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Mouse • A pointin g devic e wit h on e o r mor e buttons

This guide explores the mouse as an essential input device, detailing its functions, events, and programming implementations within Windows. It covers fundamental mouse actions like clicking, dragging, and double-clicking, as well as mouse events and handler methods defined by the Control class. Additionally, it discusses using C# to create interactive sketching applications, storing mouse movement data using ArrayLists, and managing sketches in memory. Learn how to effectively handle mouse events, capture input, and integrate mouse functionality in your applications.

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Mouse • A pointin g devic e wit h on e o r mor e buttons

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  1. TheMouseandKeyboard Mouse •Apointingdevicewithoneormorebuttons •Importantinputdevice,butnotrequired •Usermovesphysicalmouse=> –Windowsmovesasmallbitmappedimage(mousecursor)ondisplaydevice –"Hotspot"pointstoapreciselocationondisplay –Hotspotpositionconstantlyupdatedbylow-levellogicinsideWindows

  2. MouseActions •ButtonDown,ButtonUp •Wheelmovement •Movingmouse •Clicking –Pressingandreleasingamousebutton •Dragging –Movingmousewhileabuttonispresseddown •DoubleClicking –Clickingabuttontwiceinsuccession –Mustoccurwithinasetperiodoftimeandwithmousecursorinapproximatelythesameplace •Form’sSystemInformationclasshastwopropertiesthatgivethisinformation: –intDoubleClickTime –SizeDoubleClickSize InformationaboutMouse •MoreofForm’sSystemInformationProperties: –boolMousePresent –intMouseButtons •Getsnumberofmousebuttononthemouse –boolMouseButtonsSwapped –boolMouseWheelPresent

  3. MouseEvents –The“Control”Classdefines9mouseeventsand9correspondingprotectedeventhandlermethods •FormclassisderivedfromControlclass –Onlyonecontrolorformreceivesmouseevents •TheonethathasitsEnabledandVisiblepropertiessettotrue •Ifmultiplecontrolsarestacked,theenabledvisiblecontrolontopreceivestheevent –AFormobjectreceivesmouseeventsonlywhenmouseisoveritsclientarea •Butmousecanbe“captured”byacontrol--soitcanreceivemouseeventswhenmouseisnotoverit SomeBasicMouseEventsand HandlerMethods •MouseDownOnMouseDown() •MouseUpOnMouseUp() •MouseMoveOnMouseMove() •MouseWheelOnMouseWheel() –Delegateforeachevent:MouseEventHandler –2ndargumentforeachhandler:MouseEventArgs •ClickOnClick() •DoubleClickOnDoubleClick() –Delegateforeachevent:EventHandler –2ndargumentforeachhandler:EventArgs

  4. MouseEventArgsProperty •Givesaccesstoread-onlypropertiesthat comewithmouseevents –intXHorizontalpositionofmouse –intYVerticalpositionofmouse –MouseButtonsButton •MouseButtonsenumerationpossibilities: –None,Left,Right,Middle »e.g.,MouseButtons.Left –Indicateswhichbuttonorbuttonsarecurrentlypressed –Eachbuttoncorrespondstoabitset •Exampleuse: –If(e.Button==MouseButtons.Left){//Dosomething} Click/DoubleClickEventArgs StaticProperties •Giveaccesstostatic,read-onlypropertiesthat comewithmouseClickandDoubleClickevents –PointMousePosition •Resultinscreencoordinates •Toconverttoclientareacoordinates,usePointToClient() –MouseButtonsMouseButtons •Returnswhichbuttonsarecurrentlypressed

  5. SketchingExampleProgram •Sketch-dotNet –Sketchingrevisited •UsingC#andthe.NETFrameworkClassLibrary •Butifwindowisexposed,thesketchdisappears •Twowaystoavoidthis: 1.SavethepointsineachsketchandredrawalllinesegmentsinresponsetoPaintevent 2.Drawthesketchonashadowbitmapthattheprogramdrawsonwhileit’sdrawingonthescreen –ThenredrawthebitmapinresponsetoPaintevent SavingtheSketchpoints –Point[]apts=newPoint[?????] •Buthowbig? •BettertouseaC#dynamic“ArrayList” –AclassdefinedinSystem.Collectionsnamespace •Alsohasdatastructuresclasseslike:Queue,Stack,SortedList,HashTable –TocreateanewArrayList: •ArrayListarrlst=newArrayList(); –Couldholdanydatatype(s) –Toaddelements,e.g.,aPointp: •arrlst.Add(p); •CanalsoInsert()andRemove()elements –Accessinganelement:useanindexerasforanordinaryarray •Pointp=(Point)arrlst[2]; •Notetypecast –NeededbecauseindexerreturnsanobjectoftypeObject –NumberofobjectsinanArraylist:arrlst.Count •Coulduseanarray:

  6. NewSketch-dotNetusinganArrayList •Asingleruncanhavemanysketches –Oneforeachtimeleftmousebuttongoesdown –SouseoneArrayListtostorethepointsforeachsketch •Whenfinished(whenmousebuttongoesup),converttoanarrayofPoints –UseasecondArrayListtostorethearrayofpointsforeachsketch(i.e.,an ArrayListofsketches) •MouseDownevent�startanewsketch'sArrayList •MouseMoveevent�drawlinesegmentandaddthepointtocurrentsketch'sArrayList •MouseUpevent�convertcurrentArrayListofpointstoanarrayofpoints&addittotheArrayListofsketches •Paintevent�useDrawLines(…)todrawallthelinesegmentsineachArrayList g.DrawLines(Penpen,Point[]a_pts);//a_ptsisanarrayofPoints •SeeSketch-dotNet-ArrayListexampleprogram –Herewe'rereallystoringthedrawinginaMetafileformat NewSketch-dotNetusingaShadow Bitmap •Storethewindowclientareaasashadowbitmap –Drawontheshadowbitmapandonthescreenwhenmousemoveswithitsleftbuttondown –DrawtheshadowbitmaponthethescreenwhenaPainteventoccurs –Notethatwiththistechniquealloftheinformationontheoriginalpointsislost •SeetheSketch-dotNet-Bitmapexampleprogram

  7. SomeOtherMouseEventsand EventHandlers •MouseEnterOnMouseEnter() –Mousecursorhasbeenmovedontoform'sclientarea •MouseLeaveOnMouseLeave() –Mousecursorisnolongerontopofclientarea •MouseHoverOnMouseHover() –Mousecursorhasenteredclientareaandhasstoppedmoving –OnlyhappensoncebetweenMouseEnterand MouseLeaveevents •Delegateforeach:EventHandler •Argumentforeach:EventArgs •SeeMouse-Enter-Leave-Hoverexampleprogram TheMouseCursor •Alittlebitmaponscreenthatindicatesthelocationofthemouse •Canchangeitsappearance •Encapsulatedinthe‘Cursor'classdefinedin System.Windows.Forms •Getamousecursorfromthe‘Cursors'class –Consistsof28staticread-onlypropertiesthatreturnpredefinedobjectsoftype‘Cursor',e.g.: •Arrow,Cross,Default,Hand,Help,Ibeam,WaitCursor,etc. •SomeStaticread/writePropertiesof‘Cursor'class: –CursorCurrent –PointPosition –Forexampletodisplaythehourglasscursorontheform: •Cursor.Current=Cursors.WaitCursor; •SomeStaticCursormethods: –Show();Hide(); •SeeMouseCursorsexampleprogram

  8. TheKeyboard •AsharedresourceinWindows –Allapplicationsreceiveinputfromsamekeyboard –Butanykeystrokehasasingledestination •Thedestinationisalwaysa‘Control'(e.g.aForm) –Objectthatreceivesakeyboardeventhasthe“inputfocus” –theactiveForm •Usuallythetopmostform •Ifformhasacaptionbar,itishighlighted –Form.ActiveFormstaticpropertyreturnstheactiveform –this.Activate()methodcanbeusedtomakethisformtheactiveform KeysandCharacters •Thinkofkeyboardintwoways: –Acollectionofdistinctphysicalkeys •Codegeneratedbyakeypressorreleaseidentifiesthekey –Ameansofgeneratingcharactercodes •Codegeneratedidentifiesacharacterinacharacterset –Traditionally8-bitASCIIcode –InWindows,extendedto16-bitUnicode –Keyboardcombinations(Shift,etc.)takenintoaccount

  9. TypesofKeys •Keyboarddividedintofourgeneralgroupsofkeys –Togglekeys:Pressingkeychangesstate •CapsLock,NumLock,ScrollLock,Insert –Modifierkeys:Pressingkeyaffectsinterpretationofotherkeys •Shift,Ctrl,Alt –Non-characterkeys:Notassociatedwithdisplayable characters;directaprogramtocarryoutcertainactions •Functionkeys,PgUp,PgDn,Home,End,Insert,Delete,Arrow keys –Characterkeys:Letters,numbers,symbolkeys,spacebar,Backspace,Tabkey •GenerateASCII/Unicodecodeswhenpressed KeyboardEvents&Data •KeyDown,KeyEventArgs –Whenanykeyispressed(WM_KEYDOWN) •KeyPress,KeyPressEventArgs –Whenacharacter-generatingkeyispressed(WM_CHAR) –OccursafteraKeyDownevent •KeyUp,KeyEventArgs –Whenanykeyisreleased(WM_KEYUP) •NoteKeyUp/KeyDownandKeyPresseventdataisdifferent –KeyUp/KeyDowneventsprovidelow-levelinformationaboutthekeystroke–whichkey –KeyPressprovidesthecharactercode •Keyboardcombinationstakencareof

  10. KeyDown/KeyUpEvents •KeyEventArgsProperties –KeyCodeIdentifieswhichkey –ModifiersIdentifiesshiftstates –KeyDataCombinesKeyCode&Modifiers •Keys:ahugeenumeration,someexamples: –Keys.A,Keys.Z,Keys.D0(zerokey),Keys.F1,Keys.Add, Keys.Home,Keys.Left,Keys.Back,Keys.Space,Keys.LShiftKey –SeeOnlineHelpon“Keysenumeration” –boolShiftTrueifShiftkeyispressed –boolAltTrueifAltkeyispressed –boolHandledSetbyeventhandler(initiallyfalse) –intKeyValueReturnsKeyDataasaninteger KeyPressEvent •Whenkey(s)pressedcorrespondtocharacter codes •KeyPressEventArgsProperties: –charKeyCharUnicode/ASCIIcharactercode –boolHandledSetbyhandler(initiallyfalse)

  11. TwoExamplePrograms •Key: –Assemblesincomingcharactersfromkeyboardintoastringthatisdisplayedontheform'sclientarea •HandlesBackspacekeybyremovinglastcharacterfromstring –HandlesKeyPressevent •KeyArrow: –Movesanimageontheform'sclientareainresponsetokeyboardLeft/Right/Up/Downarrowkeypresses –HandlesKeyDownevent

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