Q72460: INFO: Baseline Shifts in Cell When Character Italicized

Article: Q72460
Product(s): Microsoft Windows Software Development Kit
Version(s): WINDOWS:3.1
Operating System(s): 
Keyword(s): kbSDKWin16
Last Modified: 26-JUN-1999

3.00 3.10
WINDOWS
kbprg

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The information in this article applies to:

- Microsoft Windows Software Development Kit (SDK) 3.1 
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NOTE: With TrueType fonts in Windows 3.1, this process described below is not necessary. An application should do a version check to determine if it is running under version 3.0 and perform this process only if the application is indeed running under Windows 3.0 or if the application is using non TrueType fonts in Windows 3.1.

SUMMARY
=======

When a font is italicized under Windows version 3.0, the dimensions of the
character cells change because the descender of the character may require more
space at the left edge of the character cell.

Because the character cell is larger, the relative position of the baseline of
the character within the cell changes. The baseline itself is not affected, but
when a character is drawn italic and nonitalic with the TextOut() function at
the same x coordinate, the baseline of the italic font is shifted a few pixels
to the right.

To account for this shift, calculate the slope of the font -- ascent divided by
overhang -- after italicization. Using this slope, the number of pixels by which
the character cell was expanded left is equal to descent divided by slope, or
(descent times overhang) divided by ascent. This value can be subtracted from
the x coordinate in the TextOut() call to align the baselines.

MORE INFORMATION
================

Consider the character "f". In a normal character cell, it would appear as:

         ^ ........
         | ........
         | ...xx...
         | ..x..x..
   Ascent| ..x.....
         | ..xx....
         | ..x.....
         | ..x.....
         | ..x.....
         v .xxx....<-baseline

  Descent^ ........

         v ........

When italicized, the descent is shifted to the left and the ascent is shifted to
the right, along a line of constant slope equal to the ascent divided by the
overhang:

         ^ ............
         | ............
         | .......xx...
         | ......x..x..
   Ascent| .....x......
         | .....xx.....
         | ....x.......
         | ....x.......
         | ...x........
         v ..xxx.......<-baseline

  Descent^ ............

         v ............
                    <->
                     Overhang

Because the descent of the character is shifted left according to the slope of
the line, this particular character cell has been expanded one pixel left, which
has the effect of shifting the baseline in the character cell one pixel right.

Since the overhang represents the amount the ascent of the character is shifted
right in the cell, the corresponding shift of the descent can be calculated and
can be called the "underhang":

               descent * overhang

  underhang = --------------------

                     ascent

When calling the TextOut() function, use the normal x-coordinate where the text
should be drawn, but subtract the underhang. This places the baseline of the
character exactly where it would be if the character were not italic.

Additional query words: 3.00 3.10

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Keywords          : kbSDKWin16 
Technology        : kbAudDeveloper kbWin3xSearch kbSDKSearch kbWinSDKSearch kbWinSDK310
Version           : WINDOWS:3.1
Issue type        : kbinfo

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