Q44352: DRAW Statement Doesn’t Affect WINDOW’s Physical Coordinates

Article: Q44352
Product(s): See article
Version(s): 3.00 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | SR# S890503-247 B_BasicCom | mspl13_basic
Last Modified: 20-DEC-1989

The DRAW statement does not change the screen's logical coordinates,
which are set using the WINDOW statement. The DRAW statement uses only
physical coordinates, whereas normal graphics statements (PSET, LINE,
CIRCLE) are specified with view coordinates.

While the view coordinates are not changed by the DRAW statement, the
physical coordinates [returned in POINT(0) and POINT(1)] are changed
by the normal graphics statements.

This information applies to QuickBASIC Versions 3.00, 4.00, 4.00b, and
4.50, to Microsoft BASIC Compiler 6.00 and 6.00b, and to Microsoft
BASIC PDS Version 7.00.

In the following code sample, the first CIRCLE specified with view
coordinates sets the physical coordinates [returned by POINT(0) and
POINT(1)] to the equivalent point (at the center of the CIRCLE). The
ensuing DRAW statement draws a line from the center point to the point
specified in the DRAW. This DRAW statement changes the physical
coordinates [shown by the values of POINT(0) and POINT(1)] but leaves
the view coordinates unchanged [POINT(2) and POINT(3)]. The second
CIRCLE statement will be centered on the view coordinates of the
center point of the first CIRCLE, rather than the physical coordinates
of the other end of the line created with the DRAW.

Code Example
------------

SCREEN 9
WINDOW (0, 0)-(60, 60)
CIRCLE (10, 10), 4   ' Set the 1st point Physical and view correspond

PRINT "First CIRCLE Coordinates:"
PRINT "Physical coordinates = ("; POINT(0); ","; POINT(1); ")"
PRINT "View     coordinates = ("; POINT(2); ","; POINT(3); ")"
PRINT

DRAW "M20,20"         ' DRAW line -- Physical changed; view unchanged

PRINT "DRAW Coordinates:"
PRINT "Physical coordinates = ("; POINT(0); ","; POINT(1); ")"
PRINT "View     coordinates = ("; POINT(2); ","; POINT(3); ")"
PRINT

CIRCLE STEP(0, 0), 8  ' Centers around 1st CIRCLE not far end of DRAW

PRINT "Second CIRCLE Coordinates:"
PRINT "Physical coordinates = ("; POINT(0); ","; POINT(1); ")"
PRINT "View     coordinates = ("; POINT(2); ","; POINT(3); ")"
PRINT

END

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