WebLord

Predefined Object Properties

Predefined image properties are property names that have special meaning to WebLord. Some of these properties must be defined by you to give an object meaning, and in other cases a property supplies optional information or defines alternate behavior; such a missing property definition may thus merely influence how an object is constructed.

This section describes the properties for each object that have a predefined meaning.

SITE object

PAGE objects

TEXT objects

IMAGE objects (HTML only)

Properties for use with IF / IFDEF / IFNDEF

NOTE: The SITE object occupies a special place with WebLord. Only the first such object is ever available, and its name is of little direct importance.

Properties defined in the SITE are inherited by all pages as well as the objects that these pages reference.

pages

If WebLord is run without a specific list of pages to generate, then the 'pages' property in the first SITE object supplies the list of pages that comprise the entire site. Pages that are defined in the site file, but not listed here can be generated only through explicit reference with a program argument.

The 'value' of page objects is written to the file specified by their 'output' property.

ifdef (Never inherited)

A list of identifiers, all of which must be defined (and have a non-empty value), otherwise the current object returns an empty value.

ifndef (Never inherited)

A list of identifiers; if any of them are defined (have a non-empty value), then the current object returns an empty value.

value (Never inherited)

A list of identifiers that define the contents of the page. If the object defined an 'if' operation, then the 'then' or 'else' portion is used instead of the 'value'

output

A list of identifiers that define the output filename for the page.

pre-exec (Never inherited)

A list of identifiers that define an external command to be executed before the page is generated. This may be employed to produce a backup copy of a previous version of the page, prepare specific input files needed for the page, etc. Notice that the external command to be executed is operating system specific. An example of how to implement a more operating system independent method of executing external commands, see the tools.wl file.

post-exec (Never inherited)

A list of identifiers that define an external command to be executed after the page has been generated and its output written to a file. If a page is not generated for any reason, the 'post-exec' command is not executed, either. Notice that the external command to be executed is operating system specific. An example of how to implement a more operating system independent method of executing external commands, see the tools.wl file.

The 'post-exec' command is useful for post-processing of a page, such as archiving it, running an HTML validator on the page, and/or uploading the file to an internet service provider.

post-exec-batch

By declaring a 'post-exec-batch' property, all 'post-exec' commands for pages can be caused to be "batched" (grouped) together for execution after the last page has been generated. The 'post-exec-batch' property defines the filename that is used to store the commands. A NOEXEC argument given to WebLord will suppress the creation of this file as well as suppress all 'post-exec' commands.

WebLord knows how to ensure that a the file is executable for your particular operating system.

NOTE: By avoiding TEXT object properties marked "HTML only" you ensure that your output is free of any language dependency.

ifdef (Never inherited)

A list of identifiers, all of which must be defined (and have a non-empty value), otherwise the current object returns an empty value.

ifndef (Never inherited)

A list of identifiers; if any of them are defined (have a non-empty value), then the current object returns an empty value.

if (Never inherited)

A simple comparison expression of the form "value1 operator value2" where the operator is one of the six basic equality, inequality, less-than, greater-than, less-than-or-equal, or greater-than-or-equal (= != < > <= >=); if both operands begin with a digit 0 through 9 then the operation is performed numerically, else a string comparison is used. Depending on the success or failure of the expression the value is taken from a 'then' or 'else' instead.

Not that if a 'value-in-file' property is defined, then the value of the 'then' or 'else' properties is treated no differently than the standard 'value' property: it is the name of a file.

exec (Never inherited)

Executes an external (shell) command to obtain a value for the object. The output of the command must be written to a file and the contents of this file is then retrieved by setting the 'value' property of the object to this file name and also defining the 'value-in-file' property (any value will do).

Most modern operating systems support the concept of "I/O redirection", which refers to sending the output of a program to a diskfile instead of the display. Syntactically, this is usually accomplished by placing a > symbol on the command line, followed by the name of the file that is to receive the output from the program.

By constructing the 'exec' property to include such I/O redirection, and setting the 'value-in-file' property to some value, the object can thus call upon external programs to generate values for the object dynamically.

Use the 'exec-cleanup' command to perform a cleanup operation (such as deleting the file after it is no longer needed.)

On the AMIGA, it is also possible to use named pipes, thus avoiding the use of physical diskspace and the need to cleanup a temporary file again.

exec-cleanup (Never inherited)

Executed after the object's value has been constructed (through the use of an 'exec' property). This is useful to get rid again of an external file that was needed to momentarily store an external program's output and allow WebLord to retrieve it as the object's value.

value-in-file (Never inherited)

If a 'value-in-file' property is defined then the 'value' property (or 'then' / 'else') defines the name of a file from which the value of the object is retrieved.

value (Never inherited)

A list of identifiers that that define the value for the text object.

If the object defined an 'if' operation, then the 'then' or 'else' portion is used instead of the 'value'

NOTE: The 'value' (or 'then' / 'else') property defines a file name if a 'value-in-file' property is defined.

value-is-static (Never inherited)

If this property is defined (any value will do) then the value of the object is evaluated only the first time it is encountered and is thereafter stored. This is useful especially on objects with both an 'exec' and a 'value-in-file' property where you do now wish (or need to) execute the external program again and again to retrieve the same value.

Objects with the 'value-is-static' property are only affected in future references by 'ifdef' and 'ifndef' properties; any decision as to the object's value that was made due to an 'if' property, or (possibly inherited) 'link' properties, etc. no longer apply once the value has been determined and was "frozen".

link (HTML only; Never inherited)

A list of identifiers that define a URL that is used to enclose the text object with an HTML anchor specification. Note that the use of a 'link' property

NOTE: IMAGE objects are specifically designed to improve the ease with which images (and image links) are employed on HTML pages. There is nothing that an IMAGE object does that cannot be done with TEXT objects as well. IMAGE objects are, however, more convenient to use as they already know how to assemble an reference with various optional properties.

If you are using WebLord to generate non-HTML output then you will definitely want to avoid IMAGE objects, of course.

IMAGE objects function just like TEXT objects (including all properties defined above) with the single exception that instead of the common 'value' property (which is never inherited), IMAGE objects use an inheritable 'image-url' property that supplies the filename (or URL) of the image. A 'value' property in an IMAGE object is therefore meaningless and is ignored.

image-url (HTML only)

A list of identifiers that define the URL of the image. This is given to the the "src" tag in the specification.

width and height (HTML only)

Each a list of identifiers that define the width and height, respectively, of the image. The values are given to the "width" and "height" tags in the specification.

Acceptable values depend on the HTML specification, of course; in general, they specify the dimensions of the image so that browser software can proceed with the page layout before the entire image has been downloaded and its size become known. As a result pages appear to load much faster, so the use of width and height tags is strongly encouraged. The width and height may also specify a percentage of the browser's display window size. While this is useful to ensure that an image is always scaled to the same relative size, not all browsers support this feature.

Furthermore, some browsers use the width and height tags to scale an image that is actually larger or smaller than the given numbers. Not all browsers support this feature.

border (HTML only)

A list of identifiers that define the thickness of the border that is to be placed around the image. Most browsers place this border around the image only when the image is enclosed in an anchor (see 'link' below.)

By setting this value to "0" the border is usually entirely avoided. While this tends to enhance the visual appearance of a page with such image anchors, the missing border also removes the feedback that the user would get from such a border. As a result, image anchors without borders tend to appear like any any image on the page and may never be recognized as "clickable." Use a border with "0" thickness with care!

align (HTML only)

A list of identifiers that defines the placement of the image on a page: "top", "middle", or "bottom". "Left", "center", and "right" are also available. The alignment was originally meant to align surrounding text to the "top", "middle" or "bottom" edge of the image. The HTML specification has since been extended to allow "left", "center" and "right" but it is somewhat unclear about combinations of the two (such as how to specify both "left" on the page, and "top" edge of the image.)

alt (HTML only)

A list of identifiers that defines the alternate text for the image. This text (or at least as much as will fit) is usually displayed by browsers in the space where an image will be displayed before it has been actually downloaded and made visible. Some browsers are unable to display images or are configured by their users to download image only when explicitly ordered to do so by their users (perhaps to save time because of a slow connection.) In such cases the "alt" tag can provide valuable information about the nature, purpose, or subject of the image.

hspace (HTML only)

A list of identifiers that defines the horizontal space (left and right) around the image to separate it from surrounding text.

vspace (HTML only)

A list of identifiers that defines the vertical space (above and below) around the image to separate it from surrounding text.

The following special purpose properties are defined globally, especially for use in 'if' property to conditionally select either the 'then' or the 'else' value of the the associated object:

_OS

This has one of the following values (the list will expand in the future):

AMIGA

WebLord for the Amiga computer (AmigaOS) (68K & PowerPC)

UNIX

WebLord for Unix

WIN32

WebLord for 32-bit MS Windows (Win95 or WinNT)

The following may be added in the future but are currently not defined:

WIN16

WebLord for 16-bit MS Windows (Win31)

MSDOS

WebLord for MS-DOS

MAC

WebLord for Macintosh (68K & PowerPC)

The following special purpose properties are defined globally, especially for use in the conditional 'ifdef' and 'ifndef' properties to conditionally suppress a value for the associated object:

_AMIGA

Defined (a value of '1') if running on an Amiga

_UNIX

Defined (a value of '1') if running on a Unix system

_WIN32

Defined (a value of '1') if running on a 32-bit MS Windows (Win95 or WinNT) system