This section desribes a few errors and problems that you may get working with therion, and provides hints for their solution in The Therion Way.

This occurs when you happen to click twice (a double clikc) on the same line while defining an area. In this case the contour of the area computed by therion may turn out not what you expect.

To avoid this mistake, check in the "Areas" control the list of the lines of the area contour. When you click twice on the same line, this appears on two consecutive lines. To fix the problem, select one line on the control and press the "Delete" button of the "Area control" menu.

Repeating the same line-point twice in a row is not an error, but the resulting line could not be what you wanted.

In the "Line" control you can see the list of the points that compose the line, and check if any appears twice. If this is the case, you can cancel one of them with the menu "Line edit | delete point", after selecting it (or editing the file with the text editor).

Every graphical element must appear inside a scrap, ie, between a scrap command and its endscrap command. When you insert a graphical element in the drawing canvas a new line is open on the cursore of the list in the "Objects" control, and the new element is assigned to the line. The cursore is the "black line" between the lines of list.

When the cursor is between "endscrap" and "endoffile" the new elements are placed outside of any scrap. The only thing that you can insert here is a new scrap. Infact a scrap cannot be inside another scrap. xtherion puts the cursor here every time you open a file, ready to add a new scrap.

However this is not appropriate to make corrections and additions to an existing scrap. You must move the cursor inside the scrap by clicking on the element after which you want to add the new ones, so that the cursor appears after it.

If you happen to insert elements outside the scrap, therion gives an error when you compile the map,

    missing scrap before line command

To fix this error, open the "Objects" control, select the line "endscrap", and move it down using the "Move down" button until there are no elements outside scraps.

When there are replicated points (eg, a station name assigned to more than one point) therion does not complain, but the map is likely not what you want. On the other hand when there are station points with wrong names (ie names of non-existing stations) therion gives an error message (XXX is the wrong station name)

     invalid station reference -- XXX

Something similar happens when you assign the station names wrong: the cave map is screwed up because the scraps are fit together according to the survey data (the centerline).

The debugger is useful to see the different positions where the scraps are placed while therion composes the map. It might be useful to comment the "join" commands during the debug, to inhibit the transformations that they cause [thwiki 4].

If you happen to put graphical elements in a scrap and realize that you actually wanted them in another scrap, you have to move them from one scrap to the other.

This is rather simple if the scraps are in the same file. Open the file in the map editor of xtherion and move the elements using the "Move" buttons in the "Objects" control.

It is possible to move grapgical elements between two files, but this operation requires so much more care, that it is often easier to delete them from one file and re-draw them again in the other file. If you want to try anyways, here is how to do it. As the map editor of xtherion can open one file at a time you must use a text editor. Indeed the map files are text files with commands to draw the maps.

Opne both files and use the "id" field to identify the elements that you want to move from one file to the other. Cut them from the first file and paste them in the second. This is usually not enough: the graphical elements have coordinates in different frames of reference. Even if the two scraps have the same "-scale", the frame is given by the positions of the points of type "station".

Now you can open the second file with the map editor of xtherion and position the elements that you pasted in in the proper places.

The temporary files of therion, MetaPost and pdfTeX are located in the (temporary) directory "/tmp/thPID" where PID is the process id of the running instance of therion.

When therion is invoked with the "-d" (debug) command line option, it creates the directory /tmp/thTMPDIR and stores the intermediate files there. This directory is not removed by therion, neither it is cleared of the old files before the execution. You must remove it by hand yourself.

A. Atkinson encountered the following problem: a single scrap with a white (background) triangle in it.

S. Mudrak work-around:

When I added "wall -subtype invisible" as shown on the picture, then the problem was solved. Same with "border -subtype invisible -outline out". Therion obviously did not connect walls in correct order. I am sorry for this, there must be some bug in the "outline finding" code, but it is very difficult to find and using "invisible outlines" allways helps.

To prevent this try not to use short (two point only) lines with general subtypes. It causes the error when therion is analyzing the walls and it finds the nearest possible continuation not on the "correct" wall but it jumps to another wall, which starts at a shorter distance. Use "point_of_line" subtype instead, and draw as long wall as possible (M. Sluka).