1ttk::intro(n)                  Tk Themed Widget                  ttk::intro(n)
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NAME

8       ttk::intro - Introduction to the Tk theme engine
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OVERVIEW

12       The  Tk themed widget set is based on a revised and enhanced version of
13       TIP #48 (https://tip.tcl-lang.org/48) specified style engine.  The main
14       concepts  are  described  below.  The basic idea is to separate, to the
15       extent possible, the code implementing a  widget's  behavior  from  the
16       code  implementing its appearance.  Widget class bindings are primarily
17       responsible for maintaining the widget state  and  invoking  callbacks;
18       all  aspects  of the widget's appearance are controlled by the style of
19       the widget (i.e. the style of the elements of the widget).
20

THEMES

22       A theme is a collection of elements and styles that determine the  look
23       and feel of the widget set.  Themes can be used to:
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25       •      isolate platform differences (X11 vs. classic Windows vs. XP vs.
26              Aqua ...)
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28       •      adapt to display limitations (low-color, grayscale,  monochrome,
29              tiny screens)
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31       •      accessibility (high contrast, large type)
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33       •      application suite branding
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35       •      blend in with the rest of the desktop (Gnome, KDE, Java)
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37       •      and, of course: eye candy.
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ELEMENTS

40       An  element  displays  an  individual part of a widget.  For example, a
41       vertical scrollbar  widget  contains  uparrow,  downarrow,  trough  and
42       slider elements.
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44       Element  names  use  a recursive dotted notation.  For example, uparrow
45       identifies a generic arrow  element,  and  Scrollbar.uparrow  and  Com‐
46       bobox.uparrow  identify  widget-specific elements.  When looking for an
47       element, the style engine looks for the specific name first, and if  an
48       element  of  that  name  is  not found it looks for generic elements by
49       stripping off successive leading components of the element name.
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51       Like widgets, elements have options which specify what to  display  and
52       how  to  display  it.   For example, the text element (which displays a
53       text string) has -text, -font,  -foreground,  -background,  -underline,
54       and  -width  options.  The value of an element option is taken from (in
55       precedence order):
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57       •      an option of the same name and type in the widget containing the
58              element;
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60       •      a dynamic setting specified by style map and the current state;
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62       •      the default setting specified by style configure; or
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64       •      the element's built-in default value for the option.
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LAYOUTS

67       A layout specifies which elements make up a widget and how they are ar‐
68       ranged.  The layout engine uses a simplified version of the pack  algo‐
69       rithm: starting with an initial cavity equal to the size of the widget,
70       elements are allocated a parcel within the cavity along the side speci‐
71       fied by the -side option, and placed within the parcel according to the
72       -sticky option.  For example, the layout for a horizontal scrollbar is:
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74              ttk::style layout Horizontal.TScrollbar {
75                  Scrollbar.trough -children {
76                Scrollbar.leftarrow -side left -sticky w
77                Scrollbar.rightarrow -side right -sticky e
78                Scrollbar.thumb -sticky ew
79                  }
80              }
81
82       By default, the layout for a widget is the  same  as  its  class  name.
83       Some  widgets may override this (for example, the ttk::scrollbar widget
84       chooses different layouts based on the -orient option).
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STATES

87       In standard Tk, many widgets have a -state option which (in most cases)
88       is  either normal or disabled.  Some widgets support additional states,
89       such as the entry widget which has a readonly  state  and  the  various
90       flavors of buttons which have active state.
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92       The  themed Tk widgets generalizes this idea: every widget has a bitmap
93       of independent state flags.  Widget state flags  include  active,  dis‐
94       abled,  pressed,  focus, etc., (see ttk::widget(n) for the full list of
95       state flags).
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97       Instead of a -state option, every widget now has a state widget command
98       which  is  used  to set or query the state.  A state specification is a
99       list of symbolic state names indicating which bits are  set,  each  op‐
100       tionally  prefixed with an exclamation point indicating that the bit is
101       cleared instead.
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103       For example, the class bindings for the ttk::button widget are:
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105              bind TButton <Enter>{ %W state active }
106              bind TButton <Leave>{ %W state !active }
107              bind TButton <ButtonPress-1>{ %W state pressed }
108              bind TButton <Button1-Leave>{ %W state !pressed }
109              bind TButton <Button1-Enter>{ %W state pressed }
110              bind TButton <ButtonRelease-1>\
111                  { %W instate {pressed} { %W state !pressed ; %W invoke } }
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113       This specifies that the widget becomes active when the  pointer  enters
114       the  widget, and inactive when it leaves.  Similarly it becomes pressed
115       when the mouse button is pressed, and  !pressed  on  the  ButtonRelease
116       event.  In addition, the button unpresses if pointer is dragged outside
117       the widget while Button-1 is held down, and represses if  it's  dragged
118       back  in.   Finally,  when  the  mouse button is released, the widget's
119       -command is invoked, but only if the button is currently in the pressed
120       state.   (The  actual  bindings  are a little more complicated than the
121       above, but not by much).
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STYLES

124       Each widget is associated with a style, which specifies values for ele‐
125       ment options.  Style names use a recursive dotted notation like layouts
126       and elements; by default, widgets use the class name to look up a style
127       in the current theme.  For example:
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129              ttk::style configure TButton \
130                -background #d9d9d9 \
131                -foreground black \
132                -relief raised \
133                ;
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135       Many  elements are displayed differently depending on the widget state.
136       For example, buttons have a different background when they are  active,
137       a  different  foreground  when  disabled,  and  a different relief when
138       pressed.  The style map command specifies dynamic option settings for a
139       particular style:
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141              ttk::style map TButton \
142                -background [list disabled #d9d9d9  active #ececec] \
143                -foreground [list disabled #a3a3a3] \
144                -relief [list {pressed !disabled} sunken] \
145                ;
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SEE ALSO

148       ttk::widget(n), ttk::style(n)
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152Tk                                    8.5                        ttk::intro(n)
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