New Text Extents Functions

New Text Extents Functions

X11R6 provides MB and WC versions of width and extents interrogation routines, supplying the maximum amount of space required to draw any character in a given fontset. These routines depend on fontsets to interpret strings and use locale-specific data.

The XFontSetExtents structure contains the two kinds of extents a string can have:

typedef struct {
    XRectangle max_ink_extent;
    XRectangle max_logical_extent;
} XFontSetExtents;

max_ink_extent gives the maximum boundaries needed to render the drawable characters of a fontset. It considers only the parts of glyphs that would be drawn, and gives distances relative to a constant origin. max_logical_extent gives the maximum extent of the occupied space of drawable characters of a fontset. The occupied space of a character is a rectangle specifying the minimum distance from other graphical features; other graphics generated by a client should not intersect this rectangle. max_logical_extent is used to compute interline spacing and the minimum amount of space needed for a given number of characters.

Here are descriptions of a few of the new extents-related functions (consult the appropriate reference pages for details):

XExtentsOfFontSet() returns an XFontSetExtents structure for a fontset.
XmbTextEscapement() and XwcTextEscapement() take a string and return the distance in pixels (in the current drawing direction) to the origin of the next character after the string, if the string were drawn. Escapement is always positive, regardless of direction.
XmbTextExtents() and XwcTextExtents() take a string and return information detailing the overall rectangle bounding the string's image and the space the string occupies (for spacing purposes).
XmbTextPerCharExtents() and XwcTextPerCharExtents() take a string and return ink and logical extents for each character in the string. Use this for redrawing portions of strings or for word justification. If the fontset might include context-dependent drawing, the client cannot assume that it can redraw individual characters and get the same rendering.
XContextDependentDrawing() returns a Boolean telling whether a fontset might include context-dependent drawing.