GLFM is a C API for mobile app development with OpenGL ES. It is largely inspired by GLFW.
GLFM runs on iOS 9, tvOS 9, Android 4.1 (API 16), and WebGL 1.0 (via Emscripten).
Additionally, GLFM provides Metal support on iOS and tvOS.
- OpenGL ES 2, OpenGL ES 3, and Metal display setup.
- Retina / high-DPI support.
- Touch and keyboard events.
- Accelerometer, magnetometer, gyroscope, and device rotation (iOS/Android only)
- Events for application state and context loss.
| iOS | tvOS | Android | Web | |
|---|---|---|---|---|
| OpenGL ES 2, OpenGL ES 3 | ✔️ | ✔️ | ✔️ | ✔️ |
| Metal | ✔️ | ✔️ | N/A | N/A |
| Retina / high-DPI | ✔️ | ✔️ | ✔️ | ✔️ |
| Device orientation | ✔️ | N/A | ✔️ | |
| Touch events | ✔️ | ✔️ | ✔️ | ✔️ |
| Mouse hover events | ✔️1 | ✔️ | ||
| Mouse wheel events | ✔️ | |||
| Mouse cursor style | ✔️1 | ✔️ | ||
| Key code events | ✔️2 | ✔️ | ✔️ | ✔️ |
| Key repeat events | ✔️ | ✔️ | ||
| Character input events | ✔️ | ✔️3 | ✔️ | ✔️ |
| Virtual keyboard | ✔️ | ✔️ | ||
| Virtual keyboard visibility events | ✔️ | ✔️ | ||
| Accelerometer, magnetometer, gyroscope, device rotation | ✔️ | N/A | ✔️ | |
| Haptic feedback | ✔️4 | N/A | ✔️ | |
| Clipboard | ✔️ | N/A | ✔️ | ✔️ |
| Chrome insets ("safe area") | ✔️5 | ✔️ | ✔️ | |
| Chrome insets changed events | ✔️5 | ✔️ | ✔️ | |
| Focus events | ✔️ | ✔️ | ✔️ | ✔️ |
| Resize events | ✔️ | ✔️ | ✔️ | ✔️ |
| Memory warning events | ✔️ | ✔️ | ✔️ | |
| OpenGL context loss events (surface destroyed) | ✔️ | ✔️ | ✔️ | ✔️ |
1. iPad only. Requires iOS 13.4 or newer
2. Requires iOS/tvOS 13.4 or newer
3. Requires tvOS 13.4 or newer
4. Requires iOS 13 or newer
5. Requires iOS/tvOS 11 or newer
Additionally, there is preliminary support for macOS with OpenGL 3.2. The macOS version is useful for development purposes, but is not release quality. There is no function to set the window size, for example.
GLFM is limited in scope, and isn't designed to provide everything needed for an app. For example, GLFM doesn't provide (and will never provide) the following:
- No image loading.
- No text rendering.
- No audio.
- No menus, UI toolkit, or scene graph.
- No integration with other mobile features like web views, maps, or game scores.
Instead, GLFM can be used with other cross-platform libraries that provide what an app needs.
A CMakeLists.txt file is provided for convenience, although CMake is not required.
Without CMake:
- Add the GLFM source files (in
includeandsrc) to your project. - Include a
void glfmMain(GLFMDisplay *display)function in a C/C++ file.
For release builds, define NDEBUG to remove superfluous logging statements. NDEBUG is automatically defined for
release builds in Android Studio, but not in Xcode.
This example initializes the display in glfmMain() and draws a triangle in onDraw(). A more detailed example is
available here.
#include "glfm.h"
static GLint program = 0;
static GLuint vertexBuffer = 0;
static GLuint vertexArray = 0;
static void onDraw(GLFMDisplay *display);
static void onSurfaceDestroyed(GLFMDisplay *display);
void glfmMain(GLFMDisplay *display) {
glfmSetDisplayConfig(display,
GLFMRenderingAPIOpenGLES2,
GLFMColorFormatRGBA8888,
GLFMDepthFormatNone,
GLFMStencilFormatNone,
GLFMMultisampleNone);
glfmSetRenderFunc(display, onDraw);
glfmSetSurfaceDestroyedFunc(display, onSurfaceDestroyed);
}
static void onSurfaceDestroyed(GLFMDisplay *display) {
// When the surface is destroyed, all existing GL resources are no longer valid.
program = 0;
vertexBuffer = 0;
vertexArray = 0;
}
static GLuint compileShader(const GLenum type, const GLchar *shaderString, GLint shaderLength) {
GLuint shader = glCreateShader(type);
glShaderSource(shader, 1, &shaderString, &shaderLength);
glCompileShader(shader);
return shader;
}
static void onDraw(GLFMDisplay *display) {
if (program == 0) {
const GLchar vertexShader[] =
"#version 100\n"
"attribute highp vec4 position;\n"
"void main() {\n"
" gl_Position = position;\n"
"}";
const GLchar fragmentShader[] =
"#version 100\n"
"void main() {\n"
" gl_FragColor = vec4(0.85, 0.80, 0.75, 1.0);\n"
"}";
program = glCreateProgram();
GLuint vertShader = compileShader(GL_VERTEX_SHADER, vertexShader, sizeof(vertexShader) - 1);
GLuint fragShader = compileShader(GL_FRAGMENT_SHADER, fragmentShader, sizeof(fragmentShader) - 1);
glAttachShader(program, vertShader);
glAttachShader(program, fragShader);
glLinkProgram(program);
glDeleteShader(vertShader);
glDeleteShader(fragShader);
}
if (vertexBuffer == 0) {
const GLfloat vertices[] = {
0.0, 0.5, 0.0,
-0.5, -0.5, 0.0,
0.5, -0.5, 0.0,
};
glGenBuffers(1, &vertexBuffer);
glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
}
int width, height;
glfmGetDisplaySize(display, &width, &height);
glViewport(0, 0, width, height);
glClearColor(0.08f, 0.07f, 0.07f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
#if defined(GL_VERSION_3_0) && GL_VERSION_3_0
if (vertexArray == 0) {
glGenVertexArrays(1, &vertexArray);
}
glBindVertexArray(vertexArray);
#endif
glUseProgram(program);
glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, 0);
glDrawArrays(GL_TRIANGLES, 0, 3);
glfmSwapBuffers(display);
}See glfm.h
Use cmake to generate an Xcode project:
cmake -D GLFM_BUILD_EXAMPLES=ON -B build/apple -G Xcode
open build/apple/GLFM.xcodeprojIn Xcode, switch to the glfm_touch target and run on a simulator or a device.
Use emcmake to set environmental variables for cmake, then build:
emcmake cmake -D GLFM_BUILD_EXAMPLES=ON -B build/emscripten && cmake --build build/emscriptenThen run locally:
emrun build/emscripten/examplesOr run a specific example:
emrun build/emscripten/examples/glfm_touch.htmlThere is no CMake generator for Android Studio projects, but you can include CMakeLists.txt in a new or existing
project.
- Select "Start a new Android Studio project".
- Select "No Activity".
- In "Save location", enter
[path/to/glfm]/build/androidand press "Finish". - In
AndroidManifest.xml, add the main<activity>like so:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android">
<uses-feature android:glEsVersion="0x00020000" android:required="true" />
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:supportsRtl="true">
<!-- Add this activity to your AndroidManifest.xml -->
<activity android:name="android.app.NativeActivity"
android:exported="true"
android:configChanges="orientation|screenLayout|screenSize|keyboardHidden|keyboard">
<meta-data
android:name="android.app.lib_name"
android:value="glfm_touch" /> <!-- glfm_triangle, glfm_touch, glfm_heightmap, glfm_typing, glfm_compass, or glfm_test_pattern -->
<intent-filter>
<action android:name="android.intent.action.MAIN"/>
<category android:name="android.intent.category.LAUNCHER"/>
</intent-filter>
</activity>
</application>
</manifest>- In
app/build.gradle, add theexternalNativeBuildandsourceSets.mainsections like so:
apply plugin: 'com.android.application'
android {
compileSdkVersion 34
ndkVersion '23.2.8568313' // Last version to support API 16, 17, 18
defaultConfig {
applicationId "com.brackeen.glfmexample"
minSdkVersion 16
targetSdkVersion 34
versionCode 1
versionName "1.0"
// Add externalNativeBuild in defaultConfig (1/2)
externalNativeBuild {
cmake {
arguments "-DGLFM_BUILD_EXAMPLES=ON"
}
}
}
// Add sourceSets.main and externalNativeBuild (2/2)
sourceSets.main {
assets.srcDirs = ["../../../examples/assets"]
}
externalNativeBuild {
cmake {
path "../../../CMakeLists.txt"
}
}
namespace 'com.brackeen.glfmexample'
}- Press "Sync Now" and "Run 'app'"
- OpenGL ES 3.1 and 3.2 support is only available in Android.
- GLFM is not thread-safe. All GLFM functions must be called on the main thread (that is, from
glfmMainor from the callback functions).
What IDE should I use? Why is there no desktop implementation? Use Xcode or Android Studio. For desktop, use GLFW with the IDE of your choice.
If you prefer not using the mobile simulators for everyday development, a good solution is to use GLFW instead, and then later port your app to GLFM. Not all OpenGL calls will port to OpenGL ES perfectly, but for maximum OpenGL portability, use OpenGL 3.2 Core Profile on desktop and OpenGL ES 2.0 on mobile.
Why is the entry point glfmMain() and not main()?
Otherwise, it wouldn't work on iOS. To initialize the Objective-C environment, the main() function must create an
autorelease pool and call the UIApplicationMain() function, which never returns. On iOS, GLFM doesn't call
glfmMain() until after the UIApplicationDelegate and UIViewController are initialized.
Why is GLFM event-driven? Why does GLFM take over the main loop?
Otherwise, it wouldn't work on iOS (see above) or on HTML5, which is event-driven.