The program example shown below demonstrates how to work around a
problem with the DragGrayRgn routine in QuickBasic Version 1.00 for
Macintosh. The behavior of DragGrayRgn differs from the DragGrayRgn
provided in Basic Version 3.00 or in the earlier Basic Compiler
Version 1.00 for Macintosh.
Microsoft has confirmed this DragGrayRgn problem in QuickBasic Version
1.00. We are researching this problem and will post new information as
it becomes available.
The DragGrayRgn routine (which is an MBLC routine) in QuickBasic
produces the following incorrect behavior:
DragGrayRgn copies the region into a frame (a border outline),
forgets the handle to the original region (so that EraseRgn can't
reference or erase it), and leaves you with just a frame outline
(at the wrong coordinates) when you finish the drag.
The code example below demonstrates the necessary modifications to a
Basic Version 3.00 routine to work around the problem. The program then
behaves correctly as follows:
You click on the triangle, drag its outline to a new location,
then release the button. At this time, the old triangle should
be erased and the outline of the triangle that was dragged to the
new location should be filled in.
To work around the problem in QuickBasic Version 1.00, copy the
original region to a new region before the drag, and invoke
DragGrayRgn with the new region.
The program example that follows shows a Basic Version 3.00 source
code that uses DragGrayRgn which has been modified to make it run
under QuickBasic Version 1.00:
'This example program is based on one published in Nibble Mac,
'Volume 3, Number 1, 1988, Page 59, Listing 2, DragGrayRgn Example.
'The example is shown modified to run in QuickBasic.
REM LIBRARY "ToolLib" 'Required for Basic 3.0, not for QuickBasic
OPTION BASE 1
bool% = 0
FirstReg& = 0
QBReg& =0 ' Required only for QuickBasic
DIM bnd%(4), pin%(4), p%(2), dis%(2)
SetRect bnd%(1), 0, 0, 490, 270
SetRect pin%(1), 0, 0, 490, 270
NewRgn FirstReg& : OpenRgn
MOVETO 50, 39 : LINETO 60, 21
LINETO 70, 39 : LINETO 51, 39
NewRgn QBReg& ' Required only for QuickBasic
CopyRgn FirstReg&, QBReg& ' Required only for QuickBasic
WHILE MOUSE(0) <> 0 : WEND
WHILE MOUSE(0) = 0 : WEND
PtInRgn p%(1), FirstReg&, bool%
IF NOT bool% THEN DisposeRgn FirstReg& : STOP
' On the following line, QuickBasic uses QBReg& (instead of
' FirstReg& used in Basic 3.00):
DragGrayRgn QBReg&, p%(1), pin%(1), bnd%(1), 0, dis%(1)
OffsetRgn FirstReg&, dis%(2), dis%(1)
Note the following:
- For this program to run in Basic Version 3.00, you must change the
- Change all "&" characters to "!" (because Basic Version 3.00
doesn't support the long-integer data type).
- Remove all lines that are marked "Required for QuickBasic".
- Change the DragGrayRgn routine to use FirstReg instead of
- The first line of the original program example in Nibble Mac
referred to LIBRARY "DragGrayLib". You can use "ToolLib" more
easily than "DragGrayLib". ("DragGrayLib" is a library file that
you must build from CODE resources taken from the "ToolLib" file
in Basic Version 3.00. In Basic Version 3.00, you can use
Statement Mover to move needed routines from "ToolLib" into
"DragGrayLib", if you want a library smaller than "ToolLib".)
- The original DragGrayRgn routine in the Basic Version 3.00 ToolLib
correctly remembers the region before the region is dragged with the
mouse. The DragGrayRgn routine in QuickBasic requires the workaround
Article ID: 40140 - Last Review: February 27, 2014 - Revision: 1.2
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