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 Thanks very much. After I implement this (will be doing both Hebrew and Arabic) I will write up the resulting algorithm with some additional detail. Thanks ```Paul Pedriana a écrit : ``` ```I'm trying to understand how kerning is done in RTL text and can't find any documentation (on the Internet nor in Freetype) that addresses this. Questions: - Do kerning pairs in RTL refer to two sequential glyphs in logical order or visual order? ``` ```At least for TrueType and Type 1 fonts, it only refers to visual order. Nelson just wrote something about TeX which apparently follows the opposite convention, but I can guarantee you that it is not followed by other industry-standard formats. ``` ``` - If there is a string with the logical order is CAT and a visual order of TAC, do kerning adjustment pairings apply for CA (logical order) or for AC (visual order)? ``` ```you'll need to apply the kernings for (T,A) then (A,C) ``` ``` - Given that the RTL layout alrogithm (http://freetype.sourceforge.net/freetype2/docs/glyphs/glyphs-5.html) specifies that advance width of C (from our CAT above) is applied before the positioning and drawing of C, how and when and in what way is a kerning adjustment applied? ``` ```if you write text left-to-right, independent of its logical order, you're going to do the following: prev = -1; xpos = 0; for ( n=0; n < num_visual_glyphs; n++ ) { gindex = visual_glyphs[n].index; if ( prev > 0 ) xpos += kerning( prev, gindex ); drawGlyph( gindex, xpos ); xpos += visual_glyphs[n].advance; prev = gindex; } when writing right-to-left text, you can do the following, which results in the same glyph positions, justified to the right: prev = -1; xpos = width; for ( n=num_visual_glyphs-1; n >= 0; n-- ) { gindex = visual_glyphs[n].index; xpos -= visual_glyphs[n].advance; if ( prev > 0 ) xpos -= kerning( gindex, prev ); drawGlyph( gindex, xpos ); prev = gindex; } to better understand why, here's an example with two glyphs, named 'L' (for left) and 'R' (for right): left-to-right text: L.x = 0 R.x = L.advance + kerning(L,R) xpos.final = L.advance + R.advance + kerning(L,R) xpos.final - xpos.start = L.advance + R.advance + kerning(L,R) right-to-left text: R.x = width - R.advance L.x = width - R.advance - L.advance - kerning(L,R) xpos.final = L.x xpos.final - xpos.start = -(L.advance + R.advance + kerning(L,R)) L.x - xpos.final = 0 R.x - xpos.final = L.advance + kerning(L,R) Hope this helps, - David ```