Mars Data Analysis Using IDL GG7101 Lecture 13

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Mars Data Analysis Using IDLGG710-1Lecture 13

• F. Scott Anderson
• Office POST 526B
• Phone [phone]
• Email anderson_at_higp.hawaii.edu

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Review of 11/17/04

• Homework Review
• FFT's
• Frequencies that go with FFT's
• Power Spectra

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Today

• Quiz Review Quiz
• GUIs
• Event Loop Concept
• Widgets (bases, buttons, drawing)
• Widget IDs
• Event Structures
• Controlling widgets
• Checking Events in the Event Loop
• Storing data about widgets
• Destroying widgets
• In class exercise
• Class Evaluation

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Questions from 11/17/04

• Comments, Questions, Thoughts?

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Quiz 8/9/10 HW4,4a Scores
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Quiz 11
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Quiz Answers
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Quiz Answers
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What is a GUI?

• GUIGraphical User Interface
• A windowed interface to your program
• Download example and data from website
• xdisp.pro
• Mars Topo Grav
• Try it
• Disclaimer It is not claimed that this program
  represents good GUI programming style!

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GUI versus Procedural Programs

• All codes we have written are procedural
• Read data, process, plot/write data
• GUI programs driven by user interaction

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GUI Design

• Think out design ahead of time
• Minimize total number of onscreen controls
• Avoid excessive dead space
• Align controls
• Avoid under/over sized controls
• Avoid non-standard names for controls
• Think out design ahead of time!

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Elements of a GUI Widgets

• GUI's are made out of components called widgets

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Widget Hierarchy

• All widgets are hierarchically contained in bases
• The top level base can have sub-bases
• A sub-widget is known as a child
• A widget containing a child widget is called the
  parent

Top Level Base Widget
Child Base Widget
Button Widget
Button Widget
Child Base Widget
Draw Widget
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Making a widget base

• Widget bases can hold widgets in rows or in
  columns
• Top level widget bases can have menubars and a
  title at the top of the window
• To make a top-level widget base
• ID widget_base(titlestr, /row)
• ID widget_base(titlestr, /col)
• To make a child-base
• ID widget_base(ID_parent, /row)
• ID widget_base(ID_parent, /col)

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Example Widget buttons

• Widget buttons must be contained within a widget
  base
• The words shown on the button is set with a
  parameter called value
• To make a widget button
• ID widget_button(ID_parent_base, value str)

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Structure of Widget Program

• Create widget bases
• Fill with widgets
• Show widgets on-screen (realize widgets)
• Go to event-loop (manage widgets)
• Control widgets as necessary
• Resize, draw pictures, whatever
• Destroy widgets
• Achieved by destroying top-level widget
• Let's do an example of steps 1-3

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Show me a Widget! Steps 1-3

• Create widget base to contain button
• tp widget_base(/column)
• Create button in top-level widget
• but widget_button(tp, value'Rockin!')
• Show me the money!
• widget_control, tp, /realize
• Note you can click it, but nothing happens
• Can destroy it by closing

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Widget ID

• The value returned from a widget function allows
  you to manipulate that widget or widget hierarchy
  at a later time
• Must keep track of widget ID's you intend to
  manipulate later
• Can toss widget ID's that are never used again
• In previous example
• Toss "but" ID never reused
• Keep "tp" used to realize widget hierarchy

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widget_control

• In addition to realizing widgets, widget_control
  can be used to
• Get values from existing widgets
• Set values for existing widgets
• Check for events
• Destroy widgets and widget hierarchies
• Form
• widget_control, widget_ID, get_valuevar
• widget_control, widget_ID, set_valuevar
• widget_control, widget_ID, /destroy

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Widget Value/Uvalue

• All widgets contain a field called value
• Used to carry information controlling the use of
  the widget
• Button widgets use value to hold string that will
  be shown on the button (e.g. "Rockin!")
• Draw widgets use value to hold window ID for use
  with wset
• All widgets also have a user definable field to
  carry information
• This field can be a variable of any type
  typically struct
• Can be accessed with
• widget_control, widget_ID, set_uvaluevar
• widget_control, widget_ID, get_uvaluevar

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The Event Loop Step 4

• The event loop is a subroutine to the main
  routine
• The main routine draws widgets and destroys
  widgets on exiting the the event loop
• All real action takes place in the event loop
• IDL automatically checks for user interaction
  (events) and sends a structure of event data to a
  routine identified as the event loop
• To identify the sub-routine to be used as the
  event loop, use the xmanager procedure
• Has a default name of a string handed to xmanager
  "_event"

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The Event Loop Step 4

• All event structures include the ID of the widget
  involved in the event, and the top-level widget
• For example, if the event structure variable is
  called ev
• Why hand it the top ID or widget ID? Because
  many GUI programs can run simultaneously, so you
  may want to check the ID to see which GUI/widget
  is generating the event
• Lets try implementing step 4 and manage an event
  loop

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Expanding our Example

• pro widex_event, evt
• widget_control, evt.id, get_valueres
• if (res eq 'Rockin!') then
• print, "Someone touched the button!"
• end
• pro widex
• top widget_base(/column)
• but widget_button(top, value'Rockin!')
• widget_control, top, /realize
• xmanager, 'widex', top
• end

Event Loop
widex.pro
Main Routine
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Storing Widget Information

• If we want to modify a widget in the event loop,
  we must know it's ID
• However, all ID's defined in the main routine,
  and in our example, have not been handed to our
  event loop sub-routine
• Typically, ID's from all widgets that will be
  modified are placed in a structure that is kept
  in the top-level base user value field (uvalue)
• Other information relevant to the program can
  also be kept in this structure
• Commonly used variables, etc.
• Example Change the previous example so that when
  clicked, "Rockin!" changes to "Doh!" and back on
  2nd click

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Rockin! 2 Doh!

• pro widex_event, evt
• widget_control, evt.id, get_valueres
• widget_control, evt.top, get_uvalueuvl
• if (res eq 'Rockin!') then
• widget_control, uvl.but_id, set_value"Doh!"
• else if (res eq 'Doh!') then
• widget_control, uvl.but_id, set_value"Rockin!"
• end
• pro widex
• top widget_base(/column)
• but widget_button(top, value'Rockin!')
• widget_control, top, set_uvaluebut_idbut,
  var0
• widget_control, top, /realize
• xmanager, 'widex', top
• end

Event Loop
widex.pro
Main Routine
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Step 5 Destroying Widgets

• IDL will repeat the event loop ad infinitum until
• The widget is destroyed using widget_control
• The widget is destroyed by closing the window
• When a widget is destroyed, program flow is
  resumed following xmanager
• Now lets change our example so that
• When we click once Rockin changes to Doh
• On the second click, the widget is destroyed, and
  the program ends

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Destroy a Widget Ha ha ha ha!

• pro widex_event, evt
• widget_control, evt.id, get_valueres
• widget_control, evt.top, get_uvalueuvl
• if (res eq 'Rockin!') then
• widget_control, uvl.but_id, set_value"Doh!"
• else if (res eq 'Doh!') then
• widget_control, evt.top, /destroy
• end
• pro widex
• top widget_base(/column)
• but widget_button(top, value'Rockin!')
• widget_control, top, set_uvaluebut_idbut,
  var0
• widget_control, top, /realize
• xmanager, 'widex', top
• end

Event Loop
widex.pro
Main Routine
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Draw Widgets

• Draw widgets are used to hold plots and images,
  and is like the window command
• The value of a draw widget is it's window ID
• Draw widgets can have a window size a total
  image size
• If the image size gt window size, then scroll bars
  are added
• Form
• IDwidget_draw(ID_parent, xsizex1, ysizey1,
• x_scroll_sizex2, y_scroll_sizey2)

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Draw Widgets

• Example with scroll bars
• IDwidget_draw(ID_parent, xsize500, ysize500,
  
• x_scroll_size400, y_scroll_size400)
• Note On some computers, parts of the image that
  are not currently displayed are lost.
• Fix device, retain2
• You can resize the plottable area of a draw
  widget using widget_control
• widget_control, ID, draw_xsizex1a, draw_ysizey1a

x2
y2
y1a
x1a
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In Class Exercise

• Make a GUI to display a jpeg image
• Have file "Open" "Quit" buttons
• Make the image no display area 400x400
• Assume an initial blank image of 500x500
• Read an image when "Open" is clicked
• Use scroll bars
• Resize the draw widget size to match the image
  size
• Leave the scroll bars so no more than 400x400
  area shown
• Demonstrate on jpeg from website

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In Class Exercise

• Start by making an outline of steps!

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End of Class Wahoo! Wahoo!

• In two weeks
• Class presentations
• Science, IDL Code, Results
• 15 minutes, 5 for questions (20 total)
• In closing
• It has been a blast working with all of you!
• Think about all we have covered
• Variables, procedures, graphics, math, GUIs!
• Am very pleased with everyone's progress
• For me class will be even better next time!
• More HW, more exercises, some reorganization

You have the power of IDL! Use it for good - not
evil!