Randr's GetScreenInfo broken.

[snyh]

It seems an xserver bug.

Although only tested under xgb and xpyb, but xserver didn't send the rates field of GetScreenInfoReply.

This will cause panic.

I have report it to https://bugs.freedesktop.org/show_bug.cgi?id=73180

[tv42]

I'm seeing something similar with an out of bounds slice access in randr.RefreshRatesRead. This diff hides the problem for me:

diff --git i/randr/randr.go w/randr/randr.go
index 20dc62a..d0e35ac 100644
--- i/randr/randr.go
+++ w/randr/randr.go
@@ -1299,6 +1299,9 @@ type RefreshRates struct {

 // RefreshRatesRead reads a byte slice into a RefreshRates value.
 func RefreshRatesRead(buf []byte, v *RefreshRates) int {
+       if len(buf) == 0 {
+               return 0
+       }
        b := 0

        v.NRates = xgb.Get16(buf[b:])