Action 7 & Action 9

Conditionally skip sprites or jump to label


These two actions allow you to skip a specified number or all following sprites in this .grf file. This can be used to have, for example, climate-specific graphics, patch-version checks and error messages, and deactivating in the presence of other active .grf files.


The data looks as follows:

Element	Size	Description
<sprite-number>	dec	A sequential sprite number
<length>	dec	The total number of bytes in the action
07/09	B	Action type. In this case, 07 or 09
<variable>	B	Which variable to base the decision on
<varsize>	B	How many bytes to read from the variable
<condition-type>	B	What condition to check
<value>	V	Value to compare with (size equals <varsize>)
<num-sprites>	B	How many sprites to skip

sprite-number

The current sprite number.

length

The total number of bytes in this action 7 or 9.

action

The type of action this pseudo-sprites defines. It is either 07 or 09, depending if you are using action 7 or action 9.

Both have identical format, the only difference is whether sprites will be skipped during the initialisation of the TTDPatch graphics system, or only when the .grf file becomes active.

Action 9 is always executed, both during initialisation and activation, but action 7 is executed only during activation.

Depending on the action(s) you want to skip, you cannot always use both actions. If in doubt, use action 7 except to skip an action 6 or F. You must not skip an action 2 at all unless skipping the entire rest of the file. Instead, skip the action 3 that refers to it.

Here's a table showing this whole action 7/9 issue:

Action to skip	with 7	with 9	notes
0 (new props)	yes	yes
1 (sprite blk)	yes	yes
2 (cargo ID)	n/a*	no	* skip the corresponding action 3 instead
3 (veh ID map)	yes*	no	* can't skip a livery override without skipping the main engine action 3 as well
4 (veh names)	yes	no
5 (sprite blk)	yes	yes
6 (apply param)	n/a*	yes	* "yes" since 2.0.1 alpha 51
7 (skip sprite)	yes	yes
8 (GRF ID)	yes	yes
9 (skip sprite)	yes*	yes	* not during initialization, of course
A (repl.sprite)	yes	yes
B (error msg)	yes	yes
C (NOP)	yes	yes
D (set param)	yes*	yes	* not if parameter will be used in action 6 (except for 2.0.1 alpha 51 and higher)
E (deact.GRFs)	yes	yes
F (town names)	n/a	yes
10 (goto labels)	n/a	no
11 (sound fx)	n/a	no
12 (glyphs)	yes	yes

Yes=safe to skip
No=not safe to skip, will break the grf file or TTDPatch
N/A=not applicable; it won't break anything, but it won't actually be skipped either (in other words, its definitions will continue to be used)

variable

This sets the variable to base the decision on. It can be either one of the GRF parameters (see action 6), or a built-in patch variable. If it's a GRF parameter that wasn't specified in the newgrf(w).cfg file, or variable 88 with a GRFID that doesn't exist, the action 7 or 9 is ignored and no sprites are skipped, the only exception being condition type 0A which will skip the sprites if the GRFID doesn't exist as well.

Variable	Size	Description
81	B	current year (count from 1920, max. 2175 even with eternalgame)
83	B	Current climate: 00 = temp, 01 = arctic, 02 = trop, 03 = toyland
84	D	GRF loading stage, see below
85	B	TTDPatch flags: only for bit tests
86	B	Road traffic side: bit 4 clear=left, set=right
88	4*B	Checks specified GRFID (see condition-types below)
8B	D	TTDPatch version, see below
8D	B	TTD version, 0=DOS, 1=Windows
8E	B	Y-Offset for train sprites
8F	4*B	Rail track type cost factors
92	B	Game mode, 0 in title screen, 1 in game and 2 in editor
93	D	Tile refresh offset to left
94	D	Tile refresh offset to right
95	D	Tile refresh offset upwards
96	D	Tile refresh offset downwards
9A	D	Has always all bits set; you can use this to make unconditional jumps
9D	D	TTD Platform, 0=TTDPatch, 1=OpenTTD
A1	D	OpenTTD version, see below.
A2	D	Difficulty level: 00= easy, 01=medium, 02=hard, 03=custom, since r12449 for OpenTTD and r1857 for TTDPatch
A3	D	Current date(4); long format, since r13376 in OpenTTD and r2048 in TTDPatch
A4	D	Current year(4); long format, year zero based since r13376 in OpenTTD and r2048 in TTDPatch

Note 1: All other parameter values greater than 80 (hexadecimal) are reserved and must not be used in action 7 or 9.
Note 2: The value of variable 88 can only be tested with the GRFID tests.
Note 3: The tile refresh offsets are available from 2.0.1 alpha 39. See Action D for more details on their use.
Note 4: OpenTTD doesn't report the current date and year but the date and year the game was loaded. The reason lies in the fact that it was seen that use of this variable leads to desyncs in network games.

Variable 84 is a BYTE variable up to TTDPatch 2.5r1220. Its lower byte (bits 0..7) are 0 for the post-load and GRF initialization stages and 01 for all other stages. The remaining bits are a bitmask, and including the lower byte have the following meaning:

Bit	Meaning
0	Set after the "Initialization" stage completes
1..7	Always clear
8	Set during the "Reserve" stage only
9	Set during the "Activate" stage only
10	Set during the "Test" stage only

Variable 8B has the following format: MMmrbbbb (though encoded in little endian as bb bb mr MM)

Element	Meaning	Value
MM	major	First number of the TTDPatch version
m	minor	Second number of the TTDPatch version
r	revision	Third number of the TTDPatch version*
bbbb	build	Alpha/beta version number times ten (up to an including 2.5 beta 5), SVN revision (from 2.5 beta 5 r418 on)

Examples

Version	Variable 8B	Elements
1.9.1 alpha 50	019101F4	MM=01, m=9, r=1, bbbb=50*10=01F4
2.0 beta 4	02040028	MM=02, m=0, r=4*, bbbb=4*10=0028
2.0 final	02070046	MM=02, m=0, r=7*, bbbb=70=0046
2.0 rev 1	02070050	MM=02, m=0, r=7*, bbbb=80=0050
2.0.1 alpha 3	020A001E	MM=02, m=0, r=10*, bbbb=3*10=001E
2.5 beta 2	02500014	MM=02, m=5, r=0, bbbb=2*10=0014
2.5 rev631	02500631	MM=02, m=5, r=0, bbbb=631=0631

* For 2.0, r=7 and for 2.0.1 series, r=10 due to an oversight which used r=1..4 for 2.0 beta 1..4.

To detect versions from 2.5 rev419 and up correctly, check that var. 8B is 02500419 or higher, or replace 0419 with the actual required revision (using the revision number as hex digits). Because SVN revisions are shared with other patch branches, it is important to check the actual patch version as well as the SVN revision.


Variable A1 has the following format: Mmrbbbbb (though encoded in little endian as bb bb rb Mm). This variable has only a usefull meaning when variable 9D is 1 (OpenTTD). This variable can be used since OpenTTD r11330.

Element	Meaning	Value
M	major	First number of the OpenTTD version
m	minor	Second number of the OpenTTD version
r	revision	Third number of the OpenTTD version
bbbbb	build	Subversion revision of a build leading towards a release. When a final release is done 80000h is set.

The presence of 80000h (bit 19 set) means that a release always has a higher version number than any builds leading to that release.

Examples

Version	Variable A1	Elements
0.6.0 r11330	06002C42	M=0, m=6, r=0, bbbbb=11330=2C42
0.6.0 (release)	06080000	M=0, m=6, r=0, bbbbb=0=80000 (due to release)

varsize

For GRF parameters, this is the same as <param-size> in action 6. For built-in variables, it depends on the variable, see the above table.

For bit tests, this size is ignored. Value must be a BYTE for bit tests, no matter what the size of the variable being tested.

Since r1384 it is possible to set this to 8 bytes with Variable 88 thus allowing the use of a bit mask. This is useful for if only a few bits change over several grfs.

condition-type

There are several conditions you can choose from to test against. This has an escape sequence for each valid value. See the discussion of escape sequences for further information on escape sequences in general. For your convenience they are summed up in yet another table:

Condition type	Escape	Description
00	\71	Test for bit given by value being set
01	\70	Test for bit given by value being clear
02	\7=	Parameter is equal to value
03	\7!	Parameter is not equal to value
04	\7<	Parameter is less than value
05	\7>	Parameter is greater than value
06	\7G	GRF ID (see action 8) is active (for variable 88 only)
07	\7g	GRF ID is not active (for variable 88 only)
08	\7gG	GRF ID is not active yet but will be activated (variable 88 only)
09	\7GG	GRF ID is or will be active (variable 88 only)
0A	\7gg	GRF ID is not nor will it be active (variable 88 only)
0B	\7c	Cargo type is not available (variable is ignored)*
0C	\7C	Cargo type is available (variable is ignored)*
0D		Rail type label is not defined (variable is ignored)**
0E		Rail type label is defined (variable is ignored)**

Note that for the characters, a capital letter means available, and a lowercase character means not available. For the two character GRFid sequences, the first character is its current state, and the second is its future state.

* Prior to r11358, OTTD will skip these checks with variable 88.
** Only in OpenTTD since r15418.

The tests for variable 88 depend on the current GRF Loading Stage, the order GRFs are loaded, and of course whether they are present or were disabled (by themself or by other GRFs). Consider two GRFs A and B (loaded in that order):


"Disabled" and "not present" are the same in this context.

value

This term is what the variable is compared to. Its size is given by <varsize>.

For bit tests (condition types 00 or 01), it must always be a single BYTE for bit tests and specifies the bit to test.

For conditions 0B and (since 2.0.1 alpha 72) 0C, the variable given is ignored (but must be a valid variable nonetheless), the varsize must be 4 and the value must be the cargo label to check for. If no cargo with this label is defined in case of condition 0B, the given number of sprites are skipped. For condition 0C, the sprites are skipped if the cargo label has been defined. Both tests work irrespective of the order of .grf files in newgrf(w).cfg; the cargo is considered to be available even if it is defined by a later grf file. For this to work correctly, you must not skip a cargo definition with conditions 0B or 0C.

Since r1384, setting varsize to 8, changes value slightly, the first 4 bytes are the value (generalised grfid), and the next 4 bytes are a bit mask for the grfids to check. Please note you should make sure any masked bits are also not in the grfid to check, as value to check against is not currently masked.

num-sprites

This element sets how many sprites will be skipped if the condition is true. If num-sprites is zero, the entire rest of the .grf file will be skipped, otherwise exactly that many sprites will be skipped. If this causes action 8 to be skipped, the .grf file will be deemed inactive.

If the condition is false, processing continues at the following sprite.

Starting from TTDPatch 2.0.1 alpha 49, it is possible to jump to a certain position in the grf file by defining labels with action 10. If num-sprites is the number of a label defined somewhere in the file, then processing of the grf file resumes with the sprite following the label, instead of skipping that many sprites. This is the only way to skip more than 255 sprites at once.

Since 2.0.1 alpha 70, duplicate labels are fully supported. The jump will always be to the first matching label that follows. If no matching label follows, the first matching label in the file will be used instead.

Note that it is generally not safe to skip backwards, i.e. to an earlier position. While the patch will happily do that, you will get strange results if certain actions are repeated. Only action 0, 6, 7, 9, C and D are reasonably safe to execute more than once.


Let's start with an easy Action 7:


What does this Action 7 tells TTDPatch to do with the fictional .grf file?

Byte	Meaning
47	<sprite-number>
6	<length> of the action in bytes; start counting at 07 (<action>)
07	<action>: sets this pseudo-sprite to function as action 7
83	<variable> 83 refers to the 4 different climates
01	<varsize>: amount of bytes to compare; a single byte for the climate
03	<condition-type> 03 means skip if the variable is not equal to the <value>
00	<value> 00 equals temperate climate for this variable
00	<num-sprites> 00 means to skip the whole .grf file if the condition is true, i.e. for all climates except temperate in this case

Therefore, this action 7 skips the rest of the file if it is being loaded in a climate other than the temperate climate.



Due to action 7 being skipped during initalization, and action B severity bit 7 not working before 2.0.1 alpha 66, the best way to check for the required patch version is the following sequence:

This way the GRF Status entry shows the proper error message as well as the correct name and description because the action 8 is still being processed during initialization, and all unknown sprites are skipped so that the "invalid sprites" error message is not shown first (or else it would become the permanent message shown in the GRF Status Window).



Var 9A always has all bits set, so to make an unconditional jump you can use a bit test:

What this does is that it checks if bit 0 from the first byte of variable 9A is set (which it always is), so the sprite which you put after this action 7 is always skipped.