variables

Variables and formulas

Several fields in QElectroTech accept a formula — text with % variables that QET substitutes when it draws. %f-%l%c on an element label becomes 3-B7. %id/%total in the sheet field becomes 3/12.

The catch is that there is no single variable language. Five different places accept formulas, each resolves a different set, and a variable that works in one is silently left as literal text in another. That is what this page is for.

Sources: sources/autoNum/assignvariables.cpp (AssignVariables, replaceVariable), sources/bordertitleblock.cpp, sources/titleblocktemplate.cpp (interpreteVariables).

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1. Where formulas are accepted

Where	Set in	Resolves
Element label	element information, or Project properties → element auto-numbering	position, sheet, sequences, %{…} info
Conductor text	conductor properties → formula, or conductor auto-numbering	position, sheet, sequences, wire properties
Sheet field	sheet properties → Sheet	only %autonum, %id, %total
Title block cells	the .titleblock template	whatever is in the title-block context
Cross-reference labels	Project properties → cross-references	same as element labels

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2. Sheet and position variables

These resolve on element labels, conductor texts and cross-reference labels.

Variable	Becomes
%f	sheet index, 1-based
%id	the same sheet index — %f and %id are identical here
%F	the sheet field, i.e. whatever the sheet's Sheet setting renders to
%total	total number of sheets in the project
%M	plant (installation) of the sheet
%LM	location / machine (locmach) of the sheet
%l	the row letter of the element's position in the border
%c	the column number of the element's position
%prefix	the element's prefix

%f and %F are not interchangeable

%f is the sheet's index — a plain number. %F inserts the sheet field, which is itself a formula. QET's default for that field is %id/%total, so on sheet 3 of 12:

%f  →  3
%F  →  3/12

Both then read naturally in a label, which is why the difference goes unnoticed until someone changes the sheet field and every element label changes shape with it. If you want the number, use %f.

%c counts from 0 or 1 depending on a preference

The column number comes out one lower when the columns start at 0 preference is set. The same project opened by two people with different settings produces different labels. If labels must be stable across a team, agree that setting first.

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3. Wire variables

Only on conductor formulas:

Variable	Becomes
%wf	conductor function
%wv	tension / protocol
%wc	wire colour
%ws	wire section

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4. Sequence variables

Auto-numbering supplies numbered sequences. Each comes in a per-project and a per-sheet flavour, and each takes a trailing index — _1 is the first sequence you defined in that numbering scheme, _2 the second, and so on.

Family	Per project	Per sheet
Unit	%sequ_1	%sequf_1
Ten	%seqt_1	%seqtf_1
Hundred	%seqh_1	%seqhf_1
Alphabetic	%seqa_1	—
Wrap	%seqw_1	—

A sequence variable whose index does not exist in the current numbering scheme is left in the text as-is. Seeing a literal %sequ_2 on a sheet means the scheme defines only one sequence, not that numbering failed.

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5. Element information variables — %{…}

Braced variables pull from the element's own information fields:

%{label} %{manufacturer_reference}

Commonly used: %{label}, %{plant}, %{location}, %{function}, %{comment}, %{description}, %{designation}, %{manufacturer}, %{manufacturer_reference}, %{machine_manufacturer_reference}, %{supplier}, %{quantity}, %{unity}.

Also available: %{auxiliary1} … %{auxiliary4} and their description_, designation_, manufacturer_, manufacturer_reference_, machine_manufacturer_reference_, supplier_, quantity_ and unity_ variants; the PLC fields %{plc_type}, %{plc_address}, %{plc_function}, %{plc_comment}, %{plc_crossref}, %{plc_t1} … %{plc_t4}, %{plc_tc}; the conductor fields %{conductor_color}, %{conductor_section}, %{tension_protocol}; and %{void}, which resolves to nothing.

The list is hard-coded, and eight fields are missing from it

%{…} substitution is a fixed list in AssignVariables::replaceVariable(), not a lookup over every information field. QETInformation::elementInfoKeys() lists 64 information keys; 63 braced variables are recognised, and they do not fully overlap.

Two keys are absent by design: formula (it is the formula) and xref. Eight more have no braced variable at all:

%{category}  %{model}  %{notes}  %{voltage_rating}  %{current_rating}
%{width}  %{height}  %{depth}

You can fill any of these in on an element, but none of the eight is in the substitution list, so they stay on the drawing as literal text. Put the value in another field until this is fixed.

The first five arrived with the smart-device metadata fields, and width, height and depth (the device's size in mm) with the element dimension fields; none of them was added to replaceVariable().

The four %{machine_manufacturer_reference_auxiliary1} … 4 variables were missing too, until PR #1236 (merged 2 October 2026). In builds made since then they resolve like the others; in older builds they stay on the drawing as literal text.

Measured against master b48525842. Earlier revisions of this page said 57, then 61 keys — each was correct when written, and the drift is why counting from the source matters.

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6. Sheet field variables

The sheet field is the exception on this page: it is resolved by a different function and understands three variables only.

Variable	Becomes
%id	this sheet's index
%total	number of sheets
%autonum	the sheet auto-numbering value

The default is %id/%total. %f, %l, %c, %M, %LM and %{…} do nothing here — they are left in the field verbatim and will be printed on every sheet exactly as typed. This is the single most common variable disappointment in QET.

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7. Title block variables

Title block template cells use their own mechanism: every key in the title block's context is substituted, in both the braced and bare forms — %{author} and %author both work.

The standard keys are the sheet's own information fields: title, author, filename, folio, plant, locmach, indexrev, date, display_folio. Project properties and any custom fields you add to the sheet are substituted too, as are the project's own projecttitle, projectfilename, savedfilename, saveddate and the rest — listed in Title block templates.

A placeholder in the template that nothing gives a value to — typically a custom variable not filled in yet — is drawn as nothing, not as its own name.

Two details worth knowing:

• Keys are substituted longest first, deliberately. Without that, a key named plant would eat the beginning of %plantcode and leave code stranded.
• Only the braced form %{name} can be discovered — the template editor's list of variables in use is built by scanning for %{…}. A bare %name still resolves, but nothing can enumerate it, so prefer the braced form in templates.

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8. Substitution is one pass, in a fixed order

Formulas are not evaluated recursively. QET does a sequence of ordinary text replacements, and the order is fixed:

1. %F, %f, %id, %total, %M, %LM
2. %c, %l, %prefix (elements) or %wf, %wv, %wc, %ws (conductors)
3. title-block fields, then project properties, in both %{name} and %name forms
4. sequences

Two consequences:

• %F works because it is expanded first. It inserts the sheet field, which may itself contain %id and %total — and those are substituted in the same step, just after. Anything the sheet field contains that step 1 does not know about will survive to the drawing as literal text.
• An unknown variable is never an error. It is simply not replaced. A label showing %seqh_3 or %{category} is QET telling you that variable is not resolvable here.

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9. Quick reference

I want…	Use	Where it works
the sheet number	%f	element / conductor / xref labels
the sheet number in the sheet field	%id	sheet field only
sheet number and total, e.g. 3/12	%F	element / conductor / xref labels
the element's grid position	%l%c	element labels
an incrementing number	%sequ_1	element / conductor labels
an element's part number on the drawing	%{manufacturer_reference}	dynamic texts, labels
the plant on a title block	%{plant} or %plant	title block templates

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See also: Linking elements · The project database · Project XML