ppt title

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DirectInput 9.0 C. Shane Evans / Bernard
George Program ManagerDirectX Microsoft
Corporation
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Agenda

• Mission Usability
• New Features
• Improvements
• Whats Next?

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New Features

• Frame-based Input
• Keyboard Text
• New Device Enumeration Model
• New Device Object Enumeration Model
• Device Plug/Unplug Notifications
• Modern Device Support

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Frame-based Input

• Motivation
• State tracking of buttons and axes are common to
  the most games
• Games are inherently frame-based
• Why isnt DirectInput also frame-based?
• Advantages
• Application does not need to parse buffered data
• Objects current states are reported
• Developers wont complain (as much)!

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Frame-based Input

• Application can query DirectInput for events
  since the last frame
• Data reported in each frame is tailored to
  particular controls on a device
• Buttons
• Relative Axes
• Absolute Axes/POVs

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Frame-based InputButtons

• Four states to summarize the state of a button
• Inactive
• Active
• Still Active
• Changed/Still Active

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Frame-based InputRelative Axes

• Multiple axis events may occur between frames
• Actual input is lt 15 20 30 3 10 8 gt
• To smooth these axes events, DirectInput
  reports their average
• Application receives lt 15 25 3 9 gt

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Frame-based InputAbsolute Axes/POVs

• DirectInput simply reports the current position
  of absolute axes
• POVs are reported with the current single
  position (still as angle from N).
• Single report is given because thats what games
  use.

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Frame-based InputCommon Data

• The following detailed data is provided for all
  types of controls for each frame
• dwCurrent
• Current value of the control
• dwStart
• Value at beginning of frame
• dwMin
• Minimum value at during frame
• dwMax
• Maximum value at during frame

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Keyboard Text

• Motivation
• Constructing strings by treating keys as objects
  and retrieving DIPROP_KEYNAME can be cumbersome
• Declare a DIPROPSTRING variable
• Determine ID of key that is pressed
• Call IDirectInputDevice8GetProperty to recover
  the string
• Can be slow as well, since the a keys text is
  looked up on the fly

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Keyboard Text

• Application can enable new text input with
  IDirectInput9EnableKBText
• An internal lookup table for keys is created
• Key lookups are much faster
• Application must keep track of the state of the
  shift key
• Call IDirectInput9GetKeyText with the keys
  object ID and shift status to recover a keys
  text

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New Device Enumeration Model

• Motivation
• General shift toward pull model in DirectX
• Callback functions can be complicated
• Advantages
• Developer has more control
• Simpler!

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New Device Enumeration Model

• Application can call IDirectInput9GetDeviceCount
  to retrieve the number of devices on the system
• Flags can optionally be passed to indicate that
  only subset of available devices should be
  enumerated
• Each device is internally assigned an index
  between 0 and the number of pertinent devices 1
  inclusive

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New Device Enumeration Model

• Devices are now addressed by index
• IDirectInput9CheckDevice can test a devices
  capabilities
• Force feedback
• Action mapping

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New Device Enumeration Model

• As before, devices are created by calling
  CreateDevice method
• Accepts device index
• Sets a pointer to an IDirectInputDevice9
  interface
• Dont need to set co-op level!
• Otherwise IDirectInput9 can be used as you would
  expect

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New Device Object Enumeration Model

• Pull model as with device enumeration
• Application can call IDirectInputDevice9GetObjec
  tCount to retrieve the number of objects on a
  device
• Flags can optionally be passed to indicate that
  only subset of available objects should be
  enumerated
• Each object is internally assigned an index
  between 0 and the number of pertinent objects 1
  inclusive

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New Device Object Enumeration Model

• Each object can now be referenced by its index
• Calling IDirectInputDevice9GetObject retrieves
  a DIDEVICEOBJECTINSTANCE structure
• dwOfsNative member added to DIDEVICEOBJECTINSTANCE
  

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Plug/Unplug Notifications

• Applications can request to be notified when a
  device is plugged in or unplugged
• Call RegisterWindowMessage with
  DIRECTINPUT_NOTIFICATION_DEVICEPLUG message
  string (dinput.h)

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Plug/Unplug Notifications

• When a DIRECTINPUT_NOTIFICATION_DEVICEPLUG
  message is received
• wParam is the devices index
• lParam indicates the devices status
• 0 value means the device is now unplugged
• Nonzero means the device is now plugged in

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Plug/Unplug Notifications

• If a device is new to an application
• wParam is 0xFFFFFFFF
• lParam is nonzero (plugged)
• The device can be created by calling CreateDevice
  with the index previously returned by
  GetDeviceCount 1

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Modern Device Support

• Support for new controls on todays complex
  devices
• Proportional Buttons
• Independent Axis Sets

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Modern Device Support

• Proportional Buttons
• dwButtonData member added to DIDEVICEOBJECTDATA
  to represent degree to which button is pressed
• Can also behave like standard buttons
• If button pressed past threshold, it is active
• Threshold implemented in property
  DIPROP_BUTTONTHRESHOLD
• IDirectInputGet/SetButtonThreshold can
  manipulate threshold
• Default is 10 of range

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Modern Device Support

• Independent Axis Sets
• Mainly a hardware thing. Games should see better
  mappings from DirectInput.
• Simple way of organizing axes on a device
• Sets of axes are assigned ordinals
• Ordinals differentiate between multiple, say, X -
  axes

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Improvements

• Joystick Control Panel
• Default Cooperative Level
• Simpler Device Properties

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Joystick Control Panel

• Test page
• Device image added
• Historically confusing Apply button removed

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Joystick Control Panel

• Settings Page
• Racing Wheels pedal mode configuration for legacy
  games
• Historically confusing Apply button removed

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Joystick Control Panel

• Calibration
• Better use of space in calibration wizard
• Additional racing wheel-specific calibration
• New steering wheel position indicator
• Accelerator/Brake discovery and calibration

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Joystick Control Panel
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Joystick Control Panel
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Joystick Control Panel
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Default Cooperative Level

• Cooperative level need not be explicitly set
• Default cooperative level set during device
  creation
• Similar to DISCL_FOREGROUND DISCL_NONEXCLUSIVE
  with added benefits
• Works for Force Feedback devices

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Default Cooperative Level

• Devices do not need to be explicitly reacquired
• Use DISCL_FOCUSACQUIRE in IDirectInputDevice9
  SetCooperativeLevel
• Automatic acquisition when application gains
  focus
• Only valid with foreground cooperative levels

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Simpler Device Properties

• Separate methods to set each property rather than
  just IDirectInputDevice8Get/SetProperty
• MUCH simpler than before

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Simpler Device PropertiesDirectInput 8.0 Example

• For example, the following code is needed to set
  the range of the X-axis with DirectInput 8.0
• // DirectX 8.0 code for changing a
• // property
• DIPROPRANGE diprg
• ZeroMemory(diprg, sizeof(diprg))
• diprg.diph.dwObj DIJOFS_X
• diprg.lMin -1000
• diprg.lMax 1000
• err pDIDev-gtSetProperty(DIPROP_RANGE,
  diprg.diph)

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Simpler Device PropertiesDirectInput 9.0 Example

• The same task can now be done with the following
  code
• // Equivalent DirectX 9.0 code
• err pDIDev-gtSetAxisRange(AXIS_X, -1000,
  1000)

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Device Image Display Object

• SDK sample code that performs simple device image
  rendering tasks
• Very easy to incorporate device images into your
  game
• Exposes simple methods to perform common but
  often code-intensive tasks
• Display device
• Change view
• Show callout, display text
• Highlight callout

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DirectInput 9.0

• Questions?
• Contact ShaneE_at_microsoft.com