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Tk Widgets

Tk Widgets. This material is best on several sources Slides by Dr. Ernest J. Friedman-Hill various Tcl/Tk books. Building User Interfaces With Tk. You build interfaces with Widget commands buttons, labels, list boxes, text widgets, canvases, etc. often includes callbacks

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Tk Widgets

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  1. Tk Widgets This material is best on several sources Slides by Dr. Ernest J. Friedman-Hill various Tcl/Tk books

  2. Building User Interfaces With Tk • You build interfaces with • Widget commands • buttons, labels, list boxes, text widgets, canvases, etc. • often includes callbacks • Geometry management • widget layout tools • place, pack and grid • Bindings • bind user actions to widgets / objects to invoke commands • Window Manager commands • to control your window

  3. Widgets implemented by Tk Frame Menubutton Canvas Label Menu Scrollbar Button Message Scale Checkbutton Entry Listbox Radiobutton Text Toplevel Try the Widget Tour on the PCs to get an overview Start/Tcl/Widget Tour

  4. The Widget Hierarchy . .listbox .menu .scroll .menu.file .menu.help

  5. Creating Widgets • Each widget has a class: button, listbox, scrollbar, etc. • One class command for each class, used to create instances: button .b -text Quit -command exit scrollbar .x -orient horizontal class name configuration options window name

  6. Configuration Options • Defined by class. For buttons: -activebackground -disabledforeground -justify -underline -activeforeground -font -padx -width -anchor -foreground -pady -wraplength -background -height -relief-bitmap -highlightbackground -state-borderwidth -highlightcolor -takefocus-command -highlightthickness -text-cursor -image -textvariable • Default provided by class. button .b -text Hello -command exit button .c -bitmap @$tk_library/demos/images/flagdown.bmp grid .b .c • Advanced: may be specified in an options database

  7. Widget Commands • Tcl command for each widget, named after widget. • Used to reconfigure, manipulate widget: button .b -text "Hello".b configure -text Goodbye • Configurations are readable and modifiable, anytime • very powerful, as can change anything • Widget command is deleted when widget is destroyed. • destroy .b

  8. Widgets don't control their own positions and sizes: geometry managers do. Widgets don't even appear on the screen until managed by a geometry manager. Geometry manager = algorithm for arranging slave windows relative to a master window. Constraint-based systemi.e., what to do when widgets / windows change size Geometry Management Parameters from application designer Requested size from slave Geometry of master Geometry Manager Size and location of slave Requested size for master

  9. The Placer • Simple but not very powerful • Each slave placed individually relative to its master. • Avoid using it button .b -text X place .b -x 0 -y 0

  10. The Grid • Lays out objects in virtual grid of rows and columns • powerful, but good for most simple placements entry .e .e insert 0 "Type text here" button .b1 -text "Wow!" button .b2 -text "Ho Hum" grid .e -row 0 -column 0 -columnspan 2 -sticky ew grid .b1 -row 1 -column 0 grid .b2 -row 1 -column 1

  11. The Grid • Another example label .to_label -text "To:" entry .to label .from_label -text "From:" entry .from text .t -width 24 -height 10 grid .to_label -row 0 -column 0 -sticky e grid .to -row 0 -column 1 -sticky ew grid .from_label -row 1 -column 0 -sticky e grid .from -row 1 -column 1 -sticky ew grid .t -row 2 -column 0 -columnspan 2 -sticky nsew

  12. The Packer • More powerful than the placer, but more complex • Arranges groups of slaves together (packing list). • Packs slaves around edges of master's cavity. • For each slave, in order: 3. Optionally grow slaveto fill parcel. 1. Pick side of cavity. 2. Slice off parcelfor slave. 4. Position slavein parcel.

  13. The Packer: Choosing Sides button .ok -text OKbutton .cancel -text Cancelbutton .help -text Help pack .ok .cancel .help -side left .cancel configure -text "Cancel Command" pack .ok .cancel .help -side top

  14. The Packer: Padding pack .ok .cancel .help -side left \-padx 2m -pady 1m pack .ok .cancel .help -side left \-ipadx 2m -ipady 1m pack .ok .cancel .help -side left \-padx 2m -pady 1m -ipadx 2m -ipady 1m

  15. The Packer: Filling Stretch widgets to fill parcels: pack .ok .cancel .help -side top pack .ok .cancel .help -side top -fill x

  16. The Packer: Filling, cont'd pack .menu -side toppack .scrollbar -side rightpack .listbox pack .menu -side top -fill xpack .scrollbar -side right -fill ypack .listbox

  17. The Packer: Expansion Increase parcel size to absorb extra space in master: pack .ok .cancel .help -side left pack .ok .cancel -side leftpack .help -side left -expand true pack .ok .cancel -side leftpack .help -side left \-expand true -fill x

  18. The Packer: Expansion, cont'd pack .ok .cancel .help -side left \-expand true pack .ok .cancel .help -side left \-expand 1 -fill both

  19. Hierarchical Packing Use additional frames to create more complex arrangements: frame .leftpack .left -side left -padx 3m -pady 3mframe .rightpack .right -side right -padx 3m -pady 3m foreach size {8 10 12 18 24} { radiobutton .pts$size -variable pts \ -value $size -text "$size points"}pack .pts8 .pts10 .pts12 .pts18 .pts24 \ -in .left -side top -anchor w checkbutton .bold -text Bold \ -variable boldcheckbutton .italic -text Italic \ -variable italiccheckbutton .underline -text Underline \ -variable underlinepack .bold .italic .underline \ -in .right -side top -anchor w

  20. Callbacks • How to make widgets work together with application, other widgets? Tcl scripts. • Widget actions are Tcl commands: button .a.b -command exit button release exit

  21. Bindings • Associate Tcl scripts with user events: bind .e <Control-h> {backspace .t} Window(s) Event Script

  22. Bindings: Specifying Events • Specifying events: <Double-Control-ButtonPress-1> <3> <KeyPress> a Modifiers Event Type Button or Keysym

  23. Bindings: Substitutions • % substitutions in binding scripts: • Coordinates from event: %x and %y. • Window: %W. • Character from event: %A. • Many more... • Examples: bind .c <B1-Motion> {move %x %y} bind .t <KeyPress> {insert %A}

  24. Example: Context sensitive help button .b -text "Hello World" -command exit button .c -text "Lazy Boy" label .help pack .b .c .help -side top bind .b <Enter> {.help configure -text "Press to exit"} bind .c <Enter> {.help configure -text "i do nothing"} bind Button <Leave> {.help configure -text ""}

  25. Access To Other Facilities • Keyboard focus: focus .x.y • Communication with window manager: wm title . "Editing main.c"wm geometry . 300x200wm iconify . • Deleting windows: destroy .x

  26. Summary • Creating interfaces with Tk is easy: • Create widgets. • Arrange with geometry managers. • Bind if necessary (rarely need to, except for text and canvas objects) • window management

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