[mkgmap-dev] [PATCH] Improve display of highway shields

Sun Nov 8 14:45:50 GMT 2009

The attached patch is an attempt to improve the reliability and  
flexibility for displaying highway shields. It does the following:

1. Removes the alpha balancing coding. (This coding checked that  
values for signs were primarily numeric, and therefore prevented refs  
such as "QEW" from being displayed as highway shields.)

2. Removes ALL spaces from refs, so that the complete ref will be  
displayed in the shield. (Previously only the first space was removed,  
which caused refs like "B 1 2" to be displayed as "B1" in the shield.)

3. Checks, after spaces have been removed, if the ref is too long to  
be displayed in a shield. If the ref is too long, the shield code will  
not be added; the road label will displayed normally. The maximum  
length of the ref is determined in the following manner:

3.1. The default of 8 characters is used. This is the previous  
behaviour.

3.2. If a colon character (":") followed by a number is appended to  
the highway symbol in the style file, that number will override the  
maximum length. Example: "highway-symbol:box:6" sets the maximum to 6  
characters.

3.3. If an additional colon character followed by a number is appended  
to the highway symbol, this second number will be used as the maximum  
length for alpha only refs. Example: "highway-symbol:box:6:4" sets the  
maximum to 6 for numeric and alphanumeric refs, but 4 for alpha only  
refs.

I use the following in my style file:

   '${ref|highway-symbol:box:6:4}'

This sets the maximum length of alphanumeric shields to be 6 (e.g.,  
M1234a, or 123456), and alpha only shields to be 4 (e.g., ABCD). Such  
a setting works well for me in the areas I am interested in. It  
prevents labels such as "Südring" from being displayed as shields, but  
catches most other refs which can reasonably be displayed in shields.

The approach of this patch allows creative mappers to have a certain  
amount of control over shield display, but still preserves the default  
behaviour of the

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