NAME

       tile_intro - Introduction to the Tile theme engine

OVERVIEW

       The  tile  widget  set  is based on a revised and enhanced version of the TIP #48 style engine.  The main
       concepts are described below.  The  basic  idea  is  to  separate,  to  the  extent  possible,  the  code
       implementing  a  widget's  behavior from the code implementing its appearance.  Widget class bindings are
       primarily responsible for maintaining the widget state and invoking callbacks; all aspects of the widgets
       appearance is

THEMES

       A theme is a collection of elements and styles that determine the  look  and  feel  of  the  widget  set.
       Themes can be used to:

       •      Isolate platform differences (X11 vs. classic Windows vs. XP vs. Aqua ...)

       •      Adapt to display limitations (low-color, grayscale, monochrome, tiny screens)

       •      Accessibility (high contrast, large type)

       •      Application suite branding

       •      Blend in with the rest of the desktop (Gnome, KDE, Java)

       •      And, of course: eye candy.

ELEMENTS

       An  element  displays  an individual part of a widget.  For example, a vertical scrollbar widget contains
       uparrow, downarrow, trough and slider elements.

       Element names use a recursive dotted notation.  For example, uparrow identifies a generic arrow  element,
       and  Scrollbar.uparrow  and  Combobox.uparrow  identify  widget-specific  elements.   When looking for an
       element, the style engine looks for the specific name first, and if an element of that name is not  found
       it looks for generic elements by stripping off successive leading components of the element name.

       Like  widgets,  elements  have options which specify what to display and how to display it.  For example,
       the text element (which displays a text string) has -text, -font, -foreground,  -background,  -underline,
       and -width options.  The value of an element option is taken from:

       •      An option of the same name and type in the widget containing the element;

       •      A dynamic setting specified by style map and the current state;

       •      The default setting specified by style configure; or

       •      The element's built-in default value for the option.

LAYOUTS

       A  layout  specifies which elements make up a widget and how they are arranged.  The layout engine uses a
       simplified version of the pack algorithm: starting with an initial  cavity  equal  to  the  size  of  the
       widget,  elements  are allocated a parcel within the cavity along the side specified by the -side option,
       and placed within the parcel according to the -sticky option.  For example, the layout for  a  horizontal
       scrollbar ttk::style layout Horizontal.TScrollbar {
           Scrollbar.trough  -children {      Scrollbar.leftarrow -side left -sticky w      Scrollbar.rightarrow
       -side right -sticky e      Scrollbar.thumb -side left -expand true -sticky ew
           } } By default, the layout for a widget is the same as its class name.   Some  widgets  may  override
       this (for example, the ttk::scrollbar widget chooses different layouts based on the -orient option).

STATES

       In  standard  Tk,  many  widgets have a -state option which (in most cases) is either normal or disabled.
       Some widgets support additional states, such as the entry widget which  has  a  readonly  state  and  the
       various flavors of buttons which have active state.

       The  Tile widget set generalizes this idea: every widget has a bitmap of independent state flags.  Widget
       state flags include active, disabled, pressed, focus, etc., (see widget(n) for the  full  list  of  state
       flags).

       Instead of a -state option, every widget now has a state widget command which is used to set or query the
       state.   A  state  specification  is  a  list of symbolic state names indicating which bits are set, each
       optionally prefixed with an exclamation point indicating that the bit is cleared instead.

       For example, the class bindings for the ttk::button widget are: bind TButton <Enter>          { %W  state
       active  }  bind  TButton  <Leave>          {  %W state !active } bind TButton <ButtonPress-1>  { %W state
       pressed } bind TButton <Button1-Leave>  { %W state !pressed } bind TButton  <Button1-Enter>  {  %W  state
       pressed } bind TButton <ButtonRelease-1>     \
           {  %W  instate  {pressed}  { %W state !pressed ; %W invoke } } This specifies that the widget becomes
       active when the pointer enters the widget, and inactive when it leaves.   Similarly  it  becomes  pressed
       when  the  mouse  button  is  pressed,  and !pressed on the ButtonRelease event.  In addition, the button
       unpresses if pointer is dragged outside the widget while Button-1 is held down,  and  represses  if  it's
       dragged  back in.  Finally, when the mouse button is released, the widget's -command is invoked, but only
       if the button is currently in the pressed state.  (The actual bindings are a little more complicated than
       the above, but not by much).

       Note to self: rewrite that paragraph.  It's horrible.

STYLES

       Each widget is associated with a style, which specifies values for element options.  Style  names  use  a
       recursive  dotted notation like layouts and elements; by default, widgets use the class name to look up a
       style in the current theme.  For example: ttk::style  configure  TButton  \       -background  #d9d9d9  \
            -foreground  black  \      -relief raised \      ; Many elements are displayed differently depending
       on the widget state.  For example, buttons have a different background when they are active, a  different
       foreground  when  disabled, and a different relief when pressed.  The style map command specifies dynamic
       option settings for a particular style: ttk::style map TButton \      -background [list disabled  #d9d9d9
       active  #ececec]  \       -foreground  [list  disabled  #a.TH   3tcla3a3]  \       -relief [list {pressed
       !disabled} sunken] \      ;

SEE ALSO

       widget(n), style(n), TIP #48

tile                                                   0.2                                           intro(3tcl)