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Font Creation and Selection

The Font common dialog box simplifies the process of creating and selecting fonts. By initializing the CHOOSEFONT structure and calling the ChooseFont function, an application can support the same font-selection interface that previously required many lines of custom code. (For more information about the Font common dialog box, see Common Dialog Box Library.)

Selection by the User

Most font creation and selection operations involve the user. For example, word processing applications let the user select unique fonts for headings, footnotes, and body text. After the user selects a font by using the Font dialog box and presses the OK button, the ChooseFont function initializes the members of a LOGFONT structure with the attributes of the requested font. To use this font for text-output operations, an application must first create a logical font and then select that font into its device context. A logical font is an application-supplied description of an ideal font. A developer can create a logical font by calling the CreateFont or the CreateFontIndirect functions. In this case, the application would call CreateFontIndirect and supply a pointer to the LOGFONT structure initialized by CHOOSEFONT. In general, it is more efficient to call CreateFontIndirect because CreateFont requires several parameters while CreateFontIndirect requires only one pointer to LOGFONT.

Before an application can actually begin drawing text with a logical font, it must find the closest match from the fonts stored internally on the device and the fonts whose resources have been loaded into the operating system. The fonts stored on the device or in the operating system are called physical fonts. The process of finding the physical font that most closely matches a specified logical font is called font mapping. This process occurs when an application calls the SelectObject function and supplies a handle identifying a logical font. Font mapping is performed by using an internal algorithm that compares the attributes of the requested logical font against the attributes of available physical fonts. When the font mapper algorithm completes its search and determines the closest possible match, the SelectObject function returns and the application can begin drawing text with the new font.

The SetMapperFlags function specifies whether the font mapper algorithm searches only for physical fonts with aspect ratios that match the physical device. The aspect ratio for a device is the ratio formed by the width and the height of a pixel on that device.

The system font (also known as the shell or default font) is the font used for text in the title bars, menus, and dialog boxes.

Special Font Selection Considerations

Although most font selection operations involve the user, there are some instances where this is not true. For example, a developer may want to use a unique font in an application to draw text in a control window. To select an appropriate font, the application must be able to determine what fonts are available, create a logical font that describes one of these available fonts, and then select that font into the appropriate device context.

An application can enumerate the available fonts by using the EnumFonts or EnumFontFamilies functions. EnumFontFamilies is recommended because it enumerates all the styles associated with a family name. This can be useful for fonts with many or unusual styles and for fonts that cross international borders.

Once an application has enumerated the available fonts and located an appropriate match, it should use the values returned by the font enumeration function to initialize the members of a LOGFONT structure. Then it can call the CreateFontIndirect function, passing to it a pointer to the initialized LOGFONT structure. If the CreateFontIndirect function is successful, the application can then select the logical font by calling the SelectObject function. When initializing the members of the LOGFONT structure, be sure to specify a specific character set in the lfCharSet member. This member is important in the font mapping process and the results will be inconsistent if this member is not initialized correctly. If you specify a typeface name in the lfFaceName member of the LOGFONT structure, make sure that the lfCharSet value matches the character set of the typeface specified in lfFaceName. For example, if you want to select a font such as MS Mincho, lfCharSet must be set to the predefined value SHIFTJIS_CHARSET.

The fonts for many East Asian languages have two typeface names: an English name and a localized name. CreateFont, CreateFontIndirect, and CreateFontIndirectEx take the localized typeface name for a system locale that matches the language, but they take the English typeface name for all other system locales. The best method is to try one name and, on failure, try the other. Note that EnumFonts, EnumFontFamilies, and EnumFontFamiliesEx return the English typeface name if the system locale does not match the language of the font. Starting with Windows 2000, this is no longer a problem because the font mapper for CreateFont, CreateFontIndirect, and CreateFontIndirectEx recognizes either typeface name, regardless of locale.

 

 

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