Re: [ft] Fw: freetype cache and glyph metrics

[Brady Duga]

Ah, I see. Yeah, I am pretty sure (though mainly from memory) that you can get 
the descender that way. I think you can recreate all the per-glyph metrics 
available from normal font loading using some combination of advances, 
top/left, and the bitmap data *except* for lsb/rsb deltas, which you can't 
really get using the cache.

--Brady

On Sep 29, 2010, at 11:28 AM, Michael Plitkins wrote:

> Trust me, this is a very special case of character at a time rendering
> with some character tops or baselines aligned to neighboring glyph top
> edges, etc. as opposed to a run of text. If the bitmap height - top
> will get me a descender, then I am all done.
> 
> Michael
> 
> On Wed, Sep 29, 2010 at 11:12 AM, Brady Duga <address@hidden> wrote:
>> Again, I really don't think you want descenders per-glyph. So, say you want 
>> to draw some text on a line. If we consider the upper-left of the screen to 
>> be 0,0 with y increasing as we go down, and you want to draw a line whose 
>> baseline is at y=100, then you:
>> 
>> set x to 0
>> set y to 100
>> for every glyph:
>>  get cached glyph info
>>  draw bitmap at x+glyph.left, y - glyph.top
>>  set x to x + glyph.advance.x
>> 
>> This will place all your glyphs on the same baseline. If you really want to 
>> know how much of the glyph extends below the line, then it is just the 
>> bitmap height minus top.
>> 
>> --Brady
>> 
>> On Sep 29, 2010, at 11:04 AM, Michael Plitkins wrote:
>> 
>>> Yes it does work, but there is still no way to get the descender. The
>>> FT_GlyphRec already has some of the FT_Glyph_Metrics information in
>>> the form of the advance. Why doesn't the FT_GlyphRec contain the
>>> remaining information? Memory concerns? Performance?
>>> 
>>> Thanks again for help and suggestions.
>>> 
>>> Michael
>>> 
>>> On Wed, Sep 29, 2010 at 9:50 AM, Michael Plitkins
>>> <address@hidden> wrote:
>>>> Thanks. This may well get me moving forward. I do indeed need to
>>>> measure the horiBearingY because I am trying to line up type of
>>>> different sizes to get the presentation that we need. Measuring a few
>>>> sample characters will be adequate. Using the rendered bitmap still
>>>> won't give me a way to calculate the descender though (all I will know
>>>> is the actual full height of the rendered glyph).
>>>> 
>>>> I knew that the FT_Load_Glyph(), was bogus, but it was my last ditch 
>>>> attempt.
>>>> 
>>>> Using FTC_CMapCache_Lookup() is on list my too.
>>>> 
>>>> Many thanks and I will report how this turns out.
>>>> 
>>>> Michael
>>>> 
>>>> On Wed, Sep 29, 2010 at 8:34 AM, Brady Duga <address@hidden> wrote:
>>>>> Well, I am not entirely sure what you want to do. Using horiBearingY as 
>>>>> the
>>>>> ascender seems weird - do you really want to use glyph metrics for line
>>>>> metrics? Or do you really need the ascender/descender info for every 
>>>>> glyph?
>>>>> In any case, you shouldn't be calling FT_Load_Glyph when using the cache
>>>>> system. Instead, you let the cache subsytem make that call using the load
>>>>> flags you supply to FTC_ImageCache_LookupScaler(). That gives you an
>>>>> FT_Glyph which you can use for basic glyph metrics. Specifically the
>>>>> "advance" vector of that struct tells you how far to move to account for
>>>>> this glyph. In a more interesting case, you would pass FT_LOAD_RENDER to 
>>>>> the
>>>>> cache subsystem, which should make the returned glyph be an 
>>>>> FT_BitmapGlyph.
>>>>> That in turn gives you the left/top coordinates for the actual bitmap, 
>>>>> plus
>>>>> an FT_Bitmap struct you can use for more information. Once you have the 
>>>>> top
>>>>> and left values, you can essentially calculate the horibearingX/Y, though
>>>>> you may not need to bother. The nice thing about using the cache is, in 
>>>>> most
>>>>> cases rendering is fast (already cached). It's only a problem if you plan 
>>>>> to
>>>>> measure a *lot* of glyphs that you don't plan to render. Of course, in 
>>>>> that
>>>>> case there isn't much point in using the cache at all.
>>>>> You might also want to consider caching the char map
>>>>> using FTC_CMapCache_Lookup instead of FT_Get_Char_Index.
>>>>> --Brady
>>>>> 
>>>>> 
>>>>> On Sep 28, 2010, at 11:30 PM, Werner LEMBERG wrote:
>>>>> 
>>>>> Please help this guy.
>>>>> 
>>>>> 
>>>>>    Werner
>>>>> 
>>>>> From: Michael Plitkins <address@hidden>
>>>>> Date: September 28, 2010 9:50:48 PM PDT
>>>>> To: address@hidden
>>>>> Subject: freetype cache and glyph metrics
>>>>> 
>>>>> 
>>>>> Hello Werner,
>>>>> 
>>>>> I have been using freetype for some time and have come to my first
>>>>> stumbling block: When using the image and font face caches, how can I
>>>>> get the the full metrics of a glyph (metrics.horiBearingY, etc.)? It
>>>>> seems that information is only available from the FT_GlyphSlotRec in
>>>>> the face itself. When using the cache APIs all of my attempts to get
>>>>> at the FT_Glyph_Metrics have yielded inconsistent results. Here is one
>>>>> of my latest attempts:
>>>>> 
>>>>> void nlGfxContext :: GetGlyphMetrics(nlULONG aHeight, char aGlyph,
>>>>> nlFontMetrics *aOutMetrics)
>>>>> {
>>>>>    if ((mFont != NULL) && (aOutMetrics != NULL))
>>>>>    {
>>>>>        FT_Face         font;
>>>>>        FTC_ScalerRec   scaler;
>>>>> 
>>>>>        scaler.face_id = mFont;
>>>>>        scaler.width = 0;
>>>>>        scaler.height = aHeight;
>>>>>        scaler.pixel = 1;
>>>>>        scaler.x_res = 0;
>>>>>        scaler.y_res = 0;
>>>>> 
>>>>>        font = mGlobals->LookupFontID(mFont);
>>>>> 
>>>>>        if (font != NULL)
>>>>>        {
>>>>>            FTC_ImageCache  icache = mGlobals->GetFontImageCache();
>>>>>            FT_Glyph        glyph;
>>>>>            FTC_Node        node;
>>>>>            FT_UInt         charidx = FT_Get_Char_Index(font, aGlyph);
>>>>>            FT_Error        err;
>>>>> 
>>>>>            err = FTC_ImageCache_LookupScaler(icache, &scaler,
>>>>> FT_LOAD_DEFAULT, charidx, &glyph, &node);
>>>>> 
>>>>>            FT_Load_Glyph(font, charidx, FT_LOAD_DEFAULT);
>>>>> 
>>>>>            if (err == FT_Err_Ok)
>>>>>            {
>>>>>                aOutMetrics->mHeight = font->glyph->metrics.height >> 6;
>>>>>                aOutMetrics->mAscender = font->glyph->metrics.horiBearingY 
>>>>> >>
>>>>> 6;
>>>>>                aOutMetrics->mDescender = -(aOutMetrics->mHeight -
>>>>> aOutMetrics->mAscender);
>>>>>                aOutMetrics->mMaxAdvance =
>>>>> font->glyph->metrics.horiAdvance >> 6;
>>>>> 
>>>>>                FTC_Node_Unref(node, mGlobals->GetFontCacheManager());
>>>>>            }
>>>>>        }
>>>>>    }
>>>>> }
>>>>> 
>>>>> This is my horrible attempt to use the image cache scaler to get the
>>>>> glyph that i want at the size that i want and somehow get the glyph
>>>>> metrics to be set as i want as part of the FT_Load_Glyph(). It seems
>>>>> like it shouldn't work and it doesn't.
>>>>> 
>>>>> How does one get the metrics for an individual glyph and use the
>>>>> caching subsystems at the same time?
>>>>> 
>>>>> I apologize in advance if this has been answered somewhere out on the
>>>>> internet, but I was unable to find it.
>>>>> 
>>>>> Many thanks.
>>>>> 
>>>>> Michael Plitkins
>>>>> 
>>>>> 
>>>>> _______________________________________________
>>>>> Freetype mailing list
>>>>> address@hidden
>>>>> http://lists.nongnu.org/mailman/listinfo/freetype
>>>>> 
>>>>> 
>>>> 
>> 
>>