The Selection Tool

The selection arrow is the most important tool in the Tool panel.  It is your communication with the canvas.  Its importance comes from the frequency of its use as well as what it gets used for.  Before doing any of the constructions or any of the transformations, you must select certain objects.  Most often, selection will just work in a "point and click" fashion...you see the object that you want and click on it.  But since this tool is used so much, there are some non-obvious functions that will be important to know.  These include using the Shift key and the Control key.  The selection tool is also used for dragging objects around the screen.
 

The basics:

Once you have clicked on an object within the canvas, the object will change a bit to show you that it is selected.  If a one-dimensional object is selected (like a line or circle), the object will be outlined in purple to show its selected state.  If a point is selecte, again it will be outlined in purple.  If an area is selected, its color will turn a lighter shade and an image of the icon for this program will appear. This is illustrated in the diagram below.  In every case of a selection, a message will appear in the Message Area under the Canvas telling you which object is currently selected.

 select example

To select objects that are visually behind other objects (for example a segment that is behind another segment) click on the object repeatedly until the desired selection is made.
 

The Selection Box:  This allows you to select a group of objects quickly and easily.  Click anywhere on the canvas.  One corner of the selection box will be set at that point.  As you drag you will see a red rectangle which extends from wherever you originally clicked to wherever the cursor is currently at.  When you release the mouse anything within the box will be selected.

 Multiple Selection: To select multiple items, just click on the items in sequence using the select tool.   All of the items will remain selected until you click in an open space on the canvas (at which point all selections will become unselected).  You can unselect specific items by clicking on them again.

The Shift Key: The shift key also allows you to select more than one object at a time. When holding the shift key down, you can click on any number of items and they will all remain selected until you release the Shift key and click anywhere on the canvas (at which point all selections will become unselected). While the Shift is down, you can unselect specific items by clicking on them again. 

The Control Key:  Holding down the Control key and the Shift key simultaneously, while selecting, will cause Geometry Explorer to select a region of the Canvas without changing any existing selections. This is useful when one wants to save a copy of the current state of the Canvas as an image.  For example, suppose you have a construction where a line is currently selected, but the endpoints are not. If we click and drag a selection box around the line, all points inside will be selected. If we hold the shift and control keys down while creating the selection box, no changes to selections will be made, and we can save the image exactly as it appears in the Canvas, as is illustrated here:

 select control shift
Note: On a Macintosh computer, it is not possible to do this type of Control-Chift combination. The equivalent for a Macintosh is to hold the Alt key and Shift key down simultaneously.

Dragging Objects: In order to move an object across the canvas it is necessary to click on the object and drag it until it is in the desired position. If you would like to move two objects in unison just press the Shift key while you select the objects and hold it down while you drag them.