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
       ⟨http://purl.org/tcl/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 ⟨http://purl.org/tcl/tip/48⟩