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Block Syntax

The general form of an error statement is:

error(level, message[, extra_text[, parameter1[, parameter2]]]);


  • level is the severity of the message and one of NOTICE, WARNING, ERROR, FATAL.

Severity Meaning Prefix Action taken
NOTICE Notice (none) continue loading grf file
WARNING Warning "Warning: " continue loading grf file
ERROR Error "Error: " continue loading grf file
FATAL Fatal error "Error: " abort loading of grf file

  • message can be either a user-defined string or it can be one of the pre-defined strings which already have translations. The first {STRING}-code will always be replaced by the NewGRF name. The second {STRING}-code (if present) will be replaced by the value of extra_text.
  • extra_text can be a string defined in the language files or it can be a literal string, in which case it cannot be translated. You should only use a literal string in those cases where you are sure it doesn't have to be translated, for example to provide a version string like "0.7.0".
  • parameter1, parameter2 are numeric parameters than can have any value, these can be used in the string using {COMMA}-codes.

name actual text Contents of extra_text
REQUIRES_TTDPATCH "{STRING} requires at least TTDPatch version {STRING}" version string
REQUIRES_DOS_WINDOWS "{STRING} is for the {STRING} version of TTD." [DOS | Windows] Palette type
USED_WITH "{STRING} is designed to be used with {STRING}" switchname + value, e.g. "multihead 0". This is designed to be used for incompatible settings that you can check via ttdpatch_flags.
INVALID_PARAMETER "Invalid parameter for {STRING}: parameter {STRING} ({COMMA})" extra_text should be the parameter number written out as string. {COMMA} is replaced by the value of parameter1
MUST_LOAD_BEFORE "{STRING} must be loaded before {STRING}." NewGRF name of the other grf
MUST_LOAD_AFTER "{STRING} must be loaded after {STRING}." NewGRF name of the other grf
REQUIRES_OPENTTD "{STRING} requires OpenTTD version {STRING} or better." version string
string(STR_MY_ERROR_MESSAGE) (user-defined string) The message-string can use the code {STRING} up to 2 times, the first usage will be replaced by the NewGRF name and the second usage by extra_text. After 2 {STRING}-codes you can include up to 2 {COMMA}-codes that will be replaced by the contents of parameter1 and parameter2. See also the note below.

For example:

 error(FATAL, string(STR_REGRESSION_ERROR), string(STR_ANSWER), 14, param[1] + 12 * param[2]);

Note that only the following combinations of string codes are valid in custom strings:

  • {STRING}