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IVLE File Browser Design
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========================
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This is the design for the file browser *and* editor components of IVLE.
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They are now very closely integrated, sharing a common backend.
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A prototype is available that I hacked up in Ajax/Python, available at
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/trunk/prototypes/browser.
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Separation of components
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------------------------
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The issue has arisen as to how we will separate components in terms of
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distinct browser pages. (Will things be on separate server-prepared pages or
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will the JavaScript manipulate the one page accordingly).
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We have settled on a mid-way solution. Each component (ie. the file browser,
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the text editor), will have a distinct browser page with its own HTML,
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The choice of how to split up pages within each component is up to that
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component. Most components will use JavaScript so they will have just a single
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The file browser will be a single page which uses JavaScript internally to
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navigate around. So clicking on subdirectories will not reload a new page, it
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will just change the current page.
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The editor will of course be just a single page.
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The server side is shared between the file browser and editor. It is written
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in Python and acts as basically a "shell" to the file system and subversion
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Essentially it takes input in the form of an HTTP Request (GET and POST
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accordingly), and returns material primarily as [JSON](http://www.json.org)
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data. JSON is extremely easy to write and read in both Python and JavaScript.
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It is effectively the common subset of JavaScript and Python data.
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For instance, the client may wish to perform an "ls" command. Since this has
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no side-effects on the server, it sends an "ls" request using GET to pass the
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path name. The server then returns a directory listing in JSON which might
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{"svnstatus": "unversioned", "isdir": true, "size": 4096,
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"mtime": "Fri Dec 7 16:27:54 2007", "filename": "subdir"},
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{"svnstatus": "normal", "isdir": false, "size": 22,
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"mtime": "Fri Dec 7 12:21:24 2007", "filename": "data"}
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This nicely separates the client/server with the server being completely
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independent of the interface and the client being able to make things happen
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by calling simple commands via Ajax.
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The interface is split into 4 main sections. These parallel a common file
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browser paradigm. The interface is designed to be familiar to Windows
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Explorer, etc, but adapted for the browser.
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Along the top there is the location bar. This contains a clickable set of
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links showing the current directory path.
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The main part of the page is the file list. This is a HTML table consisting of
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the following columns:
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* Checkboxes, for file selection.
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* Icon (tooltip: textual file type)
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* SVN Status icon (tooltip: textual SVN status)
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* Filename (hyperlink, tooltip if the filename had to be condensed)
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* Size (natural units)
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* Date modified (naturalised, tooltip: full date)
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Column headers are all clickable for sorting. All sorting is handled on the
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client side (note: the prototype does sorting on the server, this will
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We try to represent information rather compactly in the table view. Tooltips
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and/or sidebar gives more information. This is why there are tooltips for
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basically each column giving additional info.
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SVN Status icons are a separate column from the main one but represent the
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same as TortoiseSVN. For example, green ticks for "normal", red bangs for
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Filenames are condensed in the middle (so you see a fixed number of chars at
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the beginning and end. For instance "A very long file with a long name" is
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condensed into "A very long...long name").
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Dates are condensed according to a "naturalisation" algorithm. Files modified
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today or yesterday show "today" or "yesterday" accordingly, and the time.
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Files modified in the last 5 days show "3 days ago". Other files just show the
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date. The tooltip always gives the full date and time.
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Along the bottom is a status bar showing some static things about the current
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The main feature of interest is the side panel, which shows information and
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buttons about the selected file(s). Note that in the prototype we have buttons
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in the file list, which is quite ugly and difficult to use. It is much more
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natural to select the files, then act on them. See "side panel" later.
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### File selection ###
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There are always 0 or more files selected. Selection can be controlled
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precisely by checking or unchecking the checkboxes on the side. Clicking a
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file's name selects it and deselects all the others. If we can detect Ctrl and
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Shift we can do better selection algorithms.
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Graphically I am picturing the file list rows to be shaded as:
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* Interlacing shades of grey for deselected files.
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* Interlacing shades of blue for selected files.
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* White for rows with the mouse hovering.
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The side panel is a dynamic area which changes whenever the selections change.
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It displays detailed information and actions pertaining to the
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currently-selected file(s).
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If only one file is selected, it displays all the details about that file (eg.
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file size, full date and time, and the widest range of buttons).
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* For Python files: "Run in Browser" and "Run in Console".
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* For HTML files, PDFs, images, even text files, any other content that web
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browsers natively recognise: "View in Browser" (or just "Open").
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* For directories: "Open"
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* Edit (perhaps only for non-binary files - is there any point in letting
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students open binary files in the text editor? This could just be confusing
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as students might expect to see an image editor, for example)
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If multiple files are selected, it just displays the number of files, and
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The following buttons are available no matter how many files are selected (at
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* Cut (see "copy-paste")
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Finally there are the Subversion buttons. These vary depending on not only the
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files selected, but their SVN statuses.
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If just one file is selected, you see the following buttons:
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* "Add", if the file is unversioned.
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* "Commit", if the file is added, modified, etc.
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* "Check for updates", always.
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There may be others such as log, diff, depending on how detailed we go into
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If multiple files are selected, the "add" and "commit" buttons are visible if
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one or more files are applicable to that button. However, to prevent
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misunderstandings, only one button is ever seen at any time (with "add" taking
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precedence). This way, if the user selects modified AND unversioned files,
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they may click "commit" thinking it will add the unversioned ones (it won't).
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So they are forced to click "add" first, then "commit".
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"Check for updates" and "Commit all" will be available from the top toolbar
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which applies to the whole directory and its subdirectories.
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#### Discussion: Add and commit combined? ####
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We don't really need separate "add" and "commit". Because you can selectively
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commit, we may just dumb it down to having "commit" available on unversioned
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files, and it automatically adds. You just select all the files you want to
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add and hit "commit", along with any other files you changed.
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### Opening the editor ###
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The editor is a separate page. If a file is to be edited, it tries to open it
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in a new window. This should encourage students to use browser tabs.
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Directory-wide actions
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----------------------
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Some actions can be performed on the entire directory. These should also
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appear in the side-bar, but in a separate section. Or they could be in a
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toolbar along the top. They are:
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* New file (opens the editor)
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Mime type detection and usage
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-----------------------------
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We can use Python's builtin mimetypes module to detect mime types of the
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files. Python should send the mime types along with the listing info.
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We use mime types for the following purposes:
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* File type icons and descriptions (note: Need a mapping from mime type to
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friendly description, eg "text/python-src" to "Python source code").
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* Image types have previews in the side panel.
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* Determining other actions. eg. Python source can be executed. HTML source
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and PDF files can be viewed in the browser.
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* Editor warnings for binary types (though this may be best if we warn based
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on whether it contains invalid unicode chars instead).
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We will have a full cut-copy-paste paradigm just the same as how modern
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desktop file browsers work. The "clipboard" will be stored just on the client
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side, as a global JavaScript variable, so it is not shared across browser
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sessions or windows. (*Should it be?*)
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Quite simply, "copy" replaces the clipboard with a "copy" action associated
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with the selected files. "cut" does the same but associates a "move" action.
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(Also shades the cut files somehow differently). "paste" executes the copy or
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Discussion: Trash bin?
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----------------------
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Do we need a trash bin, given that we're using Subversion? Students should
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realise that "temporary files" are just that - if you delete them, they're
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gone. "Permanent files" can be recovered (but we should make that process less
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painful than it is currently in Subversion).
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Perhaps "novice mode" should have a trash bin but expert mode should rely on
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Subversion? (Will the transition be jarring??)
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The editor page will be a modified version of EditArea (basically with a
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It will interact with the server simply as it reads and writes files, and also
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has limited Subversion access.
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The four major features being added to EditArea are:
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* Save. Saves the file to a location in the user's directory (prompting first
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if it doesn't yet exist). Also Save As. Very familiar.
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* Save and Commit. Saves the file AND automatically SVN commits.
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* Reload. Reloads the file from the student's directory.
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* Check for updates. Does a SVN update of the file and loads it. (Is this a
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Note that EditArea's existing "save" feature is actually going to make the
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browser offer the file as a download. This will be renamed to "download".
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All the commit features will prompt for a commit log (either a JS prompt() or
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a nicer popup floating element). But the commit log is an optional feature
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which is turned off by default. That is, by default a log message like "No log
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message provided." is written to the log. Once students are more familiar with
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SVN, they can turn on log messages to be prompted when they commit.
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(Alternatively this feature may automatically come with the "advanced"
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removed
doc/notes/apps/browser.txt
