Generalities on EUC's tools

To read here, you should know More on figures

[bullet] Select a tool

As a general rule (with some exceptions) tools are grouped together according to the object they produce. There are Point-tools producing points, Segment-tools producing segments, Triangle-tools producing triangles etc. This organization is reflected on the main toolbar (figure-1). The toolbar contains buttons and next to them small drop arrows leading to corresponding menus (figure-2). The buttons activate the basic tool creating the most general object of that kind (point, segment, triangle etc.). The corresponding menu, displayed by pressing the drop arrow next to the button, contains tools related to the main object pictured on the button.
Figure-1
[toolbar] 		Figure-2

[menu-selection] 		Figure-3

[context-menu]

There is a second possibility to get a menu through the context menu: displayed by right-clicking on an object (its contour). Look at Figure 3, which displays the context menu by clicking on a semgent. Note that these context-menus are (1st:) object-kind dependent (i.e. different for each kind object, uppon which you right-click), (2nd:) user-configurable (i.e. for each particular object-kind, you can compile its context menu, so that it contains any tool you find it useful to include there).

Finally, for some tools, there is the possibility to select them From the keyboard: by pressing a key combination, known as shortcut of the tool. Every shortcut corresponds to a menu item and you see this displayed next to this item. F.e. The Selection Tool can be selected by pressing the key combination: Ctrl + 1 . Look at Figure 2 to see how the shortcuts are placed next to the menu-items. If you love your keyboard more than your mouse, then these shortcuts are for you.

[bullet] Kinds of tools available

Well, there are several criteria to group tools together:
With respect to objects they produce, there are two kinds:
a) Tools that create simple objects. For example the tool General Triangle in Figure-2.
b) Tools that create objects + scheme-components. F.e. the tool Medians _ in Figure-2.
There are also other kinds of tools that manipulate existing objects of the drawing sheet. For example the Selection Tool and the Explicit Match tool.
Finally there are user-defined tools, operating through recipes compiled by you, the user of the program.

[bullet] Tool-Stage

[stage(A,B)] [tria-construct]
Each tool operates in one or more stages. By stage I mean generally the three events associated with a mouse-click:
(1) Left-button-down click somewhere in the drawing sheet, say at point A, called the click-point.
(2) Movement dragging of mouse pointer while holding down the left-button.
(3) Left-button-up release somewhere in the drawing sheet, say at point B, called the release-point.
The above set (or cycle) of three events defines a stage of the tool, which, more precisely could be denoted by stage(A,B). It is evident that one could speak about the oriented segment AB of a stage, A being the start-point (=click-point) and B being the end-point (=release-point). Look at Figure 4. For each particular tool and each particular stage of it, the points A, B have different significance and importance. F.e. let us inspect the point-tool, segment-tool and triangle-tool, constructing respectively, the three simple objects:

[bullet] Tool-Stage kinds: selective, constructive, mixed

There are three general kinds of stages: Selective stages, constructive stages and mixed = selective+constructive stages.
A Selective stage(A,B) selects some object lying next to the click-point A. Such a stage belongs usually to a tool creating some scheme-component.
A Constructive stage(A,B) constructs something (like the "Segment-tool" above) using the click- and release-points A and B. Such a stage constructs usually some simple object or some parts of a simple object (f.e. sides of a polygon).
A mixed stage(A,B) uses A to select some object, and A and/or B to construct something else. This is usually a final stage of a tool constructing a scheme-component.

[bullet] Tool: a sequence of stages

Generally speaking, a tool is nothing more than a sequence of stages: stage1(A1,B1), stage2(A2,B2),..., stageN(AN, BN).
An example: the tool to define a closed polygon of n sides has n-1 stages. The first stage sets the first side of the polygon, its endpoints representing the first two vertices. Each subsequent stage adds a vertex and joins it to the previous one. In the last (n-1)-th stage you set the last n-th vertex of the polygon. You hold down the ctrl-key, while clicking, to define the last vertex. This causes the last vertex to be joined with both the previous and the last verex, so that the polygon is closed.
After executing stageN, the tool returns to its first stage1, ready to repeat its operation. As suggested by the example, the difficulty of use of some tool depends naturally not only on the number of its stages, but also on what kind of delicate job each stage does. There are fairly simple tools, like the three described above, which you should learn first. There are more difficult ones, which you should learn to use after you are familiar with the easy ones.
The successful operation of the tool depends on the successful operation of each individual stage of it. If something goes wrong in a stage, the tool returns to its initial stage1.

[bullet] Keys to modify the operation of a stage

The operation of most of the stages changes by pressing some key in the keyboard, usually the CTRL or/and the SHIFT key as well as the keys F2, ..., F12, on the top of the keyboard (F1 is reserved for help). F.e. suppose you choose the segment-tool and start working laying out segments. If you hold down the SHIFT key, the segment’s direction is adjusted to be exactly horizontal, vertical or at 45 degrees, depending on the direction you move the mouse. These subtleties on the function of each tool are described at the apropriate place, where the tool is explained.
Remark
Don’t confuse this remark with a previous, concerning shortcuts. Shortcuts are used to select a tool. The remark here applies after the tool’s selection, while it operates. In the example of the tool constructing a polygon, you use the Ctrl key to terminate the polygon so that it is closed. If you use instead the shift key then the polygon definition terminates and the polygon remains open (last vertex is not joined with first one).

[bullet] Save clicks (selection stages)

Some tools, as we said, operate by selecting some objects o1, ... , oM and doing then something with their data, usually in the last (M+1) stage. It happens now often in practice that we want to use the same tool and the same first M objects and differentiate only in the last (M+1) step. Imagine we have to do that, say N times. Then if we had to select each time the very same M objects, we would click (M+1)N times. To spare with clicks we often designed the tool in the following way: You choose your M objects and then the tool is ready for the M+1 stage. After the completion of this last stage, the tool is again ready for a new operation with the last stage. So it repeats only the last stage. By this method you reduce to M+N clicks and spare M(N-1). To reset the tool operation to its first stage, simply hold down the CTRL key while releasing the mouse in the last stage.

[bullet] A matter of notation

To tell you how to navigate from menu to menu, to submenu etc., until the final menu-item, where you select the tool, I use a notation like:

Point Tools \ Simple Points

This means select the menu Point Tools by pressing the drop arrow [drop] next to the [point], and then choose from the displayed menu its menu-item "Simple Points".

Several menu-items have underscores following, like:

Triangle Tools \ Complete Vert. _ _

This means that the corresponding tool has two selective stages. The tool selects two objects and uses them to extract data and do something with them. For example the above tool selects a segment o1 in its first stage and a segment o2 in its second stage. At the end of the second stage, as you release the mouse-button, it creates a triangle depending on the two segments.

[bullet] Active Help hints on the status-bar

[help_status_bar]
Before to delve into the help-chaos (using the key F1), to get the explanation of the active tool, now operating on your document, look at the bottom line (status bar: the figure shown above) of the window. There is a short hint, on the number of stages as well as the kind of the job, executed in each stage. After the symbol: => follows, there, a short description of the result of the tool's operation.

    John Keats, who was killed off by one critique,
Just as he really promised something great,
    If not intelligible, -without Greek
Contrived to talk about the gods of late,
    Much as they might have been supposed to speak.
Poor fellow! His was an untoward fate:-
    'Tis strange the mind, that very fiery particle,
Should let istelf be snuffed out by an Article.
       Byron, Don Juan, Canto XI, 60