Solving problems with “false” objects.-
Sometimes, when beginning to use Metagraf, it is possible for the user to find himself a little bit lost when the reaction to some action doesn't seem to agree with the theoretical descriptions given in this pages, or when a new problem arise which description is not included. Most of this problems are due to “false” objects.
If any of this situations arise, those are the steps to be taken:
The first step is to confirm that no “false” objects exist. Those objects are created when non respecting the general rules explained in the paragraphs corresponding to “Basic Drawing”. Unfortunately, it is quite common the fact of creating “false objects” due to clicking the mouse on the screen when in insert mode and do not drag it. The problem is serious because the first point clicked is not visible when created in this bad way. Nevertheless, there is a way to make the point visible, and be able to correct the mistake: select everything on the screen. This is done by choosing “Select_all” from menu “Actions” or pressing the corresponding button on the horizontal tool_bar.
With all the objects in the drawing screen selected, it is quite easy to confirm that no “strange” points, not forming part of any visible object, exist. When creating a point object, it is clearly visible in non selected state. So, if selecting everything, red points appear that have no corresponding objects in unselected state, those are “false objects” and should be removed.
For removing “false” points on the screen, it can be tricky to be able to select them by the standard method of having the mouse over them and click it, as they are not seen or the mouse do not recognize them. Another way of selecting an object, very useful in many situations, is, with Metagraf's screen in normal mode end the mouse in edit mode, click and drag the mouse over the object. As already explained, a red rectangle will be seen that will disappear when the mouse button is released. If the “temporal” rectangle includes all the defining points of an object, when releasing the mouse the rectangle will disappear as has been said, but the object will change to selected state.
The method just explained is the best one to select and delete any false object existing on the drawing. It is also useful to select several objects to group them.
It should be mentioned that the existence of “false objects” will make Metagraf behave in strange ways. Usually, the root of the problem is in Metapost that will not accept to compile some file with a erroneous expression inside. Metagraf itself will continue “to live” apparently without external signs, until the moment when it is wanted to see the drawing in the Viewer. The drawing will not be created and it will be shown the last acceptable one.
Madrid, January 2006 |
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