[mkgmap-dev] Some observations

Mon May 30 12:51:00 BST 2022

Hi Gerd,

thanks for explanations.

 > the option --make-opposite-cycleways is implemented like this

Somehow I imagined, that opposite cycleway is magically added at a final 
step, when the main road is already prepared by style. Your way is more 
flexible, but needs more diligence in style. Actually I had to make a 
lot corrections in my style, when I realized how it works. It would be 
good to add your explanation to options.txt.

 > The manual has this note:

"There used to be some restrictions on the kind of expression you could 
use. Now the only restriction is you must have at least one test that 
depends on a tag existing. So you cannot match on everything, regardless 
of tags, or test for an object that does not have a tag."

Sorry, I missed it. It is at the section, "Combining tag tests", while I 
was interested in a single test. I read the section "Allowed operations" 
and found no difference between using tag=value and tag!=value. This 
make me wonder, why "mkgmap:option:test=true" works but 
"mkgmap:option:test!=true" doesn't.

To be true, I'm not understanding this explanation. What does it mean 
"tag existing"? Does tag "highway" exist but "mkgmap:synthesised" doesn't?

 > I wonder why mkgmap complains. Seems it checks only the "if" part.

I guess it is about "if then", most problems appear when I try to use 
this statement. Another question: is the condition of "if then" 
statement checked once or for each line included in the conditional 
block? I wonder whether "if then" could optimize processing of style.

-- 
Best regards,
Andrzej