Return to readme CVS log

Up to [OS/2 SDKs] / pmsdk / samples / linefrac

Microsoft OS/2 SDK PM 02-24-1989

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

This archive runs on limited infrastructure. Preserving old code on modern bandwidth. Automated agents are requested to crawl responsibly.