Browser: Simple HTML Rendering
The browser library provides the following procedures and classes for parsing and viewing HTML files. The browser/htmltext library provides a simplified interface for rendering to a subclass of the MrEd text% class. The [browser/external] library provides utilities for launching an external browser (such as Firefox).
1 Browser
The browser supports basic HTML commands, plus special Scheme hyperlinks of the form <A MZSCHEME=sexpr>...</A>. When the user clicks on such a link, the string sexpr is parsed as a Scheme program and evaluated. Since sexpr is likely to contain Scheme strings, and since escape characters are difficult for people to read, a | character in sexpr is converted to a " character before it is parsed. Thus,
<A MZSCHEME="|This goes nowhere.|">Nowhere</A> |
creates a “Nowhere” hyperlink, which executes the Scheme program
"This goes nowhere."
The value of that program is a string. When a Scheme hyperlink returns a string, it is parsed as a new HTML document. Thus, where the use clicks on “Nowhere,” the result is a new page that says “This goes nowhere.”
The browser also treats comment forms containing MZSCHEME=sexpr specially. Whereas the <A MZSCHEME=sexpr>...</A> form executes the expression when the user clicks, the MZSCHEME expression in a comment is executed immediately during HTML rendering. If the result is a string, the comment is replaced in the input HTML stream with the content of the string. Thus,
<!-- MZSCHEME="(format |<B>Here</B>: ~a| (current-directory))" --> |
inserts the path of the current working directory into the containing document (and “Here” is boldfaced). If the result is a snip instead of a string, it replaces the comment in the document. Other types of return values are ignored.
If the html file is being accessed as a file: url, the current-load-relative-directory parameter is set to the directory during the evaluation of the mzscheme code (in both examples). The Scheme code is executed through eval.
The MZSCHEME forms are disabled unless the web page is a file: url that points into the doc collection.
(open-url url) → void? |
url : (or/c url? string? input-port?) |
Opens the given url in a vanilla browser frame and returns the frame. The frame is an instance of hyper-frame%.
(html-img-ok) → boolean? |
(html-img-ok ok?) → void? |
ok? : any/c |
A parameter that determines whether the browser attempts to download and render images.
(html-eval-ok) → boolean? |
(html-eval-ok ok?) → void? |
ok? : any/c |
A parameter that determines whether MZSCHEME= tags are evaluated.
hyper-frame-mixin : (class? . -> . class?) | ||
|
[url url]
...superclass-args...)
url : (or/c url? string? input-port?)
Shows the frame and visits url.
(send a-hyper-frame get-hyper-panel%) → (subclass?/c panel%)
Returns the class that is instantiated when the frame is created. Must be a panel with hyper-panel-mixin mixed in. Defaults to just returning hyper-panel%.
(send a-hyper-frame get-hyper-panel) → (is-a?/c panel%)
Returns the hyper panel in this frame.
superclass: (hyper-frame-mixin (frame:status-line-mixin frame:basic%)) |
hyper-no-show-frame-mixin : (class? . -> . class?) | ||
|
The same as the hyper-frame-mixin, except that it doesn’t show the frame and the initialization arguments are unchanged.
superclass: (hyper-no-show-frame-mixin (frame:status-line-mixin frame:basic%)) |
hyper-text-mixin : (class? . -> . class?) | ||
|
An instance of a hyper-text-mixin-extended class should be displayed only in an instance of a class created with hyper-canvas-mixin.
[url url]
[status-frame status-frame]
[post-data post-data]
...superclass-args...)
url : (or/c url? string? input-port?)
status-frame : (or/c (is-a?/c top-level-window<%>) false/c)
post-data : (or/c false/c bytes?)
The url is loaded into the text% object (using the reload method), a top-level window for status messages and dialogs, a progress procedure used as for get-url, and either #f or a post string to be sent to a web server (technically changing the GET to a POST).
Sets the autowrap-bitmap to #f.
(send a-hyper-text map-shift-style
start
end
shift-style)
→
void?
start : exact-nonnegative-integer?
end : exact-nonnegative-integer?
shift-style : style<%>
Maps the given style over the given range.
(send a-hyper-text make-link-style
start
end)
→
void?
start : exact-nonnegative-integer?
end : exact-nonnegative-integer?
Changes the style for the given range to the link style.
→ (or/c url? string? input-port? false/c)
Returns the URL displayed by the editor, or #f if there is none.
Gets the page’s title.
str : string?
Sets the page’s title.
(send a-hyper-text hyper-delta) → style-delta%
Override this method to set the link style.
name : string?
pos : exact-nonnegative-integer?
Installs a tag.
→ (or/c exact-nonnegative-integer? false/c)
name/number : (or/c string? exact-nonnegative-integer?)
Finds the location of a tag in the buffer (where tags are installed in HTML with <A NAME="name">) and returns its position. If name is a number, the number is returned (assumed to be an offset rather than a tag). Otherwise, if the tag is not found, #f is returned.
(send a-hyper-text remove-tag name) → void?
name : string?
Removes a tag.
url
[
post-data-bytes])
→
void?
url : (or/c string? url?)
post-data-bytes : (or/c bytes? false/c) = #f
Follows the link, optionally with the given post data.
start : exact-nonnegative-integer?
end : exact-nonnegative-integer?
url : (or/c url? string?)
Installs a hyperlink.
(send a-hyper-text add-scheme-callback
start
end
scheme-expr)
→
void?
start : exact-nonnegative-integer?
end : exact-nonnegative-integer?
scheme-expr : string?
Installs a Scheme evaluation hyperlink.
(send a-hyper-text add-thunk-callback
start
end
thunk)
→
void?
start : exact-nonnegative-integer?
end : exact-nonnegative-integer?
thunk : (-> any)
Installs a thunk-based hyperlink.
(send a-hyper-text eval-scheme-string str) → any
str : string?
Called to handle the <A MZSCHEME="expr">...</A> tag and <! MZSCHEME="expr"> comments (see above). Evaluates the string; if the result is a string, it is opened as an HTML page.
Reloads the current page.
The text defaultly uses the basic style named "Html Standard" in the editor (if it exists).
url : (or/c url? string?)
When visiting a new page, this method is called to remap the url. The remapped url is used in place of the original url. If this method returns #f, the page doesn’t go anywhere.
This method may be killed (if the user clicks the “stop” button).
(send a-hyper-text get-hyper-keymap) → (is-a?/c keymap%)
Returns a keymap suitable for frame-level handling of events to redirect page-up, etc. to the browser canvas.
superclass: (hyper-text-mixin text:keymap%) |
Extends the text:keymap% class to support standard key bindings in the browser window.
hyper-canvas-mixin : (class? . -> . class?) | ||
|
A hyper-can-mixin-extended canvas’s parent should be an instance of a class derived with hyper-panel-mixin.
(new hyper-canvas-mixin ...superclass-args...)
(send a-hyper-canvas get-editor%) → (subclass?/c text%)
Returns the class used to implement the editor in the browser window. It should be derived from hyper-text% and should pass on the initialization arguments to hyper-text%.
The dynamic extent of the initialization of this editor is called on a thread that may be killed (via a custodian shutdown). In that case, the editor in the browser’s editor-canvas may not be an instance of this class.
(send a-hyper-canvas current-page) → any/c
Returns a representation of the currently displayed page, which includes a particular editor and a visible range within the editor.
url
relative-to-url
[
progress-proc
post-data])
→
void?
url : (or/c url? string?)
relative-to-url : (or/c url? string? false/c)
progress-proc : (boolean? . -> . any) = void
post-data : (or/c bytes? false/c) = #f
Changes to the given url, loading it by calling the make-editor method. If relative-to-url is not #f, it must be a URL for resolving url as a relative URL. url may also be a port, in which case, relative-to-url must be #f.
The progress-proc procedure is called with a boolean at the point where the URL has been resolved and enough progress has been made to dismiss any message that the URL is being resolved. The procedure is called with #t if the URL will be loaded into a browser window, #f otherwise (e.g., the user will save the URL content to a file).
If post-data-bytes is a byte string instead of false, the URL GET is changed to a POST with the given data.
page : any/c
notify? : any/c
Changes to the given page. If notify? is not #f, the canvas’s parent is notified about the change by calling its leaving-page method.
(send a-hyper-canvas after-set-page) → void?
Called during set-page. Defaultly does nothing.
hyper-panel-mixin : (class? . -> . class?) | ||
|
[info-line? info-line?]
...superclass-args...)
info-line? : any/c
Creates controls and a hyper text canvas. The controls permit a user to move back and forth in the hypertext history.
The info-line? argument indicates whether the browser should contain a line to display special DOCNOTE tags in a page. Such tags are used primarily by the PLT documentation.
(send a-hyper-panel make-canvas container) → void?
container : (is-a?/c area-container<%>)
Creates the panel’s hypertext canvas, an instance of a class derived using hyper-canvas-mixin. This method is called during initialization.
(send a-hyper-panel get-canvas%)
→ (subclass?/c editor-canvas%)
Returns the class instantiated by make-canvas. It must be derived from hyper-canvas-mixin.
(send a-hyper-panel make-control-bar-panel container) → any/c
container : (is-a?/c area-container<%>)
Creates the panel’s sub-container for the control bar containing the navigation buttons. If #f is returned, the panel will have no control bar. The default method instantiates horizontal-panel%.
Goes back one page, if possible.
Goes forward one page, if possible.
(send a-hyper-panel get-canvas) → (is-a?/c editor-canvas%)
Gets the hypertext canvas.
(send a-hyper-panel on-navigate) → void?
Callback that is invoked any time the displayed hypertext page changes (either by clicking on a link in the canvas or by rewind or forward calls).
(send a-hyper-panel leaving-page
page
new-page)
→
any
page : any/c
new-page : any/c
This method is called by the hypertext canvas to notify the panel that the hypertext page changed. The page is #f if new-page is the first page for the canvas. See also page->editor.
(send a-hyper-panel filter-notes notes) → (listof string?)
notes : (listof string?)
Given the notes from a page as a list of strings (where each string is a note), returns a single string to print above the page.
Reloads the currently visible page by calling the reload method of the currently displayed hyper-text.
superclass: (hyper-panel-mixin vertical-panel%) |
(editor->page editor) → any/c |
editor : (is-a?/c text%) |
Creates a page record for the given editor, suitable for use with the set-page method of hyper-canvas-mixin.
(page->editor page) → (is-a?/c text%) |
page : any/c |
Extracts the editor from a page record.
(bullet-size) → exact-nonnegative-integer? |
(bullet-size n) → void? |
n : exact-nonnegative-integer? |
Parameter controlling the point size of a bullet.
superclass: snip% |
Instances of this class behave like image-snip% objects, except they have a <map> ... </map> associated with them and when clicking on them (in the map) they will cause their init arg text to follow the corresponding link.
(new image-map-snip% [html-text html-text])
html-text : (is-a?/c html-text<%>)
key : string?
Sets the key for the image map (eg, "#key").
Returns the current key.
shape
region
href)
→
void?
shape : string?
region : (listof number?)
href : string?
Registers the shape named by shape whose coordinates are specified by region to go to href when that region of the image is clicked on.
2 Browser Unit
browser@ : unit? |
Imports mred^, tcp^, and url^, and exports browser^.
3 Browser Signature
browser^ : signature |
Includes all of the bindings of the browser library.
4 HTML As Text Editor
|
Returns a base URL used for building relative URLs, or #f if no base is available.
str : string?
Registers the title str for the rendered page.
start : exact-nonnegative-integer?
end : exact-nonnegative-integer?
url : (or/c url? string?)
Registers a hyperlink for the given region in rendered page.
name : string?
pos : exact-nonnegative-integer?
Installs a tag.
(send a-html-text make-link-style
start
end)
→
void?
start : exact-nonnegative-integer?
end : exact-nonnegative-integer?
Changes the style for the given range to the link style.
(send a-html-text add-scheme-callback
start
end
scheme-expr)
→
void?
start : exact-nonnegative-integer?
end : exact-nonnegative-integer?
scheme-expr : string?
Installs a Scheme evaluation hyperlink.
(send a-html-text add-thunk-callback
start
end
thunk)
→
void?
start : exact-nonnegative-integer?
end : exact-nonnegative-integer?
thunk : (-> any)
Installs a thunk-based hyperlink.
url
[
post-data-bytes])
→
void?
url : (or/c string? url?)
post-data-bytes : (or/c bytes? false/c) = #f
Follows the link, optionally with the given post data.
html-text-mixin : (class? . -> . class?) | ||
|
Extends the given text% class with implementations of the html-text<%> methods. Hyperlinks are attached to clickbacks that use send-url from net/sendurl.
}
| ||||||||||||||||||||||||||||
in : input-port? | ||||||||||||||||||||||||||||
dest : (is-a? html-text<%>) | ||||||||||||||||||||||||||||
load-img? : any/c | ||||||||||||||||||||||||||||
eval-mz? : any/c |
Reads HTML from in and renders it to dest. If load-img? is #f, then images are rendered as Xed-out boxes. If eval-mz? is #f, then MZSCHEME hyperlink expressions and comments are not evaluated.
Uses the style named "Html Standard" in the editor’s style-list (if it exists) for all of the inserted text’s default style.
5 Launching an External Browser
(send-url str [separate-window?]) → null |
str : null |
separate-window? : void = #t |
Like send-url from net/sendurl , but under Unix, the user is prompted for a browser to use if none is recorded in the preferences file.
(browser-preference? v) → boolean? |
v : any/c |
Returns #t if v is a valid browser preference.
(update-browser-preference url) → void? |
url : (or/c string? false/c) |
Under Unix, prompts the user for a browser preference and records the user choice as a framework preference (even if one is already recorded). If url is not #f, it is used in the dialog to explain which URL is to be opened; if it is #f, the 'internal will be one of the options for the user.
(install-help-browser-preference-panel) → void? |
Installs a framework preference panel for “Browser” options.
(add-to-browser-prefs-panel proc) → void? |
proc : ((is-a?/c panel%) . -> . any) |
The proc is called when the “Browser” panel is constructed for preferences. The supplied argument is the panel, so proc can add additional option controls. If the panel is already created, proc is called immediately.
6 DrScheme Browser Preference Panel
tool@ : unit? |
A unit that implements a DrScheme tool to add the “Browser” preference panel.