Microsoft Programmer's Library 1.3/Microsoft-Programers-Library-v1.3.iso/sampcode/os2sdk/os2sdk12/linefrac/readme

Text File | 1989-11-20 | 13.2 KB | 392 lines

Comments about LINEFRAC


Notes:
------

You must run "make opendlg" and include the ..\dll directory in your
libpath before attempting to make or execute this application.

Two of the modules generate the following warning when they compile:
    warning C4058: address of frame variable taken, DS != SS
This is the result of a fairly obscure compiler warning message bug,
which will be fixed in a future release.  The emitted code is correct.



General Description:
--------------------

This program draws self-similar fractals defined by transformations
of the unit interval.  By recursively applying the transformation,
neat drawings result.

Currently you can only choose the built-in transforms.    Click on one
to get that fractal at the current level of recursion.    Choose level
one (from the miscellaneous attributes dialog box), and one side to the
frame polygon (same dialog box), to see the transformation itself.
Some fractals are shown graphically in the menu.

Clicking on the left mouse button causes the fractal to go deeper
into recursion, while clicking on the right causes it to come back
out.

In the misc. attributes dialog box you can specify "# sides of polygon",
which is the number of initial segments to which your transform
will be applied.  You always get a regular polygon of the number
of sides you choose.

With the current limited set of transforms, you can still get some
interesting effects by drawing a new fractal on top of old ones
with varying attributes.  You can also draw several independent
fractals and automatically switch between them, simulating animation.

Note that at recursion level n, an m-segment transform will be
          n
composed of  m     line segments.  Keep this in mind when playing with
the 5-segment transforms, namely StovePipe and SquareWave.

The names are, except for Koch (mathematician who proved, I think,
that the Koch curve has infinite arc length when the level of recursion
goes to infinity), weak attempts to describe the basic shape.  The
Fractal menu uses pictures, anyway.


Description of commands:
------------------------

File

    Load ...
    Load a bitmap from a BMP file. The top thread must have a
    memory DC.
    (Currently requires AutoResize option to be enabled).
    Save ...
    Save bitmap to a BMP file.  The top thread must have a memory DC.
    About ...
    Show the credits.


Edit

    Select
    Drag a rectangle (from lower left to upper right) to highlight
    it for cutting or copying.  If you don't like what you selected,
    then do it again.  Nothing's permanent until you choose cut or
    copy.  Hitting the space bar will throw away the selection
    rectangle.

    Cut
    Copy the selected rectangle of bits into the "clipboard", and
    fill with the current background color.

    Copy
    Copy the selected rectangle of bits into the "clipboard".

    Paste
    Copy the cut or copied bits back into the bitmap with the current
    rop.  The selected rectangle is highlighted in its original
    location.  Grab somewhere in the window (in the highlighted
    rectangle is suggested) and move it to the desired location.

    Use Clipboard
    Not implemented yet.  This will instruct linefrac to use the
    shell's clipboard feature for saving bits, rather than an
    internal second bitmap.

    ----------------------------------------------------------------

    Paste w/ S
         DSa
         DSo
         DSx
         Sn
         DSan
         DSon
         DSxn

    Various rops for use when pasting bits back into the bitmap.


Thread

    New
    Direct
        Creates a new thread which draws directly to the screen.
        The WM_PAINT message does nothing for this thread.    To
        see the image after the bits have been destroyed, you
        have to cause a redraw (try Control Redraw).  Only one
        thread may have a direct DC (temporary restriction).
    Memory ...
        Creates a new thread which draws into a bitmap.  If
        thread inheritance is enabled (see below) the bitmap
        parameters are taken from the top thread.  Otherwise a
        dialog box appears with the bitmap parameters set to the
        window dimensions with 0 planes and 0 bits per pixel (the
        latter two cause the device to select its favored format).
        The user can alter any of these values as desired.    When the
        dialog box is closed, a bitmap is created and a thread
        is created to draw into it.
    PostScript
        not implemented yet
    ProPrinter
        not implemented yet

    Bring to top
    Select the number of the thread to bring to the foreground.
    To switch between threads quickly via the keyboard, type a
    digit between 0 and 9.    The thread started at that position
    in the overall order will be brought to the front, e.g. its
    bitmap will be visible, in the case of a memory DC thread.
    For a direct DC thread, nothing will happen to the image
    until a redraw is caused.

    Edit DC Parameters ...
    View or edit the bitmap extents and color format.

    Kill top thread
    Kills the top thread.  Brings the next lower (lesser id)
    thread to the top.  If there's only one thread,  a new
    thread is created with the program defaults.

    Kill all threads
    Kills all the threads and leaves the program with one thread
    with the program defaults.

    ----------------------------------------------------------------

    Automatic cyclic switch
    "Animates" by automatically switching between each thread in
    turn.  The delay between switches is set by the next command.

    Switch delay ...
    Set the delay in microseconds between switches between threads.

    Update menus on thread switch
    This controls the checking or unchecking of the various menu
    items that vary per thread.  If disabled, there is less overhead
    in a thread-switch, therefore a faster possible switch time.

    ----------------------------------------------------------------

    New thread inherits from top
    If enabled, new threads will be copies of the thread which
    was on top when the new thread was started.  If disabled,
    the program will select default values for all thread variables.


Control

    Redraw
    Forces the fractal to be redrawn.

    Abort drawing
    Causes drawing of current fractal, if any, to cease.

    Clear surface
    Clear the drawing surface to the background color.

    Copy bitmap to screen.
    Copies the entire bitmap to the screen.  Does nothing for
    a direct DC.

    Square up window
    Force the window to be nearly square for aspect ratio-corrected
    drawing.

    Resize surface to window
    Resizes the drawing surface to the window dimensions.

    ----------------------------------------------------------------

    Mouse click changes recursion
    If enabled, clicking in the client area changes the level of
    recursion:  left button --> go deeper (higher level);
           right button --> go shallower (lower level)

    Animate mouse pointer
    This causes the mouse pointer to change shape as it is moved.
    It represents the koch curve going from recursive level 0 to 3
    and back to 0 again repeatedly.

    Mouse pointer preferences ...
    Let's you select the pointer shape to use when the pointer is
    not animated.  Let's you determine the speed of animation by
    setting the number of WM_MOUSEMOVE messages tallied before
    switching pointer shapes.

    Cyclic redraw timer delay ...
    Sets the delay in microseconds between automatic redraws.  Note
    that the timer proceeds independently of the drawing.  A long
    fractal will probably end up redrawing immediately, since its
    semaphore will have been cleared before the current drawing is
    finished, that is unless the delay is corresponding long.


Fractal

    SharkTooth        (2 segments)
    SawTooth        (3 segments)
    Koch        (4 segments)
    StovePipe        (5 segments)
    SquareWave        (5 segments)

    Space filling curve (4 segments) (reflections on first and fourth segs)
    (Note: the space filling curve was originally intended to be drawn
           with the custom primitive "Peano curvelet").

    Hourglass        (3 segments, crosses itself)

    Click on one of these to select a similarity transform for your
    fractal.

    ----------------------------------------------------------------

    Redraw after change
    If enabled, causes an automatic redraw to occur after any
    selection on this menu.


Primitive

    PolyLine
    PolyFillet
    PolySpline
    PolyMarker
    Peano curvelet

    These determine the primitive used to display the points
    accumulated during recursion on the fractal.

    The Peano curvelet is a "custom primitive".  It draws two lines
    between each point instead of one.  The lines meet at a right
    angle.    If the straight line between the two points is x major
    (the difference in x is greater than the difference in y),
    then the new middle point is on the left side, otherwise it's
    on the right side.  In other words,


          *      *   *
         * *       * *        ^  *      |    *
        *   *        *        |    *     |   *
                    |     *    |  *
        ---->      <----     |    *     |   *
                    |  *      V    *

    With this primitive, the existing algorithm and data structures
    can be used to draw the Peano space-filling curve.  Note that
    the directions of these arrows are relative to the canonical
    unit line segment in world coordinate space on which the
    fractal is really drawn.  If the fractal is rotated (to put
    it on the side of a polygon, for instance), the arrows all
    rotate accordingly.

    ----------------------------------------------------------------

    Redraw after change
    If enabled, causes an automatic redraw to occur after any
    selection on this menu.


Attributes

    Line attributes ...
    Marker attributes ...
    Area attributes ...
    Image attributes ...
    Set the various attributes.

    Miscellaneous attributes ...
    Calls up a dialog box in which you can select the following
    values:

        # sides to initial polygon

        number of points sent to GpiPolyLine at a time

        level of recursion at which to draw

        angle of rotation (radians, CCW positive) applied to initial
        segments of fractal

    Fractal dimensions ...
    x offset and scale, as a percentage of the width of the window
    same for y, too;  the offsets determine where in the window
    the fractal occurs, whereas the scale factors determine
    roughly how big the image is


    Drag fractal dimensions
    Lets user drag a rectangle in the client window to determine
    the approximate bounding box of the next fractal.  "Approximate"
    because fractals might flow out of the box given enough depth
    of recursion.  This call alters the values of the scale factors
    and offsets.  The fractal attributes dialog box will show the
    new values the next time it is called up.

    ----------------------------------------------------------------

    Redraw after change
    If enabled, causes an automatic redraw to occur after any
    selection on this menu.


Environment

    AutoResize bitmap
    If checked, the bitmap will be resized every time you change
    the window size (even if you iconize).

    If not checked, the bitmap will stay the same size and won't
    be redrawn when the window size changes.

    When the window is resized, each thread will react according to
    this flag.

    AutoSelect fractal dimensions
    If this is checked, the default x,y offsets and scale factors
    will be used as soon as the transform is selected.  This positions
    the fractal so as to center it in the window, with room to grow
    so that it won't be clipped as the level of recursion increases.
    Note that the space filling curve grows up, not sideways, so it
    is not centered like the others.

    Clear surface on redraw
    If enabled, the surface will be filled with the current area
    attributes on the next redraw.

    Automatic cyclic redraw
    Sets a timer which after a random delay causes a redraw.
    The upper and lower limits on the random delay are set with
    the "Control Timer delay ..." command.

    Collect bounds on fractals
    When this is checked, the minimal rectangle of bits will be
    copied to the screen after a fractal is drawn into the bitmap.
    This speeds up the drawing slightly, and the mouse pointer won't
    flash unless it's right on top of where the drawing is happening.




Bugs to fix:
------------
    sometimes the animation timer seems to stop -- moving the mouse over
       the window is enough to get it started again
    occasionally the redraw seems to not work -- selecting it again
       works though
    occasionally a fractal is not drawn to completion
    parts of the window sometimes get erased with the WM_ERASEBACKGROUND
       message, but don't get updated by WM_PAINT. Why?  Should
       LfEraseBackground invalidate what it paints for the benefit
       of LfPaint?
    sometimes the upper left of a fractal is displayed in the window
       instead of the lower left, depending on the window dimensions
       (I saw this with a bitmap much larger than the screen) --
       slowly resizing the window reveals a point at which the switch
       occurs
    the "cancel" buttons don't work as expected on various dialog
       boxes -- looking at attributes can cause the fractal to redraw
       even though nothing changes;  cancelling the new thread dialog
       box doesn't stop it from being created