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Changing rule thickness

Posted on 1998-01-19
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Last Modified: 2010-04-10
I'm a VC++ version 5 programmer. I trying to create a 1 point rule with the CPen class. What should I make the nWidth parameter?
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Question by:smcinnis011998
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nietod earned 50 total points
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by:nietod
ID: 1178517
If you want to work in the default mapping mode, MM_TEXT, then you must determine the number of pixels per point.  A point is approximately 1/72 of an inch.  You can use GetDeviceCaps() to get the number of pixels per inch using LOGPIXELSX or LOGPIXELSY.
then a the pen width should be
(Desired_ointSize)*(pixels_per_inch)/72

Note that if the line is diagonal and the X and Y pixel density is not the same, things get tougher.  However the pixel density is usually the same in both directions.  It can be worked out with a little trig, if necessary.

The other option, however, is to change to a different mapping mode.  In the MM_TWIPS mode a point is 72 units.  (twips are 1/72 of a point, I believe).  Other mapping modes could be used as well.

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by:nietod
ID: 1178518
I was wrong about the twip size.  A twip is 1/20th of a point.  so a 1 point lines is 20 twips.
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