Mouse and Keyboard

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Mouse and Keyboard
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THE MOUSE

• A pointing device with one or more buttons.
• When the user moves the physical mouse, Windows
  moves a small bitmapped image (the mouse cursor)
  on the display
• One pixel in the cursor is the "hot spot" it
  points to a precise location on the display
• The hot spot position is constantly updated by
  low-level logic inside Windows
• Mouse actions by the user
•   Moving
•   Clicking (press/release)
•   Double Clicking
•   Dragging (moving while holding down a button).

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Mouse messages

• Client area messages
• mouse message generated whenever the mouse passes
  over the window or is clicked within the window
• 21 messages in all
• E.g. WM_MOUSEMOVE , WM_LBUTTONUP
• Non-client area messages

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WM_MOUSEMOVE Message

• sent to the program whose window is under the
  cursor  each time the mouse moves
• HIWORD(lParam) Y position in the client area
  using "client area coordinates"     (pixels)
  relative to the upper lefthand corner of the
  client area.
• LOWORD(lParam) X position.
• wParam indicates if a mouse button, Shift key, or
  control key was pressed as the message was
  sent--Mouse Notification codes (MK_LBUTTON,
  MK_RBUTTON,     MK_SHIFT, MK_CONTROL,
  MK_MBUTTON).

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WM_BUTTON

• L, M, R
• DOWN, UP, DBLCLK
• (The DBLCLK message is sent only if the
  wndclass.style contains CS_DBLCLKS when the
   class is registered)

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INPUT FOCUS

• If more than one instance of a program is
  running, only one will have a highlighted top
  caption line
• That program's window is said to have  the "input
  focus
• This is the only window that will receive any
  keyboard input
• not significant for mouse input because we
  normally use the mouse to pick an active window

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Gaining/Losing the input focus

• When a window gains (loses) the input focus,
  Windows sends a WM_SETFOCUS (WM_KILLFOCUS)
  message to the window
• Common responses are to highlight an edit area or
  change a caption.
• to explicitly give a window or window control the
  input focus we can use
• SetFocus(hwnd)

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Reaction to receiving focus

• caption-barred windows have their caption bars
  highlighted
• edit controls start showing a blinking caret at
  the point of keyboard input
• button controls show a highlighted outline
• list boxes show a highlighted selection item
• combo boxes display their list box or highlight
  it (if it's displayed).

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NONCLIENT MOUSE MESSAGES

• Outside client area WM_NC messages are sent
  (MOUSEMOVE, etc.)
• lParam contains the mouse position, but in screen
  coordinates
• wParam indicates the non-client area where the
  mouse action occurred
• Usually our programs don't process nonclient
  mouse messages

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Capturing the mouse

• limiting the mouse to interact with just one
  program
• An application that does this has "captured" the
  mouse
• Only this application will receive mouse messages
  
• To do this SetCapture(hWnd)
• To release it ReleaseCapture(void)

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The keyboard

• The keyboard provides the primary means of
  entering text and numbers
• Keypresses can also be used as shortcuts for
  mouse actions (accelerators)
• Character sets
• 7-bit ASCII, for letters, numbers and some common
  keyboard symbols
• IBM-PC, additional graphic/special symbols
• ANSI, Less graphics, more accented/international
  symbols
• UNICODE, a uniform 16-bit code which allows the
  representation of every character in every
  written language of the world

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ASCII code
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ANSI code
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Compatibility

• the standard C compiler library functions
  (ischar(), toupper(), tolower()) assume ASCII
  characters and ignore accented characters
• if we use these, our programs will not work right
  in many foreign languages
• Windows provides its own functions for
  using/converting characters
• To deal correctly with accented characters
• They are part of Windows, not part of our program

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Windows functions
AnsiLower()          Convert char string to
lowercase AnsiLowerBuff()       Same, doesn't
have to be null terminated AnsiNext()          
Move to next char in a string AnsiPrev()          
  Move to previous char in a string AnsiToOem()  
     Convert a char string from ANSI to OEM
AnsiToOemBuff()  Same, doesn't have to be null
terminated AnsiUpper()           Convert char
string to uppercase AnsiUpperBuff()      
Same,... IsCharAlpha()         Determine if an
ANSI char is an alphabetic char
IsCharAlphaNumeric()  Determine if an ANSI char
is alphabetic/numeric IsCharLower()       
Determine if an ANSI char is lowercase
IsCharUpper()         Determine if an ANSI char
is uppercase OemToAnsi()           Convert a
char string from OEM to ANSI OemToAnsiBuff()  Same
,... ToAscii()             Convert from virtual
key/scan code data to ANSI
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UNICODE

• 7/8 bit character codes are unsatisfactory for
  many foreign languages
• Unicode is a character coding that uses a uniform
  16-bit code for each character
• No support in Windows 3.xx, rudimentary support
  in Windows 95 , complete support in Windows NT
• In C/C, wide character type, wchar_t is used
  for unicode

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Keyboard message processing

• The Keyboard driver's SETUP copies the selected
  country's keyboard driver into the
  \windows\system\KEYBOARD.DRV file
• Windows starts gt KEYBOARD.DRV enabled, and this
  responds by saving and updating the keyboard INT
  9 vector
• From then on KEYBOARD.DRV intercepts INT 9 (key
  press/release) from the keyboard

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Keyboard message processing (contd)

• KEYBOARD.DRV decodes the key and calls a Windows
  routine that stores it as a queued message in
  system queue
• Windows transfers the message to the correct
  application's queue
• Our program gets the message from the
  GetMessage() loop.         This is polling--like
  DOS INT 21h, Service 01 or BIOS INT 16h).        
  It's not asynchronous gt our program is never
  interrupted.         This gives all the benefits,
  but none of the headaches of INT 9!!

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Keyboard message processing (contd)

• User presses a key gt Windows sends a WM_KEYDOWN
  message to the window with the input focus
• Key released gt WM_KEYUP message
• wParam contains device-independent "virtual key
  code" for the key pressed/released
• Most keys have VK codes ANSI code
• Others have names like VK_F1, VK_TAB
• A program can use VK codes to figure out what the
  user is doing with keys

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Key down/up messages

• put data into the lParam
• bit-31  1gtkey being pressed 0gtkey being
  released.
• bit-30  1gtkey was down before message was sent
  0gtnot down
• bit-29  1gtltALTgt was held down when key was
  pressed 0gtnot down
• 25-28   Reserved
• bit-24  1gtextended key flag (e.g., function
  key or numeric keypad key)
• 16-23   Keyboard OEM scan code (the value in AH
  after INT 16h returns)
• 0-15    Repeat count ( of times char was
  repeated because held down key).

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TranslateMessage()

• converts the current combination of letter and
  shift keys to an equivalent ANSI code
• TranslateMessage() detects a keyboard action that
  translates to an ANSI character, it generates a
  WM_CHAR message
• The wParam will have the ANSI code
• Function keys and keys that don't have ANSI codes
  don't generate WM_CHAR messages

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TranslateMessage() (contd)

• assuming the event loop has a TranslateMessage()),
  the sequence of messages sent is
• WM_KEYDOWN,  key pressed
• WM_CHAR,    ANSI char provided if there is one
• WM_KEYUP     key released

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System key messages

• when no window has the input focus , or for the
  ltALTgt key the message sequence is different
• WM_SYSKEYDOWN -- a key was depressed
• WM_SYSCHAR   --  ANSI character (if there was
  one).
• WM_SYSKEYUP  --  Key released.
• ltALTgt keystroke indicates some special function.
  Usually we use   WM_SYSKEYDOWN to determine which
  VK key was depressed
• lParam and wParam are used the same as before

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FONT

• There are three basic kinds of fonts
• Stock fonts--built into Windows, always available
• Logical or GDI fonts
• Stroke fonts are continuously scalable , .fon
• Raster fonts are bitmaps, only integer scaling ,
  .fon
• TrueType fonts  are really rasterized stroke
  fonts .fot/.ttf
• Device fonts--native to the output device (e.g.,
  built-in printer fonts).

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Stock fonts
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Stroke fonts
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Raster fonts
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TrueType fonts
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Using stock fonts

• HDC      hDC
• HFONT    hFont
• hDC GetDC(hWnd)
• hFont GetStockObject (ANSI_VAR_FONT)
• SelectObject (hDC,hFont)   / now can use it /

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Using Logical Fonts

• Called logical since they come from program logic
  not just from a file
• Use CreateFont() instead of GetStockObject() to
  load and get a font handle
• Font is loaded from a separate file .fon,
  .fot/.ttf
• hFont CreateFont(Ht, Width, Escapement,
  Orientation , Weight , Italic ,  Underline,
  StrikeOut , CharSet , OutputPrecision ,
  ClipPrecision , Quality , PitchAndFamily ,
  Facename)

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Escapement and orinetation
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Text metrics

• we may not know all of the dimensions of a font
  after it's created
• use GetTextMetrics() to find out font details

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Keyboard accelerators

• Provide an alternative to using the mouse to
  select menu items
• The simplest way of doing it is to precede the
  menu item's title string with  an '' in the
  resource script file
• MyMenu    MENU
• BEGIN
•     MENUITEM "Paint",    IDM_PAINT
•     MENUITEM "Clear",    IDM_CLEAR
•     ...
• END

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Keyboard accelerators(contd)

• But if there are popup menus , using ALT key is
  cumbersome
• A better shortcut would require only one key
  combination to execute the command
• We can do this by processing WM_KEYDOWN and
  WM_CHAR messages
• But Windows gives a much simpler alternative
• define the key combinations in an "accelerator
  table" in  the resource file
• Each defined key combination sends a WM_COMMAND
  message to the program.

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Keyboard acceleratorsExample

• MyAccel    ACCELERATORS
• BEGIN
• VK_F1 , IDM_ANSI , VIRTKEY   
  / F1 activates /
• VK_F2,   IDM_OEM,  VIRTKEY, CONTROL  /
  ltCtrlgtltF2gt activates /
• "A",    IDM_NOMENU,  VIRTKEY, ALT      /
  ltAltgtltAgt activates /
• "Z",      36,   SHIFT, CONTROL  /
  ltShiftgtltCtrlgtltZgt activates/
•                                     
  / LOWORD(wParam) 36 /

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Using accelerator tables

• Use LoadAccelerators() to load the table
• TranslateAccelerator()--translates
  WM_KEYUP/WM_KEYDOWN messages into    WM_COMMAND
  messages (if there is an entry in the
  application's    accelerator table). This must be
  placed in the WinMain()'s message loop