First, check that your path directions are consistent. Then, embrace the fact that you're using a computer and can save multiple versions of your file. Keep at least one unmerged and one merged and copy changes between them.

I've seen this before. I'd bet you've got part of the character down twice. I got the same effect in the early days by copying a glyph, then at some point, inadvertently pasting it over itself. (I was making up accented characters before discovering that using the composite technique was a real time-saver when you change your mind about some little detail...)

Charles, that could be the reason. I copy and paste a lot of pieces from and to every glyph... I guess I will be naming it Frankestein )

I'm gonna check the paths and hopefully I will be able to fix everything.

Juan, just running "Contour Direction" probably won't fix things. If this is the problem, you've got to go in & remove all the extra outline -- click on & delete points. Not fun. But, you're not the first. BTDTGTTS (Been There, Done That, Got The T-shirt) ;-)

.otf or .ttf?

.otf

I don't want to merge contours yet since I'm not finished tweaking characters shapes. Is there any solution?

You should merge contours and decompose glyphs before generating test fonts, so best to save a copy and generate from that. You can automate some or all of the process by using an Action Set or a macro (see Ben Kiel's scripts for generating test fonts at http://benkiel.com/typeDesign/ ).

Weird -and hard to spot- things can happen when you merge [almost-]entirely-overlapping contours. The safest thing is to clean up the old-fashioned way!

hhp

@Gargoyle: Is there a technical reason for merging contours before generating test fonts?

@hrant: Very weird indeed, I don't remember encountering this problem while working on Shket. What do you mean by "clean up"?

@Graphirus: I believe you're looking at the technical reason in your screenshot: overlapping areas are very often rendered as negative space, especially in Postscript-based fonts.

Regarding weirdness in merging contours— in your above screenshot, merging contours in glyphs like the /a and /u probably won't pose much of an issue, but glyphs with large overlapping areas like the /p or multiple overlaps and crossing contours like the /x and /t could produce unpredictable weirdness and extra points requiring manual clean-up. So you should certainly do a thorough check for any such oddities before generating a finished font.

@Gargoyle: Excellent answer! You mention Postcript rendering problems in overlapping areas, so maybe I should test my fonts as truetype. Should I expect any rendering differences between .otf and .ttf fonts?

You should draw clean outlines no matter what your final output format. It is some work but not so terrible to keep track of outline pieces and overlaps. Keep all the pieces in the background if you need them but learn to draw cleanly.

What do you mean by "clean up"?

I mean removing stuff that shouldn't be there (and that can be hard to spot) like exact duplicate overlapping outlines.

And what Chris said.

hhp

@hrant: Oh, I see. I thought it was something a little bit more complex. As a rule all the cleaning up is relegated to the point when I feel a glyph is done or obvious extra nodes are laying around. I often click on the "Optimize" too to help me get rid of extraneous nodes.

"Should I expect any rendering differences between .otf and .ttf fonts?"
ttf
otf

As a rule all the cleaning up is relegated to the point when I feel a glyph is done or obvious extra nodes are laying around. I often click on the "Optimize" too to help me get rid of extraneous nodes.

I suppose that's OK, but it really is easier to clean up as you go along. And my experience -- for what it's worth -- is you cannot rely on program functions such as "remove overlap," "optimize," "set path direction," etc. for correcting the particular error that occasioned this post. The original purpose of these routines wasn't to correct this kind of error, so don't squawk when they don't fix it. Again, I speak as one who has paid to own the T-shirt...