Bug: ImGui is setting the font texture ID to zero everytime the font atlas is built.

[Rusettsten]

Version

1.86.11

What happened?

When trying to add fonts, I noticed that no matter what file I loaded from memory or file made every texture appear pure black in OpenGL. After some testing, I determined that even when I set the textureID on the font, it still renders as ID 0.

I'm on Windows, 64-bit, with an NVIDIA 3080 GPU.

The font code is below.

private void setupDefaultFont() {
		final ImGuiIO io = ImGui.getIO();
		ImFontAtlas fontAtlas = ImGui.getIO().getFonts();
		fontAtlas.setLocked(false);
		defaultFont = io.getFonts().addFontDefault();
		final ImFontConfig fontConfig = new ImFontConfig();

		fontConfig.setMergeMode(true);
		fontConfig.setFontDataOwnedByAtlas(false);
		fontConfig.setGlyphRanges(fontAtlas.getGlyphRangesDefault());
		defaultFont = fontAtlas.addFontFromMemoryTTF(ResourceReader.loadBytesFromResources("/fonts/Roboto-Medium.ttf"), 5, fontConfig);

		fontAtlas.setTexID(581);
		System.out.println(fontAtlas.getTexID());
		fontAtlas.build();
		System.out.println(fontAtlas.getTexID());
		fontConfig.destroy();
	}

Reproduction

I loaded different fonts using a few different calls and determined the texture ID did not change.

Relevant log output

No response

[Rusettsten]

UPDATE: I was able to replicate the bug by creating a new project with the default ImGui pom.xml for Maven and use the following code.

`import static org.lwjgl.glfw.GLFW.glfwPollEvents;
import static org.lwjgl.glfw.GLFW.glfwSwapBuffers;
import static org.lwjgl.glfw.GLFW.glfwWindowShouldClose;

import java.awt.Color;
import java.io.IOException;
import java.net.URISyntaxException;
import java.nio.IntBuffer;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.Objects;

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.opengl.GLCapabilities;
import org.lwjgl.system.MemoryStack;
import org.lwjgl.system.MemoryUtil;

import imgui.ImFont;
import imgui.ImFontAtlas;
import imgui.ImFontConfig;
import imgui.ImGui;
import imgui.ImGuiIO;
import imgui.flag.ImGuiConfigFlags;
import imgui.gl3.ImGuiImplGl3;
import imgui.glfw.ImGuiImplGlfw;

public class Main {

/*
 * VARIABLES
 */
private final ImGuiImplGlfw imGuiGlfw = new ImGuiImplGlfw();
private final ImGuiImplGl3 imGuiGl3 = new ImGuiImplGl3();

private String GLSLversion = "#version 150";
private Color colorBg = new Color(.2f, 0f, .4f, 1);

public long windowHandle;
private GLCapabilities capabilities;
private ImFont defaultFont = new ImFont();

/*
 * METHODS - MAIN
 */
public static void main(String[] args) {
	
	Main main = new Main();
	main.init();
	
	while(!glfwWindowShouldClose(main.windowHandle)) {
		main.processFrame();
	}
}

/*
 * METHODS - INIT
 */

public void init() {
	initWindow();
	ImGui.createContext();
	imGuiGlfw.init(windowHandle, true);
    imGuiGl3.init(GLSLversion);
    setupDefaultFont();
}

private void initWindow() {
	GLFWErrorCallback.createPrint(System.err).set();

    if (!GLFW.glfwInit()) {
        throw new IllegalStateException("Unable to initialize GLFW!");
    }
    
    //Set GLSL Version
    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 for Mac Support
    
    GLFW.glfwWindowHint(GLFW.GLFW_VISIBLE, GLFW.GLFW_FALSE);
    
    final GLFWVidMode vidmode = Objects.requireNonNull(GLFW.glfwGetVideoMode(GLFW.glfwGetPrimaryMonitor()));
    
    windowHandle = GLFW.glfwCreateWindow(vidmode.width(), vidmode.height(), "Font Test", MemoryUtil.NULL, MemoryUtil.NULL);
    
    if (windowHandle == MemoryUtil.NULL) {
        throw new RuntimeException("Failed to create GUI GLFW window!");
    }
    
    try (MemoryStack stack = MemoryStack.stackPush()) {
        final IntBuffer pWidth = stack.mallocInt(1); // int*
        final IntBuffer pHeight = stack.mallocInt(1); // int*

        GLFW.glfwGetWindowSize(windowHandle, pWidth, pHeight);
        GLFW.glfwSetWindowPos(windowHandle, (vidmode.width() - pWidth.get(0)) / 2, (vidmode.height() - pHeight.get(0)) / 2);
    }
    
    GLFW.glfwMakeContextCurrent(windowHandle);
    GLFW.glfwSwapInterval(GLFW.GLFW_TRUE);
    GLFW.glfwShowWindow(windowHandle);
    GLFW.glfwMaximizeWindow(windowHandle);
    
    capabilities = GL.createCapabilities();
}

public static byte[] loadBytesFromResources(String name) {
    try {
		return Files.readAllBytes(Paths.get(Main.class.getResource(name).toURI()));
	} catch (IOException | URISyntaxException e) {
		e.printStackTrace();
	}
    return null;
}

private void setupDefaultFont() {
	final ImGuiIO io = ImGui.getIO();
	ImFontAtlas fontAtlas = ImGui.getIO().getFonts();
	fontAtlas.setLocked(false);
	defaultFont = io.getFonts().addFontDefault();
	final ImFontConfig fontConfig = new ImFontConfig();

	fontConfig.setMergeMode(true);
	fontConfig.setFontDataOwnedByAtlas(false);
	fontConfig.setGlyphRanges(fontAtlas.getGlyphRangesDefault());
	defaultFont = fontAtlas.addFontFromMemoryTTF(loadBytesFromResources("/fonts/Roboto-Medium.ttf"), 5, fontConfig);

	fontAtlas.build();
	fontConfig.destroy();
}

/*
 * METHODS - RUNNING
 */
public void processFrame() {
	startFrame();
	drawWindow();
	endFrame();
}

private void startFrame() {
	GLFW.glfwMakeContextCurrent(windowHandle);
	GL.setCapabilities(capabilities);
	GL32.glClearColor(colorBg.getRed(), colorBg.getGreen(), colorBg.getBlue(), colorBg.getAlpha());
    GL32.glClear(GL32.GL_COLOR_BUFFER_BIT | GL32.GL_DEPTH_BUFFER_BIT);
    imGuiGlfw.newFrame();
    ImGui.newFrame();
    ImGui.pushFont(defaultFont);
}

private void endFrame() {
	ImGui.popFont();
	ImGui.render();
    imGuiGl3.renderDrawData(ImGui.getDrawData());

    if (ImGui.getIO().hasConfigFlags(ImGuiConfigFlags.ViewportsEnable)) {
        final long backupWindowPtr = GLFW.glfwGetCurrentContext();
        ImGui.updatePlatformWindows();
        ImGui.renderPlatformWindowsDefault();
        GLFW.glfwMakeContextCurrent(backupWindowPtr);
    }
    
    glfwPollEvents();
	glfwSwapBuffers(windowHandle);
}

private void drawWindow() {
	if(ImGui.begin("Window")) {
		if(ImGui.button("hello")) {
			
		}
		ImGui.end();
	}
}


/*
 * CONSTRUCTOR
 */
public Main() {
	
}

}
`