Font Creation and Selection

Previous versions of Windows required that the application developer provide source code and a dialog box template to support an interface that displayed the available fonts from which the user could choose. The new Font common dialog box simplifies the creation and selection process. 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 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 a 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 or not 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.

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