From 1ea9378ad3e250473464fde4ab336607a958eab1 Mon Sep 17 00:00:00 2001 From: Werner Lemberg Date: Sat, 28 Oct 2000 16:59:44 +0000 Subject: [PATCH] Revised. --- docs/ft2faq.html | 983 ++++++++++++++++++++++++++--------------------- 1 file changed, 539 insertions(+), 444 deletions(-) diff --git a/docs/ft2faq.html b/docs/ft2faq.html index 6b9cc9bdb..114758426 100644 --- a/docs/ft2faq.html +++ b/docs/ft2faq.html @@ -1,13 +1,12 @@ + -FreeType 2 FAQ - - + + + FreeType 2 FAQ http://www.freetype.org

-

+

- The FreeType Project -

The FreeType 2 FAQ

-
+ The FreeType Project +

The FreeType 2 FAQ

+ -
+
-

+

+ +
+ +

+ + Document index + +

+ +

+ + + + +
+

+ General questions & answers

+
+ + +

+ I.1 I though the FreeType project was dead. Is this true? +

+ +

Well, not exactly :-) It's true that the TrueType patents + issues have been less than a graceful event to handle but it didn't not + really killed the project per se, as Apple hasn't made an official + statement yet regarding the use of the patented "technology" in open + source projects (or other products).

+ +

We have thus continued updating FreeType 1.x, and started + developing FreeType 2 with the idea of providing this time a + completely patent free font engine. However, we largely preferred not + to broadly communicate about it until we've got a satisfying + implementation to show.

+ + +

+ I.2 Why did it take so long to release FreeType 2? +

+ +

Several factors come to mind. The first one is that FreeType 2 + is a much more complex and dense project that was mostly developed + during non-working hours. And surely some important changes in the life + (like marriage, new jobs and kids) of some the FreeType developers + cannot be ignored :-)

+ +

A second one is that a first version of the library was designed one + year ago (and already worked with a multitude of font drivers), though + with a design that was judged by its authors as well as beta testers as + not enough flexible or consistent. In short, it worked well but we were + not exactly proud of it (call us perfectionists). It has then be + significantly reworked to become what we are now distributing as + FreeType 2

+ +

Finally, it would have been hard to distribute such a library without + an alternative technology to replace the patented bytecode interpreter. + This involved significant research work that could only be performed + correctly full-time, and we had to found a company to fund such a + development and still make it available under a BSD-like license. Huge + thanks to Catharon Productions, + Inc. for their commitment to this project.

+ +

And of course, we added support for more font files, and we will + continue to as long as the specifications are available and that we find + an interest in it. For example, FreeType 2 is to date the only + software library available on the market that supports the new Adobe + "CEF" font format.

+ + +

+ I.3 Is FreeType 2 a Unix-only project? +

+ +

Absolutely not, even though many people still seem to think + so :-) FreeType 2, just like version 1.x, can be compiled + on any platform with an ANSI compiler. Some beta versions of the + library are even heavily used in brand new OSes (see the AtheOS screenshots for examples).

+ +

The library is itself mainly developed on several platforms (Windows + & Linux, though a great deal has also been achieved on OS/2) and the + code is highly generic and modular to adapt even the most strict + environments like low-memory embedded systems.

+ + +

+ I.4 When will X11/XFree support anti-aliased text? +

+ +

This question isn't exactly related to FreeType as we have no direct + connection to the XFree people, but we have been asked so frequently + about it that it deserves a prominent place in this FAQ :-)

+ +

FreeType has been capable of anti-aliasing since version 1.0. + The reason why XFree doesn't support it is directly related to the + limitations of the design and specification of X11. More + specifically:

-DOCUMENT INDEX:
-
+ +
+ + + +
+

+ Compilation & Configuration +

+
+ + +

+ II.1 How do I compile the FreeType 2 library? +

+ +

The library can be compiled in various ways, and a detailed + documentation is available in the file freetype2/docs/BUILD. + However, we will summarize the process to a few cases:

+ +

+ a. Using the command-line 2 build system +

+ +

The engine comes with a sophisticated build system that is used to + configure and compile a build of the library. You will need GNU + Make installed on your platform (Note: It will + not work with other Make tools).

+ +

Basically, you will need to invoke make a first time in + the top-level FreeType 2 directory in order to set up the build. + This will detect your current platform and choose a configuration + sub-makefile to drive the build. A specific compiler can be selected + on some platforms by providing an additional target. For example, on + Win32:

+ +
    +
  • + make visualc will select the Visual  C++ + compiler +
    • +
  • + make lcc will select the Win32-lcc compiler +
    • +
+ +

Note that on Unix, when the first time make is called, a configure + script located in freetype2/builds/unix will be run in order + to automatically detect the platform & compiler.

+ +

A summary will be displayed showing the detected platform and + compiler selected. You will then be able to start the build by + invoking make a second time. In case of problem, consult the + BUILD document.

+ +

+ b. Direct compilation +

+ +

You can also directly compile the library from the command line by + using these simple rules:

+ +
    +
  • + You should place the directories freetype2/include and + freetype2/src in your include path in order to compile + any component of the library. You can also add the + system-specific build directory (i.e. + builds/system/) in the case where an alternate + implementation of some of the components is available there (e.g. + the memory-mapped i/o implementation on some Unix systems). +
    • +
  • + The components of the library are located in sub-directories of + src, for example: src/base, + src/truetype, etc. +
    • +
  • + Each component is normally compiled through a single C file that + wraps other sources in the component's directory. For + example, you should build the TrueType font driver by compiling + the file src/truetype/truetype.c. The list of + C files to compile for a feature-complete build of the + library is given in the BUILD document. +
    • +
+ +

+ c. Using a graphical IDE +

+ +

Well, the process is vastly similar to the one described in b., + except that you need to set the include paths, source code paths, etc. + in dialog boxes before running the compilation.

+ + +

+ II.2 How do I configure my build of the library? +

+ +

Each build of the library is configured through two header files + located in include/freetype/config:

+ -

-

  • Other questions -

    -
    • -

    - - -

    - -
    -

    General questions & answers

    -
    - - -

    I.1. I though the FreeType project was dead. Is this true?

    -
      -

      Well, not exactly :-) It's true that the TrueType patents issues - have been less than a graceful event to handle but it didn't not - really killed the project per se, as Apple hasn't made an official - statement yet regarding the use of the patented "technology" in - open source projects (or other products).

      - -

      We have thus continued updating FreeType 1.x, and started developping - FreeType 2 with the idea of providing this time a completely patent - free font engine. However, we largely preferred not to broadly - communicate about it until we've got a satisfying implementation - to show.

      -
    - - -     -

    I.2. Why did it take so long to release FreeType 2?

    -     - - -

    I.3. Is FreeType 2 a Unix-only project?

    -     - - -

    I.4. When will X11/XFree support anti-aliased text?

    -
      -

      This question isn't exactly related to FreeType as we have no direct - connection to the XFree people, but we've been asked so frequently - about it that it deserves a prominent place in this FAQ :-)

      - -

      FreeType has been capable of anti-aliasing since version 1.0. The - reason why XFree doesn't support it is directly related to the - limitations of the design and specification of X11. More specifically:

      - -
        -

      • - X11 assumes that all glyph images are monochrome bitmaps, - hence the X font library and server are unable to send anything - else to the X server. -

        • - -

      • - Even if the X font library/server was able to generate anti-aliased - bitmaps (and this has been already done through extensions), the X - rendering model doesn't allow translucent composition of "gray" pixmaps - onto an arbitrary drawable. -

        • -
      - -

      As both the font and rendering models of X11 are limited, it's basically - impossible to draw anti-aliased glyphs without performing huge - hacks within the server.

      - -

      Note that Keith Packard, from XFree fame, has recently started working - on a new rendering model for X11 in order to support new features - (mainly transparency and anti-aliased fonts). This will be provided - through protocol extensions. The question of knowing wether legacy X - applications will be able to display anti-aliased text is still very - uncertain. -

      -
    - -     -

    I.5. Is FreeType 2 backwards compatible with FreeType 1.x?

    -
      -

      Not directly, though we had the project to provide an optional binary - compatibility layer on top of it in order to easily re-link applications - with the new version. However, this idea has been dropped as it is - possible to install and use the two versions independtly on any - system (read: no namespace conflicts).

      - -

      The FreeType 2 API is a lot simpler than the one in 1.x while being - much more powerful. We thus encourage you to adapt your source code - to it as this should not involve much work.

      - -
    - -     -

    I.6. Can I use FreeType 2 to edit fonts or create new ones?

    -
      -

      The answer is a definitive NO, because the library was specifically - designed to read font files with small code size and very - low memory usage.

      - -

      We thus do not plan to support editing or creation in the font - engine in any way, as this would imply a complete rewrite. This - doesn't mean that we won't introduce a font editing/creation library - in the future, as this really depends on how many people are asking - for it (or how much they would be willing to pay for it), as well as - the time of the FreeType developers.

      - -

      Do not expect anything in this direction until we officially announce - something though. There are other axis of development for this project - (like text-layout capabilities, glyph caching, etc..) that may be more - important to us at the moment..

      -
    - -
    - - +
    -

    Compilation & Configuration

    -
    - - -

    II.1. How do I compile the FreeType 2 library?

    -
      -

      The library can be compiled in various ways, and a detailed documentation - is available in the file "freetype2/docs/BUILD". However, we'll - summarize the process to a few cases:

      - -

      a. by using the command-line 2 build system

      - -

      The engine comes with a sophisticated build system that is used - to configure and compile a build of the library. You'll need - GNU Make installed on your platform (NOTE: It will not - work with other Make tools).

      - -

      Basically, you'll need to invoke make a first time in the - top-level FreeType 2 directory in order to setup the build. This will - detect your current platform and choose a configuration sub-makefile to - drive the build. A specific compiler can be selected on some platforms - by providing an additional target. For example, on Win32:

      - -
        -
      • make visualc will select the Visual C++ compiler
        • -
      • make lcc will select the Win32-lcc compiler
        • -
      - -

      Note that on Unix, the first time make is called, a configure script - located in "freetype2/builds/unix" will be run in order to - automatically detect the platform & compiler.

      - -

      A summary will be displayed showing the detected platform and compiler - selected. You'll then be able to start the build by invoking make - a second time. In case of problem, consult the BUILD document.

      - - -

      b. by direct compilation

      - -

      You can also directly compile the library from the command line by - using these simple rules:

      - -
        -

      • - You should place the directories "freetype2/include" and - "freetype2/src" in your include path in order to compile - any component of the library. You can also add the system-specific - build directory (i.e. "builds/system/") in the - case where an alternate implementation of some of the components - is available there (e.g. the memory-mapped i/o implementation - on some Unix systems). -

        • - -

      • - The components of the library are located in sub-directories of - "src", for example: "src/base", - "src/truetype", etc.. -

        • - -

      • - Each component is normally compiled through a single C file that - "wraps" other sources in the component's directory. For example, - your should compile the TrueType font driver by compiling the - file "src/truetype/truetype.c". The list of C files to - compile for a feature-complete build of the library is given in - the BUILD document. -

        • -
      - -

      c. in a graphical IDE

      -
        -

        Well, the process is vastly similar to the one described in b., - except that you need to set the include paths, source code paths, - etc.. in dialog boxes before running the compilation. -

        -
      - -
    - -     -

    II.2. How do I configure my build of the library?

    -
      -

      Each build of the library is configured through two header files - located in "include/freetype/config":

      - -
        -

      • ftoption.h
        - This file contains various configuration macros whose definition - can be toggled on a per-build basis. Each macro is heavily - commented in this file's comment, and we invite you to refer - to it directly.

        • - -

      • ftmodule.h
        +

      • + ftoption.h +
        + This file contains various configuration macros whose definition can + be toggled on a per-build basis. Each macro is heavily commented in + this file's comment, and we invite you to refer to it directly. +
        • +
      • + ftmodule.h +
        This file contains the list of all the modules that are initially - registered (added) when the function FT_Init_FreeType - is called. See the next answer to know how to change it and - why it may be important.

        • -
      + registered (added) when the function FT_Init_FreeType() is + called. See the next answer to know how to change it and why it may + be important. + +
    -

    Alternatively, some specific implementations of some FT2 components - can be provided in a "builds/system/" directory - (e.g. the Unix-specific ftsystem.c that uses memory-mapped - file for i/o).

    - +

    Alternatively, some specific implementations of some FreeType 2 + components can be provided in a builds/system/ + directory (e.g. the Unix-specific ftsystem.c that uses + memory-mapped file for i/o).

    -     -

    II.3. How do I select the modules I need in my build?

    -     +

    Some projects may need, for the sake of simplicity or ease of + building, to compile the FreeType 2 library with all source files + copied to a single directory. This is possible.

    -     -

    II.4. How do I compile all FreeType 2 files in a single directory?

    -
      -

      Some projects may need, for the sake of simplicity or ease of - building, to compile the FT2 library with all source files - copied to a single directory. This is possible.

      +

      To do so, you have to copy all source files located under + src to your own directory (you must retain the include files in + a distinct hierarchy though), then compile each of the FreeType 2 + component with the macro FT_FLAT_COMPILE. This will change the + way #include works during the build.

      -

      To do so, you'll need to copy all source files located under - "src" to your own directory (you must retain the - include files in a distinct hierarchy though), then compile - each of the FreeType 2 component with the macro - FT_FLAT_COMPILE. This will change the way - #include works during the build.

      -
    +
    -

    +
    -
    -

    Using the FreeType 2 library

    -
    + + +
    +

    + The FreeType 2 auto-hinter +

    +
    -
    + +

    + III.1 Under which license is the FreeType 2 auto-hinter released? +

    - +
    -

    The FreeType 2 auto-hinter

    -
    +

    The auto-hinter was initially designed and implemented under contract + for Catharon Productions, Inc + which gladly accepted to released it under an open-source license + compatible with the FreeType one.

    - -

    IV.1. Under which license is the FreeType 2 auto-hinter released

    -
      -

      The auto-hinter was initially designed and implemented under contract - for Catharon Productions, Inc - which gladly accepted to released it under an open-source license - compatible with the FreeType one.

      +

      This license can be found in + src/autohint/CatharonLicense.txt and requires that you cite + Catharon Productions in your documentation (just like you do with + FreeType) when using the auto-hinting module.

      -

      This license can be found in "src/autohint/CatharonLicense.txt" - and requires that you cite Catharon Productions in your documentation - (just like you do with FreeType) when using the auto-hinting module.

      +

      Other than that, you still have the same freedom than with the good + old FreeType license. Enjoy!

      -

      Other than that, you still have the same freedom than with the good old - FreeType license. Enjoy !

      -
    + +

    + III.2 How does the auto-hinter work? +

    -     -

    IV.2. How does the auto-hinter works ?

    -
      -

      Well, a complete description would be difficult. Have a look at the - dedicated auto-hinter pages on the FreeType - site, as they describe most of its details with graphics and explanations. - You could also look at the source code if you want to :-)

      +

      Well, a complete description would be difficult. Have a look at the + dedicated auto-hinter pages on the + FreeType site, as they describe most of its details with graphics and + explanations. You could also look at the source code if you want + to :-)

      -

      To give a few details, the auto-hinter is used to perform grid-fitting - on scalable font formats that use bezier outlines as their primary glyph - image format (this means nearly all scalable font formats today). When - a given font driver doesn't provide its own hinter, the auto-hinter is - used by default. When a format-specific hinter is provided, it is still - possible to use the auto-hinter using the - FT_LOAD_FORCE_AUTOHINT bit flag when calling - FT_Load_Glyph.

      +

      To give a few details, the auto-hinter is used to perform + grid-fitting on scalable font formats that use Bézier outlines as + their primary glyph image format (this means nearly all scalable font + formats today). If a given font driver doesn't provide its own hinter, + the auto-hinter is used by default. If a format-specific hinter is + provided, it is still possible to use the auto-hinter using the + FT_LOAD_FORCE_AUTOHINT bit flag when calling + FT_Load_Glyph().

      -

      The auto-hinter currently doesn't use external hints to do its job, - as it automatically computes global metrics (when it "opens" a font - for the first time) and glyph "hints" from their outline. Note that - we plan the ability to specify external hints, given that it is based - on a constraint system. That could be used to support native hints - in Type 1/Type 2 fonts, for example.

      -
    +

    The auto-hinter currently doesn't use external hints to do its job, + as it automatically computes global metrics (when it "opens" a font for + the first time) and glyph "hints" from their outline. Note that we plan + the ability to specify external hints, given that it is based on a + constraint system. That could be used to support native hints in + Type 1/Type 2 fonts, for example.

    - -

    IV.3. Why does the auto-hinter doesn't work correctly with CJK fonts ?

    -     +

    The auto-hinter was first designed to manage and hint Latin-based + fonts, as they consist of most of the fonts available today. It doesn't + hint Asian fonts, as well as a few other complex scripts, because we + didn't put enough research on the topic yet. Hinting CJK isn't really + more difficult than Latin, just different, with a set of different + constraints (basically, more distortion of glyphs is acceptable as long + as certain features like triple-stem positions are respected more + strictly).

    +

    We thus plan to handle such a case in the near future. Please be + patient.

    +
    -
    +
    - +
    -

    Other questions

    -
    + + +
    +

    + Other questions +

    +
    - -

    V.1. What is the anti-aliasing algorithm used by FreeType 2 ?

    -     +

    The FreeType 2 anti-aliasing renderer is indeed faster + than the monochrome renderer for small character sizes (typically + <20 pixels). The reason is that the monochrome renderer must + perform two passes on the outline in order to perform drop-out control + according to the TrueType specification (we could drop this requirement + later though).

    - -

    V.2. When will FreeType 2 support OpenType ?

    -     +

    For FreeType 2, we have decided that the layout operations + provided through these tables are better placed in a specific + text-layout library, (many people having asked for such a thing). This + new engine will not depend on FreeType2 explicitly and will be developed + as a separate project. We plan to announce it in a few weeks with all + gory details, once the definitive 2.0 release of FreeType has been + made.

    -
    +
    -
    -

    -Back to FreeType homepage

    +

    -
    + Back to FreeType homepage

    + +