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This technical note documents a bug in the implementation of the PrGeneral
procedure in the LaserWriter driver version 4.0. The bug has to do with the
format of the information returned by the GetRslData opcode. This technical
note will also describe a workaround for the problem.
[Nov 01 1987]
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Introduction
One of the opcodes supported by the PrGeneral procedure (Technical
Note #128) is named GetRslData. The GetRslData operation
initializes a resolution record that is of the following form:
TRslRg = RECORD {used in TGetRslBlk}
iMin: Integer; {0 if printer only supports discrete resolutions}
iMax: Integer; {0 if printer only supports discrete
resolutions}
END;
TRslRec = RECORD {used in TGetRslBlk}
iXRsl: Integer; {a discrete, physical X resolution}
iYRsl: Integer; {a discrete, physical Y resolution}
END;
TGetRslBlk = RECORD {data block for GetRslData call}
iOpCode: Integer; {input; = getRslDataOp}
iError: Integer; {output}
lReserved: LongInt; {reserved for future use}
iRgType: Integer; {output; this declaration is for RgType1}
XRslRg: TRslRg; {output; range of X resolutions}
YRslRg: TRslRg; {output; range of Y resolutions}
iRslRecCnt: Integer; {output; how many RslRecs follow}
rgRslRec: ARRAY[1..27]
OF TRslRec; {output; number used depends on printer type}
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The LaserWriter 4.0 implementation has a bug that affects the YRslRg
and XRslRg fields of the TGetRslBlk record. The correct
values for the fields are:
TGetRslBlk.XRslRg.iMin := 25;
TGetRslBlk.XRslRg.iMax := 1500;
TGetRslBlk.YRslRg.iMin := 25;
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Unfortunately, the information returned by the LaserWriter 4.0 version of
PrGeneral is:
TGetRslBlk.XRslRg.iMin := 25;
TGetRslBlk.XRslRg.iMax := 25;
TGetRslBlk.YRslRg.iMin := 1500;
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The recommended workaround for this problem is to use the PrDrvrVers
function (Inside Macintosh II-163) to find out which version of the
print driver you are using. If you are using 4.0, modify the resolution data
before using it. The following code fragment illustrates this workaround:
PROCEDURE CheckRslRecord(VAR theRslRecord: TGetRslBlk);
CONST
BogusDriver = 40;
BEGIN
IF PrDrvrVers = BogusDriver THEN BEGIN
theRslRecord.XRslRg.iMax := theRslRecord.YRslRg.iMax;
theRslRecord.YRslRg.iMin := theRslRecord.XRslRg.iMin;
END;
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When the bug is fixed in a future version of the driver, the
CheckRslRecord procedure will no longer have any effect on the
resolution record. This will make sure your application gets the correct
resolution data no matter which version of the driver is being used.
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References
The Print Manager
Technical Note M.IM.PrGeneral-- PrGeneral
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