[SOLVED] LWJGL 3 - glfwCreateCursor returning null

Newbie & Debugging Questions
#1

I’m trying to create a custom cursor for my window. However, I constantly run into a problem, which is that glfwCreateCursor returns NULL. My code looks like this:


ByteBuffer buffer = FileUtils.imageToByteBuffer(ImageIO.read(new File("../res/cursor.png")));
GLFWImage cursorimg = new GLFWImage(buffer);
long cursorID = glfwCreateCursor(cursorimg, 0, 0);

Mouse.setCursor(cursorID)

Here’s the custom method for the image-to-buffer conversion, BTW:


public static ByteBuffer imageToByteBuffer(BufferedImage image)
{
	int[] pixels = new int[image.getWidth() * image.getHeight()];
	image.getRGB(0, 0, image.getWidth(), image.getHeight(), pixels, 0, image.getWidth());

	ByteBuffer buffer = BufferUtils.createByteBuffer(image.getWidth() * image.getHeight() * 4);

	for (int y = 0; y < image.getHeight(); y++)
	{
		for (int x = 0; x < image.getWidth(); x++)
		{
			int pixel = pixels[y * image.getWidth() + x];
			buffer.put((byte) ((pixel >> 16)    & 0xFF));
			buffer.put((byte) ((pixel >> 8)     & 0xFF));
			buffer.put((byte) ((pixel)          & 0xFF));
			buffer.put((byte) ((pixel >> 24)    & 0xFF));
		}
	}

	buffer.flip();

	return buffer;
}

And here’s the one for setting the cursor itself:


public static void setCursor(long cursor)
{
	if (currCursor != 0) glfwDestroyCursor(currCursor);
	glfwSetCursor(Window.id(), currCursor = cursor);
}

I ran it through my debugger, and the cursor.png image loads correctly, the error happens either when I put the data in the buffer, when I create the GLFWImage, or when I create the cursor object itself.

Anyone know what could be causing this issue?

I’m using LWJGL 3 build #79 on Ubuntu 14.04, by the way.

#2

In the constructor GLFWImage(ByteBuffer) the ByteBuffer argument is not meant to be the image. It is meant to be the native memory of the whole GLFWImage structure. Instead, use the no-args constructor and use GLFWImage.pixels() as well as .width() and .height() to specify the image data.

#3

Oh, wow, that seems a bit unnecessary. But it works. Thanks!

#4

Well, LWJGL 3 provides bindings for the native libraries, and in this case the respective native structures of GLFW in C code. Actually that is very nice, because you simply have to look at an example of the native library in C and can directly map that to LWJGL 3 then.

#5

Yep, know that, it really feels like LWJGL wants to stay as close to native code as possible.

But this is a little issue with that, since the buffer is used as a pointer and, well, the struct itself, which could easily confuse others (like me). I dunno, maybe there’s a specific reason why it had to be done like this, it just seems a little bit all-around-the-place to me. I don’t know C, so I don’t know if it has to be done this way there, too.