<*PRAGMA LL*>

UNSAFE INTERFACE TrestleOnX;

IMPORT Trestle, X, TrestleComm, VBT;

TYPE Display <: Trestle.T;

PROCEDURE Dpy (t: Display): X.DisplayStar;

You must use Enter and Exit (see below) around any calls which manipulate the dpy. If Enter raises an exception, you must not call any X procedures using that dpy. Any X procedure can raise the TrestleComm.Failure exception; once that happens, you must not call any X procedures.

PROCEDURE Drawable (v: VBT.T): X.Drawable; <* LL.sup = VBT.mu *>

Return the window id associated with a VBT (or X.None)

PROCEDURE Cage (v: VBT.T): X.Window; <* LL.sup = VBT.mu *>

Return the window id of the cage window for a VBT (or X.None)

<*INLINE*> PROCEDURE Enter (t: Display) RAISES {TrestleComm.Failure};

Lock t. The exception is raised when the X connection is closed.

<*INLINE*> PROCEDURE Exit (t: Display; deltaCoverage: [-1 .. 1] := 0)
  RAISES {TrestleComm.Failure};

Release the lock on t, after possibly flushing the queue of pending operations.

Each t: T contains a cardinal t.coverage, which is incremented by deltaCoverage as the Exit happens. If the result is zero, the x connection is flushed. A thread making a sequence of calls to Enter/Exit can minimize unnecessary flushing by setting deltaCoverage to +1 on the first exit, to -1 on the last exit, and to 0 on the other exits.

LL = t.

TYPE EventProc = PROCEDURE (t: Display; READONLY ev: X.XEvent);

PROCEDURE EventHook (t: Display; p: EventProc): EventProc; <* LL.sup = t *>

This procedure will be called with all events received on the connection t which Trestle doesn't want to handle. This means all events received on windows not created by Trestle, or root windows, and certain events received on Trestle windows. The old EventHook is returned; if non-NIL, you should pass on any events that you can't handle.

VAR Visibility: VBT.MiscCodeType;

CONST
  VisibilityUnobscured        = 0;
  VisibilityPartiallyObscured = 1;
  VisibilityFullyObscured     = 2;

END TrestleOnX.