AbstractFont defines the generic interface that all fonts need to implement.

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	displayString:on:from:to:at:kern: installOn:foregroundColor:backgroundColor:

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	composeWord:in:beginningAt: widthOf: widthOfString:

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	characterToGlyphMap Return the character to glyph mapping table. If the table is not provided the character scanner will query the font directly for the width of each individual character.
	xTable Return the xTable for the font. The xTable defines the left x-value for each individual glyph in the receiver. If such a table is not provided, the character scanner will ask the font directly for the appropriate width of each individual character.

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	displayString:on:from:to:at:kern: Draw the given string from startIndex to stopIndex at aPoint on the (already prepared) display context.
	installOn:foregroundColor:backgroundColor: Install the receiver on the given DisplayContext (either BitBlt or Canvas) for further drawing operations.

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	composeWord:in:beginningAt: Non-primitive composition of a word--add up widths of characters, add sum to beginning x and answer the resulting x. Similar to performance of scanning primitive, but without stop conditions.
	widthOf: Return the width of the given character
	widthOfString: