Potential Underflow Issue

[chrisgoldberg1]

I tried the following part of your code in a personal Wingrid tool. When _NET_FRAME_EXTENTS is 0, 0, 0, 0 and _GTK_FRAME_EXTENTS is 2, 2, 22, 10 (or similar values), the tool subtracts 2, 2, 22, 10 from 0, 0, 0, 0. However, since ext is a uint array, this results in underflow, producing values like [18446744073709551600, 18446744073709551600, 18446744073709551606, 18446744073709551584].

// Window extents (server/client decorations of the window)
extNet, _ := xprop.PropValNums(xprop.GetProperty(X, w, "_NET_FRAME_EXTENTS"))
extGtk, _ := xprop.PropValNums(xprop.GetProperty(X, w, "_GTK_FRAME_EXTENTS"))

ext := make([]uint, 4)
for i, e := range extNet {
	ext[i] += e
}
for i, e := range extGtk {
	ext[i] -= e
}

[leukipp]

I see, do you have any real world application where this happens? What should be the behavior then, negative margins or would it be enough to ensure the values never get negative?

[chrisgoldberg1]

I use Xfce, and there are many unusual return value situations and behaviors. This way does not always work reliably in obtaining the correct frame borders. I made some manual overrides based on the window class, such as for Telegram Desktop (correcting frameborders + window position).

Speaking about this part, I fixed it as follows:

func (a *ActiveWindow) GetExtents() {
	a.NetFrameExt, _ = xprop.PropValNums(xprop.GetProperty(Xutil, a.WindowID, "_NET_FRAME_EXTENTS"))
	a.GtkFrameExt, _ = xprop.PropValNums(xprop.GetProperty(Xutil, a.WindowID, "_GTK_FRAME_EXTENTS"))

	a.FrameBorders = make([]int, 4)
	for i, e := range a.NetFrameExt {
		a.FrameBorders[i] += int(e)
	}

	for i, e := range a.GtkFrameExt {
		if !a.IsGtkFrame && e > 0 {
			a.IsGtkFrame = true
		}

		a.FrameBorders[i] -= int(e)
	}
}