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 u 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

Widgets implemented by Tk FrameMenubuttonCanvas LabelMenuScrollbar ButtonMessageScale CheckbuttonEntryListbox RadiobuttonTextToplevel Try the Widget Tour on the PCs to get an overview Start/Tcl/Widget Tour

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

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

Configuration Options u 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 u Default provided by class. button.b -text Hello -command exit button.c grid.b.c u Advanced: may be specified in an options database

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

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

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

The Grid u Lays out objects in virtual grid of rows and columns u 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

The Grid u 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

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

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

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

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

The Packer: Filling, cont'd pack.menu -side top pack.scrollbar -side right pack.listbox pack.menu -side top -fill x pack.scrollbar -side right -fill y pack.listbox

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

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

Hierarchical Packing Use additional frames to create more complex arrangements: frame.left pack.left -side left -padx 3m -pady 3m frame.right pack.right -side right -padx 3m -pady 3m foreach size { } { 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 bold checkbutton.italic -text Italic \ -variable italic checkbutton.underline -text Underline \ -variable underline pack.bold.italic.underline \ -in.right -side top -anchor w

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

Bindings u Associate Tcl scripts with user events: bind.e {backspace.t} Window(s)EventScript

Bindings: Specifying Events u Specifying events: a Modifiers Event Type Button or Keysym

Bindings: Substitutions u % substitutions in binding scripts: –Coordinates from event: %x and %y. –Window: %W. –Character from event: %A. –Many more... u Examples: bind.c {move %x %y} bind.t {insert %A}

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 {.help configure -text "Press to exit"} bind.c {.help configure -text "i do nothing"} bind Button {.help configure -text ""}

Access To Other Facilities u Keyboard focus: focus.x.y u Communication with window manager: wm title. "Editing main.c" wm geometry. 300x200 wm iconify. u Deleting windows: destroy.x

Summary u 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