C
C===========================================================================
C
C	Graphics driver for the GRINNELL GMR 37-30 color display
C
C	9.0" x 7.0"		(512 x 512)
C
C===========================================================================
C
	JDEV = JDEV - 1
	IF (JDEV .NE. 0) GOTO 3999
C
	IF ((IMODE .LT. -5) .OR. (IMODE .GT. 6)) RETURN
	GOTO (3000,3001,3005,90,90,3010,3020,3030,90,3040,3050,3060),
	1					IMODE+6
C
C	mode -5: we exist
C
3000	X = 1.0
	GOTO 90
C
C	mode -4: initialize
C
3001	CALL GTATT(LUNGRP)		! attach the device
	CALL GTGRIN("120000)		! select the only device
	CALL GTGRIN("100001)		! load display channel 1
	CALL GTGRIN("010017)		! load subchannel mask (all colors)
	CALL GTGRIN("026012)		! load update mode
	CALL GTGRIN("024060)		! load write mode
	CALL GTGRIN("010007)		! set the default color to white
	CALL GTF			! and send this stuff out
	GOTO 90
C
C	mode -3: return screen size
C
3005	X = 9.0
	Y = 7.0
	GOTO 90
C
C	mode 0: clear screen
C
3010	CALL GTGRIN("030000)		! erase selected subchannels
	CALL GTF
	GOTO 90
C
C	mode 1: unwritten vector
C
3020	IX = MIN1(511.,AMAX1(0.,56.88888*XT+0.5))
	IY = MIN1(511.,AMAX1(0.,73.14286*YT+0.5))
	CALL GTGRIN(IX .OR. "044000)
	CALL GTGRIN(IY .OR. "064000)
	GOTO 90
C
C	mode 2: written vector
C
3030	IX = MIN1(511.,AMAX1(0.,56.88888*XT+0.5))
	IX = IX - MIN1(511.,AMAX1(0.,56.88888*XTLAST+0.5))
	IY = MIN1(511.,AMAX1(0.,73.14286*YT+0.5))
	IY = IY - MIN1(511.,AMAX1(0.,73.14286*YTLAST+0.5))
	CALL GTGRIN((IX .AND. "777) .OR. "050000)
	CALL GTGRIN((IY .AND. "777) .OR. "072000)
	GOTO 90
C
C	mode 4: complete the plot
C
3040	CALL GTF			! flush the buffer
	CALL GTATT(-LUNGRP)		! deattach the device
	CALL CLOSE(LUNGRP)
	GOTO 90
C
C	mode 5: nibs (X; color) and line pattern (Y; ignored)
C
3050	NIBS = X
	IX = (NIBS/256) .AND. "17
	IF (IX .LE. 0) IX = 7		! color 0 ==> white
	CALL GTGRIN(IX .OR. "010000)
	LINPAT = Y
	GOTO 90
C
C	mode 6: identify ourself
C
3060	WRITE (LUN,3070)
3070	FORMAT('+	Grinnell GMR-37 Color Graphics display')
C
C	link to the next device
C
3999	CONTINUE