[ttx_diff] Normalize axis labels in fvar and STAT tables

[khaledhosny]

Like it is done for named instance name IDs.

[cmyr]

just to sanity check, do you have a link to an example font where this was causing a problem?

[khaledhosny]

I’m testing with https://github.com/aliftype/mada/tree/main/sources/, without this change I get the following diff in fvar:

--- fontc.fvar.ttx	2024-09-11 22:19:16
+++ fontmake.fvar.ttx	2024-09-11 22:19:17
@@ -7,7 +7,7 @@
       <MinValue>200.0</MinValue>
       <DefaultValue>400.0</DefaultValue>
       <MaxValue>900.0</MaxValue>
-      <AxisNameID>256</AxisNameID>
+      <AxisNameID>259</AxisNameID>
     </Axis>

     <!-- ExtraLight -->

and STAT:

--- fontc.STAT.ttx	2024-09-11 22:19:16
+++ fontmake.STAT.ttx	2024-09-11 22:19:17
@@ -5,7 +5,7 @@
     <DesignAxisRecord>
       <Axis index="0">
         <AxisTag value="wght"/>
-        <AxisNameID value="256"/>  <!-- Weight -->
+        <AxisNameID value="259"/>  <!-- Weight -->
         <AxisOrdering value="0"/>
       </Axis>
     </DesignAxisRecord>

(the different name IDs are probably caused by #950, but that shouldn’t be relevant)

[cmyr]

great, thanks!