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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
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