The cairo_text_extents_t structure stores the extents of a single
glyph or a string of glyphs in user-space coordinates. Because text
extents are in user-space coordinates, they are mostly, but not
entirely, independent of the current transformation matrix. If you call
cairo_scale(cr, 2.0, 2.0), text will
be drawn twice as big, but the reported text extents will not be
doubled. They will change slightly due to hinting (so you can't
assume that metrics are independent of the transformation matrix),
but otherwise will remain unchanged.
double x_bearing;
the horizontal distance from the origin to the
leftmost part of the glyphs as drawn. Positive if the
glyphs lie entirely to the right of the origin.
double y_bearing;
the vertical distance from the origin to the
topmost part of the glyphs as drawn. Positive only if the
glyphs lie completely below the origin; will usually be
negative.
double width;
width of the glyphs as drawn
double height;
height of the glyphs as drawn
double x_advance;
distance to advance in the X direction
after drawing these glyphs
double y_advance;
distance to advance in the Y direction
after drawing these glyphs. Will typically be zero except
for vertical text layout as found in East-Asian languages.
Since 1.0

The cairo_text_extents_t structure stores the extents of a single glyph or a string of glyphs in user-space coordinates. Because text extents are in user-space coordinates, they are mostly, but not entirely, independent of the current transformation matrix. If you call cairo_scale(cr, 2.0, 2.0), text will be drawn twice as big, but the reported text extents will not be doubled. They will change slightly due to hinting (so you can't assume that metrics are independent of the transformation matrix), but otherwise will remain unchanged. double x_bearing; the horizontal distance from the origin to the leftmost part of the glyphs as drawn. Positive if the glyphs lie entirely to the right of the origin. double y_bearing; the vertical distance from the origin to the topmost part of the glyphs as drawn. Positive only if the glyphs lie completely below the origin; will usually be negative. double width; width of the glyphs as drawn double height; height of the glyphs as drawn double x_advance; distance to advance in the X direction after drawing these glyphs double y_advance; distance to advance in the Y direction after drawing these glyphs. Will typically be zero except for vertical text layout as found in East-Asian languages. Since 1.0