LOCATE - QB64Official/qb64 GitHub Wiki

The LOCATE statement locates the screen text row and column positions for a PRINT or INPUT procedure.

Syntax

LOCATE [row%][, column%] [, cursor%][, cursorStart%, cursorStop%]

Parameter(s)

  • optional text row% INTEGER values are from 1 to 25, 43 or 50 in SCREEN 0 and 25 in most other legacy graphic screen modes, except screens 11 and 12 which can have 30 or 60 rows.
  • optional column% INTEGER values are from 1 to 40 or 80 in SCREEN 0 and 80 in all other legacy screen modes.
  • optional cursor% value can be 0 to turn displaying the cursor off or 1 to turn it on.
  • optional cursorStart% and cursorStop% values define the shape of the cursor by setting the start and stop scanline (values range from 0 to 31) for the cursor character.

Description

  • WIDTH statement can be used to determine the text width and height in SCREEN 0 and height of 30 or 60 in SCREEN 11 or 12.
  • In _NEWIMAGE graphic screen the number of text rows are calculated as _HEIGHT \ 16 except when a _FONT is used. Use _FONTHEIGHT to calculate font rows.
  • _NEWIMAGE graphic screen text columns are calculated as _WIDTH (function) \ 8 except when a _FONT is used. Use _PRINTWIDTH to measure a line of font text.
  • The text row position is not required if the PRINT is going to be on the next row. The comma and a column value are required to set the column.
  • If only the row parameter is given, then the column position remains the same. Neither row or column parameter can be 0.
  • When PRINTing on the bottom 2 rows, use a semicolon after the PRINT expression to avoid a screen roll.
  • If the cursorStart% line is given, the cursorStop% line must also be given. A wider range between them produces a taller cursor.
  • If you use LOCATE beyond the current number of rows in text mode, QB64 will try to adapt the screen instead of tossing an error.
  • When writing to the console, only the row and column arguments are used, all others are ignored. Furthermore, on non-Windows systems LOCATE statements that do not give both a row and column will be ignored entirely.

Example(s)

Moving the cursor around (now you can finally create a Commodore 64 emulator!). Default SCREEN 0 only:


crx = 10
cry = 10
DO
  LOCATE cry, crx, 1, 0, 8
  a$ = INKEY$
  SELECT CASE a$
     CASE CHR$(0) + "H": IF cry > 1 THEN cry = cry - 1 'up
     CASE CHR$(0) + "P": IF cry < 25 THEN cry = cry + 1 'down
     CASE CHR$(0) + "K": IF crx > 1 THEN crx = crx - 1 'left
     CASE CHR$(0) + "M": IF crx < 80 THEN crx = crx + 1 'right
     CASE CHR$(27): END
  END SELECT
LOOP

Explanation: The CHR$(0) + "H", "P", "K", "M" represents the cursor arrow keys. start = 0, stop = 8 is the tallest cursor, experiment with the start and stop values for different effects (start = 8, stop = 8 is the default producing a _ cursor).

See Also