<h2>Additions to NewGRF Specifications in JGR's Patchpack in NML</h2>
<p>This document describes non-standard additions to the <ahref="https://newgrf-specs.tt-wiki.net/wiki/NML:Main">Official OpenTTD NML Specifications</a> which are present in this patchpack and the associated <ahref="https://github.com/JGRennison/nml">NML fork</a>.
<p>These additions MAY also be present in other patchpacks. They MAY be removed or moved in future, if necessary.</p>
<p>Not all standard NewGRF features are supported by NML, consequently not all non-standard additions to the specifications are supported by this patchpack's associated NML fork, or are listed in this document.<br/>
See the associated <ahref="newgrf-additions.html">non-NML document</a> for more details.</p>
<p>All of the non-standard features listed below will automatically emit suitable feature tests, conditionals, etc. such that NewGRFs which use these features will work correctly
on OpenTTD versions which do not support these features, including standard trunk OpenTTD and older/other patchpack versions.</p>
<tr><td>enable_programmable_pre_signals</td><td>0 or 1</td>
<td>
Enable programmable pre-signal graphics in <ahref="https://newgrf-specs.tt-wiki.net/wiki/NML:Railtypes#signals">railtype signals</a>.<br/>
Programmable pre-signals have a signal type (<spanclass="code">getbits(extra_callback_info2, 16, 8)</span>) of 6.
</td>
</tr>
<tr><td>enable_restricted_signals</td><td>0 or 1</td>
<td>
Enable restricted signal flag in <ahref="https://newgrf-specs.tt-wiki.net/wiki/NML:Railtypes#signals">railtype signals</a>.<br/>
When enabled, bit 24 of variable <spanclass="code">extra_callback_info2</span> is set if the signal is restricted (has a routing restriction program attached).<br/>
When enabled, the "Show restricted electric signals using default graphics" client setting and signal post recolouring is not applied.<br/>
This flag must only be set if a different sprite is returned when bit 24 of <spanclass="code">extra_callback_info2</span> is set.
<dd>Scripts (AI/GS) may not build this tramtype</dd>
<dt>NO_TOWN_MODIFY</dt>
<dd>Towns may not modify tiles of this tramtype in any way whatsoever</dd>
</dl>
</td>
</tr>
</table>
<h3><ahref="https://newgrf-specs.tt-wiki.net/wiki/NML:Replace_new_sprites">Replace new sprites</a></h3>
<table>
<tr><th>Type</th><th>Number of sprites </th><th>Comment</th></tr>
<tr><td>PROGRAMMABLE_PRE_SIGNAL</td><td>32</td>
<td>
<b>Programmable pre-signals</b>
<p>Signal graphics come in groups of 16. These groups contain sprites in the same order as sprites 1275-1290 in trg1[r].grf and <ahref="https://newgrf-specs.tt-wiki.net/wiki/Action5#04_Signal_graphics.">Action 5 type 4 (signals)</a>;
red, then green, for each of: SW-facing, NE-facing, NW-facing, SE-facing, E-facing, W-facing, S-facing, N-facing.
This feature allows signal sprites to be specified using switches in a very similar manner to <ahref="https://newgrf-specs.tt-wiki.net/wiki/NML:Railtypes#signals">railtype signals</a> in
However this applies to all signals, not only those of a particular rail type.<br/>
Railtype signal graphics have a higher priority than general signal graphics as set here.<br/>
<br/>
Variables: <spanclass="code">extra_callback_info1</span>, <spanclass="code">extra_callback_info2</span>, and <spanclass="code">terrain_type</span>
are the same as for <ahref="https://newgrf-specs.tt-wiki.net/wiki/NML:Railtypes#signals">railtype signals</a>.<br/>
<br/>
This feature is not supported by standard OpenTTD or by standard NML.<br/>
If the use of this feature is not optional, the feature name: <spanclass="code">action3_signals_custom_signal_sprites</span> should be checked using the
<spanclass="code">extended_feature_test</span> function
and if necessary a suitable fallback used or error message shown.<br/>
<br/>
An <spanclass="code">item (FEAT_SIGNALS, custom_signals, 0) { }</span> block should be used to define properties and graphics.<br/>
The graphics block should contain a single default switch.
<tr><td>enable_programmable_pre_signals</td><td>0 or 1</td>
<td>
Enable programmable pre-signal graphics.<br/>
Programmable pre-signals have a signal type (<spanclass="code">getbits(extra_callback_info2, 16, 8)</span>) of 6.
</td>
</tr>
<tr><td>enable_restricted_signals</td><td>0 or 1</td>
<td>
Enable restricted signal flag.<br/>
When enabled, bit 24 of variable <spanclass="code">extra_callback_info2</span> is set if the signal is restricted (has a routing restriction program attached).<br/>
When enabled, the "Show restricted electric signals using default graphics" client setting and signal post recolouring is not applied.<br/>
This flag must only be set if a different sprite is returned when bit 24 of <spanclass="code">extra_callback_info2</span> is set.
</td>
</tr>
<tr><td>enable_signal_recolour</td><td>0 or 1</td>
<td>
Enable recolouring of graphics<br/>
When enabled, in addition to returning a sprite, register 0x100 may be set to the following using STORE_TEMP:
<table>
<tr><th>Bits</th><th>Meaning</th></tr>
<tr><td>0 - 23</td><td>Recolour sprite to use. Set to 0 for no recolouring.</td></tr>
<tr><td>24 - 31</td><td>Reserved, set to zero.</td></tr>
</table>
</td>
</tr>
</table>
<p>
Custom signal sprites example:
<preclass="code">
grf {
...
}
if (!extended_feature_test("action3_signals_custom_signal_sprites")) {
