path: root/libraries/evas/README

Evas 1.1.0

******************************************************************************

 FOR ANY ISSUES PLEASE EMAIL:
 enlightenment-devel@lists.sourceforge.net

******************************************************************************

Requirements:
-------------

Must:
  libc
  libm
  eina (1.1.0 or better)
  freetype (2.1.9 or better)

Recommended:
  libX11 + libXext + libXrender
  OpenGL2.0 or OpenGL-ES 2.0
  fontconfig
  libpng
  libjpeg (6.0 or better)
  eet (1.5.0 or better)
  firbidi
  harfbuzz
  liblinebreak

Optional:
  XCB SDL OpenGL librsvg libtiff libgif edb DirectFB evas_generic_loaders

Evas is a clean display canvas API for several target display systems
that can draw anti-aliased text, smooth super and sub-sampled scaled
images, alpha-blend objects much and more.

Evas is designed to be portable to different display systems. Evas uses very
little RAM too (try profiling it in memprof if you want to
know) most of the ram allocated, if you look, is for freetype itself,
image pixel data, and font glyph data. You can't really avoid this, though
evas tries to share this data as much as possible and not duplicate where it
can. Feel free to point me at sensible memory optimizations etc. though :) I
want this baby to be lean, mean tiny, fast and do everything from your
massive multi-cpu desktop with gobs of ram and disk to a tiny watch.

Evas also supports full UTF-8 for text object strings, thus allowing for
full internationalized text strings (if your font gives you all the
characters). I've tested with quite a few fonts and it works quite well.
Though this requires a unicode compatible font with unicode charmap support
(cyberbit is quite good actually as a font). For now Evas draws the fonts
only from left to right, so arabic, hebrew etc. won't display quite right,
direction-wise, but the characters do.

------------------------------------------------------------------------------
COMPILING AND INSTALLING:

  ./configure
  make
(as root unless you are installing in your users directories):
  make install

if you want to know what options to enable
./configure --help

Evas's rendering code assumes a decently optimizing compiler. For
example gcc with -O2 -march=nocona for example (compile for core2 duo
x86 or better). You may choose not to compile for a very modern
architecture, and Evas still has MMX/SSE, NEON and other hand-crafted
assembly, but not for everything, so make use of your compiler
optimizing as much as possible. At least use -O2 or equivalents.

Notes:
  the small dither mask is faster on the ipaq, but is not as good looking. on
  desktop machines it makes no speed difference so only use
  --enable-small-dither-mask if you really need the speed for low depth
  you need at least 1 image loader if you want to load images.
  gcc 3.0.x on solaris screws up the jpeg code so erroring out doesn't work.
  use gcc 3.2 on solaris.

notes on features (--enable-FEATURE enables it and --disable-FEATURE
disables it, some being enabled or disabled by default or if
dependencies are found):


------------------------------------------------------------------------------
SCALING:
--enable-scale-sample

this enables the sampling scaler code. this is the fastest image scaling
code, but also the lowest quality. when scaling up pixels will become blocky
and when scaling down you will see shimmering/aliasing artifacts. this is a
speed vs. quality tradeoff


--enable-scale-smooth

this is the nicest looking scaler that is not that much slower than
tri-linear, but it looks really good.


------------------------------------------------------------------------------
DITHERING:
--enable-small-dither-mask

this uses a 4x4 dither mask instead of 128x128. on desktop boxes these days
(pentium, pentium2, amd etc.) the speed difference is not really measurable,
but the quality of the 128x128 dither mask is quite a lot better. patterns
of dithering are much less noticeable, so it is recommended to not enable
this unless you are struggling for speed. the compaq ipaq for example shows
a slowdown with this large a dither mask so enabling a small dither mask is
recommended unless you really want to forgo the speed.


--enable-line-dither-mask

this is a faster alternative to the small or large dither masks above.
this dithers only on an alternating-line basis. this only provides 1
intermediate "dither" level whose odd and even pixels alternate
between the 2 closest colors available, but it is very fast. almost as
fast as no dithering. quality though will not be as good as small or
default "large" dither masks.


--enable-no-dither-mask

this disables dithering entirely. this is the fastest option, but the
lowest quality. not suggested in general unless you are really in need
of an extra few percent speed and are willing to have fairly awful
quality. but in general this is the standard rendering for most
"realtime graphics" if it has to drop to lower bit-depths, so it's
not anything unusual. just in the evas world the quality is considered
poor enough to be discouraged as evas's internal rendering is so much
higher quality.


------------------------------------------------------------------------------
ENGINES:

All engines can be compiled statically inside libevas.so in order to
reduce runtime time at dynamically loaded modules. All you have to do
is to enable your chosen modules with "=static" suffix. If they depend
on software_generic (most do), you need that as well. Examples:

  ./configure --enable-static-software-generic --enable-software-xlib=static


--enable-software-xlib[=static]

this enables the software x11 rendering engine that renders to X drawable
targets using highly optimized software routines. there is no hardware
assist here. this engine requires X11 to be installed to build (and run).
This is a good generic engine that is fast and can run in X for good
development and debugging purposes.


--enable-software-xcb[=static]

this enable the software xcb rendering engine. It allows the same
features than the software xlib engine. It require the XCB and XCBImage
libraries. For the test programs, XCBICCCM is also needed. It is not
recommended to use this as it's experimental and will create problems
with both ecore_evas and enlightenment itself.


--enable-fb[=static]

this is the software framebuffer driving engine. this uses the linux
framebuffer device (/dev/fb{X}) and will currently just inherit the current
framebuffer settings on the fb device and use them to run in. this engine is
almost fully functional except for the fb management itself. this engine is
specifically geared towards people writing minimalist display systems for
embedded devices such as the ipaq, zaurus, etc. it also scales up to high-res
desktop systems as
well.


--enable-directfb[=static]

this is the direct fb engine that uses direcftb (http://www.directfb.org) on
linux to access the framebuffer with (or maybe without) acceleration. for
people making set-top boxes or just wanting an alternative to X this is
really good. it may also be useful for embedded devices supported by
directfb that offer acceleration (otherwise the fb driver will likely be
faster). as such this engine is in relative disrepair and is not
maintained. use with great care.


--enable-buffer[=static]

this enables the memory buffer rendering engine. this engine renders
to a region of memory that is considered to be a 32bit ARGB buffer of
pixels, allowing the results of rendering to be directly read out or
used again for other purposes.


--enable-gl-x11[=static]

this is the opengl engine. it is intended for an x11 target (via xlib)
rather than framebuffer (even if you use EGL, the EGL flavor is
expected to be an x11 one). it is a full opengl based rendering engine
with all rendering implemented as a texture + triangle pipeline and
more. it also supports opengl-es2.0 and is reliant on modern opengl2.0+
shader support. this engine also supports the native surface api for
adopting pixmaps directly to textures for compositing.

some environment variables that control the opengl engine are as
follows:

export EVAS_GL_INFO=1
  set this environment variable to enable output of opengl information
such as vendor, version, extensions, maximum texture size etc. unset
the environment variable to make the output quiet again.

export EVAS_GL_MEMINFO=1
  set this environment variable to enable dumping of debug output
whenever textures are allocated or freed, giving the number of
textures of each time and how many kb worth of pixel data are
allocated for the textures. unset it again to stop this dumping of
information.

export EVAS_GL_WIN_RESURF=1
  set this environment variable to enable the gl engine to try and
ddelete the window surface, if it can, when told to "dump resources"
to save memory, and re-allocate it when needed (when rendering
occurs). unset it to not have this behavior.

export EVAS_GL_CUTOUT_MAX=N
  set this environment variable to the maximum number of rectangles
applied to a rendering of a primitive that "cut away" parts of that
primitive to render to avoid overdraw. default is 512. unset it to use
defaults, otherwise set N to the max value desired or to -1 for
"unlimited rectangles".

export EVAS_GL_PIPES_MAX=N
  set the maximum number of parallel pending pipelines to N. the
default number is 32 (except on tegra2 where is it 1). evas keeps 1 (or more)
pipelines of gl draw commands in parallel at any time, to allow for merging
of non-overlapping draw commands to avoid texture binding and context
changes which allows for more streamlining of the draw arrays that are
filled and passed to gl per frame. the more pipelines exist, the more
chance evas has of merging draw commands that have the same modes,
texture source etc., but the more overhead there is in finding a
pipeline slot for the draw command to merge into, so there is a
compromise here between spare cpu resources and gpu pipelining. unset
this environment variable to let evas use it's default value.

export EVAS_GL_ATLAS_ALLOC_SIZE=N
  set the size (width in pixels) of the evas texture atlas strips that
are allocated. the default is 1024. unset this to let evas use its
default. if this value is larger than the maximum texture size, then it
is limited to that maximum size internally anyway. evas tries to
store images together in "atlases". these are large single textures
that contain multiple images within the same texture. to do this evas
allocates a "wide strip" of pixels (that is a certain height) and then
tries to fit all images loaded that need textures into an existing
atlas texture before allocating a new one. evas tries a best fit
policy to avoid too much wasting of texture memory. texture atlas
textures are always allocated to be EVAS_GL_ATLAS_ALLOC_SIZE width,
and a multiple of EVAS_GL_ATLAS_SLOT_SIZE pixels high (if possible -
power of 2 limits are enforced if required).

export EVAS_GL_ATLAS_ALLOC_ALPHA_SIZE=N
  this is exactly the same as EVAS_GL_ATLAS_ALLOC_SIZE, but for
"alpha" textures (texture used for font glyph data). it works exactly
the same way as for images, but per font glyph being put in an atlas
slot. the default value for this is 4096.

export EVAS_GL_ATLAS_MAX_W=N
  set this to limit the maximum image size (width) that will be
allowed to go into a texture atlas. if an image exceeds this size, it
gets allocated its own separate individual texture (this is to help
minimize fragmentation). the default value for this is 512. if you set
this environment variable it will be overridden by the value it is set
to. the maximum value possible here is 512. you may set it to a
smaller value.

export EVAS_GL_ATLAS_MAX_H=N
  this is the same as EVAS_GL_ATLAS_MAX_W, but sets the maximum height
of an image that is allowed into an atlas texture.

export EVAS_GL_ATLAS_SLOT_SIZE=N
  this sets the height granularity for atlas strips. the default (and
minimum) value is 16. this means texture atlas strips are always a
multiple of 16 pixels high (16, 32, 48, 64, etc...). this allows you
to change the granularity to another value to avoid having more
textures allocated or try and consolidate allocations into fewer atlas
strips etc.

export EVAS_GL_NO_MAP_IMAGE_SEC=1
  if this environment variable is set, it disabled support for the SEC
map image extension (a zero copy direct-texture access extension that
removes texture upload overhead). if you have problems with dynamic
evas images, and this is detected by evas (see EVAS_GL_INFO above to
find out if its detected), then setting this will allow it to be
forcibly disabled. unset it to allow auto-detection to keep working.


--enable-gl-flavor-gles

this enables the opengl-es 2.0 flavor of opengl (as opposed to desktop
opengl) when building evas's gl-x11 engine above. this will be needed
if you are building evas for opengl-es 2.0 enabled embedded devices.
evas works on several opengl-es 2.0 compliant gpu's and gains more
testing and optimization regularly. it is also capable of
texture-from-pixmap support in opengl-es like it is in desktop opengl.


--enable-gles-variety-sgx

this tells evas that you are building the gl-es engine for a
shader-compiler "sgx style" opengl-es 2.0 implementation. this is
where the shader compiler is provided at runtime and can accept the
shader glsl source and work


--enable-gles-variety-s3c6410

this tells evas that you have an s3c6410 style opengl-es
implementation that has an offline shader compiler and that needs
pre-compiled shader binaries (provided with evas). this has not been
tested in quite a while as the drivers and environment for this system
have gone missing


--enable-software-gdi[=static]

windows gdi based engine for evas


--enable-software-ddraw[=static]

windows direct-draw engine for evas


--enable-direct3d[=static]

evas direct3d engine (experimental)


--enable-software-sdl[=static]

this is the sdl engine that uses sdl library (http://www.libsdl.org). This
library should work on many operating system. the buffer is
software-rendered with evas's default software rendering core.


--enable-gl-sdl[=static]

opengl (and opengl-es2.0) rendering engine that uses sdl as the front
end interface. see --enable-gl-x11 etc. for information.


--enable-software-8-x11[=static]

8bit only rendering core. intended for greyscale output on things like
e-paper or simplistic greyscale LCD devices which have no color, such
as ebook readers.

if compiling with =static suffix, then must
"./configure --enable-static-software-8" as well.


--enable-software-16-x11[=static]

16bit specific renderer. lower quality than the default. also limited
in abilities (no support for smooth scale or transformations/map). in
a state of disrepair. do not use unless your hardware is just 16bpp
and very limited in CPU and memory.

if compiling with =static suffix, then must
"./configure  --enable-static-software-16" as well.


--enable-software-16-ddraw[=static]

16bit renderer for direct-draw. same as software-16-x11 - don't use.
in disrepair.

if compiling with =static suffix, then must
"./configure --enable-static-software-16" as well.


--enable-software-16-wince[=static]

same as software-16-ddraw but for windows-ce. in disrepair. don't use.

if compiling with =static suffix, then must
"./configure --enable-static-software-16" as well.


------------------------------------------------------------------------------
CPU:
--enable-cpu-c

this enabled the c code. you can actually build the code without the c
fallback code and only have the mmx routines for example. it is suggested to
always use this regardless unless you have some definite size issues with the
code.


--enable-cpu-mmx

this enables the mmx optimized routines. this works for pentium, pentium2,
pentium3, pentium4, athlon and duron processors. it can get quite
considerable speedups, souse it if you can. ppc owners just have to live with
the c fallback functions unfortunately as no one has provided any ALTIVEC asm 
routines yet. :) arm owners will also have to rely on the c fallback
routines as i haven't managed to come up with any arm assembly that actually
can beat the c code (when compiled with all optimizations) in speed.


--enable-cpu-sse

this enables sse optimizations available in he pentium3 and 4 cpus (not
athlon and duron or pentium 2 or pentium cpu's). ppc owners just have to
live with the c fallback functions unfortunately as no one has provided any
ALTIVEC asm routines yet. :) arm owners will also have to rely on the c
fallback routines as i haven't managed to come up with any arm assembly that 
actually can beat the c code (when compiled with all optimizations) in speed.

--enable-cpu-sse3

this enables sse3 optimizations available in the Intel Pentium4, Core, Xeon,
and Atom processors, as well as the AMD Athlon64, Phenom, Opteron, and Turion
processors.


--enable-cpu-neon

This enables support for the Arm Cortex-A8 and later Neon register
set.  In particular it will use neon optimized code for rotations and
drawing with the software engines.  Open GL based renderers will gain
nothing from the use of neon.

To use neon with gcc-4.4 you need a post-2009 gcc and options
something like: -mcpu=cortex-a8 -mfloat-abi=softfp -mfpu=neon
Note that this slightly slows down non-optimized parts of evas  but
the gains in drawing are more then worth it overall.

This is enabled by default, and turns off if a small test program is
unable to compile.

Performance is at least 50%, and in some real world tests approaches
100%.

If you have any issues with neon, please report them to either the
edevel mailing list or Brett Nash <nash@nash.id.au>


------------------------------------------------------------------------------
IMAGE LOADERS:
--enable-image-loader-png[=static]

this enables the loader code that loads png files using libpng. there may be
call for embedded devices later that have custom written small image
loaders that uses less disk space than libpng to load custom format images.
for now this is the only loader so you may as well include it.


--enable-image-loader-jpeg[=static]

this enables the loader code that loads jpeg files using libjpeg. this
loader also supports load options to pre-scale jpeg images down to
provide much faster load times while also getting downscaling by 1/2,
1/4 or 1/8th the size in each dimension for "free". with an added
patch to libjpeg7, it can also fast-decode a specific region of a jpeg
file (without the patch it take a slow-path to do this).


--enable-image-loader-edb[=static]

edb image loader- can load images inside edb database files. not very
useful as edb itself is no longer used by enlightenment. may be
removed at some point, so unless you have a burning need for this,
don't use edb files to store image data and rely on this loader


--enable-image-loader-eet[=static]

loads image data from eet files. eet files are the backing for edje
storage, so this is needed for edje to work. it is very useful as it
can load an image from anywhere in the eet archive by key value so eet
files are like "zip" files where you can pack a whole lot of image and
other data together and just pick out the pieces you need at runtime.
requires the eet library.


--enable-image-loader-gif[=static]

gif image loader. gif is an obsolete format, but due to its longevity,
sitll has lots of existing data around.

NOTE: evas has no notion of time, thus animated gif file are not
supported!


--enable-image-loader-pmaps[=static]

ppm/pnm/pgm image loader that can load the "pnm" style image format.
not very common, but the files are simple raw RGB, greyscale image or
bitmap data in binary or ascii format


--enable-image-loader-svg[=static]

this loader can load svg files via librsvg (thus it is a dependency).
this loader supports load options to set the dpi to decode the svg at
etc. which can then be used to create scalable images that scale to
any size without becoming blocky or blurry, if the source is an svg
file.


--enable-image-loader-tiff[=static]

this loader uses libtiff to load tiff image files


--enable-image-loader-xpm[=static]

this is an xpm format image loader. xpm format images are ascii files
that look like c/c++ source code that contain images. these files are
old-fashioned unix+x11 images you may encounter, but are inefficient
for storage and decoding and have been superseded by png files in
almost every way


--enable-image-loader-bmp[=static]

this enables the bmp image format loader. note that there seems to be
a disagreement on 32bit bmp format images where alpha channels are
concerned and you may run into issues with bmps generated by the gimp
that have alpha channels. there is a problem where they don't seem to
be spec-conformant.


--enable-image-loader-tga[=static]

this loader load tga format files. these files are very old-fashioned
but found often in the 3d graphics world.


------------------------------------------------------------------------------
FONT LOADERS:
--enable-font-loader-eet[=static]

this loader can load font (ttf) files directly from eet archives like
the eet image loader. requires the eet library


------------------------------------------------------------------------------
CONVERTERS:
--enable-convert-yuv

this enables an optimized yuv (yv12 601 colorspace) to ARGB32
converter in evas


--enable-convert-16-rgb-565

the most common converter you'll want for 16bpp. this means 5 bits for red,
6 bits for green and 5 bits for blue are used.


--enable-convert-16-rgb-555

this is a converter for what many people know as "15 bit" color. you might
want to enable this for X output as it used to be common to find many cards
that do this.


--enable-convert-16-rgb-444

this converter outputs to 12bit packed (int 16 bit WORDS).


--enable-convert-16-rgb-ipq

this converter was written specifically for the ipaq (and may apply to
similarly configured devices) because it lies about its screen depth. it
says it is 16bit 565 (that means 5 upper bits of the WORD are red, the next 6
bits are for green abd the next 5 for blue) but in fact only the upper 4
bits of each color component (red green and blue) are significant and work,
so effectively the display is 12 bits of color, not 16, but padded out to
fill 16bits, with unused bits in the color masks. X on the ipaq advertises
it as a full 16bpp 565 display (i can't remember what the linux framebuffer
advertised it as) and so many lumps of code can be fooled into rendering
data badly because they think the output will look as the expect. This
renderer assumes the upper 4 bits fo each color primitive only are
significant and renders accordingly. this produces nice quality images on
the ipaq and even still works in 16bpp 565 on your pc. it is highly
recommended to use this renderer if your target is an ipaq or your device
displays similar qualities of the ipaq for display purposes.


--enable-convert-16-rgb-rot-0

this enables the 16bpp converters to run with 0 degrees rotation - this is 
normal display and you should really include this (though it is optional if you
only ever want to do portrait mode - perhaps like on an ipaq embedded device)


--enable-convert-16-rgb-rot-270

this enables the portrait mode (270 degree rotation) converters for 16bpp.
this is the standard display mode for things like pocketpc on the ipaq and
the zaurus etc. this is an optimized part of the rendering pipeline to allow
portrait display with a much lower overhead than doing it through X.


--enable-convert-16-rgb-rot-180

same as --enable-convert-16-rgb-rot-270 but for 180 degrees


--enable-convert-16-rgb-rot-90

same as --enable-convert-16-rgb-rot-270 but for 90 degrees


--enable-convert-24-rgb-888

this converts evas's 32bit ARGB to 24bit RGB packed format for output
if needed


--enable-convert-24-bgr-888

this converts evas's 32bit ARGB to 24bit packed BGR format for output
if needed


--enable-convert-32-rgb-8888

32bit RGB output conversion support. byteswapping compared to evas's
native colorspace


--enable-convert-32-bgr-8888

conversion (reduces toa memory copy) from evas's native colorspace to
the same color format.


--enable-convert-32-rgb-rot-0

copies without rotation evas's native image format


--enable-convert-32-rgb-rot-270

copies evas's native ARGB32 pixels but at a rotation of 270 degrees.


--enable-convert-32-rgb-rot-180

same as --enable-convert-32-rgb-rot-270 but for 180 degrees


--enable-convert-32-rgb-rot-90

same as --enable-convert-32-rgb-rot-270 but for 90 degrees


--enable-convert-24-rgb-ezx

a special colorspace handler for 18bit color packed into 24bit output
(where only 6 bits per r, g and b byte are used). the only known
platform that did this was the motorola esx based phones that used
qtopia originally and have open ezx ports for them.


--enable-convert-8-gry-1

enable 8bit gray to 1 bit black & white converter


--enable-convert-8-gry-16

8bit grey to 16 level grayscale converter


--enable-convert-8-grayscale-64

8bit grey to 64 level grayscale converter


--enable-convert-8-rgb-332

enable converter from 32bit ARGB to 8bit color "332" colorspace (3bits
red, 3 bits green, 2 bits blue)


--enable-convert-8-rgb-666

enable converter from 32bit ARGB to 8bit color "216" "websafe" 
colorspace (6 values for red, 6 for green and 6 for blue - 6x6x6 being
216 colors).


--enable-convert-8-rgb-232

same as convert-8-rgb-332 but 2 bits red, 3 green, 2 blue


--enable-convert-8-rgb-222

same as convert-8-rgb-332 but 2 bits red, 2 green, 2 blue


--enable-convert-8-rgb-221

same as convert-8-rgb-332 but 2 bits red, 2 green, 1 blue


--enable-convert-8-rgb-121

same as convert-8-rgb-332 but 1 bit red, 2 green, 1 blue


--enable-convert-8-rgb-111

same as convert-8-rgb-332 but 1 bit red, 1 green, 1 blue. this is the
lowest sized colorspace supported for rgb (3bits, 8 color).


------------------------------------------------------------------------------
MISC:
--enable-pthreads

this enables pthread support in evas so multiple threads may run
internally for parallel rendering, loading etc.


--enable-async-events

this provides the ability for evas to have an asynchronous event
notification pipe to provide events when background threads are done
with tasks, like pre-loading image files


--enable-async-preload

evas can load images (preload) them in the background using a thread
if you ask it to, and provide events when done. this goes hand-in-hand
with --enable-pthreads and --enable-async-events. you really want all
of these available.


--enable-async-render **CAUTION - MAY NOT WORK RIGHT**

this enables a software multi-frame threaded renderer. this will
allocate (for example) 2 frames to 2 cores, with one core of the cpu
rendering the previous frame while the next frame starts rendering on
another core in the meantime allowing for higher framerates with
software rendering, using more cpu resources that are available on
modern multi-core cpu's.

This is buggy! it will likely cause crashes and rendering corruption.
Do not enable it unless you plan to actually work on it. This requires you
also set the environment variable EVAS_RENDER_MODE to "non-blocking" to
enable it at runtime, as the compile-time enable simply sets up the feature
to be ready to work. The runtime switch actually turns it on. If you don't
plan to use this feature, don't enable it in the build as there is a general
performance hit of maintaining this feature at all, so beware that
enabling it for single core systems will likely take a performance hit.


--enable-pipe-render **DISABLED DUE TO BUGS**

this enables a multiple-thread renderer that divides the rendering
into N regions (1 per core) to speed up rendering in software when you
have multiple cpu cores.


--enable-word-cache **DISABLED DUE TO BUGS**

Cache rendered words and draw them as a single object, instead of
individual characters.  This is a big gain for things like neon which
draw large runs effectively.

However it is useless on GL and similar back-ends as the cost in
sending a word sized texture kills the performance gain (and GL is
pretty good at drawing lots of small things anyway).  If it detects a GL
backend is in use, it disables itself.

By default words (strings) of more then 50 characters are not cached.
The system caches 40 words by default, but this can be changed by
setting EVAS_WORD_CACHE_MAX_WORDS to another number.  Setting it to 0
will disable word-cache at run time.

Text based benchmarks are 50-100% quicker.

If you have any issues with word caching, please report them to either
the e-devel mailing list or Brett Nash <nash@nash.id.uau>

For GL see metric caching...


--enable-metric-cache **DISABLED DUE TO BUGS**

Metric caching saves character metrics between characters in words.
This enables it to render words much quicker as it avoids things like
space calculations and kerning calculation.

The cache size is also controlled by EVAS_WORD_CACHE_MAX_WORDS.

It is useful for GL in particular, although software engines do get
some gain.

Generally it is recommended you enable one or both of word or metric caching,
depending on your engine use.  If you are only using software, enable word
caching (and neon on arm if you can), for GL, turn on metric caching.
A simple solution is enable both, and let the engine sort it out at run time.

If you have any issues with metric caching, please report them to either
the e-devel mailing list or Brett Nash <nash@nash.id.uau>


--enable-fontconfig

this enables fontconfig support for loading font files by using
generic fontconfig font names and styles. you really should use this
by default on any linux/unix platform for universal font support.


--enable-fribidi

this enables support for the fribidi library to have right to left and
left to right font rendering so languges such as arabic, hebrew and
other "RTL" langauges display properly.


--enable-harfbuzz

this enables support for the harfbuzz shaping library for complex
shaping support in arabic, hindi and other similar languages.

--enable-liblinebreak

this enables support of complex line breaking rules using liblinebreak.

--enable-evas-magic-debug

this allows you to enable and disable evas's extra magic number
checks.  these allow better stability with runtime object magic
"number" checks to make sure you are accessing a real object in memory
of the right type, and will avoid doing "bad things" if they detect
the wrong object type being passed in. if you are absolutely sure your
system has no bugs in accessing objects of the wrong type with the
wrong calls, you can gain some small performance by disabling this.


------------------------------------------------------------------------------
NOTES:

For the arm optimizations you want to try:
  export CFLAGS="-O2 -march=armv5te -mcpu=arm1136jf-s -fomit-frame-pointer"

To enable the async renderer compile with:
  --enable-async-render
and also runtime set this environment variable:
  export EVAS_RENDER_MODE=non-blocking

For compilation with MinGW, fnmatch.h is probably missing. That file can be
found here:
  http://www.koders.com/c/fid2B518462CB1EED3D4E31E271DB83CD1582F6EEBE.aspx
It should be installed in the mingw include directory.