Copyright (C) 1994, Digital Equipment Corp.
Digital Internal Use Only
Created on Mon Jan 16 10:06:59 PST 1995 by najork
INTERFACEA Child object serves as the mediator between a top-level VBT.T and a Trestle.T. CallingWinTrestle ; IMPORT ProperSplit, Trestle, TrestleClass, TrestleComm, VBT, WinDef; TYPE T <: Trestle.T; REVEAL TrestleClass.RootVBT <: ProperSplit.T;
trsl.beChild(v) creates a Child object which
contains Windows-specific data for the top-level VBT.T (such as its
window handle). The Child object is stored in v.upRef.
TYPE
Child <: PubChild;
PubChild = ProperSplit.Child OBJECT (* created by WinTrestle.BeChild *)
hwnd: WinDef.HWND; (* The window handle *)
hdc: WinDef.HDC; (* The device context *)
hpal: WinDef.HPALETTE; (* The palette handle or NIL *)
offScreen: BOOLEAN; (* TRUE for an off-screen window *)
sh, sv: VBT.SizeRange; (* horizontal and vertical
min/pref/max window sizes *)
trsl: T; (* The Trestle on which the window is
installed *)
END;
PROCEDURE Init();
PROCEDURE Enter (trsl: T) RAISES {TrestleComm.Failure};
Lock t. The exception is raised when t.dead is true.
I'm not sure if that can actually ever happen.
PROCEDURE Exit (trsl: T; deltaCoverage: [-1 .. 1] := 0)
RAISES {TrestleComm.Failure};
Release the lock on t, after possibly flushing the GDI batch.
If t.dead is true, TrestleComm.Failure is raised.
Each Trestle.T t contains a cardinal t.coverage, which is incremented by
deltaCoverage as the Exit happens. If the result is zero, the GDI
batch 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.
END WinTrestle.