LOCATE: Difference between revisions

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''Example:'' Moving the cursor around (now you can finally create a Commodore 64 emulator!). '''Default SCREEN 0 only:'''
''Example:'' Moving the cursor around (now you can finally create a Commodore 64 emulator!). '''Default SCREEN 0 only:'''
{{CodeStart}}
{{CodeStart}}
crx = 10
crx = {{Text|10|#F580B1}}
cry = 10
cry = {{Text|10|#F580B1}}
DO
{{Cl|DO}}
  {{Cl|LOCATE}} cry, crx, 1, 0, 8
    {{Cl|LOCATE}} cry, crx, {{Text|1|#F580B1}}, {{Text|0|#F580B1}}, {{Text|8|#F580B1}}
  a$ = {{Cl|INKEY$}}
    a$ = {{Cl|INKEY$}}
  {{Cl|SELECT CASE}} a$
    {{Cl|SELECT CASE}} a$
    {{Cl|CASE}} {{Cl|CHR$}}(0) + "H": {{Cl|IF...THEN|IF}} cry > 1 {{Cl|THEN}} cry = cry - 1 'up
        {{Cl|CASE}} {{Cl|CHR$}}({{Text|0|#F580B1}}) + {{Text|<nowiki>"H"</nowiki>|#FFB100}}: {{Cl|IF}} cry > {{Text|1|#F580B1}} {{Cl|THEN}} cry = cry - {{Text|1|#F580B1}} {{Text|<nowiki>'up</nowiki>|#919191}}
    {{Cl|CASE}} {{Cl|CHR$}}(0) + "P": {{Cl|IF...THEN|IF}} cry < 25 {{Cl|THEN}} cry = cry + 1 'down
        {{Cl|CASE}} {{Cl|CHR$}}({{Text|0|#F580B1}}) + {{Text|<nowiki>"P"</nowiki>|#FFB100}}: {{Cl|IF}} cry < {{Text|25|#F580B1}} {{Cl|THEN}} cry = cry + {{Text|1|#F580B1}} {{Text|<nowiki>'down</nowiki>|#919191}}
    {{Cl|CASE}} {{Cl|CHR$}}(0) + "K": {{Cl|IF...THEN|IF}} crx > 1 {{Cl|THEN}} crx = crx - 1 'left
        {{Cl|CASE}} {{Cl|CHR$}}({{Text|0|#F580B1}}) + {{Text|<nowiki>"K"</nowiki>|#FFB100}}: {{Cl|IF}} crx > {{Text|1|#F580B1}} {{Cl|THEN}} crx = crx - {{Text|1|#F580B1}} {{Text|<nowiki>'left</nowiki>|#919191}}
    {{Cl|CASE}} {{Cl|CHR$}}(0) + "M": {{Cl|IF...THEN|IF}} crx < 80 {{Cl|THEN}} crx = crx + 1 'right
        {{Cl|CASE}} {{Cl|CHR$}}({{Text|0|#F580B1}}) + {{Text|<nowiki>"M"</nowiki>|#FFB100}}: {{Cl|IF}} crx < {{Text|80|#F580B1}} {{Cl|THEN}} crx = crx + {{Text|1|#F580B1}} {{Text|<nowiki>'right</nowiki>|#919191}}
    {{Cl|CASE}} {{Cl|CHR$}}(27): {{Cl|END}}
        {{Cl|CASE}} {{Cl|CHR$}}({{Text|27|#F580B1}}): {{Cl|END}}
  {{Cl|END SELECT}}
    {{Cl|END SELECT}}
LOOP
{{Cl|LOOP}}
{{CodeEnd}}
{{CodeEnd}}


Revision as of 09:33, 9 April 2023

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


Syntax

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


Parameters

  • 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 \ 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.


Examples

Example: 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


Navigation:
Main Page with Articles and Tutorials
Keyword Reference - Alphabetical
Keyword Reference - By usage
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