Fill-Out Form Support
| HTML Form Input Types Quick Reference
| My Reference Manual to HTML
Form Detailed Subject Reference
The FORM Tag
The FORM tag specifies a fill-out form within an HTML document.
More than one fill-out form can be in a single document, but forms cannot
<FORM ACTION="url"> ... </FORM>
The attributes are as follows:
ACTION is the URL of the query server to which the form contents
will be submitted; if this attribute is absent, then the current document
URL will be used.
METHOD is the HTTP/1.0 method used to submit the fill-out form
to a query server. Which method you use depends on how your particular
server works; we strongly recommend use of (or near-term migration to)
POST. The valid choices are:
GET -- this is the default method and causes the fill-out form
contents to be appended to the URL as if they were a normal query.
POST -- this method causes the fill-out form contents to be sent
to the server in a data body rather than as part of the URL.
ENCTYPE specifies the encoding for the fill-out form contents.
This attribute only applies if METHOD is set to POST
-- and even then, there is only one possible value (the default, application/x-www-form-urlencoded)
NOTE: If you want to use the METHOD of type
POST with the HTTPd you will need to get version 1.0a5 or
Inside a FORM you can have anything except another FORM.
Specifically, INPUT, SELECT, and TEXTAREA tags
are used to specify interface elements within the form.
Forms are not automatically visually differentiated from the rest of
a document. We recommend using the HR (horizontal rule) tag before
and after a form to cleanly differentiate it from surrounding text and/or
The INPUT Tag
The INPUT tag is used to specify a simple input element inside
a FORM. It is a standalone tag; it does not surround anything
and there is no terminating tag -- i.e., it is used in much the same way
In Mosaic for X, various types of INPUT tags are instantiated
as Motif widgets (text entry fields, toggle buttons, pushbuttons, etc.).
The attributes to INPUT are as follows:
TYPE must be one of:
"text" (text entry field; this is the default)
"password" (text entry field; entered characters
are represented as asterisks)
"checkbox" (a single toggle button; on or off)
"radio" (a single toggle button; on or off; other toggles
with the same NAME are grouped into "one of many" behavior)
"submit" (a pushbutton that causes the current form
to be packaged up into a query URL and sent to a remote server)
"reset" (a pushbutton that causes the various input elements in the form
to be reset to their default values)
NAME is the symbolic name (not a displayed name -- normal HTML
within the form is used for that) for this input field. This must be
present for all types but "submit" and "reset", as it is used
when putting together the query string that gets sent to the remote server
when the filled-out form is submitted.
VALUE, for a text or password entry field, can be used to specify
the default contents of the field. For a checkbox or a radio button, VALUE
specifies the value of the button when it is checked (unchecked
checkboxes are disregarded when submitting queries); the default value
for a checkbox or radio button is "on". For types "submit" and "reset",
VALUE can be used to specify the label for the pushbutton.
CHECKED (no value needed) specifies that this checkbox or radio
button is checked by default; this is only appropriate for checkboxes
and radio buttons.
SIZE is the physical size of the input field in characters; this
is only appropriate for text entry fields and password entry fields.
If this is not present, the default is 20. Multiline text entry fields
can be specified as SIZE=width,height; e.g. SIZE=60,12.
Note: the SIZE attribute should not be used to specify multiline
text entry fields now that the TEXTAREA tag is available.
MAXLENGTH is the maximum number of characters that are accepted
as input; this is only appropriate for text entry fields and password
entry fields (and only for single-line text entry fields at that).
If this is not present, the default will be unlimited. The text entry field
is assumed to scroll appropriately if MAXLENGTH is greater than
The SELECT Tag
Inside <FORM> ... </FORM>, any number of SELECT
tags are allowed, freely intermixed with other HTML elements (including
INPUT and TEXTAREA elements) and text (but not
additional forms). In Mosaic for X, SELECT tags are instantiated
as Motif option menus and scrolled lists.
Unlike INPUT, SELECT has both opening and closing
tags. Inside SELECT, only a sequence of OPTION tags --
each followed by an arbitrary amount of plain text (no HTML markup)
-- is allowed; for example:
<OPTION> First option.
<OPTION> Second option.
The attributes to SELECT are as follows:
The attributes to OPTION are as follows:
NAME is the symbolic name for this SELECT element. This
must be present, as it is used when putting together the query string for
the submitted form.
SIZE: if SIZE is 1 or if the SIZE attribute
is missing, by default the SELECT will be represented as a Motif
option menu. If SIZE is 2 or more, the SELECT will be
represented as a Motif scrolled list; the value of SIZE then determines
how many items will be visible.
MULTIPLE, if present (no value), specifies that the SELECT
should allow multiple selections (n of many behavior). The presence
of MULTIPLE forces the SELECT to be represented as a
Motif scrolled list, regardless of the value of SIZE.
SELECTED specifies that this option is selected by default. If
the SELECT allows multiple selections (via the MULTIPLE
attribute), multiple options can be specified as SELECTED.
The TEXTAREA Tag
The TEXTAREA tag can be used to place a multiline text entry field
with optional default contents in a fill-out form. The attributes to TEXTAREA
are as follows:
TEXTAREA fields automatically have scrollbars; any amount of text
can be entered in them.
NAME is the symbolic name of the text entry field.
ROWS is the number of rows (vertical height in characters) of
the text entry field.
COLS is the number of columns (horizontal width in characters)
of the text entry field.
The TEXTAREA element requires both an opening and a
closing tag. A TEXTAREA with no default contents looks like this:
<TEXTAREA NAME="foo" ROWS=4 COLS=40></TEXTAREA>
A TEXTAREA with default contents looks like this:
<TEXTAREA NAME="foo" ROWS=4 COLS=40>
Default contents go here.
The default contents must be straight ASCII text. Newlines are respected
(so in the above example there will be a newline both before and after
"Default contents go here.").
For Method = GET
When the submit button is pressed, the contents of the form will be assembled
into a query URL that looks like this:
("action" here is the URL specified by the ACTION attribute
to the FORM tag, or the current document URL if no ACTION
attribute was specified.)
Strange characters in any of the "name" or "value" instances will be
escaped as usual; this includes "=" and "&". Note: This means
that instances of "=" that separate names and values, and instances of
"&" that separate name/value pairs, are not escaped.
For text and password entry fields, whatever the user typed in will
be the value; if the user didn't type anything, the value will be empty
but the "name=" part of the query string will still be present.
For checkboxes and radio buttons, the VALUE attribute specifies
the value of a checkbox or radio button when it is checked. An unchecked
checkbox is disregarded completely when assembling the query string. Multiple
checkboxes can have the same NAME (and different VALUEs),
if desired. Multiple radio buttons intended to have "one of many" behavior
should have the same NAME and different VALUEs.
For Method = POST
The contents of the form are encoded exactly as with the GET
method (above), but rather than appending them to the URL specified by
the form's ACTION attribute as a query, the contents are sent
in a data block as part of the POST operation. The ACTION
attribute (if any) is the URL to which the data block is POSTed.
If you wish to write a prototype fill-out form and test it against a query
server that simply shows you what you submitted (with name/value pairs
decoded and itemized), you can use the following:
C source code for the query and post-query programs here in this cgi-src
For METHOD="POST", use ACTION="http://hoohoo.ncsa.uiuc.edu/cgi-bin/post-query"
For METHOD="GET", use ACTION="http://hoohoo.ncsa.uiuc.edu/cgi-bin/query"
Important note: If you use the GET method in your form,
you will notice that the GET server will choke if too
much data (more than a couple hundred bytes) is submitted at a time --
the server is passing the data to the form-processing module via a shell
command line, and the maximum shell command line length is being exceeded.
This problem does not exist with the POST method and server.
Now that we have this fancy fill-out form support, we're supporting the
ISINDEX tag differently. Instead of having a browser-interface
method (dialog box or text field) for entering a query, an instance of
ISINDEX is instantiated as a preloaded fill-out form suitable
for entering a query; the form is inlined at the location of the ISINDEX
tag itself in the document.
Justifications for change:
Consistent approach to query mechanisms inside Mosaic.
Allow code and interface complexity to be reduced.
A few nasty problems were hitting the "popup text entry field" approach
attempted for prerelease 2; notably, lots of unavoidable flashing when
field popped up and down and intermittent but crippling Motif geometry
management problem. This change removes those problems.
Everyone wants the ability to enter a query (and the corresponding widgets)
to be present only when the document is actually an ISINDEX document;
this provides that very cleanly.
This solves existing problem of when to retain contents of search field
-- since search field now exists on a per-document basis, this is very
Encourage experimentation with fill-out forms by presenting an example
for existing query engines.
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