Re: [HarfBuzz] harfbuzz coordinate system
On 10/29/10 18:19, Jonathan Kew wrote: So FWIW, my preference would be to keep the y-axis pointing up. I think that's right for a text-centric API, and I don't think making a change will really gain anything. I don't completely agree, but since the two responses I got both prefer the current direction, I let it be as is for now and revisit during the API hackfest before 1.0. Thanks, behdad ___ HarfBuzz mailing list HarfBuzz@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/harfbuzz
Re: [HarfBuzz] harfbuzz coordinate system
On 29 Oct 2010, at 01:55, Martin Hosken wrote: Dear Behdad, I think I'm going to make that change, especially since everytime I hooked up HarfBuzz to another system, it worked the first try except for a missing negation sign for y_offset. I don't think it matters too much which way you jump on this one so long as: 1. You clearly state the directionality in lots of places in the documentation and code. 2. You make it clear where the different y directionalities are used. For example, what should a call to a font metrics function return? If it is as per a font with y increasing up the page, then where in the code does the y directionality switch? I sympathise with the quandary: font designers think in terms of y going up the page, while graphics programmers think of y increasing down the page. Yes, there are arguments either way. Personally, I'd recommend that harfbuzz keeps y increasing upwards, as I think that is the natural way to deal with text -- in the context of horizontal, left-to-right (or indeed right-to-left) text, I'd instinctively think of a positive y-displacement as raising a glyph. I'm certainly aware of the potential for y-direction bugs in higher-level text+graphics systems, having both made and fixed such errors personally, but I don't think flipping harfbuzz's coordinate system will particularly prevent this. Whichever way you do it, mistakes will be made, and not noticed until people test fonts that actually use y-displacements. So FWIW, my preference would be to keep the y-axis pointing up. I think that's right for a text-centric API, and I don't think making a change will really gain anything. JK ___ HarfBuzz mailing list HarfBuzz@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/harfbuzz
Re: [HarfBuzz] harfbuzz coordinate system
On 10/27/10 15:56, James Cloos wrote: BE == Behdad Esfahbod beh...@behdad.org writes: BE I'm wondering, should increasing y move upwards, or downwards? Most BE graphics API I've seen (PS-based API being the only exception) has y BE moving downward. I find that more intuitive in a text layout BE library, so we can say: in-line glyphs are stacked in the BE increasing x direction, lines are stacked in the increasing y BE direction. I've always thought of y going up w/in a font. It would be weird for the capsheight to be negative and descender depth to be positive. But that's exactly what pango and cairo have been doing. And FreeType too IIRC. And Xft? I'm sure they are not the only ones. Especially since everything else has -ve descenders and +ve ascenders. That's not true. Many places where you see ascenders and descenders, both are positive. That is, they are in different directions. Anyway, the HarfBuzz API doesn't really deal with font-space. The main API is about shaped glyphs. Having top-left corner of the glyphs have a negative y_offset is not unusual. I think I'm going to make that change, especially since everytime I hooked up HarfBuzz to another system, it worked the first try except for a missing negation sign for y_offset. behdad -JimC ___ HarfBuzz mailing list HarfBuzz@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/harfbuzz
Re: [HarfBuzz] harfbuzz coordinate system
Dear Behdad, I think I'm going to make that change, especially since everytime I hooked up HarfBuzz to another system, it worked the first try except for a missing negation sign for y_offset. I don't think it matters too much which way you jump on this one so long as: 1. You clearly state the directionality in lots of places in the documentation and code. 2. You make it clear where the different y directionalities are used. For example, what should a call to a font metrics function return? If it is as per a font with y increasing up the page, then where in the code does the y directionality switch? I sympathise with the quandary: font designers think in terms of y going up the page, while graphics programmers think of y increasing down the page. Yours, Martin ___ HarfBuzz mailing list HarfBuzz@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/harfbuzz
Re: [HarfBuzz] harfbuzz coordinate system
On 10/28/10 20:55, Martin Hosken wrote: I don't think it matters too much which way you jump on this one so long as: Right. What adds to the confusion is that in simple text, y_offset is always zero, so you can build an entire system without discovering your error... b ___ HarfBuzz mailing list HarfBuzz@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/harfbuzz
Re: [HarfBuzz] harfbuzz coordinate system
BE == Behdad Esfahbod beh...@behdad.org writes: BE I'm wondering, should increasing y move upwards, or downwards? Most BE graphics API I've seen (PS-based API being the only exception) has y BE moving downward. I find that more intuitive in a text layout BE library, so we can say: in-line glyphs are stacked in the BE increasing x direction, lines are stacked in the increasing y BE direction. I've always thought of y going up w/in a font. It would be weird for the capsheight to be negative and descender depth to be positive. Especially since everything else has -ve descenders and +ve ascenders. -JimC -- James Cloos cl...@jhcloos.com OpenPGP: 1024D/ED7DAEA6 ___ HarfBuzz mailing list HarfBuzz@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/harfbuzz
