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1 files changed, 45 insertions, 0 deletions

diff --git a/sys/gio/cursor/gtrdelete.x b/sys/gio/cursor/gtrdelete.x
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+++ b/sys/gio/cursor/gtrdelete.x
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+# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
+
+include	<gio.h>
+include	<gki.h>
+include	"gtr.h"
+
+# GTR_DELETE -- Delete an instruction from the frame buffer.  This prevents
+# the instruction from being executed if the frame is redrawn.
+
+procedure gtr_delete (tr, gki)
+
+pointer	tr			#I giotr descriptor
+pointer	gki			#I instruction to be deleted
+
+pointer	inext
+int	nwords, shift, ilen
+
+begin
+	ilen = Mems[gki+GKI_HDR_LENGTH-1]
+	inext = gki + ilen
+
+	if (inext >= TR_OP(tr)) {
+	    # Instruction is the last one in the buffer.
+	    TR_OP(tr) = gki
+	    TR_LASTOP(tr) = TR_OP(tr)
+	    if (TR_IP(tr) >= gki)
+		TR_IP(tr) = gki
+
+	} else {
+	    # If the instruction is small and would be expensive to delete
+	    # just change the opcode to disable it, otherwise shift the
+	    # buffer contents back to overwrite the deleted instruction.
+
+	    nwords = TR_OP(tr) - inext
+	    if (ilen < 32 && nwords > 2048)
+		Mems[gki+GKI_HDR_OPCODE-1] = GKI_UNKNOWN
+	    else {
+		call amovs (Mems[inext], Mems[gki], nwords)
+		shift = inext - gki
+		TR_IP(tr) = TR_IP(tr) - shift
+		TR_OP(tr) = TR_OP(tr) - shift
+		TR_LASTOP(tr) = TR_OP(tr)
+	    }
+	}
+end