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OpenTTD-patches/docs/newgrf-additions.html
Jonathan G Rennison 156e53a519 Documentation: Reference road stops from main NewGRF pages
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<title>JGR's Patchpack - Additions to NewGRF Specifications</title>
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<h2>Additions to NewGRF Specifications in JGR's Patchpack</h2>
<p>This document describes non-standard additions to the <a href="https://newgrf-specs.tt-wiki.net/wiki/Main_Page">Official OpenTTD NewGRF Specifications</a> which are present in this patchpack.
<p>These additions MAY also be present in other patchpacks. They MAY be removed or moved in future, if necessary.</p>
<p>A subset of the features listed below are also supported in a fork of NML, see the associated <a href="newgrf-additions-nml.html">NML document</a> for more details.</p>
<p>NewGRFs which use any of these features SHOULD use the <a href="#feature-test">feature testing</a> mechanism described below to check whether individual added features are supported.</p>
<h3 id="separate_features">Features with separate pages</h3>
<ul>
<li><a href="newgrf-roadstops.html">Road stops</a></li>
</ul>
<h3 id="feature-test">Action 14 - Feature Tests</h3>
<p>See <a href="https://newgrf-specs.tt-wiki.net/wiki/Action14">Action 14 Specification</a> for background information.</p>
<h4 id="FTST">Feature Test: C "FTST"</h4>
<p>Each FTST chunk (type C) describes an individual feature test.<br />
Sub-chunks within each FTST chunk may appear in any order, however each sub-chunk SHOULD only appear ONCE within an individual FTST chunk.</p>
<p>Feature tests can be safely used on implementations which do not implement the described feature test mechanism because unknown Action 14 blocks are ignored,
and the observable result (in global variable 0x9D) is equivalent to the case where all feature tests have failed, indicating that the feature is not present.</p>
<h4 id="FTST-NAME">Feature Name: C "FTST" -> T "NAME"</h4>
<p>Within an FTST chunk, the NAME text (type T) field contains the name of the feature to test for. The value of the language ID byte is ignored.<br />
If the named feature is not present, or if this field is omitted, the version is 0.<br />
If the named feature is present, the version number will be at least 1.</p>
<p>The feature testing mechanism itself has the feature name: <font face="monospace">feature_test</font>, this document describes version 1.</p>
<h4 id="FTST-MINV">Feature Minimum Version: C "FTST" -> B "MINV"</h4>
<p>Within an FTST chunk, the MINV binary (type B) field contains the minimum (inclusive) (&ge;) version to accept. This is a Word (2 bytes).<br />
The default value is 1.</p>
<h4 id="FTST-MAXV">Feature Maximum Version: C "FTST" -> B "MAXV"</h4>
<p>Within an FTST chunk, the MAXV binary (type B) field contains the maximum (inclusive) (&le;) version to accept. This is a Word (2 bytes).<br />
The default value is 0xFFFF (no maximum).</p>
<h4 id="FTST-SETP">Feature Set Global Variable 0x9D Bit: C "FTST" -> B "SETP"</h4>
<p>Within an FTST chunk, the SETP binary (type B) field contains the bit number to set/clear in
<a href="https://newgrf-specs.tt-wiki.net/wiki/GlobalVariables">global variable</a> 0x9D (TTD Platform) to store the result of the test. This is 1 byte.<br />
If the test is successful, the bit is set (to 1), otherwise the bit is cleared (to 0).<br />
The bit number MUST be in the range: 4 &le; bit number &le; 31. These bits can be assumed to be 0 on implementations which do not support this feature test mechanism.<br />
Global variable 0x9D can then be tested by using a standard <a href="https://newgrf-specs.tt-wiki.net/wiki/Action7">Action 7 or 9</a>, or a standard <a href="https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2">Variational Action 2</a>.<br />
If this field is omitted, no bit is set or cleared, and the test is not observable.
</p>
<br />
<h4 id="FTST-example">Example NFO:</h4>
<pre>
// Set bit 4 of global variable 0x9D if sample_feature_1 is present with a version of at least 4
// Set bit 5 of global variable 0x9D if sample_feature_2 is present with a version of at least 5 and at most 6
-1 * -1 14
"C" "FTST"
"T" "NAME" 00 "sample_feature_1" 00
"B" "MINV" \w2 \w4
"B" "SETP" \w1 04
00
"C" "FTST"
"T" "NAME" 00 "sample_feature_2" 00
"B" "MINV" \w2 \w5
"B" "MAXV" \w2 \w6
"B" "SETP" \w1 05
00
00
....
// Skip 1 sprite if bit 4 of global variable 0x9D is not set (indicating that sample_feature_1 with a version of at least 4 is NOT present)
-1 * -1 07 9D 01 \70 04 01
</pre>
<br />
<h3 id="property-mapping">Action 14 - Property Mapping for Action 0</h3>
<p>See <a href="https://newgrf-specs.tt-wiki.net/wiki/Action14">Action 14 Specification</a> and <a href="https://newgrf-specs.tt-wiki.net/wiki/Action0">Action 0 Specification</a> for background information.</p>
<p>The property mapping mechanism has the feature name: <font face="monospace">property_mapping</font>, this document describes version 1.</p>
<p>Users of this mechanism SHOULD at minimum test for the presence of the feature above or test variable 8D, below.</p>
<h4 id="A0PM">Property Mapping: C "A0PM"</h4>
<p>Each A0PM chunk (type C) describes an individual property mapping.<br />
Sub-chunks within each A0PM chunk may appear in any order, however except where otherwise noted each sub-chunk SHOULD only appear ONCE within an individual A0PM chunk.</p>
<p>Property mapping can be safely used on implementations which do not implement the property mapping mechanism if Action 0 sprites which use mapped property IDs are skipped if one or more of:
<ul>
<li>The global variable 0x8D is checked to determine whether the property mapping operation was successful.</li>
<li>The feature name <font face="monospace">property_mapping</font> is checked for.</li>
</ul>
Unknown Action 14 blocks are ignored, and do not need to be skipped.</p>
<h4 id="A0PM-NAME">Property Name: C "A0PM" -> T "NAME"</h4>
<p>Within an A0PM chunk, the NAME text (type T) field contains the name of the property to map. The value of the language ID byte is ignored.</p>
<h4 id="A0PM-FEAT">Action 0 Feature ID: C "A0PM" -> B "FEAT"</h4>
<p>Within an A0PM chunk, the FEAT binary (type B) field contains the <a href="https://newgrf-specs.tt-wiki.net/wiki/Action0#Feature">Action 0 feature ID</a>. This is 1 byte.</p>
<h4 id="A0PM-PROP">Property ID: C "A0PM" -> B "PROP"</h4>
<p>Within an A0PM chunk, the PROP binary (type B) field contains the property ID to allocate to the named property, this value can used in Action 0 sprites. This is 1 byte.<br />
It is possible to override existing properties, however this use is not recommended.</p>
<h4 id="A0PM-SETT">Success Indicator Global Variable 0x8D Bit: C "A0PM" -> B "SETT"</h4>
<p>Within an A0PM chunk, the SETT binary (type B) field contains the bit number to set/clear in
<a href="https://newgrf-specs.tt-wiki.net/wiki/GlobalVariables">global variable</a> 0x8D (TTD version) to store whether the mapping operation was successful. This is 1 byte.<br />
If the operation is successful, the bit is set (to 1), otherwise the bit is cleared (to 0).<br />
The bit number MUST be in the range: 4 &le; bit number &le; 31. These bits can be assumed to be 0 on implementations which do not support this property mapping mechanism.<br />
Global variable 0x8D can then be tested by using a standard <a href="https://newgrf-specs.tt-wiki.net/wiki/Action7">Action 7 or 9</a>, or a standard <a href="https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2">Variational Action 2</a>.<br />
If this field is omitted, no bit is set or cleared.
</p>
<h4 id="A0PM-FLBK">Fallback Mode: C "A0PM" -> B "FLBK"</h4>
<p>Within an A0PM chunk, the FLBK binary (type B) field contains the fallback mode. This is 1 byte.<br />
The fallback mode may take the following values:
<table>
<tr><th>Value</th><th>Behaviour</th></tr>
<tr><td>0</td><td>Attempts to map an unknown property name are ignored. Use of the mapped property in an Action 0 is ignored. This is the default.</td></tr>
<tr><td>1</td><td>Attempts to map an unknown property name are ignored. Use of the mapped property in an Action 0 is an error.</td></tr>
<tr><td>2</td><td>Attempting to map an unknown property name is an error.</td></tr>
</table>
Attempts to set a fallback mode other than those listed above are silently ignored. More fallback modes MAY be added in future versions of this mechanism.<br />
This chunk MAY be specified more than once, in which case the last specified valid value is used.<br />
Note that even when using fallback mode 0, above, if the property mapping feature is not present, then use of the mapped property ID in an Action 0 is an error.
</p>
<h4 id="A0PM-format">Format of remapped properties</h4>
All properties which are mapped by this mechanism have the format:
<table>
<tr><th>Size</th><th>Name</th><th>Meaning</th></tr>
<tr><td>B*</td><td>num</td><td>Size of the data in bytes</td></tr>
<tr><td>V</td><td>data</td><td>Property data</td></tr>
</table>
Note that num is an extended byte, see <a href="https://newgrf-specs.tt-wiki.net/wiki/GRFActionsDetailed">GRFActionsDetailed</a>.<br />
If the size of the data provided is not valid for the given property, the attempt to set the property MAY be ignored or partially applied.<br />
Note that each use of the mapped property ID is followed by Num-info iterations of the size and data pair above. See: <a href="https://newgrf-specs.tt-wiki.net/wiki/Action0">Action 0 Specification</a>.
<h4 id="A0PM-example">Example NFO:</h4>
<pre>
// Map station property "sample_station_property" to property id 0xF8, and set bit 4 of global variable 0x8D if successful
-1 * -1 14
"C" "A0PM"
"T" "NAME" 00 "sample_station_property" 00
"B" "FEAT" \w1 04
"B" "PROP" \w1 F8
"B" "SETT" \w1 4
00
00
....
// Skip 1 sprite if bit 4 of global variable 0x8D is not set (indicating that station property sample_station_property is NOT present)
-1 * -1 07 8D 01 \70 04 01
// Set sample_station_property for station ID 10 to 2 byte value: AB CD
-1 * -1 00 04 01 01 10 F8 02 AB CD
</pre>
<br />
<h3 id="a0stations"><a href="https://newgrf-specs.tt-wiki.net/wiki/Action0/Stations">Action 0 - Stations</a></h3>
<h4 id="station_min_bridge_height"><a href="https://newgrf-specs.tt-wiki.net/wiki/Action0/Stations#Minimum_bridge_height_.281B.29">Minimum bridge height (1B, or mappable property: station_min_bridge_height)</a></h4>
<p>This property allows building bridges over stations.<br />
The bridge height property defines minimum clearances required for a bridge for each of the 8 station layouts (or 0 to not allow any bridge). Values are given in height level units (1 level == 8px).<br />
Each height value is 1 byte, the total property length is 8 bytes.
</p>
<p>This is indicated by the feature name: <font face="monospace">action0_station_prop1B</font>, version 1</p>
<h4 id="station_disallowed_bridge_pillars">Disallowed bridge pillars (mappable property: station_disallowed_bridge_pillars)</h4>
<p>This property describes which bridge pillars are not allowed on the station tile.<br />
It consists of 8 pillar flags, for each of the 8 station layouts.<br />
Each set of flags is 1 byte, the total property length is 8 bytes.<br />
Each set of flags has the format described in the bridge_pillar_flags property section, below.
</p>
<p>This is indicated by the feature name: <font face="monospace">action0_station_disallowed_bridge_pillars</font>, version 1</p>
<br />
The 8 station layouts are described below.
<table>
<tr><th>Station layout</th><th>Axis</th><th>Default Appearance</th></tr>
<tr><td>0</td><td>X</td><td>plain platform</td></tr>
<tr><td>1</td><td>Y</td><td>plain platform</td></tr>
<tr><td>2</td><td>X</td><td>platform with building</td></tr>
<tr><td>3</td><td>Y</td><td>platform with building</td></tr>
<tr><td>4</td><td>X</td><td>platform with roof, left side</td></tr>
<tr><td>5</td><td>Y</td><td>platform with roof, left side</td></tr>
<tr><td>6</td><td>X</td><td>platform with roof, right side</td></tr>
<tr><td>7</td><td>Y</td><td>platform with roof, right side</td></tr>
</table>
<br />
<h3 id="a0bridges"><a href="https://newgrf-specs.tt-wiki.net/wiki/Action0/Bridges">Action 0 - Bridges</a></h3>
<h4 id="bridge_menu_icon">Menu icons (14, or mappable property: bridge_menu_icon)</h4>
<p>This property sets the GUI menu icon for bridge type, this is displayed when constructing a bridge<br />
This has the format:
<table>
<tr><th>Size</th><th>Field</th><th>Description</th></tr>
<tr><td>W</td><td>Sprite</td><td>Sprite ID</td></tr>
<tr><td>W</td><td>Recolour</td><td>Recolour sprite/value</td></tr>
</table>
The total property length is 4 bytes.
</p>
<p>This is indicated by the feature name: <font face="monospace">action0_bridge_prop14</font>, version 1</p>
<h4 id="bridge_pillar_flags">Bridge pillars (mappable property: bridge_pillar_flags)</h4>
<p>This property describes the pillars present for each bridge sprite table.<br />
It consists of 6 pairs of pillar flags, for bridge sprite tables 0 - 5.<br />
Each pair consists of: X direction flags, Y direction flags<br />
Each set of flags is 1 byte, the total property length is 12 bytes.<br />
Each set of flags has the format:
<table>
<tr><th>Bit</th><th>Value</th><th>Meaning</th></tr>
<tr><td>0</td><td>1</td><td>Pillar is present in west corner</td></tr>
<tr><td>1</td><td>2</td><td>Pillar is present in south corner</td></tr>
<tr><td>2</td><td>4</td><td>Pillar is present in east corner</td></tr>
<tr><td>3</td><td>8</td><td>Pillar is present in north corner</td></tr>
<tr><td>4</td><td>10</td><td>Pillar is present along entire north-east edge</td></tr>
<tr><td>5</td><td>20</td><td>Pillar is present along entire south-east edge</td></tr>
<tr><td>6</td><td>40</td><td>Pillar is present along entire south-west edge</td></tr>
<tr><td>7</td><td>80</td><td>Pillar is present along entire north-west edge</td></tr>
</table>
</p>
<p>This is indicated by the feature name: <font face="monospace">action0_bridge_pillar_flags</font>, version 1</p>
<h4 id="bridge_availability_flags">Bridge availability flags (mappable property: bridge_availability_flags)</h4>
<p>This property sets the availability flags for this bridge type.<br />
The property length is 1 byte. The format is:
<table>
<tr><th>Bit</th><th>Value</th><th>Meaning</th></tr>
<tr><td>0</td><td>1</td><td>Towns may not build this bridge type</td></tr>
<tr><td>1</td><td>2</td><td>Scripts (AI/GS) may not build this bridge type</td></tr>
</table>
</p>
<p>This is indicated by the feature name: <font face="monospace">action0_bridge_availability_flags</font>, version 1</p>
<h4 id="more_bridge_types">More bridges (16 instead of 13)</h4>
<p>This is indicated by the feature name: <font face="monospace">more_bridge_types</font>, version 1</p>
<h3 id="a0railtypes"><a href="https://newgrf-specs.tt-wiki.net/wiki/Action0/Railtypes">Action 0 - Railtypes</a></h3>
<h4 id="railtype_enable_programmable_signals">Enable custom signal sprites for programmable pre-signals (mappable property: railtype_enable_programmable_signals)</h4>
<p>This enables <a href="https://newgrf-specs.tt-wiki.net/wiki/Action3/Railtypes#Signal_sprites_.280B.29">Action 2/3 - Railtype custom signal sprites</a> for programmable pre-signals.<br />
Programmable pre-signals have the signal type value: 06.<br />
The property length is 1 byte. 0 is disabled (default). 1 is enabled.
</p>
<p>This is indicated by the feature name: <font face="monospace">action0_railtype_programmable_signals</font>, version 1</p>
<h4 id="railtype_enable_no_entry_signals">Enable custom signal sprites for no-entry signals (mappable property: railtype_enable_no_entry_signals)</h4>
<p>This enables <a href="https://newgrf-specs.tt-wiki.net/wiki/Action3/Railtypes#Signal_sprites_.280B.29">Action 2/3 - Railtype custom signal sprites</a> for no-entry signals.<br />
No-entry signals have the signal type value: 07.<br />
The property length is 1 byte. 0 is disabled (default). 1 is enabled.
</p>
<p>This is indicated by the feature name: <font face="monospace">action0_railtype_no_entry_signals</font>, version 1</p>
<h4 id="railtype_enable_restricted_signals">Enable restricted signal flag for custom signal sprites (mappable property: railtype_enable_restricted_signals)</h4>
<p>This applies to <a href="https://newgrf-specs.tt-wiki.net/wiki/Action3/Railtypes#Signal_sprites_.280B.29">Action 2/3 - Railtype custom signal sprites</a>.<br />
When enabled, bit 24 of variable 18 (extra callback info) 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 should only be set if the Action 2/3 actually returns a different sprite when bit 24 of variable 18 is set.<br />
The property length is 1 byte. 0 is disabled (default). 1 is enabled.
</p>
<p>This is indicated by the feature name: <font face="monospace">action0_railtype_restricted_signals</font>, version 1</p>
<h4 id="railtype_enable_signal_recolour">Enable recolouring for custom signal sprites (mappable property: railtype_enable_signal_recolour)</h4>
<p>This applies to <a href="https://newgrf-specs.tt-wiki.net/wiki/Action3/Railtypes#Signal_sprites_.280B.29">Action 2/3 - Railtype custom signal sprites</a>.<br />
When enabled, in addition to returning a sprite, register 0x100 may be set to the following:
<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></p>
<p>The property length is 1 byte. 0 is disabled (default). 1 is enabled.</p>
<p>This is indicated by the feature name: <font face="monospace">action0_railtype_recolour</font>, version 1</p>
<h4 id="railtype_extra_aspects">Set number of additional signal aspects (mappable property: railtype_extra_aspects)</h4>
<p>This applies to <a href="https://newgrf-specs.tt-wiki.net/wiki/Action3/Railtypes#Signal_sprites_.280B.29">Action 2/3 - Railtype custom signal sprites</a>.<br />
The value is the number of additional signal aspects to use (e.g. 4-aspect signalling should use a value of 2).<br />
When set, the lowest byte of variable 0x18 (SS: signal state) may have the given number of additional values starting from 02:
<table>
<tr><th>Value</th><th>Meaning</th></tr>
<tr><td>00</td><td>Red signal</td></tr>
<tr><td>01</td><td>Green signal</td></tr>
<tr><td>02</td><td>1st extra aspect (e.g. yellow)</td></tr>
<tr><td>03</td><td>2nd extra aspect (e.g. double yellow)</td></tr>
<tr><td>...</td><td>Further extra aspects...</td></tr>
</table></p>
<p>The property length is 1 byte.<br />
The provided value is currently clamped to be within the range 0 - 6 (inclusive).</p>
<p>N.B. Realistic braking must be enabled for additional signal aspects to be used.</p>
<p>This is indicated by the feature name: <font face="monospace">action0_railtype_extra_aspects</font>, version 1</p>
<h4 id="railtype_disable_realistic_braking">Disable use of realistic braking with this rail type (mappable property: railtype_disable_realistic_braking)</h4>
<p>When this property is set realistic braking is disabled for trains of this railtype even when realistic braking is otherwise in effect.<br />
The property length is 1 byte. 0 is realistic braking is not disabled for this railtype. 1 is disable realistic braking for this railtype.
</p>
<p>This is indicated by the feature name: <font face="monospace">action0_railtype_disable_realistic_braking</font>, version 1</p>
<br />
<h3 id="a0roadtypes"><a href="https://newgrf-specs.tt-wiki.net/wiki/Action0/Roadtypes">Action 0 - Roadtypes</a> and <a href="https://newgrf-specs.tt-wiki.net/wiki/Action0/Tramtypes">Action 0 - Tramtypes</a></h3>
<h4 id="roadtype_extra_flags">Extra road/tram type flags (mappable property: roadtype_extra_flags)</h4>
<p>This property sets the extra flags for this road/tram type.<br />
The property length is 1 byte. The format is:
<table>
<tr><th>Bit</th><th>Value</th><th>Meaning</th></tr>
<tr><td>0</td><td>1</td><td>Scripts (AI/GS) may not build this road/tram type</td></tr>
<tr><td>1</td><td>2</td><td>Towns may not modify tiles of this road/tram type in any way whatsoever</td></tr>
</table>
</p>
<p>This is indicated by the feature name: <font face="monospace">action0_roadtype_extra_flags</font>, version 1</p>
<br />
<h3 id="a0globalsettings"><a href="https://newgrf-specs.tt-wiki.net/wiki/Action0/Global_Settings">Action 0 - Global Settings</a></h3>
<h4 id="global_extra_station_names">Extra station names (mappable property: global_extra_station_names)</h4>
<p>This adds extra station names for use when all the available station names for a given town have been used.<br />
The string should have the same format and use the same ID range as
<a href="https://newgrf-specs.tt-wiki.net/wiki/Action0/Industries#Default_name_for_nearby_station_.2824.29">industry - default name for nearby station</a>.<br />
The Action 0 ID field is ignored. This property always adds a new station name string instead of overwriting an existing one.<br />
The property length is 4 bytes. The format is:
<table>
<tr><th>Size</th><th>Field</th><th>Description</th></tr>
<tr><td>W</td><td>String ID</td><td>String to use for the station name</td></tr>
<tr><td>W</td><td>Flags</td><td>See table below</td></tr>
</table>
<br />
Flags field:
<table>
<tr><th>Bit</th><th>Value</th><th>Meaning</th></tr>
<tr><td>0</td><td>1</td><td>May be used for rail stations</td></tr>
<tr><td>1</td><td>2</td><td>May be used for road stations</td></tr>
<tr><td>2</td><td>4</td><td>May be used for airport stations</td></tr>
<tr><td>3</td><td>8</td><td>May be used for oil rig stations</td></tr>
<tr><td>4</td><td>10</td><td>May be used for dock stations</td></tr>
<tr><td>5</td><td>20</td><td>May be used for heliport stations</td></tr>
<tr><td>8</td><td>100</td><td>May only be used for stations near the town centre</td></tr>
<tr><td>9</td><td>200</td><td>May not be used for stations near the town centre</td></tr>
<tr><td>10</td><td>400</td><td>May only be used for stations near water</td></tr>
<tr><td>11</td><td>800</td><td>May not be used for stations near water</td></tr>
</table>
</p>
<p>This is indicated by the feature name: <font face="monospace">action0_global_extra_station_names</font>, version 1</p>
<h4 id="global_lighthouse_generate_amount">Lighthouse object map generation amount (mappable property: global_lighthouse_generate_amount)</h4>
<p>This sets the map generation amount value for the lighthouse default object (0 is no generation, 255 is maximum).<br />
The Action 0 ID field is ignored. The property length is 1 byte.
</p>
<p>This is indicated by the feature name: <font face="monospace">action0_global_default_object_generate_amount</font>, version 1</p>
<h4 id="global_transmitter_generate_amount">Transmitter object map generation amount (mappable property: global_transmitter_generate_amount)</h4>
<p>This sets the map generation amount value for the transmitter default object (0 is no generation, 255 is maximum).<br />
The Action 0 ID field is ignored. The property length is 1 byte.
</p>
<p>This is indicated by the feature name: <font face="monospace">action0_global_default_object_generate_amount</font>, version 1</p>
<br />
<h3 id="a0signals"><a href="https://newgrf-specs.tt-wiki.net/wiki/Action0">Action 0 - Signals (Feature 0E)</a></h3>
<p>Note that Action 0 feature 0E is not supported (does nothing) in standard OpenTTD.</p>
<p>This implementation of feature 0E is not the same as that in TTDPatch.</p>
<h4 id="signals_enable_programmable_signals">Enable custom signal sprites for programmable pre-signals (mappable property: signals_enable_programmable_signals)</h4>
<p>This enables <a href="#a3signals_custom_signal_sprites">Action 2/3 Signals (Feature 0E) custom signal sprites</a> for programmable pre-signals for this GRF.<br />
Programmable pre-signals have the signal type value: 06.<br />
The property length is 1 byte. 0 is disabled (default). 1 is enabled.<br />
The Action 0 Id field is not used, the value is ignored.
</p>
<p>This is indicated by the feature name: <font face="monospace">action0_signals_programmable_signals</font>, version 1</p>
<h4 id="signals_enable_no_entry_signals">Enable custom signal sprites for no-entry signals (mappable property: signals_enable_no_entry_signals)</h4>
<p>This enables <a href="#a3signals_custom_signal_sprites">Action 2/3 Signals (Feature 0E) custom signal sprites</a> for no-entry signals for this GRF.<br />
No-entry signals have the signal type value: 07.<br />
The property length is 1 byte. 0 is disabled (default). 1 is enabled.
</p>
<p>This is indicated by the feature name: <font face="monospace">action0_signals_no_entry_signals</font>, version 1</p>
<h4 id="signals_enable_restricted_signals">Enable restricted signal flag for custom signal sprites (mappable property: signals_enable_restricted_signals)</h4>
<p>This applies to <a href="#a3signals_custom_signal_sprites">Action 2/3 Signals (Feature 0E) custom signal sprites</a> for this GRF.<br />
When enabled, bit 24 of variable 18 (extra callback info) 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 should only be set if the Action 2/3 actually returns a different sprite when bit 24 of variable 18 is set.<br />
The property length is 1 byte. 0 is disabled (default). 1 is enabled.<br />
The Action 0 Id field is not used, the value is ignored.
</p>
<p>This is indicated by the feature name: <font face="monospace">action0_signals_restricted_signals</font>, version 1</p>
<h4 id="signals_enable_signal_recolour">Enable recolouring for custom signal sprites (mappable property: signals_enable_signal_recolour)</h4>
<p>This applies to <a href="#a3signals_custom_signal_sprites">Action 2/3 Signals (Feature 0E) custom signal sprites</a> for this GRF.<br />
When enabled, in addition to returning a sprite, register 0x100 may be set to the following:
<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></p>
<p>The property length is 1 byte. 0 is disabled (default). 1 is enabled.<br />
The Action 0 Id field is not used, the value is ignored.
</p>
<p>This is indicated by the feature name: <font face="monospace">action0_signals_recolour</font>, version 1</p>
<h4 id="signals_extra_aspects">Set number of additional signal aspects (mappable property: signals_extra_aspects)</h4>
<p>This applies to <a href="#a3signals_custom_signal_sprites">Action 2/3 Signals (Feature 0E) custom signal sprites</a> for this GRF.<br />
The value is the number of additional signal aspects to use (e.g. 4-aspect signalling should use a value of 2).<br />
When set, the lowest byte of variable 0x18 (SS: signal state) may have the given number of additional values starting from 02:
<table>
<tr><th>Value</th><th>Meaning</th></tr>
<tr><td>00</td><td>Red signal</td></tr>
<tr><td>01</td><td>Green signal</td></tr>
<tr><td>02</td><td>1st extra aspect (e.g. yellow)</td></tr>
<tr><td>03</td><td>2nd extra aspect (e.g. double yellow)</td></tr>
<tr><td>...</td><td>Further extra aspects...</td></tr>
</table></p>
<p>The property length is 1 byte.<br />
The provided value is currently clamped to be within the range 0 - 6 (inclusive).</p>
<p>N.B. Realistic braking must be enabled for additional signal aspects to be used.</p>
<p>This is indicated by the feature name: <font face="monospace">action0_signals_extra_aspects</font>, version 1</p>
<br />
<h3 id="a0objects"><a href="https://newgrf-specs.tt-wiki.net/wiki/Action0/Objects">Action 0 - Objects</a></h3>
<h4 id="object_use_land_ground">Object uses land ground sprite (mappable property: object_use_land_ground)</h4>
<p>This property sets whether to use the underlying ground as the object ground sprite, ignoring the ground sprite provided in the sprite layout.<br />
When enabled, the ground sprite will be bare ground, grass, snow, desert, etc. as if it were a clear ground tile.<br />
In edge foundation mode, the ground may be coast/shore when flooded.<br />
The property length is 1 byte. 0 is disabled (default). 1 is enabled.</p>
<p>This is indicated by the feature name: <font face="monospace">action0_object_use_land_ground</font>, version 1</p>
<h4 id="object_edge_foundation_mode">Enable object edge foundation mode (mappable property: object_edge_foundation_mode)</h4>
<p>This property enables edge foundation mode for the object.<br />
This property is intended for objects which are positioned at the edge of a tile, and only require a level edge, not a completely level tile.<br />
Foundations will only be added as required to get a suitable level edge.<br />
The property length is 4 bytes, 1 byte per view. If the object has fewer than 4 views then some of the values provided in the property will not be used, and may be 0.<br />
The format of each byte is:
<table>
<tr><th>Bit</th><th>Value</th><th>Meaning (for this view)</th></tr>
<tr><td>0 - 1</td><td></td><td>
Which tile edge to use:<br />
<table>
<tr><th>Value</th><th>Meaning</th></tr>
<tr><td>0</td><td>North-east edge</td></tr>
<tr><td>1</td><td>South-east edge</td></tr>
<tr><td>2</td><td>South-west edge</td></tr>
<tr><td>3</td><td>North-west edge</td></tr>
</table>
</td></tr>
<tr><td>2</td><td>4</td><td>Change z-position for the building sprite to the height of the edge</td></tr>
<tr><td>3</td><td>8</td><td>If the height of the edge is lower than the maximum height of the tile, build a foundation</td></tr>
<tr><td>4</td><td>10</td><td>Use inclined instead of a flat foundations where possible. (Slopes with one corner raised where the height of the edge is at the maximum height of the tile).<br />
Support for this bit is indicated by the feature name: <font face="monospace">action0_object_edge_foundation_mode</font>, version 2.</td></tr>
</table>
</p>
<p>This is indicated by the feature name: <font face="monospace">action0_object_edge_foundation_mode</font>, version 1</p>
<h4 id="object_flood_resistant">Object is flood resistant (mappable property: object_flood_resistant)</h4>
<p>This property sets whether the object is flood resistant.<br />
Flood resistance is always enabled for objects which can be built on water.<br />
This property can be used to enable flood resistance without enabling the object to be built on water.<br />
The property length is 1 byte. 0 is disabled (default). 1 is enabled.</p>
<p>This is indicated by the feature name: <font face="monospace">action0_object_flood_resistant</font>, version 1</p>
<h4 id="object_viewport_map_tile_type">Set tile type used for display in viewport map mode and the small-map window (mappable property: object_viewport_map_tile_type)</h4>
<p>This property sets how object tiles are displayed in viewport map mode and the small-map window.<br />
The property length is 1 byte.</p>
<table>
<tr><th>Value</th><th>Meaning</th><th>Notes</th></tr>
<tr><td>00</td><td>Default object</td><td></td></tr>
<tr><td>01</td><td>Clear/bare dirt</td><td>If object_use_land_ground is enabled, the underlying ground type will be used instead</td></tr>
<tr><td>02</td><td>Grass</td><td></td></tr>
<tr><td>03</td><td>Rough ground</td><td></td></tr>
<tr><td>04</td><td>Rocky ground</td><td></td></tr>
<tr><td>05</td><td>Farm fields</td><td>The specific type of field can be set using object_viewport_map_tile_subtype</td></tr>
<tr><td>06</td><td>Snow</td><td></td></tr>
<tr><td>07</td><td>Desert</td><td></td></tr>
<tr><td>08</td><td>Trees</td><td>The specific tree count and ground type/density can be set using object_viewport_map_tile_subtype</td></tr>
<tr><td>09</td><td>House</td><td></td></tr>
<tr><td>0A</td><td>Water</td><td></td></tr>
</table></p>
<p>This is indicated by the feature name: <font face="monospace">action0_object_viewport_map_tile_type</font>, version 1</p>
<h4 id="object_viewport_map_tile_subtype">Set tile sub-type used for display in viewport map mode and the small-map window (mappable property: object_viewport_map_tile_subtype)</h4>
<p>This property can be used to further refine the type set in object_viewport_map_tile_type.<br />
The property length is 2 bytes.</p>
<p>Farm fields:
<table>
<tr><th>Bit</th><th>Value</th><th>Meaning</th></tr>
<tr><td>0 - 2</td><td>0 - 7</td><td>
Which field type to use
</td></tr>
</table></p>
<p>Trees:
<table>
<tr><th>Bit</th><th>Meaning</th></tr>
<tr><td>0 - 3</td><td>
Tree ground type
<table>
<tr><th>Value</th><th>Meaning</th></tr>
<tr><td>0</td><td>Grass</td></tr>
<tr><td>1</td><td>Rough ground</td></tr>
<tr><td>2</td><td>Snow/desert</td></tr>
<tr><td>3</td><td>Shore</td></tr>
<tr><td>4</td><td>Rough snow</td></tr>
</table>
</td></tr>
<tr><td>4 - 7</td><td>
Tree ground density (clamped to: 0 - 3)
</td></tr>
<tr><td>8 - 11</td><td>
Number of trees on the tile (clamped to: 1 - 4)
</td></tr>
</table></p>
<p>This is indicated by the feature name: <font face="monospace">action0_object_viewport_map_tile_type</font>, version 1</p>
<br />
<h3 id="variable-mapping">Action 14 - Variable Mapping for Variational Action 2</h3>
<p>See <a href="https://newgrf-specs.tt-wiki.net/wiki/Action14">Action 14 Specification</a> and <a href="https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2">Variational Action 2 Specification</a> for background information.</p>
<p>The variable mapping mechanism has the feature name: <font face="monospace">variable_mapping</font>, this document describes version 1 (and where indicated, version 2).</p>
<p>Unlike property mappings, it is not necessary to perform a feature test or check a mapping success variable before using a mapped variable.</p>
<p>Remapped variables are accessed by reading from variable 0x11 using a varadjust shift-num and and-mask which exactly matches that specified in the variable mapping.<br />
In the absence of any successful variable mapping, variable 0x11 has all bits set to 0 and attempting to read from it with any shift-num and and-mask value
results in a value of 0 without producing an error.</p>
<p>Reading a mapped variable on a version of OpenTTD which does not support this variable mapping mechanism or which does not support the requested variable, returns a value of 0.</p>
<p>If more than one variable mapping is made for the same combination of feature ID, shift-num and and-mask, it is implementation-defined which mapping is used.<br />
Each variable mapping SHOULD use a unique combination of feature ID, shift-num and and-mask.</p>
<p>From version 2 of the <font face="monospace">variable_mapping</font> feature name, variable remapping can also be used with variable 0x7B.<br />
In this case the parameter of variable 0x7B should be set to 0x11, and the shift and mask fields set the same way in the direct 0x11 variable case.<br />
The "VPRM" parameter field is ignored, and the parameter used is the accumulator of the previous adjust part in the usual way for variable 0x7B.</p>
<h4 id="A2VM">Variable Mapping: C "A2VM"</h4>
<p>Each A2VM chunk (type C) describes an individual variable mapping.<br />
Sub-chunks within each A2VM chunk may appear in any order, however each sub-chunk SHOULD only appear ONCE within an individual A2VM chunk.</p>
<p>Unknown Action 14 blocks are ignored, and do not need to be skipped.</p>
</p>
<h4 id="A2VM-NAME">Property Name: C "A2VM" -> T "NAME"</h4>
<p>Within an A2VM chunk, the NAME text (type T) field contains the name of the variable to map. The value of the language ID byte is ignored.</p>
<h4 id="A2VM-FEAT">Action 0 Feature ID: C "A2VM" -> B "FEAT"</h4>
<p>Within an A2VM chunk, the FEAT binary (type B) field contains the <a href="https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2#Feature">Variational Action 2 feature ID</a>. This is 1 byte.</p>
<h4 id="A2VM-RSFT">Shift to replace: C "A2VM" -> B "RSFT"</h4>
<p>Within an A2VM chunk, the RSFT binary (type B) field contains the Variational Action 2 varadjust shift-num value to look for. This is 1 byte.<br />
The shift-num value must be &lt; 32 (0x20).<br />
If this is not specified, a value of 0 is assumed.</p>
<h4 id="A2VM-RMSK">Mask to replace: C "A2VM" -> B "RMSK"</h4>
<p>Within an A2VM chunk, the RMSK binary (type B) field contains the Variational Action 2 varadjust and-mask value to look for. This is 4 bytes.<br />
When using byte or word sized variational action 2s, the and-mask is zero-extended to 32 bits before comparing with this value.<br />
If this is not specified, a value of 0 is assumed.</p>
<h4 id="A2VM-VSFT">Replacement shift: C "A2VM" -> B "VSFT"</h4>
<p>Within an A2VM chunk, the VSFT binary (type B) field contains the replacement Variational Action 2 varadjust shift-num value to use on the mapped variable. This is 1 byte.<br />
The shift-num value must be &lt; 32 (0x20).<br />
If this is not specified, a value of 0 is assumed.</p>
<h4 id="A2VM-VMSK">Replacement mask: C "A2VM" -> B "VMSK"</h4>
<p>Within an A2VM chunk, the RMSK binary (type B) field contains the replacement Variational Action 2 varadjust and-mask value to use on the mapped variable. This is 4 bytes.<br />
If this is not specified, a value of 0 is assumed.</p>
<h4 id="A2VM-SETT">Success Indicator Global Variable 0x8D Bit: C "A2VM" -> B "SETT"</h4>
<p>This behaves identically to the <a href="#A0PM-SETT">C "A0PM" -> B "SETT"</a> case, above</p>
<h4 id="A2VM-VPRM">Replacement parameter: C "A2VM" -> B "VPRM"</h4>
<p>Within an A2VM chunk, the VPRM binary (type B) field contains the Variational Action 2 parameter value (as in 60+X variables) to use on the mapped variable. This is 4 bytes.<br />
If this is not specified, a value of 0 is assumed.<br />
Support for this field is indicated by the feature name <font face="monospace">variable_mapping</font>, version 2.</p>
<h4 id="A2VM-example">Example NFO:</h4>
<pre>
// Map station variable "sample_station_variable" with a shift-num of 4 and an and-mask of 0xFF, to reads of variable 0x11 with a shift-num of 1 and an and-mask of 0x2, and set bit 4 of global variable 0x8D if successful
-1 * -1 14
"C" "A2VM"
"T" "NAME" 00 "sample_station_variable" 00
"B" "FEAT" \w1 04
"B" "RSFT" \w1 1
"B" "RMSK" \w4 \dx00000002
"B" "VSFT" \w1 4
"B" "VMSK" \w4 \dx000000FF
"B" "SETT" \w1 4
00
00
....
-1 * 15 02 04 03 81 // Action2, Feature 04 (stations), action2ID 03, 1-byte variable
11 01 02 // variable 11 (remapping variable or 0), shift 01, mask 0x02 (these exactly match the remapping above)
// This is remapped to &dash;&dash;&gt; sample_station_variable with a shift of 04 and a mask of 0xFF
01 // check one range
02 00 00 04 // range 00 - 04: link to action2ID 02
01 00 // default: link to action2ID 01
</pre>
<br />
<h3 id="varaction2_station"><a href="https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Stations">Variational Action 2 - Stations</a></h3>
<h4 id="varaction2_station_var42">Track type in purchase list (42)</h4>
<p>This is indicated by the feature name: <font face="monospace">varaction2_station_var42</font>, version 1</p>
<br />
<h3 id="varaction2_object"><a href="https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Objects">Variational Action 2 - Objects</a></h3>
<h4 id="object_foundation_tile_slope">Tile slope after foundation applied (mappable variable: object_foundation_tile_slope)</h4>
<p>This has the same format as bits 8-12 of object variable 41.</p>
<p>This is indicated by the feature name: <font face="monospace">action0_object_edge_foundation_mode</font>, version 2</p>
<h4 id="object_foundation_change_tile_slope">Tile slope after foundation applied xor underlying tile slope (mappable variable: object_foundation_change_tile_slope)</h4>
<p>This has the same format as bits 8-12 of object variable 41, but has bits set only where the foundation slope differs from the underlying tile slope.<br />
If this variable is non-zero a foundation is present.<br />
This is useful for xoring with bits 8-12 of variable 41, because if this variable is unavailable then the result is still the underlying tile slope.</p>
<p>This is indicated by the feature name: <font face="monospace">action0_object_edge_foundation_mode</font>, version 2</p>
<br />
<br />
<h3 id="a3signals"><a href="https://newgrf-specs.tt-wiki.net/wiki/Action3">Action 3 - Signals (Feature 0E)</a></h3>
<p>Note that Action 3 feature 0E is not supported (does nothing) in standard OpenTTD.</p>
<p>This implementation of feature 0E is not the same as that in TTDPatch.</p>
<h4 id="a3signals_custom_signal_sprites">Custom signal sprites using Action 2/3 (action 3 ID: 0)</h4>
<p>This feature allows using Action 3 to assign an Action 2 chain which dynamically resolves signal sprites, in a very similar way to that of <a href="https://newgrf-specs.tt-wiki.net/wiki/Action3/Railtypes#Signal_sprites_.280B.29">Action 2/3 - Railtype custom signal sprites</a>,<br />
however, this applies to all signals, not only those of a particular rail type.</p>
<p>Variational Action 2 variables 10, 18 and 40 are available and have the same format as in <a href="https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Railtypes">VariationalAction2/Railtypes</a>.</p>
<p>Rail type custom signal sprites have a higher priority than custom signal sprites for all signals as set here.</p>
<p>Note that this is not a generic callback, the sprite group must be assigned to ID 0 (further IDs may be allocated for other purposes in future).</p>
<p>This is indicated by the feature name: <font face="monospace">action3_signals_custom_signal_sprites</font>, version 1</p>
<br />
<h3 id="action5">Action 14 - Type ID Mapping for Action 5</h3>
<p>See <a href="https://newgrf-specs.tt-wiki.net/wiki/Action14">Action 14 Specification</a> and <a href="https://newgrf-specs.tt-wiki.net/wiki/Action5">Action 5 Specification</a> for background information.</p>
<p>The action 5 type ID mapping mechanism has the feature name: <font face="monospace">action5_type_id_mapping</font>, this document describes version 1.</p>
<p>Users of this mechanism SHOULD at minimum test for the presence of the feature above or test variable 8D, below.</p>
<h4 id="A5TM">Action 5 type ID Mapping: C "A5TM"</h4>
<p>Each A5TM chunk (type C) describes an individual action 5 type ID mapping.<br />
Sub-chunks within each A5TM chunk may appear in any order, however except where otherwise noted each sub-chunk SHOULD only appear ONCE within an individual A5TM chunk.</p>
<p>Action 5 type ID mapping can be safely used on implementations which do not implement the type ID mapping mechanism if Action 5 sprites which use mapped type IDs are skipped if one or more of:
<ul>
<li>The global variable 0x8D is checked to determine whether the type ID mapping operation was successful.</li>
<li>The feature name <font face="monospace">action5_type_id_mapping</font> is checked for.</li>
</ul>
Unknown Action 14 blocks are ignored, and do not need to be skipped.</p>
<h4 id="A5TM-NAME">Property Name: C "A5TM" -> T "NAME"</h4>
<p>Within an A5TM chunk, the NAME text (type T) field contains the name of the type to map. The value of the language ID byte is ignored.</p>
<h4 id="A5TM-TYPE">Property ID: C "A5TM" -> B "TYPE"</h4>
<p>Within an A5TM chunk, the TYPE binary (type B) field contains the type ID to allocate to the named type, this value can used in Action 5 sprites. This is 1 byte. The value MUST be &lt; 128 (i.e bit 7 must be clear).<br />
It is possible to override existing type IDs, however this use is not recommended.</p>
<h4 id="A5TM-SETT">Success Indicator Global Variable 0x8D Bit: C "A5TM" -> B "SETT"</h4>
<p>This behaves identically to the <a href="#A0PM-SETT">C "A0PM" -> B "SETT"</a> case, above</p>
<h4 id="A5TM-FLBK">Fallback Mode: C "A5TM" -> B "FLBK"</h4>
<p>This behaves identically to the <a href="#A0PM-FLBK">C "A0PM" -> B "FLBK"</a> case, above</p>
<h4 id="A5TM-example">Example NFO:</h4>
<pre>
// Map action5 type "sample_action5_type" to type id 0x70, and set bit 5 of global variable 0x8D if successful
-1 * -1 14
"C" "A5TM"
"T" "NAME" 00 "sample_action5_type" 00
"B" "TYPE" \w1 70
"B" "SETT" \w1 5
00
00
....
// Skip 3 sprites if bit 5 of global variable 0x8D is not set (indicating that station property sample_action5_type is NOT present)
-1 * -1 07 8D 01 \70 05 03
// Set 2 sprites at offset 7 into sample_action5_type
-1 * -1 05 F0 02 07
-1 sprites/sample.png 546 8 09 23 33 -26 0
-1 sprites/sample.png 594 8 09 23 33 -5 0
</pre>
<h4 id="programmable_signals">Programmable pre-signal graphics (mappable type: programmable_signals)</h4>
<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 <a href="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.
<table>
<tr><th>Group</th><th>Contents</th></tr>
<tr><td>0</td><td>Semaphore programmable pre-signals</td></tr>
<tr><td>1</td><td>Lighted programmable pre-signals</td></tr>
</table>
</p>
<p>This is indicated by the feature name: <font face="monospace">action5_programmable_signals</font>, version 1</p>
<h4 id="no_entry_signals">No-entry signal graphics (mappable type: no_entry_signals)</h4>
<p>No-entry signal graphics come in groups of 8. These groups contain sprites in the same order as the red sprites of 1275-1290 in trg1[r].grf and <a href="https://newgrf-specs.tt-wiki.net/wiki/Action5#04_Signal_graphics.">Action 5 type 4 (signals)</a>;
red only, for each of: SW-facing, NE-facing, NW-facing, SE-facing, E-facing, W-facing, S-facing, N-facing.
<table>
<tr><th>Group</th><th>Contents</th></tr>
<tr><td>0</td><td>Semaphore no-entry signals</td></tr>
<tr><td>1</td><td>Lighted no-entry signals</td></tr>
</table>
</p>
<p>This is indicated by the feature name: <font face="monospace">action5_no_entry_signals</font>, version 1</p>
<h4 id="misc_gui">Miscellaneous GUI graphics (mappable type: misc_gui)</h4>
<p>There is currently one misc GUI sprite.</p>
<p>This is indicated by the feature name: <font face="monospace">action5_misc_gui</font>, version 1</p>
<h4 id="road_waypoints">Road waypoint graphics (mappable type: road_waypoints)</h4>
<p>This is 4 sprites, in the same order and format as the drive-through bus or truck road stop graphics.</p>
<p>This is indicated by the feature name: <font face="monospace">action5_road_waypoints</font>, version 1</p>
<br />
<h3 id="feature-id-mapping">Action 14 - Feature ID Mapping</h3>
<p>See <a href="https://newgrf-specs.tt-wiki.net/wiki/Action14">Action 14 Specification</a> and <a href="https://newgrf-specs.tt-wiki.net/wiki/Features">Feature Specifications</a> for background information.</p>
<p>The feature ID mapping mechanism has the feature name: <font face="monospace">feature_id_mapping</font>, this document describes version 1.</p>
<p>Users of this mechanism SHOULD at minimum test for the presence of the feature above or test variable 8D, below.</p>
<h4 id="FIDM">Feature ID Mapping: C "FIDM"</h4>
<p>Each FIDM chunk (type C) describes an individual feature ID mapping.<br />
Sub-chunks within each FIDM chunk may appear in any order, however except where otherwise noted each sub-chunk SHOULD only appear ONCE within an individual FIDM chunk.</p>
<p>Feature ID mapping can be safely used on implementations which do not implement the feature ID mapping mechanism if all sprites which use mapped feature IDs are skipped if one or more of:
<ul>
<li>The global variable 0x8D is checked to determine whether the feature ID mapping operation was successful.</li>
<li>The feature name <font face="monospace">feature_id_mapping</font> is checked for.</li>
</ul>
Unknown Action 14 blocks are ignored, and do not need to be skipped.</p>
<p>After this mapping, the mapped feature ID value can used in all sprites which expect a feature ID (including Action 0, Action 1, Action 2, Action 3, Action 4, Action D, Action 14).</p>
<p><b>Note that implementations which are not aware of a particular feature ID and which do not implement the feature ID mapping mechanism will automatically skip sprites with unknown feature IDs.<br />
However: if/when the specification and/or the implementation assigns the chosen feature ID to an unrelated feature in future, sprites using that feature will not be skipped.<br />
This means that the GRF has the potential to inexplicably fail in the distant future if the sprites are not correctly skipped.<br />
Do not rely on the behaviour where unknown feature IDs are skipped.</b></p>
<h4 id="FIDM-NAME">Property Name: C "FIDM" -> T "NAME"</h4>
<p>Within an FIDM chunk, the NAME text (type T) field contains the name of the feature to map. The value of the language ID byte is ignored.</p>
<h4 id="FIDM-FTID">Property ID: C "FIDM" -> B "FTID"</h4>
<p>Within an FTID chunk, the FTID binary (type B) field contains the feature ID to allocate to the named feature. This is 1 byte.<br />
Note that the remapped feature ID can only be used after this FIDM chunk in the GRF. It is not applied retrospectively to sprites earlier in the GRF file, or earlier parts of the current Action 14 sprite.<br />
It is possible to override existing feature IDs, however this use is STRONGLY NOT RECOMMENDED due to a high potential for confusion when your code is inspected by someone else.<br />
At the time of writing known existing feature IDs include the values: 0x00 - 0x13 (inclusive) and 0x48.</p>
<h4 id="FIDM-SETT">Success Indicator Global Variable 0x8D Bit: C "FIDM" -> B "SETT"</h4>
<p>This behaves identically to the <a href="#A0PM-SETT">C "A0PM" -> B "SETT"</a> case, above</p>
<h4 id="FIDM-FLBK">Fallback Mode: C "FIDM" -> B "FLBK"</h4>
<p>This behaves identically to the <a href="#A0PM-FLBK">C "A0PM" -> B "FLBK"</a> case, above</p>
<h4 id="FIDM-example">Example NFO:</h4>
<pre>
// Map feature "sample_feature" to feature id 0xB0, and set bit 6 of global variable 0x8D if successful
-1 * -1 14
"C" "FIDM"
"T" "NAME" 00 "sample_feature" 00
"B" "FTID" \w1 B0
"B" "SETT" \w1 6
00
00
....
// Skip 3 sprites if bit 6 of global variable 0x8D is not set (indicating that the sample_feature feature is NOT present)
-1 * -1 07 8D 01 \70 06 03
// Use action 1 to define 1 sample_feature spriteset of 2 views
-1 * -1 01 B0 01 02
-1 sprites/sample.png 546 8 09 23 33 -26 0
-1 sprites/sample.png 594 8 09 23 33 -5 0
</pre>
<h4 id="FIDM-features">Available features:</h4>
<table>
<tr><th>Feature name</th><th>Description</th></tr>
<tr><td><font face="monospace">road_stops</font></td><td><a href="newgrf-roadstops.html">Custom road stops (bus stops, lorry stops and road waypoints)</a></d></tr>
</table>
</body>
</html>
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