fix for overview panel

internal/hoststats/mem_windows.go

@@ -0,0 +1,50 @@
+//go:build windows
+
+package hoststats
+
+import (
+	"fmt"
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+)
+
+// x/sys/windows doesn't wrap GlobalMemoryStatusEx (unlike GetDiskFreeSpaceEx,
+// which diskFreeBytes uses directly), so it's called through kernel32.dll by
+// hand -- the same LazyDLL/NewProc pattern the x/sys/windows package itself
+// uses internally for the calls it does wrap.
+var (
+	modkernel32              = windows.NewLazySystemDLL("kernel32.dll")
+	procGlobalMemoryStatusEx = modkernel32.NewProc("GlobalMemoryStatusEx")
+)
+
+// memoryStatusEx mirrors the Win32 MEMORYSTATUSEX struct. Field order and
+// sizes must match exactly -- this is passed by pointer straight to the
+// syscall.
+type memoryStatusEx struct {
+	cbSize                  uint32
+	dwMemoryLoad            uint32
+	ullTotalPhys            uint64
+	ullAvailPhys            uint64
+	ullTotalPageFile        uint64
+	ullAvailPageFile        uint64
+	ullTotalVirtual         uint64
+	ullAvailVirtual         uint64
+	ullAvailExtendedVirtual uint64
+}
+
+// memStats reads host RAM usage via GlobalMemoryStatusEx.
+func memStats() (used, total int64, err error) {
+	var m memoryStatusEx
+	m.cbSize = uint32(unsafe.Sizeof(m))
+	r, _, callErr := procGlobalMemoryStatusEx.Call(uintptr(unsafe.Pointer(&m)))
+	if r == 0 {
+		return 0, 0, fmt.Errorf("hoststats: GlobalMemoryStatusEx: %w", callErr)
+	}
+	total = int64(m.ullTotalPhys)
+	used = total - int64(m.ullAvailPhys)
+	if used < 0 {
+		used = 0
+	}
+	return used, total, nil
+}