font-ascent

Arguments: struct

Returns the maximum height of a character from the baseline for the fontmetrics structure specified by the argument. This height measured in stream units of the stream associated with the argument, which must be a fontmetrics object.

There are font methods for the graphical-stream class (formerly called windows-graphics) and subclasses of it, for various dialog-item classes that display text, and for grid-subsection and outline-item.

The setf of this function may be called to set the current font of the object. The setf takes an additional optional argument called set-line-height-too. This is used only when the object is a graphical-stream (which includes windows and other objects on which drawing may be done). When true, the line-height of the stream is set to the font-height of the font. The default value is t; this is usually the appropriate value, so that newlines printed to the stream will advance the current y position as appropriate for this font. Therefore a font is typically set with a form such as this:

(setf (font my-window) (make-font-ex nil "Arial" 18))

though to avoid changing the window's line-height you could instead use this:

(setf (font my-window nil)(make-font-ex nil "Arial" 18))

The font of an object may also be set by passing a :font initarg when creating the object, and by calling with-font.

Regarding outline-items: while the font of an individual outline-item may be set, all of the items in the outline will retain the same height, which is the font-height of the font of the outline. For this reason, the font of an outline-item should not be taller than the general font of the outline, or else the text will be clipped.

See also Text and Fonts in cg-drawing.htm.

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Created 2010.1.21.