[boost] [gui] GUI Taxonomy

From: Alan Gutierrez (alan-boost_at_[hidden])
Date: 2004-12-24 02:16:40

The OS Direction

    I'm looking over wxWindows. I'd like to avoid this sort of
    thing, yet another wrapper library.
    
    They seem to have done as Andy Little and Reece Dunn have
    cautioned against, and started with a particular OS as a model,
    rather than starting with a model.

    As I look closer, or stand back and squint, the object heirarchy
    appears to be a usual-suspects collection of GUI objects, wxPen,
    wxWindow, wxFocusEvent, et al. Oh, and wxObject. *sigh*
    
    Perhaps they didn't start with an particular OS, but they
    certialy started at the OS and worked their way up, rather than
    starting at application and working their way back.

    It is vital to address the design of the primitives.

    It is a mistake to think of a GUI as merely a collection of
    primitives.

    After thirty years, the GUI has begun to develop a set of
    canonical forms. Any new GUI library should recognize these
    forms, and cater to the needs of the developer who must
    implement them.

A Taxonomy

  - The Dialog

    A collection of widgets, gathered together in a window that
    usually of a fixed size, usually presented to the user in a
    modal state. Hence the term dialog, indicating a back and forth
    between the user and the application.

    Most dialog systems include a means to specify the layout of a
    dialog from a resource file.

    Dialog applications include setting preferences, choosing files,
    notification of errors, specification of search criteria.

  - The Grid

    A collection of widgets, arranged in scrollable rows and
    columns, in a resizable window, where widgets can be added or
    removed as the inserts or deletes data.

    Newer windowing libraries such as Delphi's VCL or Swing provide
    a grid library, for a time it seemed to be a defining
    characteristic of a new entry into the GUI arena.

    Grid heavy applications include spreadsheets, databases, and
    accounting applications.

  - The Document

    Text with a flow direction, broken by whitespace and
    hyphenation, along with imagry, and object, grouped by blocks,
    gathered into columns and tables. 

    Most recent application frameworks provide support for the
    document model by making a component of a web browser, or
    providing a rich text edit control.

    Document applications include web browsering, word processing,
    and reporting.  

  - The Canvas

    A blank surface onto which shapes are input, usually through
    manipulation of the mouse, as in drag and drop, and grabbing
    handles, or else output but still responsive to mouse clicks.

    There are many shape libraries available, but this is generally
    the sort of thing that gets written time and again.

    Canvas applications include illustration, diagraming, charting.

  - An Example

    A contemporary personal finance program uses The Dialog to set
    preferences and to open files, The Grid to display a check
    register for editing, The Document to display a nicely formatted
    balance sheet and a hyperlinked start page, and The Canvas to
    render a pie chart of spending by category.

    What did I miss?
    
The Application Direction

    I'm representing this taxonomy since in discussion I'm finding
    that there are different needs for different problems, and we
    should know which problems we are addressing.

    Hit-testing a widget in a dialog or a grid ought to be a trivial
    operation, hit-testing a line of text in a document somewhat
    more difficult, and hit-testing a partially exposed polygon on a
    canvas a real challenge.

    One should not pay for what one does not need.

    Validation is a concern for dialogs and grids, but it isn't a
    concern of a bar chart.

    Even if when developing a full-blown drawing application, one
    should not have to pick up the pen and draw out each tool-tip,
    or call out, when those could be rendered as little documents.

--
Alan Gutierrez - alan_at_[hidden]