[API] Add imgui-app and example modules

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

@@ -0,0 +1,186 @@
+package imgui.app;
+
+import imgui.ImGui;
+import imgui.flag.ImGuiConfigFlags;
+import imgui.gl3.ImGuiImplGl3;
+import imgui.glfw.ImGuiImplGlfw;
+import org.lwjgl.glfw.Callbacks;
+import org.lwjgl.glfw.GLFW;
+import org.lwjgl.glfw.GLFWErrorCallback;
+import org.lwjgl.glfw.GLFWVidMode;
+import org.lwjgl.opengl.GL;
+import org.lwjgl.opengl.GL32;
+import org.lwjgl.system.MemoryStack;
+import org.lwjgl.system.MemoryUtil;
+
+import java.awt.Color;
+import java.nio.IntBuffer;
+import java.util.Objects;
+
+/**
+ * Low-level abstraction, which creates application window and starts the main loop.
+ * It's recommended to use {@link Application}, but this class could be extended directly as well.
+ * Take a note, that in this case you need to call all application loop methods ({@link #init(Configuration)}, {@link #run()}, {@link #dispose()}) manually.
+ */
+public abstract class Window {
+    private final ImGuiImplGlfw imGuiGlfw = new ImGuiImplGlfw();
+    private final ImGuiImplGl3 imGuiGl3 = new ImGuiImplGl3();
+
+    private String glslVersion = null;
+
+    /**
+     * Pointer to native GLFW window.
+     */
+    protected long handle;
+    /**
+     * Background color of the window.
+     */
+    protected Color colorBg = Color.GRAY;
+
+    /**
+     * Method to initialize application.
+     *
+     * @param config configuration object with basic window information
+     */
+    protected final void init(final Configuration config) {
+        initWindow(config);
+        initImGui(config);
+        imGuiGlfw.init(handle, true);
+        imGuiGl3.init(glslVersion);
+    }
+
+    /**
+     * Method to dispose all used application resources and destroy its window.
+     */
+    protected final void dispose() {
+        imGuiGl3.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) {
+        GLFWErrorCallback.createPrint(System.err).set();
+
+        if (!GLFW.glfwInit()) {
+            throw new IllegalStateException("Unable to initialize GLFW");
+        }
+
+        decideGlGlslVersions();
+
+        GLFW.glfwWindowHint(GLFW.GLFW_VISIBLE, GLFW.GLFW_FALSE);
+        handle = GLFW.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 = MemoryStack.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);
+        }
+
+        GLFW.glfwMakeContextCurrent(handle);
+        GLFW.glfwSwapInterval(GLFW.GLFW_TRUE);
+        GLFW.glfwShowWindow(handle);
+
+        if (config.isFullScreen()) {
+            GLFW.glfwMaximizeWindow(handle);
+        }
+
+        GL.createCapabilities();
+    }
+
+    private void decideGlGlslVersions() {
+        final boolean isMac = System.getProperty("os.name").toLowerCase().contains("mac");
+        if (isMac) {
+            glslVersion = "#version 150";
+            GLFW.glfwWindowHint(GLFW.GLFW_CONTEXT_VERSION_MAJOR, 3);
+            GLFW.glfwWindowHint(GLFW.GLFW_CONTEXT_VERSION_MINOR, 2);
+            GLFW.glfwWindowHint(GLFW.GLFW_OPENGL_PROFILE, GLFW.GLFW_OPENGL_CORE_PROFILE);  // 3.2+ only
+            GLFW.glfwWindowHint(GLFW.GLFW_OPENGL_FORWARD_COMPAT, GLFW.GLFW_TRUE);          // Required on Mac
+        } else {
+            glslVersion = "#version 130";
+            GLFW.glfwWindowHint(GLFW.GLFW_CONTEXT_VERSION_MAJOR, 3);
+            GLFW.glfwWindowHint(GLFW.GLFW_CONTEXT_VERSION_MINOR, 0);
+        }
+    }
+
+    /**
+     * 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();
+    }
+
+    /**
+     * Main application loop.
+     */
+    protected final void run() {
+        while (!GLFW.glfwWindowShouldClose(handle)) {
+            startFrame();
+            process();
+            endFrame();
+        }
+    }
+
+    /**
+     * Method to be overridden by user to provide main application logic.
+     */
+    public abstract void process();
+
+    private void startFrame() {
+        if (colorBg != null) {
+            GL32.glClearColor(colorBg.getRed() / 255f, colorBg.getGreen() / 255f, colorBg.getBlue() / 255f, colorBg.getAlpha() / 255f);
+        }
+
+        GL32.glClear(GL32.GL_COLOR_BUFFER_BIT | GL32.GL_DEPTH_BUFFER_BIT);
+        imGuiGlfw.newFrame();
+        ImGui.newFrame();
+    }
+
+    private void endFrame() {
+        ImGui.render();
+        imGuiGl3.renderDrawData(ImGui.getDrawData());
+
+        if (ImGui.getIO().hasConfigFlags(ImGuiConfigFlags.ViewportsEnable)) {
+            final long backupWindowPtr = GLFW.glfwGetCurrentContext();
+            ImGui.updatePlatformWindows();
+            ImGui.renderPlatformWindowsDefault();
+            GLFW.glfwMakeContextCurrent(backupWindowPtr);
+        }
+
+        GLFW.glfwSwapBuffers(handle);
+        GLFW.glfwPollEvents();
+    }
+
+    /**
+     * Method to destroy Dear ImGui context.
+     */
+    protected void disposeImGui() {
+        ImGui.destroyContext();
+    }
+
+    /**
+     * Method to destroy GLFW window.
+     */
+    protected void disposeWindow() {
+        Callbacks.glfwFreeCallbacks(handle);
+        GLFW.glfwDestroyWindow(handle);
+        GLFW.glfwTerminate();
+        Objects.requireNonNull(GLFW.glfwSetErrorCallback(null)).free();
+    }
+}