PRESET - QB64 Wiki

PRESET

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The PRESET graphic SCREEN statement turns a pixel at a coordinate to the background color or a designated color attribute.


Syntax:

PRESET [STEP](column%, row%)[, color_attribute]


Parameters:

  • Can use STEP when relative graphics coordinates are required.
  • column and row coordinates can be literal ot variable INTEGER values which can be offscreen.
  • If the color attribute is omitted, a PRESET will be the background color 0, normally black.


Usage:

  • Color attributes are limited to those available in the SCREEN mode used. PSET can be used to adopt previously used colors.
  • Any color value other than 0 will be white in monochrome SCREEN modes 2 and 11 where the COLOR statement cannot be used.
  • PRESET can invisibly locate other graphics objects like CIRCLEs and add color to subsequent graphic objects and DRAW when used.
  • The PRESET action can be used in a graphics PUT to produce a color inverted image on any background. See Example 2.
  • The QB64 and QB graphic cursor is set to the center of the program window on program start for STEP relative coordinates.
  • PRESET can be used in any graphic screen mode, but cannot be used in the default screen mode 0 as it is text only!


Example 1: Using PRESET to locate a DRAW statement that draws a box that is bright red.

SCREEN 12 PRESET(100, 100) DRAW "C12 U20 R20 D20 L20"

Explanation: The DRAW string required a color designation as PRESET defaulted to the black background color.


Example 2: Displays the flags of countries that use simple horizontal or vertical color blocks with a highlighted arrow key menu.

DIM SHARED c$(21), x$(21), gg%(477) ARRAY SETUP SELECTION TERMINATE END SUB ARRAY c$(1) = "Armenia H040914" c$(2) = "Austria H041504" c$(3) = "Belgium V001404" c$(4) = "Bulgaria H150204" c$(5) = "Chad V011404" c$(6) = "C“te D'Ivoire V061502" c$(7) = "Estonia H090015" c$(8) = "France V011504" c$(9) = "Germany H000414" c$(10) = "Hungary H041502" c$(11) = "Ireland V021506" c$(12) = "Italy V021504" c$(13) = "Lithuania H140204" c$(14) = "Luxembourg H041509" c$(15) = "Mali V021404" c$(16) = "Netherlands H041501" c$(17) = "Nigeria V021502" c$(18) = "Romania V091404" c$(19) = "Russia H150104" c$(20) = "Sierra Leone H021509" c$(21) = "Yemen H041500" END SUB SUB DISPLAY.FLAG (calc%) f% = VAL(MID$(x$(calc%), 2, 2)) s% = VAL(MID$(x$(calc%), 4, 2)) t% = VAL(MID$(x$(calc%), 6, 2)) IF LEFT$(x$(calc%), 1) = "V" THEN LINE (120, 225)-(253, 465), f%, BF LINE (254, 225)-(385, 465), s%, BF LINE (386, 225)-(519, 465), t%, BF END IF IF LEFT$(x$(calc%), 1) = "H" THEN LINE (120, 225)-(519, 305), f%, BF LINE (120, 306)-(519, 386), s%, BF LINE (120, 387)-(519, 465), t%, BF END IF END SUB SUB SELECTION 'menu selection using arrow keys x% = 2: y% = 4 DO WHILE (x% <> prevx% OR y% <> prevy%) AND k$ <> CHR$(27) k$ = INKEY$ x% = x% + (k$ = (CHR$(0) + "K") AND x% > 1) + ABS(k$ = (CHR$(0) + "M") AND x% < 3) y% = y% + (k$ = (CHR$(0) + "H") AND y% > 1) + ABS(k$ = (CHR$(0) + "P") AND y% < 7) calc% = (x% - 1) * 7 + y%: LOCATE 14, 18: PRINT c$(calc%); SPACE$(10) x1% = 140 + (x% - 1) * 128 x2% = x1% + LEN(c$(calc%)) * 8 + 7 y1% = 48 + y% * 16 IF x1% <> prevx1% OR y1% <> prevy1% THEN IF g% THEN PUT(prevx1%, prevy1%), gg%(), PSET GET(x1%, y1%)-(x2%, y1% + 16), gg%(): g% = 1 PUT(x1%, y1%), gg%(), PRESET prevx1% = x1%: prevx2% = x2%: prevy1% = y1% DISPLAY.FLAG calc% END IF WEND LOOP UNTIL k$ = CHR$(27) END SUB SUB SETUP SCREEN 12 COLOR 6 c% = 1 FOR x% = 11 TO 50 STEP 16 FOR y% = 1 TO 7 x$(c%) = RIGHT$(c$(c%), 7) c$(c%) = RTRIM$(LEFT$(c$(c%), LEN(c$(c%)) - 7)) LOCATE y% + 4, x% + 8: PRINT c$(c%) c% = c% + 1 NEXT y%, x% COLOR 11: LOCATE 3, 20: PRINT "Use the Cursor Keys to Select a Country:" LINE (119, 224)-(520, 466), 7, B END SUB SUB TERMINATE FOR c% = 1 TO 219 LINE (116 + c%, 29 + c%)-(523 - c%, 469 - c%), 0, B NEXT END SUB

Code by AlGoreIthm
Explanation: Using the PUT PRESET action highlights the menu selection in graphic screen modes by returning a negative image.


See also:



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