bindbc-glfw 1.0.2

bindbc-glfw

This project provides both static and dynamic bindings to the GLFW library. They are @nogc and nothrow compatible and can be compiled for compatibility with -betterC. This package is intended as a replacement of DerelictGLFW3, which is not compatible with @nogc, nothrow, or -betterC.

Usage

NOTE: This documentation describes how to use bindbc-glfw. As the maintainer of this library, I do not provide instructions on using the GLFW library. However, since this is a direct binding to the GLFW API, the existing GLFW documentation and tutorials can be adapted to D with few modifications (those being minor differences in the language, such as array declaration syntax). I learned how to use GLFW solely from the API documentation and examples at glfw.org. There are tutorials out there of varying quality, but the documentation is detailed enough that they probably aren't necessary.

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

dub.json

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

dub.sdl

dependency "bindbc-glfw" 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 runtime, the GLFW 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 GLFW DLL with your program. On other systems, it usually means the user must install the GLFW runtime library through a package manager.

To load the shared library, you need to call the loadGLFW function. This returns a member of the GLFWSupport enumeration:

• GLFWSupport.noLibrary indicating that the library failed to load (it couldn't be found)
• GLFWSupport.badLibrary indicating that one or more symbols in the library failed to load
• a member of GLFWSupport indicating a version number that matches the version of GLFW that bindbc-glfw was configured at compile-time to load. By default, that is GLFWSupport.glfw30, but can be configured via a version identifier (see below). This value will match the global manifest constant, glfwSupport.

import bindbc.glfw;

/*
 This version attempts to load the GLFW shared library using well-known variations of the library name for the host
 system.
*/
GLFWSupport ret = loadGLFW();
if(ret != glfwSupport) {

    /*
     Handle error. For most use cases, it's 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 == GLFWSupport.noLibrary) {
        // The GLFW shared library failed to load
    }
    else if(GLFWSupport.badLibrary) {
        /*
         One or more symbols failed to load. The likely cause is that the shared library is for a lower version than bindbc-glfw was configured to load (via GLFW_31, GLFW_32 etc.)
        */
    }
}
/*
 This version attempts to load the GLFW 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 `glfw3.dll` from the `libs` subdirectory,
 relative to the executable, only on Windows.
*/
version(Windows) loadGLFW("libs/glfw3.dll");

The error reporting API in bindbc-loader can be used to log error messages.

// Import the dependent package
import bindbc.glfw;

/*
 Import the sharedlib module for error handling. Assigning an alias ensures the function names do not conflict with
 other public APIs. This isn't strictly necessary, but the API names are common enough that they could appear in other
 packages.
*/
import loader = bindbc.loader.sharedlib;

bool loadLib() {
    /*
     Compare the return value of loadGLFW with the global `glfwSupport` constant to determine if the version of GLFW
     configured at compile time is the version that was loaded.
    */
    auto ret = loadGLFW();
    if(ret != glfwSupport) {
        // Log the error info
        foreach(info; loader.errors) {
            /*
             A hypothetical logging function. Note that `info.error` and `info.message` are `const(char)*`, not
             `string`.
            */
            logError(info.error, info.message);
        }

        // Optionally construct a user-friendly error message for the user
        string msg;
        if(ret == GLFWSupport.noLibrary) {
            msg = "This application requires the GLFW library.";
        } else {
            msg = "The version of the GLFW library on your system is too low. Please upgrade."
        }
        // A hypothetical message box function
        showMessageBox(msg);
        return false;
    }
    return true;
}

By default, the bindbc-glfw binding is configured to load GLFW 3.0. This ensures the widest level of compatibility at run time. This behavior can be overridden via the -version compiler switch or the versions DUB directive with the desired GLFW version number. It is recommended that you always select the minimum version you require and no higher. In this example, the GLFW dynamic binding is compiled to support GLFW 3.1:

dub.json

"dependencies": {
    "bindbc-glfw": "~>1.0.0"
},
"versions": ["GLFW_31"]

dub.sdl

dependency "bindbc-glfw" version="~>1.0.0"
versions "GLFW_31"

With this example configuration, glfwSupport is configured at compile time as GLFWSupport.glfw31. If GLFW 3.1 or later is installed on the user's system, loadGLFW will return GLFWSupport.glfw31. If only GLFW 3.0 is installed, loadGLFW will return GLFWSupport.badLibrary. In this scenario, calling loadedGLFWVersion() will return a GLFWSupport member indicating which version of GLFW, if any, actually loaded.

If a lower version is loaded, it's still possible to call functions from that version of GLFW, but any calls to functions from versions between that version and the one you configured will result in a null pointer access. For example, if you configured GLFW 3.2 and loaded GLFW 3.0, then function pointers from both 3.1 and 3.2 will be null. For this reason, it's recommended to always specify your required version of the GLFW library at compile time and abort when you receive a GLFWSupport.badLibrary return value from loadGLFW.

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

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

The function isGLFWLoaded returns true if any version of GLFW was successfully loaded and false otherwise.

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

Library & Version	Version ID	GLFWSupport Member
GLFW 3.0	Default	GLFWSupport.glfw30
GLFW 3.1	GLFW_31	GLFWSupport.glfw31
GLFW 3.2	GLFW_32	GLFWSupport.glfw32
GLFW 3.3	GLFW_33	GLFWSupport.glfw33

The static binding

First things first: the static binding does not require static linking. It allows for both static and dynamic linking. The static binding has a link-time dependency on either the shared or the static GLFW library. On Windows, you can link with the static library or with the import library for dynamic linking, i.e., to use the shared library (glfw3.dll). On other systems, you can link with either the static library or directly with the shared library. This requires the GLFW development package be installed on your system at compile time, either by compiling the GLFW source yourself, downloading the GLFW precompiled binaries for Windows, or installing via a system package manager. See the GLFW download page for details.

When linking with the shared library (or the import library on Windows), the runtime dependency is the same as that of the dynamic binding. The difference is that the shared library is no longer loaded manually—loading is handled automatically by the system when the program is launched. Attempting to call loadGLFW with the static binding enabled will result in a compilation error.

When linking with the static library, there is no runtime dependency on GLFW. However, you will also need to link with all of GLFW's dependencies for your target platform.

Enabling the static binding can be done in two ways.

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

Pass the BindGLFW_Static version to the compiler and link with the appropriate library. Note that BindGLFW_Static will also enable the static binding for any satellite libraries used.

When using the compiler command line or a build system that doesn't support DUB, this is the only option. The -version=BindGLFW_Static option should be passed to the compiler when building your program. All of the required C libraries, as well as the bindbc-glfw 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-glfw": "~>1.0.0"
},
"versions": ["BindGLFW_Static"],
"libs": ["glfw3"]

dub.sdl

dependency "bindbc-glfw" version="~>1.0.0"
versions "BindGLFW_Static"
libs "glfw3"

Via DUB subconfigurations

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

dub.json

"dependencies": {
    "bindbc-glfw": "~>1.0.0"
},
"subConfigurations": {
    "bindbc-glfw": "static"
},
"libs": ["glfw3"]

dub.sdl

dependency "bindbc-glfw" version="~>1.0.0"
subConfiguration "bindbc-glfw" "static"
libs "glfw3"

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. Using the version approach, the related modules are still passed to the compiler, but their contents are versioned out.

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-glfw": "~>1.0.0"
},
"subConfigurations": {
    "bindbc-glfw": "staticBC"
},
"libs": ["glfw3"]

dub.sdl

dependency "bindbc-glfw" version="~>1.0.0"
subConfiguration "bindbc-glfw" "staticBC"
libs "glfw3"

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 (and -version=BindGLFW_Static if you used the staticBC configuration).

Optional platform-specific functions

GLFW ships with some platform-specific "native" functions that are useful for obtaining native window handles, OpenGL context handles, etc. By default, these are not compiled into the binding. Doing so would require either importing specific platform bindings or using private declarations for the platform-specific types. Both approaches would potentially conflict with user code imports from a different platform-specific binding.

To enable these functions, string constants are provided that can be mixed into user code. Doing so will declare the relevant functions along with a loader function that must be called in addition to loadGLFW. This loader function returns true if the functions are successfully loaded and false otherwise.

The string constants are named with the prefix bindGLFW_, followed by a platform-specific identifer. The load functions are use the prefix loadGLFW_ followed by the same platform-specific identifier.

For example, to declare and load the Windows-specific functions:

/*
 Ideally, these functions should be mixed in where they are needed, or in a module that can be imported where they are
 needed, such as a project-specific platform module.
*/
module myproject.platform;

import bindbc.glfw;

version(Windows) {
    // Import the platform API bindings
    import core.sys.windows.windows;

    // Mixin the function declarations and loader
    mixin(bindGLFW_Windows);
}

// Then wherever you choose to load the shared libraries, say in the `main` funcion in a `myproject.app` module:
module myproject.app;

void main() {
    import myproject.platform : loadGLFW_Windows;

    // Load the GLFW library's core API
    if(loadGLFW() != glfwSupport) {
        // handle error
    }

    // Load the Windows-specific GLFW native API
    if(!loadGLFW_Windows()) {
        // handle error
    }
}

The platform-specific functions are categorized as UI-related APIs (for Window handles, etc.) and OpenGL-related APIs (for platform-specific OpenGL contexts). The following table shows the available constants and loaders. For details on the specifics of the plaform-specific functions, please see the GLFW "Native access" documentation.

Platform API	Constant	Loader	Note
Windows UI (Win32)	bindGLFW_Windows	loadGLFW_Windows
Windows GL (WGL)	bindGLFW_WGL	loadGLFW_WGL
OSX UI (Cocoa)	bindGLFW_Cocoa	loadGLFW_Cocoa
OSX GL (NGL)	bindGLFW_NGL	loadGLFW_NGL
Linux/BSD UI (X11)	bindGLFW_X11	loadGLFW_X11
Linux/BSD GL (GLX)	bindGLFW_GLX	loadGLFW_GLX
Linux UI (Wayland)	bindGLFW_Wayland	loadGLFW_Wayland
Linux UI (Mir)	bindGLFW_Mir	loadGLFW_Mir	GLFW 3.2 only
Mobile UI/GL (EGL)	bindGLFW_EGL	loadGLFW_EGL
All UI (Vulkan)	bindGLFW_Vulkan	loadGLFW_Vulkan	GLFW 3.2 and higher

@nogc callbacks

GLFW makes use of C-style callbacks for event handling. By default, these are aliased as extern(C) nothrow function pointers in bindbc-glfw. So any function you want to designate as a GLFW callback must not only match the function signature that GLFW expects, but also must be annotated as extern(C) nothrow.

@nogc is not applied to the callback aliases because it is perfectly reasonable to use the GC on the D side of a C callback. And since the callback will usually be called from GLFW and not from the D code, then the @nogc attribute is largely irrelevant here even in programs where it is used everywhere else.

However, it is not impossible that a function intended to serve as a GLFW callback may also be implemented with the intent that it can be called directly from D. In that situation, if the calling function is @nogc, then the callback should also be.

The binding supports @nogc callbacks via the BindGLFW_NoGC_Callbacks version. Add this to your dub recipe's versions directive or the compiler command line. Just remember that any function you want to designate as a GLFW callback will then need to be extern(C) @nogc nothrow.