Implement a backend for BGFX

imgui-app/build.gradle

@@ -18,11 +18,13 @@ dependencies {
     api 'org.lwjgl:lwjgl'
     api 'org.lwjgl:lwjgl-glfw'
     api 'org.lwjgl:lwjgl-opengl'
+    api 'org.lwjgl:lwjgl-bgfx'
 
     ['natives-linux', 'natives-windows', 'natives-macos'].each {
         api "org.lwjgl:lwjgl::$it"
         api "org.lwjgl:lwjgl-glfw::$it"
         api "org.lwjgl:lwjgl-opengl::$it"
+        api "org.lwjgl:lwjgl-bgfx::$it"
     }
 
     api project(':imgui-binding')

imgui-app/src/main/java/imgui/app/BGFXWindow.java

@@ -0,0 +1,273 @@
+package imgui.app;
+
+import imgui.ImGui;
+import imgui.bgfx.ImGuiImplBGFX;
+import imgui.flag.ImGuiConfigFlags;
+import imgui.glfw.ImGuiImplGlfw;
+import org.lwjgl.BufferUtils;
+import org.lwjgl.bgfx.BGFXInit;
+import org.lwjgl.glfw.GLFW;
+import org.lwjgl.glfw.*;
+import org.lwjgl.system.MemoryStack;
+import org.lwjgl.system.MemoryUtil;
+import org.lwjgl.system.Platform;
+
+import java.nio.IntBuffer;
+import java.util.Objects;
+
+import static org.lwjgl.bgfx.BGFX.*;
+import static org.lwjgl.glfw.GLFW.*;
+import static org.lwjgl.system.Configuration.GLFW_LIBRARY_NAME;
+import static org.lwjgl.system.MemoryStack.stackPush;
+
+public abstract class BGFXWindow {
+    private final ImGuiImplBGFX imGuiBGFX = new ImGuiImplBGFX();
+    private final ImGuiImplGlfw imGuiGlfw = new ImGuiImplGlfw();
+
+    /**
+     * Pointer to the native GLFW window.
+     */
+    protected long handle;
+
+    /**
+     * Background color of the window.
+     */
+    protected final Color colorBg = new Color(.5f, .5f, .5f, 1);
+
+    /**
+     * Method to initialize application.
+     *
+     * @param config configuration object with basic window information
+     */
+    protected void init(final Configuration config) {
+        initWindow(config);
+        initImGui(config);
+        imGuiGlfw.init(handle, true);
+        imGuiBGFX.init();
+    }
+
+    /**
+     * Method to dispose all used application resources and destroy its window.
+     */
+    protected void dispose() {
+        imGuiBGFX.dispose();
+        imGuiGlfw.dispose();
+        disposeImGui();
+        disposeWindow();
+    }
+
+    /**
+     * Method to create and initialize GLFW window.
+     *
+     * @param config configuration object with basic window information
+     */
+    protected void initWindow(final Configuration config) {
+        if (Platform.get() == Platform.MACOSX) {
+            GLFW_LIBRARY_NAME.set("glfw_async");
+        }
+
+        GLFWErrorCallback.createPrint(System.err).set();
+
+        if (!GLFW.glfwInit()) {
+            throw new IllegalStateException("Unable to initialize GLFW");
+        }
+
+        glfwWindowHint(GLFW_CLIENT_API, GLFW_NO_API);
+
+        handle = glfwCreateWindow(config.getWidth(), config.getHeight(), config.getTitle(), MemoryUtil.NULL, MemoryUtil.NULL);
+
+        if (handle == MemoryUtil.NULL) {
+            throw new RuntimeException("Failed to create the GLFW window");
+        }
+
+        try (MemoryStack stack = stackPush()) {
+            final IntBuffer pWidth = stack.mallocInt(1); // int*
+            final IntBuffer pHeight = stack.mallocInt(1); // int*
+
+            GLFW.glfwGetWindowSize(handle, pWidth, pHeight);
+            final GLFWVidMode vidmode = Objects.requireNonNull(GLFW.glfwGetVideoMode(GLFW.glfwGetPrimaryMonitor()));
+            GLFW.glfwSetWindowPos(handle, (vidmode.width() - pWidth.get(0)) / 2, (vidmode.height() - pHeight.get(0)) / 2);
+        }
+
+        try (MemoryStack stack = stackPush()) {
+            BGFXInit init = BGFXInit.malloc(stack);
+
+            bgfx_init_ctor(init);
+            init.resolution(it -> it
+                .width(config.getWidth())
+                .height(config.getHeight())
+                .reset(BGFX_RESET_VSYNC));
+            switch (Platform.get()) {
+                case LINUX:
+                    init.platformData()
+                        .ndt(GLFWNativeX11.glfwGetX11Display())
+                        .nwh(GLFWNativeX11.glfwGetX11Window(handle));
+                    break;
+                case MACOSX:
+                    init.platformData()
+                        .nwh(GLFWNativeCocoa.glfwGetCocoaWindow(handle));
+                    break;
+                case WINDOWS:
+                    init.platformData()
+                        .nwh(GLFWNativeWin32.glfwGetWin32Window(handle));
+                    break;
+            }
+
+            if (!bgfx_init(init)) {
+                throw new RuntimeException("Error initializing bgfx renderer");
+            }
+        }
+
+        if (config.isFullScreen()) {
+            GLFW.glfwMaximizeWindow(handle);
+        } else {
+            GLFW.glfwShowWindow(handle);
+        }
+
+        clearBuffer();
+        renderBuffer();
+
+        GLFW.glfwSetWindowSizeCallback(handle, new GLFWWindowSizeCallback() {
+            @Override
+            public void invoke(final long window, final int width, final int height) {
+                bgfx_reset(width, height, BGFX_RESET_NONE, BGFX_TEXTURE_FORMAT_COUNT);
+                runFrame();
+            }
+        });
+    }
+
+    /**
+     * Method to initialize Dear ImGui context. Could be overridden to do custom Dear ImGui setup before application start.
+     *
+     * @param config configuration object with basic window information
+     */
+    protected void initImGui(final Configuration config) {
+        ImGui.createContext();
+    }
+
+    /**
+     * Method called every frame, before calling {@link #process()} method.
+     */
+    protected void preProcess() {
+    }
+
+    /**
+     * Method called every frame, after calling {@link #process()} method.
+     */
+    protected void postProcess() {
+    }
+
+    /**
+     * Main application loop.
+     */
+    protected void run() {
+        while (!GLFW.glfwWindowShouldClose(handle)) {
+            runFrame();
+        }
+    }
+
+    /**
+     * Method used to run the next frame.
+     */
+    protected void runFrame() {
+        startFrame();
+        preProcess();
+        process();
+        postProcess();
+        endFrame();
+    }
+
+    /**
+     * Method to be overridden by user to provide main application logic.
+     */
+    public abstract void process();
+
+    /**
+     * Method used to clear the OpenGL buffer.
+     */
+    private void clearBuffer() {
+        int color = Math.round(colorBg.getRed() * 255);
+        color = (color << 8) + Math.round(colorBg.getGreen() * 255);
+        color = (color << 8) + Math.round(colorBg.getBlue() * 255);
+        color = (color << 8) + Math.round(colorBg.getAlpha() * 255);
+        bgfx_set_view_clear(0, BGFX_CLEAR_COLOR | BGFX_CLEAR_DEPTH,  color, 1.0f, 0);
+        IntBuffer w = BufferUtils.createIntBuffer(1);
+        IntBuffer h = BufferUtils.createIntBuffer(1);
+        glfwGetWindowSize(getHandle(), w, h);
+        int width = w.get(0);
+        int height = h.get(0);
+        bgfx_set_view_rect(0, 0, 0, width, height);
+    }
+
+    /**
+     * Method called at the beginning of the main cycle.
+     * It clears OpenGL buffer and starts an ImGui frame.
+     */
+    protected void startFrame() {
+        clearBuffer();
+        imGuiGlfw.newFrame();
+        ImGui.newFrame();
+    }
+
+    /**
+     * Method called in the end of the main cycle.
+     * It renders ImGui and swaps GLFW buffers to show an updated frame.
+     */
+    protected void endFrame() {
+        ImGui.render();
+        imGuiBGFX.renderDrawData(ImGui.getDrawData());
+
+        if (ImGui.getIO().hasConfigFlags(ImGuiConfigFlags.ViewportsEnable)) {
+            final long backupWindowPtr = GLFW.glfwGetCurrentContext();
+            ImGui.updatePlatformWindows();
+            ImGui.renderPlatformWindowsDefault();
+            GLFW.glfwMakeContextCurrent(backupWindowPtr);
+        }
+
+        renderBuffer();
+    }
+
+    /**
+     * Method to render the OpenGL buffer and poll window events.
+     */
+    private void renderBuffer() {
+        bgfx_frame(false);
+        GLFW.glfwPollEvents();
+    }
+
+    /**
+     * Method to destroy Dear ImGui context.
+     */
+    protected void disposeImGui() {
+        ImGui.destroyContext();
+    }
+
+    /**
+     * Method to destroy GLFW window.
+     */
+    protected void disposeWindow() {
+        bgfx_shutdown();
+        Callbacks.glfwFreeCallbacks(handle);
+        GLFW.glfwDestroyWindow(handle);
+        GLFW.glfwTerminate();
+        Objects.requireNonNull(GLFW.glfwSetErrorCallback(null)).free();
+    }
+
+    /**
+     * @return pointer to the native GLFW window
+     */
+    public final long getHandle() {
+        return handle;
+    }
+
+    /**
+     * @return {@link Color} instance, which represents background color for the window
+     */
+    public final Color getColorBg() {
+        return colorBg;
+    }
+
+    public ImGuiImplBGFX getImGuiBGFX() {
+        return imGuiBGFX;
+    }
+}

imgui-lwjgl3/build.gradle

@@ -17,6 +17,7 @@ dependencies {
     implementation 'org.lwjgl:lwjgl'
     implementation 'org.lwjgl:lwjgl-glfw'
     implementation 'org.lwjgl:lwjgl-opengl'
+    implementation 'org.lwjgl:lwjgl-bgfx'
 
     implementation project(':imgui-binding')
 }