Converting dialog template units to twips

[c.haslam]

I am working on Rich Edit UDFs, specifically EM_SETTABSTOPS. MSDN says that tab stops are specified in dialog template units. But I wish to give the user the opportunity to enter them in twips, inches or centimeters. (EM_SETPARAFORMAT PFM_TABSTOPS expects twips.)

So: how does one convert from twips to dialog template units?

I experimented: when, calling _SendMessage, I ask for every 100 template dialog units, and stream out to a file, Word tells me that tabstops are set every 1.30 inches. When I look at the file using TextPad, the RTF includes \tx1875 . 1.30 times 1440 twips/inch = 1875 twips: great!

But why is 100 template dialog units = 1875 twips?

I tried:

$hDc = _misc_GetDC(0)
$iPixPerLU =  _MISC_GetDeviceCaps($hDc,$LOGPIXELSX)

and as expected, got 96 pixels per inch.

...chris

Edited March 13, 2009 by c.haslam

[martin]

I am working on Rich Edit UDFs, specifically EM_SETTABSTOPS. MSDN says that tab stops are specified in dialog template units. But I wish to give the user the opportunity to enter them in twips, inches or centimeters.

So: how does one convert from twips to dialog template units?

I experimented: when, calling _SendMessage, I ask for every 100 template dialog units, and stream out to a file, Word tells me that tabstops are set every 1.30 inches. When I look at the file using TextPad, the RTF includes \tx1875 . 1.30 times 1440 twips/inch = 1875 twips: great!

But why is 100 template dialog units = 1875 twips?

I tried:

$hDc = _misc_GetDC(0)
$iPixPerLU =  _MISC_GetDeviceCaps($hDc,$LOGPIXELSX)

and as expected, got 96 pixels per inch.

...chris

I think a horizontal dialog unit is 1/4 of the average character width of the font used in the dialog. That means that the average width of the font would be

1.3*96*4/100

which is 4.99 pixels

Doesn't sound very likely does it?

[c.haslam]

I think a horizontal dialog unit is 1/4 of the average character width of the font used in the dialog. That means that the average width of the font would be

1.3*96*4/100

which is 4.99 pixels

Doesn't sound very likely does it?

No. But I have read that 1/4 stuff somewhere on MSDN.