Gdx.graphics.getDensity() returns infinity inside VirtualBox

Issue details

Calling Gdx.graphics.getDensity() inside VirtualBox (Linux guest/host) returns Infinity (because display size reported by Lwjgl is 0). I understand that on some platforms the display density can not be computed, but I think there should be a special value UNKNOWN or an exception thrown to force client code to handle this case. I got an exception in the JNI code of FreeType (because I use density for font size scaling), and getDensity() doesn’t indicate it can return a completely invalid value.

It returns an estimate in any case, so if the value is too low / too high it can just default to 1 or something.

Version of LibGDX and/or relevant dependencies

GDX version 1.10.0 (latest at time of writing)

Please select the affected platforms

• Android
• iOS
• HTML/GWT
• Windows
• Linux
• MacOS

[ichernev]

@crykn I will report to GLFW. The setup is not too crazy – virtualbox + linux (Arch). In any case I’m glad you worked around it. There is always a chance that GLFW will return wrong data.

[tommyettinger]

@Timvisser1994 That won’t help with the original problem, which is a density of Infinity. Infinity wouldn’t be considered <= 0 and isNaN() returns false. NaN is an oddity, but looking at the OpenJDK source code gives a solution:

public float getDensity () {
	float ppiX = getPpiX();
	return (ppiX > 0 && ppiX <= Float.MAX_VALUE) ? ppiX / 160f : 1f;
}

The important thing here is that all valid finite floats are <= Float.MAX_VALUE (NaN is not, so it gets ruled out), and we only want positive and non-zero floats, so the check for > 0 also rules out negative infinity. The check against MAX_VALUE is used by isFinite() in Java 8. I changed getDensity() to single-return form because I think some JDKs can analyze that form a little easier, or at least it won’t be harder.

There’s still the issue that an invalid density is now indistinguishable from a common one, 1f. I think in the cases where we would get an invalid density, the display density doesn’t really matter as long as it doesn’t cause problems, so 1f is probably fine; users could check on their own if getPpiX() returns a value they can handle, also.