<Chapter Label="chap:browse-user">
<Heading>Browsing Tables in &GAP; using <C>ncurses</C>
&ndash;The User Interface</Heading>

As stated in Section&nbsp;<Ref Sect="sec:intro"/>,
one aim of the &Browse; package is to provide tools for the quite usual task
to show a two-dimensional array or certain rows and columns of it
on a character screen in a formatted way,
to navigate in this array via key strokes (and mouse events), and
to search for strings, to sort the array by row or column values etc.
<P/>
The idea is that one starts with an array of data,
the <E>main table</E><Index>main table of a browse table</Index>.
Optionally, labels for each row of the main table are given,
which are also arranged in an array (with perhaps several columns),
the <E>row labels table</E><Index>row labels of a browse table</Index>;
analogously,
a <E>column labels table</E><Index>column labels of a browse table</Index>
of labels for the columns of the main table may be given.
The row labels are shown to the left of the main table, the column labels are
shown above the main table.
The space above the row labels and to the left of the column labels
can be used for a fourth table,
the <E>corner table</E><Index>corner table of a browse table</Index>,
with information about the labels or about the main table.
Optionally, a <E>header</E><Index>header of a browse table</Index>
and a <E>footer</E><Index>footer of a browse table</Index>
may be shown above and below these four tables, respectively.
Header and footer are not separated into columns.
So the shown window has the following structure.
<P/>
<Alt Only="Text">
<Verb>
      ----------------------------------
      |             header             |
      ----------------------------------
      |        |                       |
      | corner |     column labels     |
      |        |                       |
      ----------------------------------
      |        |                       |
      |        |                       |
      |  row   |         main          |
      | labels |         table         |
      |        |                       |
      |        |                       |
      |        |                       |
      ----------------------------------
      |             footer             |
      ----------------------------------
</Verb>
</Alt>
<Alt Only="LaTeX">
<![CDATA[
\begin{center}
\begin{tabular}{|c|c|}
\hline
\multicolumn{2}{|c|}{header} \\
\hline
corner & column labels \\
\hline
 & \\
row & main \\
labels &  table \\
 & \\
\hline
\multicolumn{2}{|c|}{footer} \\
\hline
\end{tabular}
\end{center}
]]>
</Alt>
<Alt Only="HTML">
<![CDATA[
</p>
<table rules="all" border="3">
<thead>
<tr>
<td colspan="2" align="center">header</td>
</tr>
</thead>
<tfoot>
<tr>
<td colspan="2" align="center">footer</td>
</tr>
</tfoot>
<tbody>
<tr>
<td align="center">corner</td>
<td align="center">column labels</td>
</tr>
<tr>
<td align="center">row labels</td>
<td align="center">main table</td>
</tr>
</tbody>
</table><p>
]]>
</Alt>
<P/>
If not the whole tables fit into the window then only subranges of rows
and columns of the main table are shown,
together with the corresponding row and column labels.
Also in this case, the row heights and column widths are computed w.r.t.
the whole table not w.r.t. the shown rows and columns.
This means that the shown row labels are unchanged if the range of shown
columns is changed,
the shown column labels are unchanged if the range of shown rows is changed,
and the whole corner table is always shown.
<P/>
The current chapter describes the user interface for
<E>standard applications</E> of this kind, i.&nbsp;e.,
those applications for which one just has to collect the data to be shown
in a record
&ndash;which we call a <E>browse table</E>&ndash;
without need for additional &GAP; programming.
<P/>
Section&nbsp;<Ref Sect="sec:features"/> gives an overview of the features
available in standard browse table applications,
and Section&nbsp;<Ref Sect="sec:browsebasicdata"/> describes
the data structures used in browse tables.
Finally, Section&nbsp;<Ref Sect="sec:browsegeneric"/> introduces
the function <Ref Func="NCurses.BrowseGeneric"/>,
which is the generic function for showing browse table in visual mode.
<P/>
For technical details needed to extend these applications
and to build other applications,
see Chapter&nbsp;<Ref Chap="chap:browse-prg"/>.
<P/>
Examples of browse table applications are shown
in Chapter&nbsp;<Ref Chap="ch:appl"/>.


<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->
<Section Label="sec:features">
<Heading>Features Supported by the Function <C>NCurses.BrowseGeneric</C>
</Heading>

Standard applications of the function <Ref Func="NCurses.BrowseGeneric"/>
have the following functionality.
Other applications may provide only a subset, or add further functionality,
see Chapters&nbsp;<Ref Chap="chap:browse-prg"/>
and&nbsp;<Ref Chap="ch:appl"/>.
<P/>
<List>
<Mark>Scrolling:<Index>scrolling in a browse table</Index></Mark>
<Item>
  The subranges of shown rows and columns of the main table can be modified,
  such that the focus area is moved to the left, to the right, up, or down;
  depending on the context, the focus is moved by one character, by one table
  cell or a part of it, by the window height/width (minus one character or
  minus one table cell).
  If mouse events <Index>mouse events</Index>
  are enabled then cells can be selected also via mouse clicks.
</Item>
<Mark>Selecting:<Index>selecting entries of a browse table</Index></Mark>
<Item>
  A cell, row, or column of the main table can be selected;
  then it is shown highlighted on the screen (by default using the attribute
  <C>NCurses.attrs.STANDOUT</C>,
  see Section&nbsp;<Ref Subsect="ssec:ncursesAttrs"/>).
  The selection can be moved inside the main table to a neighboring cell,
  row, or column; this causes also scrolling of the main table
  when the window borders are reached.
</Item>
<Mark>Searching:<Index>searching in a browse table</Index></Mark>
<Item>
  A search string is entered by the user, and the first matching cell
  becomes selected; one can search further for the next matching cell.
  Global search parameters define what matching means (case sensitive or
  not, search for substrings or complete words) and what the first and
  the next matching cells are (search in the whole table or just in the
  selected row or column, search for whole words or prefixes or suffixes,
  search forwards or backwards).
</Item>
<Mark>Sorting:<Index>sorting a browse table</Index></Mark>
<Item>
  If a row or column is selected then the main table can be sorted w.r.t.
  the entries in this row or column.
  Global sort parameters describe for example whether one wants to sort
  ascending or descending, or case sensitive or not.
  <P/>
  If a categorized table is sorted by a column then the category rows
  are removed and the current sorting and filtering by rows is reset
  before the table is sorted by the given column.
  If a table is sorted by a column/row that is already sorted by a column/row
  then this ordering is reset first.
  <P/>
  Sorting can be undone globally, i.&nbsp;e., one can return to the
  unsorted table.
</Item>
<Mark>Sorting and Categorizing:<Index>categorizing a browse table</Index>
</Mark>
<Item>
  If a column is selected then the main table can be sorted w.r.t.
  the entries in this column,
  and additionally these entries are turned into <E>category rows</E>,
  i.&nbsp;e.,
  additional rows are added to the main table, appearing immediately above
  the table rows with a fixed value in the selected column, and showing
  this column value.
  (There should be no danger to mix up this notion of categories with the one
  introduced in&nbsp;<Ref Sect="Categories" BookName="ref"/>.)
  The category rows can be <E>collapsed</E>
  <Index>collapsed category row</Index>
  (that is, the table rows that belong to this category row are not shown)
  or <E>expanded</E><Index>expanded category row</Index>
  (that is, the corresponding table rows are shown).
  Some of the global search parameters affect the category rows,
  for example, whether the category rows shall involve a counter showing the
  number of corresponding data rows,
  or whether a row of the browse table appears under different category rows.
  <P/>
  <!--
  When a table gets sorted and categorized that is already categorized,
  the new category rows are created on the outermost category level,
  so successively categorizing by several columns yields a category hierarchy.
  <P/>
  -->
  Sorting and categorizing can be undone globally, i.&nbsp;e.,
  one can return to the unsorted table without category rows.
</Item>
<Mark>Filtering:<Index>filtering a browse table</Index>
</Mark>
<Item>
  The browse table can be restricted to those rows or columns in which
  a given search string occurs.
  (Also entries in collapsed rows can match; they remain collapsed then.)
  As a consequence, the category rows are restricted to those
  under which a matching row occurs.
  (It is irrelevant whether the search string occurs in category rows.)
  <P/>
  If the search string does not occur at all then a message is printed,
  and the table remains as it was before.
  If a browse table is restricted then this fact is indicated by the message
  <Q>restricted table</Q> in the lower right corner of the window.
  <P/>
  When a column or row is selected then the search is restricted to the
  entries in this column or row, respectively.
  Besides using a search,
  one can also explicitly hide the selected row or column.
  Filtering in an already restricted table restricts the shown rows or
  columns further.
  <P/>
  Filtering can be undone globally, i.&nbsp;e., one can return to the
  unrestricted table.
</Item>
<Mark>Help:<Index>help window for a browse table</Index></Mark>
<Item>
  Depending on the application and on the situation,
  different sets of user inputs may be available
  and different meanings of these inputs are possible.
  An overview of the currently available inputs and their meanings
  can be opened in each situation, by hitting the <B>?</B> key.
</Item>
<Mark>Re-entering:</Mark>
<Item>
  When one has called <Ref Func="NCurses.BrowseGeneric"/> with a browse table,
  and returns from visual mode to the &GAP; prompt after some navigation steps,
  calling <C>NCurses.BrowseGeneric</C> again with this table
  will enter visual mode in the same situation where it was left.
  For example, the cell in the top-left position will be the same as before,
  and if a cell was selected before then this cell will be selected now.
  (One can avoid this behavior using the optional second argument of
  <C>NCurses.BrowseGeneric</C>.)
</Item>
<Mark>Logging:<Index>log of a browse table session</Index></Mark>
<Item>
  The integers corresponding to the user inputs in visual mode
  are collected in a list that is stored in the component
  <C>dynamic.log</C> of the browse table.
  It can be used for repeating the inputs with the replay feature.
  (For browse table applications that give the user no access to the
  browse table itself, one can force the log to be assigned to the component
  <C>log</C> of the global variable <C>BrowseData</C>,
  <Index>BrowseData.log</Index>
  see Section&nbsp;<Ref Subsect="BrowseData"/>.)
</Item>
<Mark>Replay:<Index>replay of a browse table session</Index></Mark>
<Item>
  Instead of interactively hitting keys in visual mode, one can prescribe
  the user inputs to a browse table via a <Q>replay record</Q>;
  the inputs are then processed with given time intervals.
  The easiest way to create a meaningful replay record is via the function
  <Ref Func="BrowseData.SetReplay"/>, with argument the <C>dynamic.log</C>
  component of the browse table in question that was stored in an
  interactive session.
</Item>
</List>
<P/>
The following features are not available in standard applications.
They require additional programming.
<P/>
<List>
<Mark>Clicking:<Index>click on an entry of a browse table</Index></Mark>
<Item>
  One possible action is to <Q>click</Q> a selected cell, row, or column,
  by hitting the <B>Enter</B> key.
  It depends on the application what the effect is.
  A typical situation is that a corresponding &GAP; object is added to the
  list of return values of <Ref Func="NCurses.BrowseGeneric"/>.
  Again it depends on the application what this &GAP; object is.
  In order to use this feature, one has to provide a record whose components
  are &GAP; functions, see Section&nbsp;<Ref Subsect="BrowseData"/>
  for details.
  If mouse events <Index>mouse events</Index> are enabled
  then also mouse clicks can be used as an alternative
  to hitting the <B>Enter</B> key.
</Item>
<Mark>Return Value:<Index>return value of a browse table session</Index>
</Mark>
<Item>
  The function <Ref Func="NCurses.BrowseGeneric"/> may have
  an application dependent return value.
  A typical situation is that a list of objects corresponding to those
  cells is returned that were <Q>clicked</Q> in visual mode.
  In order to use this feature, one has to assign the desired value to
  the component <C>dynamic.Return</C> of the browse table.
</Item>
</List>

</Section>


<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->
<Section Label="sec:browsebasicdata">
<Heading>Data Structures used by <C>NCurses.BrowseGeneric</C></Heading>

<#Include Label="IsBrowseTableCellData_man">

<#Include Label="BlockEntry_man">

<#Include Label="IsBrowseTable_man">

</Section>


<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->
<Section Label="sec:browsegeneric">
<Heading>The Function <C>NCurses.BrowseGeneric</C></Heading>

<#Include Label="NCurses.BrowseGeneric_man">

</Section>

</Chapter>


<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->
<Chapter Label="chap:browse-prg">
<Heading>Browsing Tables in &GAP; using <C>ncurses</C>
&ndash;The Programming Interface</Heading>

This chapter describes some aspects of the internals of the browse table
handling.
The relevant objects are
<E>action functions</E> that implement the individual navigation steps
(see Section&nbsp;<Ref Sect="sec:actions"/>),
<E>modes</E> that describe the sets of available navigation steps in given
situations (see Section&nbsp;<Ref Sect="sec:modes"/>),
and <E>browse applications</E> that are given by the combination of several
modes (see Section&nbsp;<Ref Sect="sec:applications"/>).
Most of the related data is stored in the global variable
<Ref Var="BrowseData"/>.

For more details, one should look directly at the code in the file
<F>lib/browse.gi</F> of the &Browse; package.

<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->
<Section Label="sec:actions">
<Heading>Navigation Steps in Browse Tables</Heading>

Navigating in a browse table means that after entering visual mode
by calling <Ref Func="NCurses.BrowseGeneric"/>,
the user hits one or several keys, or uses a mouse button,
and if this input is in a given set of admissible inputs
then a corresponding function is executed with argument the browse table
(plus additional information in the case of mouse events).
The function call then may change components in this table
(recommended: components in its <C>dynamic</C> component),
such that the appearance in the window may be different afterwards,
and also the admissible inputs and their effects may have changed.

<P/>

The relation between the admissible inputs and the corresponding functions
is application dependent.
However, it is recommended to associate the same input to the same function
in different situations;
for example,
the <B>?</B> key and the <B>F1</B> key should belong to a function
that shows a help window
(see Section <Ref Subsect="BrowseData.actions.ShowHelp"/>),
the <B>q</B> key and the <B>Esc</B> key should belong to a function
that exits the current mode
(Note that the <B>Esc</B> key may be recognized as input
only after a delay of about a second.),
the <B>Q</B> key should belong to a function that exits the browse
application (see Section <Ref Subsect="BrowseData.actions.QuitMode"/>),
the <B>F2</B> key should belong to a function that saves the current
window contents in a global variable
(see Section <Ref Subsect="BrowseData.actions.SaveWindow"/>),
and
the <B>E</B> key should belong to a function that enters a break loop
(see Section&nbsp;<Ref Subsect="BrowseData.actions.Error"/>).
The <B>Enter</B> and <B>Return</B> keys should belong to a <Q>click</Q>
on a selected table entry, and if a category row is selected then they
should expand/collapse this category.
The <B>M</B> key should toggle enabling and disabling mouse events.
Mouse events on a cell or on a category row of a browse table
should move the selected entry to this position;
it is recommended that no functionality is lost if no mouse events are used,
although the number of steps might be reduced when the mouse is used.

<P/>

Each such function is wrapped into a record with the components <C>action</C>
(the function itself) and <C>helplines</C> (a list of attribute lines that
describes what the function does).
<Index>action record of a browse table</Index>
The help lines are used by the help feature of <C>NCurses.BrowseGeneric</C>,
see Section <Ref Subsect="BrowseData.actions.ShowHelp"/>.

<P/>

The action functions need not return anything.
Whenever the shown screen shall be recomputed after the function call,
the component <C>dynamic.changed</C> of the browse table must be set to
<K>true</K> by the action functions.

<P/>

After entering the first characters of an admissible input
that consists of more characters, 
the last line of the window with the browse table shows these characters
behind the prefix <Q>partial input:</Q>.
<Index>partial input in a browse table</Index>
One can delete the last entered character of a partial input via the
<B>Delete</B> and <B>Backspace</B> keys.
It is not possible to make these keys part of an admissible input.
When a partial input is given, only those user inputs have an effect
that extend the partial input to (a prefix of) an admissible input.
For example, asking for help by hitting the <B>?</B> key will in general
not work if a partial input had been entered before.

</Section>

<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->
<Section Label="sec:modes">
<Heading>Modes in Browse Tables</Heading>
<Index>mode of a browse table</Index>

In different situations, different inputs may be admissible for the same
browse table, and different functions may belong to the same input.
For example, the meaning of <Q>moving down</Q> can be different depending on
whether a cell is selected or not.

<P/>

The set of admissible user inputs and corresponding functions for a
particular situation is collected in a <E>mode</E> of the browse table.
(There should be no danger to mix up this notion of mode with the
<Q>visual mode</Q> introduced in Section&nbsp;<Ref Sect="sec:intro"/>.)
A mode is represented by a record with the components
<C>name</C>
(a string used to associate the mode with the components of <C>header</C>,
<C>headerLength</C>, <C>footer</C>, <C>footerLength</C>, <C>Click</C>,
and for the help screen),
<C>flag</C>
(a string that describes properties of the mode but that can be equal for
different modes),
<C>actions</C>
(a list of records describing the navigation steps that are admissible
in the mode, see Section&nbsp;<Ref Sect="sec:actions"/>),
and <C>ShowTables</C>
(the function used to eventually print the current window contents,
the default is <C>BrowseData.ShowTables</C>).
<Index>BrowseData.ShowTables</Index>
Due to the requirement that each admissible user input uniquely determines
a corresponding function, no admissible user input can be a prefix of
another admissible input, for the same mode.

<P/>

Navigation steps (see Section <Ref Sect="sec:actions"/>) can change
the current mode or keep the mode.
It is recommended that each mode has an action to leave this mode;
also an action to leave the browse table application is advisable.

<P/>

In a browse table, all available modes are stored in the component
<C>work.availableModes</C>, whose value is a list of mode records.
The value of the component <C>dynamic.activeModes</C> is a list of
mode records that is used as a stack:
The <E>current mode</E> is the last entry in this list,
changing the current mode is achieved
by unbinding the last entry (so one returns to the mode
from which the current mode had been entered by adding it to the list),
by adding a new mode record (so one can later return to the current mode),
or by replacing the last entry by another mode record.
As soon as the <C>dynamic.activeModes</C> list becomes empty,
the browse table application is left.
(In this situation,
if the browse table had been entered from the &GAP; prompt then
visual mode is left, and one returns to the &GAP; prompt.)

<P/>

The following modes are predefined by the &Browse; package.
Each of these modes admits the user inputs
<B>?</B>, <B>F1</B>, <B>q</B>, <B>Esc</B>,
<B>Q</B>, <B>F2</B>, <B>E</B>, and <B>M</B>
that have been mentioned in Section <Ref Sect="sec:actions"/>.

<List>
<Mark>browse</Mark>
<Item>
  This mode admits scrolling of the browse table by a cell or by a screen,
  searching for a string, selecting a row, a column, or an entry,
  and expanding or collapsing all category rows.
</Item>
<Mark>help</Mark>
<Item>
  This mode is entered by calling <C>BrowseData.ShowHelpTable</C>;
  it shows a help window concerning the actions available in the mode
  from which the <C>help</C> mode was entered.
  The <C>help</C> mode admits scrolling in the help table
  by a cell or by a screen.
  See Section <Ref Subsect="BrowseData.actions.ShowHelp"/>
  for details.
</Item>
<Mark>select_entry</Mark>
<Item>
  In this mode, one table cell is regarded as selected;
  this cell is highlighted using the attribute in the component
  <C>work.startSelect</C> as a prefix of each attribute line,
  see the remark in Section <Ref Subsect="NCurses.IsAttributeLine"/>.
  The mode admits moving the selection by one cell in the four directions,
  searching for a string and for further occurrences of this string,
  expanding or collapsing the current category row or all category rows,
  and executing the <Q>click</Q> function of this mode,
  provided that the component <C>work.Click.( "select_entry" )</C>
  of the browse table is bound.
</Item>
<Mark>select_row</Mark>
<Item>
  This is like the <C>select_entry</C> mode,
  except that a whole row of the browse table is highlighted.
  Searching is restricted to the selected row, and <Q>click</Q> refers to the
  function <C>work.Click.( "select_row" )</C>.
</Item>
<Mark>select_row_and_entry</Mark>
<Item>
  This is a combination of the <C>select_entry</C> mode and the
  <C>select_row</C> mode.
</Item>
<Mark>select_column</Mark>
<Item>
  This is like the <C>select_row</C> mode,
  just a column is selected not a row.
</Item>
<Mark>select_column_and_entry</Mark>
<Item>
  This is like the <C>select_row_and_entry</C> mode,
  just a column is selected not a row.
</Item>
</List>

</Section>

<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->
<Section Label="sec:applications">
<Heading>Browse Applications</Heading>

The data in a browse table together with the set of its available modes and
the stack of active modes forms a browse application.
So the part of or all functionality of the &Browse; package can be available
(<Q>standard application</Q>),
or additional functionality can be provided by extending available modes or
adding new modes.

<P/>

When <Ref Func="NCurses.BrowseGeneric"/> has been called
with the browse table <A>t</A>, say, the following loop is executed.

<List>
<Mark>1.</Mark>
<Item>
  If the list <A>t</A><C>.dynamic.activeModes</C> is empty then exit
  the browse table, and if the component <A>t</A><C>.dynamic.Return</C>
  is bound then return its value.
  Otherwise proceed with step 2.
</Item>
<Mark>2.</Mark>
<Item>
  If <A>t</A><C>.dynamic.changed</C> is <K>true</K> then
  call the <C>ShowTables</C> function of the current mode;
  this causes a redraw of the window that shows the browse table.
  Then go to step 3.
</Item>
<Mark>3.</Mark>
<Item>
  Get one character of user input.
  If then the current user input string is the name of an action of the
  current mode then call the corresponding action function and go to step 1;
  if the current user input string is just a prefix of the name of some
  actions of the current mode then go to step 3;
  if the current user input string is not a prefix of any name of an action
  of the current mode then discard the last read character and go to step 3.
</Item>
</List>

When one designs a new application, it may be not obvious whether some
functionality shall be implemented via one mode or via several modes.
As a rule of thumb, introducing a new mode is recommended when one needs
a new set of admissible actions in a given situation,
and also if one wants to allow the user to perform some actions
and then to return to the previous status.

</Section>

<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -->
<Section Label="sec:browse-avail">
<Heading>Predefined Browse Functionalities</Heading>

<#Include Label="BrowseData_man">

<#Include Label="SetReplay_man">

<#Include Label="AlertWithReplay_man">

<#Include Label="ShowHelp_man">

<#Include Label="SaveWindow_man">

<#Include Label="QuitMode_man">

<#Include Label="Error_man">

</Section>
</Chapter>