bindbc-harfbuzz 0.1.0

bindbc-harfbuzz

This project provides both static and dynamic bindings to the HarfBuzz library. They are @nogc and nothrow compatible can be compiled for compatibility with -betterC.

Usage

By default, bindbc-harfbuzz is configured to compile as a dynamic binding that is not -betterC compatible. The dynamic binding has no link-time dependency on the HarfBuzz library, so the HarfBuzz shared library must be manually loaded at runtime. When configured as a static binding, there is a link-time dependency on the HarfBuzz library---either the static library or the appropriate file for linking with shared libraries on your platform (see below).

When using DUB to manage your project, the static binding can be enabled via a DUB subConfiguration statement in your project's package file. -betterC compatibility is also enabled via subconfigurations.

To use HarfBuzz, add bindbc-harfbuzz as a dependency to your project's package config file. For example, the following is configured to HarfBuzz as a dynamic binding that is not -betterC compatible:

dub.json

dependencies {
    "bindbc-harfbuzz": "~>0.1.0",
}

dub.sdl

dependency "bindbc-harfbuzz" version="~>0.1.0"

The dynamic binding

The dynamic binding requires no special configuration when using DUB to manage your project. There is no link-time dependency. At runtime, the HarfBuzz shared library is required to be on the shared library search path of the user's system. On Windows, this is typically handled by distributing the HarfBuzz DLL with your program. On other systems, it usually means the user must install the HarfBuzz runtime library through a package manager.

To load the shared library, you need to call the loadHarfBuzz function. This returns a member of the HBSupport enumeration (See the README for bindbc.loader for the error handling API):

• HBSupport.noLibrary indicating that the library failed to load (it couldn't be found)
• HBSupport.badLibrary indicating that one or more symbols in the library failed to load
• a member of HBSupport indicating a version number that matches the version of HarfBuzz that bindbc-harfbuzz was configured at compile-time to load. By default, that is HBSupport.hb26, but can be configured via a version identifier (see below). This value will match the global manifest constant, hbSupport.

import bindbc.harfbuzz;

/*
This version attempts to load the HarfBuzz shared library using well-known variations
of the library name for the host system.
*/
HBSupport ret = loadHarfBuzz();
if(ret != hbSupport) {

    // Handle error. For most use cases, its reasonable to use the the error handling API in
    // bindbc-loader to retrieve error messages for logging and then abort. If necessary, it's
    // possible to determine the root cause via the return value:

    if(ret == HBSupport.noLibrary) {
        // HarfBuzz shared library failed to load
    }
    else if(HBSupport.badLibrary) {
        // One or more symbols failed to load. The likely cause is that the
        // shared library is for a lower version than bindbc-harfbuzz was configured
        // to load (via HB_26, etc.)
    }
}
/*
This version attempts to load the HarfBuzz library using a user-supplied file name.
Usually, the name and/or path used will be platform specific, as in this example
which attempts to load `harfbuzz.dll` from the `libs` subdirectory, relative
to the executable, only on Windows.
*/
// version(Windows) loadHarfBuzz("libs/harfbuzz.dll")

By default, the bindbc-harfbuzz binding is configured to compile to load HarfBuzz 2.6. This is currently the only supported version. This behavior can be overridden via the -version compiler switch or the versions DUB directive with the desired HarfBuzz version number. It is recommended that you always select the minimum version you require and no higher. In this example, the HarfBuzz dynamic binding is compiled to support HarfBuzz 2.6 manually:

dub.json

"dependencies": {
    "bindbc-harfbuzz": "~>0.1.0"
},
"versions": ["HB_26"]

dub.sdl

dependency "bindbc-harfbuzz" version="~>0.1.0"
versions "HB_26"

With this example configuration, hbSupport == HBSupport.hb26. If HarfBuzz 2.6 or later is installed on the user's system, loadHarfBuzz will return HBSupport.hb26. If only HarfBuzz 2.5 is installed, loadHarfBuzz will return HBSupport.badLibrary. In this scenario, calling loadedHarfBuzzVersion() will return a HBSupport member indicating which version of HarfBuzz, if any, actually loaded. If a lower version was loaded, it's still possible to call functions from that version of HarfBuzz, but any calls to functions from higher versions will result in a null pointer access. For this reason, it's recommended to always specify your required version of the HarfBuzz library at compile time and abort when you receive a HBSupport.badLibrary return value from loadHarfBuzz.

No matter which version was configured, the successfully loaded version can be obtained via a call to loadedHarfBuzzVersion. It returns one of the following:

• HBSupport.noLibrary if loadHarfBuzz returned HBSupport.noLibrary
• HBSupport.badLibrary if loadHarfBuzz returned HBSupport.badLibrary and no version of HarfBuzz successfully loaded
• a member of HBSupport indicating the version of HarfBuzz that successfully loaded. When loadHarfBuzz returns HBSupport.badLibrary, this will be a version number lower than that configured at compile time. Otherwise, it will be the same as the manifest constant hbSupport.

The function isHarfBuzzLoaded returns true if any version of HarfBuzz was successfully loaded and false otherwise.

Following are the supported versions of HarfBuzz, the corresponding version IDs to pass to the compiler, and the corresponding HBSupport members.

Library & Version	Version ID	HBSupport Member
HarfBuzz 2.6.1	Default	HBSupport.hb26

The static binding

The static binding has a link-time dependency on either the shared or the static HarfBuzz library. On Windows, you can link with the static library or, to use the shared library (harfbuzz.dll), with the import library. On other systems, you can link with either the static library or directly with the shared library. This requires the HarfBuzz development package be installed on your system at compile time, either by compiling the HarfBuzz source yourself, downloading the HarfBuzz precompiled binaries for Windows, or installing via a system package manager. See the HarfBuzz documentation for details.

When linking with the static library, there is no runtime dependency on HarfBuzz. When linking with the shared library (or the import library on Windows), the runtime dependency is the same as the dynamic binding, the difference being that the shared library is no longer loaded manually---loading is handled automatically by the system when the program is launched.

Enabling the static binding can be done in two ways.

Via the compiler's -version switch or DUB's versions directive

Pass the BindHB_Static version to the compiler and link with the appropriate library.

When using the compiler command line or a build system that doesn't support DUB, this is the only option. The -version=BindHB_Static option should be passed to the compiler when building your program. All of the required C libraries, as well as the bindbc-harfbuzz and bindbc-loader static libraries must also be passed to the compiler on the command line or via your build system's configuration.

When using DUB, its versions directive is an option. For example, when using the static binding:

dub.json

"dependencies": {
    "bindbc-harfbuzz": "~>0.1.0"
},
"versions": ["BindHB_Static"],
"libs": ["harfbuzz"]

dub.sdl

dependency "bindbc-harfbuzz" version="~>0.1.0"
versions "BindHB_Static"
libs "harfbuzz"

Via DUB subconfigurations

Instead of using DUB's versions directive, a subConfiguration can be used. Enable the static subconfiguration for the bindbc-harfbuzz dependency:

dub.json

"dependencies": {
    "bindbc-harfbuzz": "~>0.1.0"
},
"subConfigurations": {
    "bindbc-harfbuzz": "static"
},
"libs": ["harfbuzz"]

dub.sdl

dependency "bindbc-harfbuzz" version="~>0.1.0"
subConfiguration "bindbc-harfbuzz" "static"
libs "harfbuzz"

This has the benefit that it completely excludes from the build any source modules related to the dynamic binding, i.e. they will never be passed to the compiler.

betterC support

betterC support is enabled via the dynamicBC and staticBC subconfigurations, for dynamic and static bindings respectively. To enable the static binding with -betterC support:

dub.json

"dependencies": {
    "bindbc-harfbuzz": "~>0.1.0"
},
"subConfigurations": {
    "bindbc-harfbuzz": "staticBC"
},
"libs": ["harfbuzz"]

dub.sdl

dependency "bindbc-harfbuzz" version="~>0.1.0"
subConfiguration "bindbc-harfbuzz" "staticBC"
libs "harfbuzz"

When not using DUB to manage your project, first use DUB to compile the BindBC libraries with the dynamicBC or staticBC configuration, then pass -betterC to the compiler when building your project.