Margins and components strange behaviour in Fontlab

[Telex]

If I simply change a sidebearing in accents, by code, the components move.

This doesn't happen changing the sidebearing manually.

For example, executing this simple code will disalign components in Ntilde, ntilde, etc. 

So I have to rebuild these glyphs

f=CurrentFont()

f['tildecomb'].leftMargin=0

f.update()

Any ideas?

[Erik van Blokland]

The left margin does not exist independently of the glyph contours. By setting the leftMargin to 0 you really move the outlines in tildecomb to the left until the leftmost point in the leftmost contour hits the x=0. This move then shows up in all glyphs that have a component referencing tildecomb. 

Erik

[Telex]

I imagined that...

Do you know a simple way to assign new sidebearing values to components without altering composites?

Thanks for your quick response Eric.