the key Delete.
Handles of rotating a vertex (figure 17-1, d) are displayed for marked vertices in the mode of rotating feature vertices. They look like squares of green color. Such handles can be moved along the circular arc with the specified rotation center. If several vertices are marked, they are moved around the center as a whole.
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