This is only an example to show the effect . I can see the green line and even the blue line which is drawn after the set-visible command .
But i can not see the red line after pressing the run button .
If i minimize the Mdialog-window and then maximize it again i see the red line - or if i set the background after drawing to eg. green ( but not white what is already the background) .
The next question , how can i get rid of all tags , is there a clear-canvas function ?
I have a clear-button, which should clear the canvas back to white .
First i've named all lines with the same tag-id , and i use gs:delete-tag, but with this i have no possibility to select single lines or tags . Brute force with gs:dispose 'Mcanvas doesn't work . Or should i generate a list of tags while drawing to delete them later ?
That will work, but I would use strings for the tags and than have it easier filtering with regular expressions etc.
Wherever symbols are used in guiserver you can use strings instead. Symbols are nice because it is one quote less to type and looks better recognizable in syntax highlighted code. But for the kind of operation you want, the string is better.
How do you access tags? I can see that you can keep a record of the ones that you use, but is there a way of getting the tags that have already been used? Can you obtain a list using some form of wildcard?