Metrics for Portable Documents
The following table specifies the most important font metrics for applications
that require portable documents and the functions that allow an application to
retrieve them.
Function
| Metric
| Use
|
EnumFontFamilies
| ntmSizeEM
| Retrieval of design metrics; conversion to device metrics
|
GetCharABCWidths
| ABCWidths
| Accurate placement of characters at the start and end of margins, picture
boundaries, and other text breaks
|
GetCharWidth32
| AdvanceWidths
| Placement of characters on a line
|
GetOutlineTextMetrics
| otmfsType
| Font-embedding bits
|
| otmsCharSlopeRise
| Y-component for slope of cursor for italic fonts
|
| otmsCharSlopeRun
| X-component for slope of cursor for italic fonts
|
| otmAscent
| Line spacing
|
| otmDescent
| Line spacing
|
| otmLineGap
| Line spacing
|
| otmpFamilyName
| Font identification
|
| otmpStyleName
| Font identification
|
| otmpFullName
| Font identification (typically, family and style name)
|
The
otmsCharSlopeRise,
otmsCharSlopeRun,
otmAscent,
otmDescent, and
otmLineGap members of the
OUTLINETEXTMETRIC structure are scaled or transformed to correspond to the current device mode
and physical height (as given in the
tmHeight member of the
NEWTEXTMETRIC structure).
Font identification is important in those instances when an application must
select the same font
for example, when a document is reopened or moved to a different operating
system. The font mapper always selects the correct font when an application
requests a font by full name. The family and style names provide input to the
standard font dialog box, which ensures that the selection bars are properly placed.
The
otmsCharSlopeRise and
otmsCharSlopeRun values are used to produce a close approximation of the main italic angle of
the font. For typical roman fonts,
otmsCharSlopeRise is 1 and
otmsCharSlopeRun is 0. For italic fonts, the values attempt to approximate the sine and cosine
of the main italic angle of the font (in counterclockwise degrees past
vertical); note that the italic angle for upright fonts is 0. Because these values are
not expressed in design units, they should not be converted into device units.
The character placement and line spacing metrics enable an application to
compute device-independent line breaks that are portable across screens, printers,
typesetters, and even platforms.
Device-independent page layout requires the following seven basic steps:
- Normalize all design metrics to a common ultra-high resolution (UHR) value
(for example, 65,536 DPI); this prevents round-off errors.
- Compute line breaks based on UHR metrics and physical page width; this yields
a starting point and an ending point of a line within the text stream.
- Compute the device page width in device units (for example, pixels).
- Fit each line of text into the device page width, using the line breaks
computed in step 2.
- Compute page breaks by using UHR metrics and the physical page length; this
yields the number of lines per page.
- Compute the line heights in device units.
- Fit the lines of text onto the page, using the lines per page from step 5 and
the line heights from step 6.
If all applications adopt these techniques, developers can virtually guarantee
that documents moved from one application to another will retain their
original appearance and format.
- Software for developers
-
Delphi Components
.Net Components
Software for Android Developers
- More information resources
-
MegaDetailed.Net
Unix Manual Pages
Delphi Examples
- Databases for Amazon shops developers
-
Amazon Categories Database
Browse Nodes Database
