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

[Michael Plitkins]

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
>>
>>
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>>
>>
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