5.7.GRAPHICSMODULEREFERENCE 79
5.7 GraphicsModuleReference
Theexamplesinthischapterhave touchedonmostoftheelementsinthegraphicsmodule.Thissection
providesa completereferencetotheobjectsandfunctionsprovidedinthegraphicslibrary. Experienced
programmersusethesesortsofguidestolearnaboutnew libraries.Youwillprobablywanttoreferbackto
thissectionoftenwhenyouarewritingyourowngraphicalprograms.
5.7.1 GraphWinObjects
AGraphWinobjectrepresentsa window onthescreenwheregraphicalimagesmaybedrawn.A program
maydefineany numberofGraphWins. AGraphWinunderstandsthefollowingmethods.
GraphWin(title, width,height)Constructsa new graphicswindow fordrawingonthescreen.
Theparametersareoptional,thedefaulttitleis “GraphicsWindow,” andthedefaultsizeis 200x 200.
plot(x, y, color)Drawsthepixel at
xy inthewindow. Coloris optional,blackis thedefault.plotPixel(x, y, Color)Drawsthepixel at the“raw”position
xy ignoringany coordinatetrans-
formationssetupbysetCoords.setBackground(color)Setsthewindowbackgroundtothegivencolor. Theinitialbackgroundis
gray. Seesection5.7.5forinformationonspecifyingcolors.
close()Closestheon-screenwindow.
getMouse()Pausesfortheusertoclicka mouseinthewindow andreturnswherethemousewasclicked
asaPointobject.
setCoords(xll, yll,xur, yur)Setsthecoordinatesystemofthewindow. Thelowerleftcorner
is
xllyll andtheupperrightcorneris
xuryur. Allsubsequentdrawingwillbedonewithrespect
tothealteredcoordinatesystem(exceptforplotPixel).flush()Updatestheappearanceofthewindowtoreflectalldrawingoperationsthathave beendoneso
far. Innormaloperation,thewindowis onlyupdatedduring“idle”periods.Asequenceofdrawing
commandsmayendupappearingallat once.If youwanttogetananimationeffect,flushshouldbe
calledat appropriateplacesintheprogramtoperformdrawingoperationsincrementally.
5.7.2 GraphicsObjects
Themoduleprovidesthefollowingclassesofdrawableobjects:Point,Line,Circle,Oval,Rectangle,
Polygon, andText. Allobjectsareinitiallycreatedunfilledwitha blackoutline.Allgraphicsobjectssup-
portthefollowinggenericsetofmethods.
setFill(color)Setstheinterioroftheobjecttothegivencolor.
setOutline(color)Setstheoutlineoftheobjecttothegivencolor.
setWidth(pixels)Setsthewidthoftheoutlineoftheobjecttothismany pixels.
draw(aGraphWin)DrawstheobjectintothegivenGraphWin.
undraw()Undrawstheobjectfroma graphicswindow. Thisproducesanerrorif theobjectis notcurrently
drawn.
move(dx,dy)Movestheobjectdxunitsinthexdirectionanddyunitsintheydirection.If theobjectis
currentlydrawn,theimageis adjustedtothenew position.
clone()Returnsa duplicateoftheobject.Clonesarealwayscreatedinanundrawnstate.Otherthanthat,
they areidenticaltotheclonedobject.