Updated overview
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@25082 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
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Robin Dunn
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@ -969,8 +969,100 @@ def runTest(frame, nb, log):
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#----------------------------------------------------------------------------
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overview = """\
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<html>
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<body>
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<h1>wx.Joystick</h1>
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This demo illustrates the use of the wx.Joystick class, which is an interface to
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one or more joysticks attached to your system.
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<p>The data that can be retrieved from the joystick comes in four basic flavors.
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All of these are illustrated in the demo. In fact, this demo illustrates everything
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you <b>can</b> get from the wx.Joystick control.
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<ul>
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<li>Static information such as Manufacturer ID and model name,
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<li>Analog input from up to six axes, including X and Y for the actual stick,
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<li>Button input from the fire button and any other buttons that the stick has,
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<li>and the POV control (a kind of mini-joystick on top of the joystick) that many sticks come with.
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</ul>
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<p>Getting data from the joystick can be event-driven thanks to four event types associated
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with wx.JoystickEvent, or the joystick can be polled programatically to get data on
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a regular basis.
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<h2>Data types</h2>
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Data from the joystick comes in two flavors: that which defines the boundaries, and that
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which defines the current state of the stick. Thus, we have Get*Max() and Get*Min()
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methods for all axes, the max number of axes, the max number of buttons, and so on. In
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general, this data can be read once and stored to speed computation up.
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<h3>Analog Input</h3>
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Analog input (the axes) is delivered as a whole, positive number. If you need to know
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if the axis is at zero (centered) or not, you will first have to calculate that center
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based on the max and min values. The demo shows a bar graph for each axis expressed
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in native numerical format, plus a 'centered' X-Y axis compas showing the relationship
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of that input to the calculcated stick position.
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Analog input may be jumpy and spurious, so the control has a means of 'smoothing' the
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analog data by setting a movement threshold. This demo sets the threshold to 10, but
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you can set it at any valid value between the min and max.
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<h3>Button Input</h3>
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Button state is retrieved as one int that contains each button state mapped to a bit.
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You get the state of a button by AND-ing its bit against the returned value, in the form
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<pre>
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# assume buttonState is what the stick returned, and buttonBit
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# is the bit you want to examine
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if (buttonState & ( 1 << buttonBit )) :
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# button pressed, do something with it
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</pre>
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<p>The problem here is that some OSs return a 32-bit value for up to 32 buttons
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(imagine <i>that</i> stick!). Python V2.3 will generate an exception for bit
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values over 30. For that reason, this demo is limited to 16 buttons.
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<p>Note that more than one button can be pressed at a time, so be sure to check all of them!
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<h3>POV Input</h3>
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POV hats come in two flavors: four-way, and continuous. four-way POVs are restricted to
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the cardinal points of the compass; continuous, or CTS POV hats can deliver input in
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.01 degree increments, theoreticaly. The data is returned as a whole number; the last
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two digits are to the right of the decimal point, so in order to use this information,
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you need to divide by 100 right off the bat.
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<p>Different methods are provided to retrieve the POV data for a CTS hat
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versus a four-way hat.
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<h2>Caveats</h2>
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The wx.Joystick control is in many ways incomplete at the C++ library level, but it is
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not insurmountable. In short, while the joystick interface <i>can</i> be event-driven,
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the wx.JoystickEvent class lacks event binders for all event types. Thus, you cannot
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rely on wx.JoystickEvents to tell you when something has changed, necessarilly.
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<ul>
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<li>There are no events associated with the POV control.
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<li>There are no events associated with the Rudder
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<li>There are no events associated with the U and V axes.
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</ul>
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<p>Fortunately, there is an easy workaround. In the top level frame, create a wx.Timer
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that will poll the stick at a set interval. Of course, if you do this, you might as
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well forgo catching wxEVT_JOYSTICK_* events at all and rely on the timer to do the
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polling.
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<p>Ideally, the timer should be a one-shot; after it fires, collect and process data as
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needed, then re-start the timer, possibly using wx.CallAfter().
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</body>
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</html>
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"""
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#----------------------------------------------------------------------------
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