Negative render rules don't work as intended

[andilem]

According to the documentation, a negative rule like <m key="k" value="~|false"> should match when the key "k" is not present or it has the value "false".
But that is not the case - the rule matches when the key "k" is not present or any key (not just k) has the value "false".
The code reads:

static class NegativeRule extends Rule {
...
        @Override
        public boolean matchesTags(Tag[] tags) {
            if (!containsKeys(tags))
                return true;

            for (Tag tag : tags)
                for (String value : values)
                    if (Utils.equals(value, tag.value))
                        return !exclusive;

            return exclusive;
        }
}

It is clear that any tags are evaluated, not just the specified one(s).
Is this behavior intended? If yes, it seems very strange and there is no way to specify a rule like described in the first place.

[devemux86]

@andilem I do not understand, what do you mean?

Is the documentation somewhere in the code or the guides wrong?

See the render theme documentation with its examples:

"A tilde "~" matches if the map element does not have a tag with the specified key."

<m e="way" closed="no">
    <m k="highway" v="motorway">
        <m k="tunnel" v="true|yes">
            …
        </m>
        <m k="tunnel" v="~|no|false">
            …
        </m>
    </m>
</m>

Also study the rules in the render themes:

<!-- match tunnel-tag that are not 'no' or 'false' -->
<m k="tunnel" v="-|no|false">
    <!-- match area-tag that are 'no' or 'false' or not present -->
    <m k="area" v="~|no|false">

VTM rules should work exactly like the Mapsforge rules that have been in use for a long time.

[devemux86]

Mapsforge class: https://github.com/mapsforge/mapsforge/blob/master/mapsforge-map/src/main/java/org/mapsforge/map/rendertheme/rule/NegativeRule.java

[andilem]

Yes, the VTM rules work like the Mapsforge rules.
But it is not according to the documentation and I think it is a bug - not sure, that's why I'm asking.
According to the documentation:

<!-- match area-tag that are 'no' or 'false' or not present -->
<m k="area" v="~|no|false">

so I expect this rule to match elements with no tag "area", with tag "area"="no" and with tags "area"="false".
But this rule also matches an element with tags ("area"="yes", "whatever"="no"), because the value "no" is not bound to the specified key ("area") in the code which checks the values!

[devemux86]

Yes, the VTM rules work like the Mapsforge rules.

This is good, as Mapsforge rules are the standard ones and are used everywhere.
e.g. in OpenAndroMaps and Elevate theme.

@andilem

Do you have a specific location (better in the small Berlin map) where this rendering can be checked?

Changing the rules will change all maps and themes that are used all this time.

If it is an understanding problem, we can improve the documentation.

Better also report this in OpenAndroMaps forum for Mapsforge rules and get their opinions:

https://www.openandromaps.org/en/oam-forums

[tumic0]

so I expect this rule to match elements with no tag "area", with tag "area"="no" and with tags "area"="false".

So do I and GPXSee which has a theme parser written according to the documentation, not the Mapsforge library implementation should behave correct in this case. The documentation is IMHO clear here, if Mapsforge does something different, than it is a implementation bug.

[devemux86]

https://www.openandromaps.org/en/oam-forums/topic/negative-rule-in-render-themes

[devemux86]

I created pull requests in Mapsforge and VTM repositories.

See the change and if the negative rule works properly now.

• Mapsforge: Negative rule improvement mapsforge#1755

• VTM: Negative rule improvement #1270

[devemux86]

I merged the pull requests in Mapsforge and VTM repositories.