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.. _text-layout:
***************
Text Layout
***************
.. currentmodule:: urwid
Mapping a text string to screen coordinates within a widget is called text
layout. The :class:`Text` widget's default layout class supports
aligning text to the left, center or right, and can wrap text on space
characters, at any location, or clip text that is off the edge.
::
Text("Showing some different alignment modes", align=...)
align='left' (default)
+----------------+ +------------------------+
|Showing some | |Showing some different |
|different | |alignment modes |
|alignment modes | +------------------------+
+----------------+
align='center'
+----------------+ +------------------------+
| Showing some | | Showing some different |
| different | | alignment modes |
|alignment modes | +------------------------+
+----------------+
align='right'
+----------------+ +------------------------+
| Showing some| | Showing some different|
| different| | alignment modes|
| alignment modes| +------------------------+
+----------------+
::
Text("Showing some different wrapping modes\nnewline", wrap=...)
wrap='space' (default)
+----------------+ +------------------------+
|Showing some | |Showing some different |
|different | |wrapping modes |
|wrapping modes | |newline |
|newline | +------------------------+
+----------------+
wrap='any'
+----------------+ +------------------------+
|Showing some dif| |Showing some different w|
|ferent wrapping | |rapping modes |
|modes | |newline |
|newline | +------------------------+
+----------------+
wrap='clip'
+----------------+ +------------------------+
|Showing some dif| |Showing some different w|
|newline | |newline |
+----------------+ +------------------------+
If this is good enough for your application feel free to skip the rest of this
section.
.. seealso::
:class:`Text widget reference <Text>`
Custom Text Layouts
===================
The :class:`StandardTextLayout` is set as the class variable
:attr:`Text.layout`. Individual :class:`Text`
widgets may use a different layout class, or you can change the default by
setting the :attr:`Text.layout` class variable itself.
A custom text layout class should extend the
:class:`TextLayout` base class and return text layout
structures from its ``layout()`` method.
.. seealso::
:class:`TextLayout reference <TextLayout>`
Text Layout Structures
======================
::
"This is how a string of text might be displayed"
0----5---10---15---20---25---30---35---40---45--
0----5---10---15---+ right_aligned_text_layout = [
| This is how a| [(5, 0), (13, 0, 13)],
| string of text| [(4, 13), (14, 14, 28)],
|might be displayed| [(18, 29, 47)]
+------------------+ ]
The mapping from a text string to where that text will be displayed in the
widget is expressed as a text layout structure.
Text layout structures are used both for rendering :class:`Text`
widgets and for mapping ``(x, y)`` positions within a widget back to the
corresponding offsets in the text. The latter is used when moving the cursor in
:class:`Edit` widgets up and down or by clicking with the mouse.
A text layout structure is a list of one or more line layouts. Each line layout
corresponds to a row of text in the widget, starting from its top.
A line layout is a list zero or more of the following tuples, each expressing
text to be displayed from left to right:
A. (*column width*, *starting text offset*, *ending text offset*)
B. (*column width of space characters to insert*, *text offset* or ``None``)
C. (*column width*, *text offset*, *new text to insert*)``
Tuple A displays a segment of text from the :class:`Text` widget.
Column width is explicitly specified because some characters within the text
may be zero width or double width.
Tuple B inserts any number of space characters, and if those characters
correspond to an offset within the text, that may be specified.
Tuple C allows insertion of arbitrary text. This could be used for hyphenating
split words or any other effect not covered by A or B. The
:class:`StandardTextLayout` does not currently use this
tuple in its line layouts.
.. seealso::
:class:`TextLayout reference <TextLayout>`,
:class:`StandardTextLayout reference <StandardTextLayout>`
|
