OBJECTS GEOMETRICALY ATTACHED
I feel very proud to be able to present a new and very important capability of METAGRAF. I have called it "Geometrical attachments". The idea is not new at all, but his use mixed with MetaPost is totally original. Moreover, few graphics programs not specialised on this subject have it. (To my knowledge, no one, appart MG now.)
The idea, as has been said, is simple, and to explain it I will use an example. If in the middle of a drawing it is wanted to draw a line from one point perpendicular to another line, now MG lets do that just by clicking a button. The object created, the new line, has "special" caracteristics apart from the standard ones, that it maintains. This new line will go from the point and will be perpendicular to the other line always. That's mean, if the position of the point or the one of the line is changed, the created line will change accordingly to acomplish the two conditions mentioned. What is not possible is to modify the line created modifying its behavior. It can be deleted at any time. Otherwise, and with respect to metapost it will be a normal, usual line, colored or not, with arrow or without it. Plain or not, and with its thickness modified or not. It will be seen when launching ghostview as any other line.
At present there exist the possibilities that follow for geometrically attached objects
Usually, if one "mother" object is selected and moved with the mouse, the effect will be seen only when deselecting the object. Nevertheless, if a point is selected and displaced with the use of the arrow-keys on the keyboard, the whole movement is visible (and can be quite astonishing).
Hereby is an example of a figure where everything is "connected"
To use this new capability there has been provided a new buttons-window, with icons over the buttons there are self-explanatory. Here we can see one of them. .This window is launched if the MG-icon-button is clicked. Once the window in view it can be placed anywhere, depending also on the window-manager used. One recommended site is just over the tools panel with the standard buttons. When clicking the central screen of MG, the new window will desappear and the objects to be used can be drawn. It is neede to select the objects to be geometrically attached and once done, the MG-Icon-button can be clicked to make visible the new buttons window. The button corresponding with the operation wanted must be clicked and then, a new click on central screen will show the new object and deselect the other selected ones.
This new tool of MG will be expanded in the future to permit a bigger simplicity in drawing and a more precise one. I look forward to receive suggestions on which kind of attachments could be useful as (almost) everything can be done.