bindbc-thorvg ~main

bindbc-thorvg

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

Please note that this repo's setup is essentially the same as that of bindbc-freetype developed and maintained by Mike Parker. Since the setup and configurations are the same I took the liberty to copy the bindbc-freetype README and just changed the names. Not all functionality has been fully tested that is written in this README!.

Usage

By default, bindbc-thorvg is configured to compile as a dynamic binding that is not -betterC compatible. The dynamic binding has no link-time dependency on the ThorVG library, so the ThorVG shared library must be manually loaded at run time. When configured as a static binding, there is a link-time dependency on the ThorVG 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 ThorVG, add bindbc-thorvg as a dependency to your project's package config file. For example, the following is configured to compile bindbc-thorvg as a dynamic binding that is not -betterC compatible:

dub.json

dependencies {
    "bindbc-thorvg": "~>1.0.0",
}

dub.sdl

dependency "bindbc-thorvg" version="~>1.0.0"

The dynamic binding

The dynamic binding requires no special configuration when using DUB to manage your project. There is no link-time dependency. At run time, the ThorVG 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 ThorVG DLL with your program. On other systems, it usually means the user must install the ThorVG shared library through a package manager.

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

• TVGSupport.noLibrary indicating that the library failed to load (it couldn't be found)
• TVGSupport.badLibrary indicating that one or more symbols in the library failed to load
• a member of TVGSupport indicating a version number that matches the version of ThorVG that bindbc-thorvg was configured at compile time to load. By default, that is TVGSupport.tvg07, but can be configured via a version identifier (see below). This value will match the global manifest constant, tvgSupport.

import bindbc.thorvg;

/*
This version attempts to load the ThorVG shared library using well-known variations
of the library name for the host system.
*/
TVGSupport ret = loadThorVG();
if(ret != tvgSupport) {

    // 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 == TVGSupport.noLibrary) {
        // ThorVG shared library failed to load
    }
    else if(TVGSupport.badLibrary) {
        // One or more symbols failed to load. The likely cause is that the
        // shared library is for a lower version than bindbc-thorvg was configured
        // to load
    }
}
/*
This version attempts to load the ThorVG 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 `thorvg.dll` from the `libs` subdirectory, relative
to the executable, only on Windows.
*/
// version(Windows) loadThorVG("libs/thorvg.dll")

By default, the bindbc-thorvg binding is configured to load ThorVG 0.8. This behavior can be overridden via the -version compiler switch or the versions DUB directive with the desired ThorVG version number. It is recommended that you always select the minimum version you require and no higher.

In this example, the ThorVG dynamic binding is compiled to support ThorVG 0.10:

dub.json

"dependencies": {
    "bindbc-thorvg": "~>1.0.0"
},
"versions": ["TVG_0_10"]

dub.sdl

dependency "bindbc-thorvg" version="~>1.0.0"
versions "TVG_0_10"

With this example configuration, tvgSupport == TVGSupport.v0_9 after a successful load. If ThorVG 0.9 or later is installed on the user's system, loadThorVG will return TVGSupport.v0_9. If ThorVG 0.8 is installed, loadThorVG will return TVGSupport.badLibrary. In this scenario, calling loadedThorVGVersion() will return a TVGSupport member indicating which version of ThorVG, if any, actually loaded. If a lower version was loaded, it's still possible to call functions from that version of ThorVG, 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 ThorVG library at compile time and abort when you receive a TVGSupport.badLibrary return value from loadThorVG.

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

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

The function isThorVGLoaded returns true if any version of ThorVG was successfully loaded and false otherwise.

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

Library & Version	Version ID	TVGSupport Member
ThorVG 0.8.x and earlier	Default	TVGSupport.v0_8
ThorVG 0.9.x		TVGSupport.v0_9
ThorVG 0.10.x		TVGSupport.v0_10

The static binding

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

When linking with the static library, there is no run-time dependency on ThorVG. When linking with the shared library (or the import library on Windows), the run-time dependency is the same as that of 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 BindTVG_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 choice. The -version=BindTVG_Static option should be passed to the compiler when building your program. All of the required C libraries, as well as the bindbc-thorvg 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, set the BindTVG_Static version via its versions directive. For example:

dub.json

"dependencies": {
    "bindbc-thorvg": "~>1.0.0"
},
"versions": ["BindTVG_Static"],
"libs": ["thorvg"]

dub.sdl

dependency "bindbc-thorvg" version="~>1.0.0"
versions "BindTVG_Static"
libs "thorvg"

When using multiple BindBC packages, the BindBC_Static version will enable the static binding for all that support it.

Via DUB subconfigurations

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

dub.json

"dependencies": {
    "bindbc-thorvg": "~>1.0.0"
},
"subConfigurations": {
    "bindbc-thorvg": "static"
},
"libs": ["thorvg"]

dub.sdl

dependency "bindbc-thorvg" version="~>1.0.0"
subConfiguration "bindbc-thorvg" "static"
libs "thorvg"

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 dynamic binding with -betterC support:

dub.json

"dependencies": {
    "bindbc-thorvg": "~>1.0.0"
},
"subConfigurations": {
    "bindbc-thorvg": "dynamicBC"
},
"libs": ["thorvg"]

dub.sdl

dependency "bindbc-thorvg" version="~>1.0.0"
subConfiguration "bindbc-thorvg" "dynamicBC"
libs "thorvg"

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.