Example program - Choosing colors with Windows common dialog

This example uses $DECLARE to invoke a standard Windows component on the client which can pick a color interactively and return the RGB color value. For more on the Windows Common Dialogs see the MSDN site.

REM Using the Windows common dialog color chooser
$DECLARE 'ChooseColor((INT(),INT(),INT(),INT(),TO RETURN DIM(),INT(),INT(),INT(),INT()))="comdlg32.ChooseColor"
$DECLARE 'CommDlgExtendedError()="comdlg32.CommDlgExtendedError"
$DECLARE 'GetActiveWindow()
DIM nStructSize=9 * 4, hWndOwner, rgbColor=0, rgbDefColors$(16)4, hInstance=0
DIM c$(3)1, i, rc
REM RGB components of the triple
DIM _BLUE=1
DIM _GREEN=2
DIM _RED=3
REM available flags
DIM _CC_RGBINIT=0x0001, _CC_FULLOPEN=0x0002, _CC_PREVENTFULLOPEN=0x0004, _CC_SHOWHELP=0x0008
DIM _CC_ENABLEHOOK=0x0010, _CC_SOLIDCOLOR=0x0080, _CC_ANYCOLOR=0x0100
REM set custom colors to white, preserve the values returned here for any subsequent call
FOR i = 1 TO 16
rgbDefColors$(i) = HEX(00FF FFFF)
NEXT i
REM default is red say
c$(_BLUE) = HEX(00)
c$(_RED) = HEX(FF)
c$(_GREEN) = HEX(00)
rgbColor = VAL(c$(), 3)
REM ensure dialog is owned by current window
hWndOwner = 'GetActiveWindow()
REM invoke the dialog
IF ('ChooseColor(nStructSize, hWndOwner, hInstance, BYREF rgbColor, rgbDefColors$(), _CC_RGBINIT + _CC_SOLIDCOLOR + _CC_FULLOPEN, 0, 0, 0))
REM non-zero result means OK
c$() = BIN(rgbColor, 3)
rc = 0
ELSE
REM zero result above means ESC or error, get reason rc==0 means ESC, +ve is an error
rc = 'CommDlgExtendedError()
END IF