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phoenix_title HTML Overview

The html library provides classes for parsing and displaying HTML.

It is not intended to be a high-end HTML browser. If you are looking for something like that try http://www.mozilla.org/.

html can be used as a generic rich text viewer - for example to display a nice About Box (like those of GNOME apps) or to display the result of database searching. There is a FileSystem class which allows you to use your own virtual file systems.

HtmlWindow supports tag handlers. This means that you can easily extend html library with new, unsupported tags. Not only that, you can even use your own application-specific tags!

There is a generic HtmlParser class, independent of HtmlWindow.

HTML quick start

Displaying HTML

Class HtmlWindow (derived from ScrolledWindow) is used to display HTML documents.

It has two important methods: LoadPage and SetPage. LoadPage loads and displays HTML file while SetPage displays directly the passed string. See the example:

mywin.LoadPage("test.htm")
mywin.SetPage("htmlbody" \
              "h1Error/h1" \
              "Some error occurred :-H)" \
              "/body/hmtl")

Setting up HtmlWindow

Because HtmlWindow is derived from ScrolledWindow and not from Frame, it doesn’t have visible frame. But the user usually wants to see the title of HTML page displayed somewhere and the frame’s titlebar is the ideal place for it.

HtmlWindow provides 2 methods in order to handle this: SetRelatedFrame and SetRelatedStatusBar. See the example:

html = wx.html.HtmlWindow(self)
html.SetRelatedFrame(self, "HTML : %%s")
html.SetRelatedStatusBar(0)

The first command associates the HTML object with its parent frame (this points to Frame object there) and sets the format of the title. Page title “Hello, world!” will be displayed as “HTML : Hello, world!” in this example.

The second command sets which frame’s status bar should be used to display browser’s messages (such as “Loading...” or “Done” or hypertext links).

Customizing HtmlWindow

You can customize HtmlWindow by setting font size, font face and borders (space between border of window and displayed HTML). Related functions:

The last two functions are used to store user customization info ConfigBase stuff (for example in the registry under Windows, or in a dotfile under Unix).

HTML Printing

The html library provides printing facilities with several levels of complexity. The easiest way to print an HTML document is to use the HtmlEasyPrinting class.

It lets you print HTML documents with only one command and you don’t have to worry about deriving from the Printout class at all. It is only a simple wrapper around the HtmlPrintout, normal wxPython printout class.

And finally there is the low level class HtmlDCRenderer which you can use to render HTML into a rectangular area on any DC.

It supports rendering into multiple rectangles with the same width. (The most common use of this is placing one rectangle on each page or printing into two columns.)

Help Files Format

html library can be used to show an help manual to the user; in fact, it supports natively (through HtmlHelpController) a reduced version of MS HTML Workshop format.

A book consists of three files: the header file, the contents file and the index file.

You can make a regular zip archive of these files, plus the HTML and any image files, for HTML (or helpview) to read; and the ".zip" file can optionally be renamed to ".htb".

Header file (.hhp)

The header file must contain these lines (and may contain additional lines which are ignored):

Contents file=filename.hhc
Index file=filename.hhk
Title=title of your book
Default topic=default page to be displayed.htm

All filenames (including the Default topic) are relative to the location of the ".hhp" file.

Note

For localization, in addition the ".hhp" file may contain the line:

Charset=rfc_charset

which specifies what charset (e.g. “iso8859_1”) was used in contents and index files. Please note that this line is incompatible with MS HTML Help Workshop and it would either silently remove it or complain with some error.

Contents file (.hhc)

Contents file has HTML syntax and it can be parsed by regular HTML parser. It contains exactly one list (<ul> ... </ul> statement):

<ul>

    <li><object type="text/sitemap">
                <param name="Name" value="@topic name@">
                <param name="ID" value=@numeric_id@>
                <param name="Local" value="@filename.htm@">
            </object></li>
    <li><object type="text/sitemap">
                <param name="Name" value="@topic name@">
                <param name="ID" value=@numeric_id@>
                <param name="Local" value="@filename.htm@">
            </object></li>
</ul>

You can modify value attributes of param tags. The topic name is name of chapter/topic as is displayed in contents, filename.htm is the HTML page name (relative to the ".hhp" file) and numeric_id is optional - it is used only when you use Display.

Items in the list may be nested - one <li> statement may contain a <ul> sub-statement:

<ul>

    <li><object type="text/sitemap">
            <param name="Name" value="Top node">
            <param name="Local" value="top.htm">
        </object></li>
    <ul>
        <li><object type="text/sitemap">
            <param name="Name" value="subnode in
            topnode">
            <param name="Local" value="subnode1.htm">
            </object></li>

    </ul>

    <li><object type="text/sitemap">
            <param name="Name" value="Another Top">
            <param name="Local" value="top2.htm">
        </object></li>

</ul>

Index file (.hhk)

Index files have same format as contents files except that ID params are ignored and sublists are not allowed.

Input Filters

The html library provides a mechanism for reading and displaying files of many different file formats.

LoadPage can load not only HTML files but any known file. To make a file type known to HtmlWindow you must create a HtmlFilter filter and register it using AddFilter.

Cells and Containers

This article describes mechanism used by HtmlWinParser and HtmlWindow to parse and display HTML documents.

Cells

You can divide any text (or HTML) into small fragments. Let’s call these fragments cells. Cell is for example one word, horizontal line, image or any other part of document. Each cell has width and height (except special “magic” cells with zero dimensions - e.g. colour changers or font changers). See HtmlCell.

Containers

Container is kind of cell that may contain sub-cells. Its size depends on number and sizes of its sub-cells (and also depends on width of window). See HtmlContainerCell, Layout. This image shows the cells and containers:

overview_html_contbox.png

Using Containers in Tag Handler

HtmlWinParser provides a user-friendly way of managing containers. It is based on the idea of opening and closing containers.

Use OpenContainer to open new a container within an already opened container. This new container is a sub-container of the old one. (If you want to create a new container with the same depth level you can call CloseContainer(); OpenContainer(); ).

Use CloseContainer to close the container. This doesn’t create a new container with same depth level but it returns “control” to the parent container. See explanation:

overview_html_cont.png

There clearly must be same number of calls to OpenContainer as to CloseContainer.

Example

This code creates a new paragraph (container at same depth level) with “Hello, world!”:

myParser.CloseContainer()
c = myParser.OpenContainer()

myParser.AddText("Hello, ")
myParser.AddText("world!")

myParser.CloseContainer()
myParser.OpenContainer()

and here is image of the situation:

overview_html_hello.png

You can see that there was an opened container before the code was executed. We closed it, created our own container, then closed our container and opened new container.

The result was that we had same depth level after executing. This is general rule that should be followed by tag handlers: leave depth level of containers unmodified (in other words, number of OpenContainer and CloseContainer calls should be same within HandleTag ‘s body).

Note

Notice that it would be usually better to use InsertCell instead of adding text to the parser directly.

Tag Handlers

The html library provides architecture of pluggable tag handlers. Tag handler is class that understands particular HTML tag (or tags) and is able to interpret it.

HtmlWinParser has a static table of modules. Each module contains one or more tag handlers. Each time a new HtmlWinParser object is constructed all modules are scanned and handlers are added to HtmlParser’s list of available handlers.

How it works

Common tag handler’s HandleTag method works in four steps:

  • Save state of parent parser into local variables
  • Change parser state according to tag’s params
  • Parse text between the tag and paired ending tag (if present)
  • Restore original parser state

See HtmlWinParser for methods for modifying parser’s state. In general you can do things like opening/closing containers, changing colors, fonts etc...

Providing own tag handlers

See the lib.wxpTag on how to provide your own tag handlers.

Tag handlers

The handler is derived from HtmlWinTagHandler (or directly from HtmlTagHandler).

Tags supported by html

html is not a full implementation of HTML standard. Instead, it supports most common tags so that it is possible to display simple HTML documents with it. (For example it works fine with pages created in Netscape Composer or generated by tex2rtf).

Following tables list all tags known to html, together with supported parameters.

A tag has general form of tagname param_1 param_2 ... param_n where param_i is either paramname="paramvalue" or paramname=paramvalue - these two are equivalent. Unless stated otherwise, html is case- insensitive.

Table of common parameter values

We will use these substitutions in tags descriptions:

[alignment] CENTER
LEFT
RIGHT
JUSTIFY
[v_alignment] TOP
BOTTOM
CENTER
[color] HTML 4.0-compliant colour specification
[fontsize] -2
-1
+0
+1
+2
+3
+4
1
2
3
4
5
6
7
[pixels] integer value that represents dimension in pixels
[percent] i%
where i is integer
[url] an URL
[string] text string
[coords] c(1),c(2),c(3),...,c(n)
where c(i) is integer

List of supported tags

A NAME=[string]
HREF=[url]
TARGET=[target window spec]
ADDRESS  
AREA SHAPE=POLY
SHAPE=CIRCLE
SHAPE=RECT
COORDS=[coords]
HREF=[url]
BIG  
BLOCKQUOTE  
BODY TEXT=[color]
LINK=[color]
BGCOLOR=[color]
BR ALIGN=[alignment]
CENTER  
CITE  
CODE  
DD  
DIV ALIGN=[alignment]
DL  
DT  
EM  
FONT COLOR=[color]
SIZE=[fontsize]
FACE=[comma-separated list of facenames]
HR ALIGN=[alignment]
SIZE=[pixels]
WIDTH=[percent|pixels]
NOSHADE
H1  
H2  
H3  
H4  
H5  
H6  
I  
IMG SRC=[url]
WIDTH=[percent|pixels]
HEIGHT=[pixels]
ALIGN=TEXTTOP
ALIGN=CENTER
ALIGN=ABSCENTER
ALIGN=BOTTOM
USEMAP=[url]
KBD  
LI  
MAP NAME=[string]
META HTTP-EQUIV=”Content-Type”
CONTENT=[string]
OL  
P ALIGN=[alignment]
PRE  
SAMP  
SMALL  
SPAN  
STRIKE  
STRONG  
SUB  
SUP  
TABLE ALIGN=[alignment]
WIDTH=[percent|pixels]
BORDER=[pixels]
VALIGN=[v_alignment]
BGCOLOR=[color]
CELLSPACING=[pixels]
CELLPADDING=[pixels]
TD ALIGN=[alignment]
VALIGN=[v_alignment]
BGCOLOR=[color]
WIDTH=[percent|pixels]
COLSPAN=[pixels]
ROWSPAN=[pixels]
NOWRAP
TH ALIGN=[alignment]
VALIGN=[v_alignment]
BGCOLOR=[color]
WIDTH=[percent|pixels]
COLSPAN=[pixels]
ROWSPAN=[pixels]
TITLE  
TR ALIGN=[alignment]
VALIGN=[v_alignment]
BGCOLOR=[color]
TT  
U  
UL  

List of supported styles

html doesn’t really have CSS support but it does support a few simple styles: you can use "text-align", "width", "vertical-align" and "background" with all elements and for SPAN elements a few other styles are additionally recognized:

  • color
  • font-family
  • font-size (only in point units)
  • font-style (only “oblique”, “italic” and “normal” values are supported)
  • font-weight (only “bold” and “normal” values are supported)
  • text-decoration (only “underline” value is supported)