SPREADSHEET.md

Spreadsheet

f4 ships with a built-in spreadsheet, reached with Ctrl+Alt+S, from the Commands menu, or from the command palette. It is a deliberate re-creation of the spreadsheet that used to live inside Dos Navigator: the same cell model, the same formula language and the same key map, so muscle memory carries over.

The implementation is original Go code written against the published DN documentation and observable behaviour. No Pascal sources were copied, and nothing here derives from Turbo Vision.

Files

The native format is a SQLite database, since f4 already depends on ncruces/go-sqlite3. A sheet is a plain .f4s.sqlite file holding three tables. The extension is double on purpose: the second half is what makes every SQLite tool -- f4's own client included -- open the file without being told, and the first half keeps a sheet recognisable as a sheet. Files written under the earlier .f4s name still open.

table	contents
sheet_meta	schema version, title, separator display mode
sheet_columns	per-column widths
sheet_cells	one row per cell: text, display format, justification, decimals, protection

Only the raw text of a cell is stored; values are recomputed on load, so a file never carries stale results. IsSheetFile checks the schema before offering to open a database from the panel, which keeps unrelated .db files alone.

Import and export cover:

• XLSX — read and written directly with archive/zip and encoding/xml, so no new module dependency was added. Formulas are translated in both directions (^ becomes POWER, function names are mapped, @ markers are dropped); when a workbook formula cannot be parsed, the cached value is imported instead of failing the load.
• CSV — for exchanging data with anything else.
• Plain text — the "save text" of the original, laid out with the current column widths and honouring the separator mode.

Cells

The kind of a cell follows from what was typed, exactly as it did in DN:

input	kind
a decimal number	value
text starting with =	formula
anything else	text

Each cell carries a display format (as is, decimal, comma, exponent, logical, currency, percent, hidden), a justification, a number of decimals, and a protection flag. Protected cells survive block clears.

Formulas

The expression language is the DN calculator plus references:

• Infix operators by rising precedence: comparisons (= # != <> < > >= <=), additive (+ - | or & and), multiplicative (* / div % mod \ >> shr << shl), power (^), and time (:, where a:b is a*60+b).
• Prefix +, -, ~, and every function, bind tighter than any infix operator, so log 2+1 means log(2, +1).
• Comparisons yield 0xFFFFFFFF or zero, which lets the bitwise operators act as logical ones.
• Functions: trigonometric, hyperbolic, exp fact lg ln log sqr sqrt root round sign, and if(cond, then, else).
• sum and mul require parentheses and commas. Their arguments may be expressions, references, or rectangular ranges such as B1:C2. Inside a range, empty and text cells are skipped — this is why =mul(B1:C2) and =B1*B2*C1*C2 differ when a cell is blank.

References are relative by default and are rewritten when rows or columns are inserted or deleted, and when a block is pasted somewhere else. A @ before the letter or the digits pins that part: @A@2 never moves, @A2 keeps its column, A@2 keeps its row. A reference whose target was deleted becomes #REF.

Cycles are detected during recalculation and reported on the offending cell rather than hanging the UI.

Keys

key	action
F1	help
F2 / Shift+F2	save / save as
F3 / Shift+F3	open / export
F5	recalculate
F6	go to cell
F7 / Ctrl+F7 / Shift+F7	find / replace / search again
F10	menu
Alt+I / Alt+C	insert row / column
Alt+L / Alt+D	delete row / column
Alt+O	cell format
Alt+S	toggle column separators
Alt+← / Alt+→	narrow / widen the column
Alt+BackSpace	undo
Ctrl+Ins / Shift+Ins / Shift+Del	copy / paste / cut
Ctrl+Del, Del	clear the block
Shift+arrows	mark a block
Home / End	first cell / last used cell

Typing a printable character starts editing the cell under the cursor; Enter commits and steps down, Esc cancels.