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Major internal updates

From: David Turner
Subject: Major internal updates
Date: Thu, 22 Jun 2000 12:11:57 +0200


  I've recently commited major internal updates to the library recently.
  You'll find a summary below of what has changed. Note that the new code
  isn't completely debugged (I suspect some problems in the drivers) so
  do not consider it as "finished" as beta 7 was. Hopefully, this will
  change soon.. The high-level API has changed a bit, but should not
  break existing applications that uses the engine..

  The changes came from basically two things:

    - first, not all modules are font drivers, and the FT_Module
      type was introduced. FT_Add_Driver, FT_Get_Driver, etc.. have
      been replaced by FT_Add_Module, FT_Get_Module, etc.. and the
      module API is now publicly available in <freetype/ftmodule.h>

    - a new class of modules, called "renderers" are used to perform
      various operations on native glyph image formats:

            - transform them
            - convert them to bitmaps
            - get their bounding box

      this is needed to truly support future glyph image formats (e.g.
      bicolor glyphs, SVG glyphs, etc..) transparently. The old approach
      didn't deal with transform and bboxes, and this could create a
      few problems.

      additionally, FT_Get_Raster, FT_Set_Raster, etc.. have been replaced
      by FT_Get_Renderer, FT_Set_Renderer, etc..

      there is a new directory named "src/renderer" containing the
      renderers corresponding to the "standard" and "smooth" rasters

  As usual, any comments are appreciated, but I'll warn you when the move
  is over..


- David


    A lot of internal modifications have been performed lately on the
    source in order to provide the following enhancements:
      - more generic module support:
        The FT_Module type is now defined to represent a handle to a given
        module. The file <freetype/ftmodule.h> contains the FT_Module_Class
        definition, as well as the module-loading public API

        The FT_Driver type is still defined, and still represents a pointer
        to a font driver. Note that FT_Add_Driver is replaced by FT_Add_Module,
        FT_Get_Driver by FT_Get_Module, etc..

      - support for generic glyph image types:

        The FT_Renderer type is a pointer to a module used to perform various
        operations on glyph image.
        Each renderer is capable of handling images in a single format
        (e.g. ft_glyph_format_outline). Its functions are used to:
           - transform an glyph image
           - render a glyph image into a bitmap
           - return the control box (dimensions) of a given glyph image

        The scan converters "ftraster.c" and "ftgrays.c" have been moved
        to the new directory "src/renderer", and are used to provide two
        default renderer modules.
        One corresponds to the "standard" scan-converter, the other to the
        "smooth" one.
        The current renderer can be set through the new function
        The old raster-related function FT_Set_Raster, FT_Get_Raster and
        FT_Set_Raster_Mode have now disappeared, in favor of the new:

        see the file <freetype/ftrender.h> for more details..

        These changes were necessary to properly support different scalable
        formats in the future, like bi-color glyphs, etc..

      - glyph loader object:

        A new internal object, called a 'glyph loader' has been introduced
        in the base layer. It is used by all scalable format font drivers
        to load glyphs and composites.
        This object has been created to reduce the code size of each driver,
        as each one of them basically re-implemented its functionality.

        See <freetype/internal/ftobjs.h> and the FT_GlyphLoader type for
        more information..

      - FT_GlyphSlot had new fields:

        In order to support extended features (see below), the FT_GlyphSlot
        structure has a few new fields:
           linearHoriAdvance:  this field gives the linearly scaled (i.e.
                               scaled but unhinted) advance width for the glyph,
                               expressed as a 16.16 fixed pixel value. This
                               is useful to perform WYSIWYG text.
           linearVertAdvance:  this field gives the linearly scaled advance
                               height for the glyph (relevant in vertical glyph
                               layouts only). This is useful to perform
                               WYSIWYG text.                               

        Note that the two above field replace the removed "metrics2" field
        in the glyph slot.
           advance:   this field is a vector that gives the transformed
                      advance for the glyph. By default, it corresponds
                      to the advance width, unless FT_LOAD_VERTICAL_LAYOUT
                      was specified when calling FT_Load_Glyph or FT_Load_Char

           bitmap_left: this field gives the distance in integer pixels from
                        the current pen position to the left-most pixel of
                        a glyph image WHEN IT IS A BITMAP. It is only valid
                        when the "format" field is set to
                        "ft_glyph_format_bitmap", for example, after calling
                        the new function FT_Render_Glyph.
           bitmap_top:  this field gives the distance in integer pixels from
                        the current pen position (located on the baseline) to
                        the top-most pixel of the glyph image WHEN IT IS A
                        BITMAP. Positive values correspond to upwards Y.

           loader:  this is a new private field for the glyph slot. Client
                    applications should not touch it..

      - support for transforms and direct rendering in FT_Load_Glyph:

        Most of the functionality found in <freetype/ftglyph.h> has been
        moved to the core library. Hence, the following:
          - a transform can be specified for a face through FT_Set_Transform.
            this transform is applied by FT_Load_Glyph to scalable glyph images
            (i.e. NOT TO BITMAPS) before the function returns, unless the
            bit flag FT_LOAD_IGNORE_TRANSFORM was set in the load flags..

          - once a glyph image has been loaded, it can be directly converted to
            a bitmap by using the new FT_Render_Glyph function. Note that this
            function takes the glyph image from the glyph slot, and converts
            it to a bitmap whose properties are returned in "face.glyph.bitmap",
            "face.glyph.bitmap_left" and "face.glyph.bitmap_top". The original
            native image might be lost after the conversion.

          - when using the new bit flag FT_LOAD_RENDER, the FT_Load_Glyph
            and FT_Load_Char functions will call FT_Render_Glyph automatically
            when needed.

  - reformated all modules source code in order to get rid of the basic
    data types redifinitions (i.e. "TT_Int" instead of "FT_Int", "T1_Fixed"
    instead of "FT_Fixed"). Hence the format-specific prefixes like "TT_",
    "T1_", "T2_" and "CID_" are only used for relevant structures..

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