This is README for QLogo.

Downloading

I am not providing compiled versions of QLogo at this time.

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QLogo is an interpreter for the Logo language written in C++ using Qt. It mimics (as much as I find reasonable) the UCBLogo interpreter developed by Brian Harvey at U.C. Berkeley.

Copyright (C) 2017-2024 Jason Sikes

Redistribution and use in source and binary forms, with or without modification, are permitted under the conditions specified in the license found in the LICENSE file in the project root.

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You can find the UCBLogo Manual here:

http://people.eecs.berkeley.edu/~bh/usermanual

The differences between QLogo and UCBLogo are described in the nuances section below. There aren't many.

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Compiling

Building QLogo requires Qt6.5 and CMake.

To build in MacOS and Windows:

Simply open the CMakeLists.txt file in QtCreator and build within there.

To build in Linux:

If you have qtcreator, you can use qtcreator in Linux in the same manner as in Windows and MacOS described above.

Otherwise, you can follow the standard CMake build procedure. First, create a build directory somewhere outside of the QLogo source directory.

In my case, since I keep my projects in a "Projects" directory under my home directory, my QLogo directory can be found at "~/Projects/QLogo". Thus, one place to create my "build" would be adjacent to my QLogo directory, "~/Projects/build".

Then have CMake create the build structure.

$ cd ~/Projects
$ mkdir build
$ cmake -S QLogo -B build

Then enter into your build directory and issue make, and, optionally, if all goes well (it will) you can run make install

$ cd build
$ make
$ sudo make install

This will give you two executables and supporting files:

1. "qlogo": this is the Logo interpreter that can be run from a script or command line.

2. "QLogo-GUI": this is the graphical user interface that will run qlogo and provides the turtle and editor.

3. "qlogo_library.db": this is the SQLite database that stores the standard library.

4. "qlogo_help.db": this is the SQLite database that stores the help texts.

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Here are the nuances (they're mostly insignificant, I think):

• Colors can be specified in one of five ways:

  1. as a palette index (0 to 100), same as UCBLogo

  2. as a list of three percentages, one for each of red, green, blue [0 0 0] is black, [100 100 100] is white, also same as UCBLogo.

  3. as a list of four percentages, similar to Option 2 above, with the fourth value being "alpha". 100 is fully opaque, and 0 means fully transparent.

  4. as a named color from the X Color Database, e.g. white or lemonchiffon. The list of color names can be retrieved using the ALLCOLORS command or from the X Color database found here: https://en.wikipedia.org/wiki/X11_color_names

  5. as a hex RGB triplet, preceded by "#"

• Changes in font properties (size, color, family) do not affect characters already printed. This enables multiple colors and fonts on the same console.

• QLogo does not look for nor automatically load STARTUP.LG.

• COMMANDLINE contains ALL of the parameters used to start qlogo instead of just the ones that appear after a hyphen.

• If ERRACT is set and its size is greater than zero, then any errors execute PAUSE.

• Garbage collection is on-the-fly, meaning that memory is freed the moment a word/list/array is no longer needed. GC and .SETSEGMENTSIZE are no-ops.

• No scunching. UCBLogo provided a scrunch to compensate for older CRT screens with non-square pixels. This enabled turtle operations to maintain consistent physical height-width. The drawback is that some orientation queries are inaccurate. SCRUNCH and SETSCRUNCH are no-ops.

• SAVEPICT saves a copy of the canvas in the format given by the filename's extension. For example: SAVEPICT "MY_PICTURE.PNG will save in PNG format. QLogo can save an image in the following formats: BMP, JPG/JPEG, PNG, PPM, XBM, and XPM

• WINDOW no longer simply allows the turtle to run away from the canvas. WINDOW now also allows the canvas to zoom out to accommodate the turtle's position.

• There is no facility yet for translation/internationalization.

The following commands are not implemented:

SETMARGINS:

The original purpose of the command was to enable text to be visible on projectors which cut off outer boundaries of a computer screen. Projectors and monitors produced in recent years show all of the computer screen. In addition, QLogo is a windowed application so an instructor or presentor can move the window to a different position.

FILL:

One of the user interface principles for QLogo is that the canvas should be device resolution-independent. When the QLogo window is resized or the separator between the text and the graphics is moved then the graphics will be redrawn with the new dimensions.

The Flood Fill algorithm depends on specific pixels which means that what is filled can change dramatically depending on the size of the canvas.

The other reason is that the Flood Fill algorithm can slow down window resizing. FILLED is still available.

EPSPICT:

This is replaced by SVGPICT. See below.

CSLSLOAD:

Not implemented yet.

SETCSLSLOC:

Not implemented yet.

SETEDITOR:

The QLogo GUI has its own built-in editor. If you run the qlogo program from a command line, such as in a terminal, no editor is available.

SETLIBLOC:

Not implemented. QLogo uses a SQLite database to store its standard library. You can use the setlibloc command line parameter to tell qlogo where to find the SQLite database if it is in a different location than where qlogo expects it.

SETHELPLOC:

Not implemented. QLogo uses a SQLite database to store its help text. You can use the sethelploc command line parameter to tell qlogo where to find the SQLite database if it is in a different location than where qlogo expects it.

SETTEMPLOC:

QLogo doesn't create temporary files.

NOREFRESH and REFRESH:

QLogo is designed from the ground up to have a very responsive user interface. The canvas will always redraw itself whenever the window is resized.

SETPENPATTERN and PENPATTERN:

This isn't implemented yet because I haven't yet decided what kinds of patterns are wanted or useful.

The following variables have no special meaning:

REDEFP:

Qt has strong support for internationalization, but in QLogo it is only partially implemented. Internationalization will be supported soon.

USEALTERNATENAMES:

Qt has strong support for internationalization, but in QLogo it is only partially implemented. Internationalization will be supported soon.

The following commands are NEW:

SVGPICT has been added and is a replacement for EPSPICT. SVGPICT will save the image on the canvas in Scalable Vector Graphics format.

ALLFONTS:

Returns a list of all the fonts available on your system.

ALLCOLORS:

Returns a list of all the named colors that QLogo knows about.

TIME:

This is mostly for my own curiosity and for debugging. TIME will take one parameter, a list, which it will execute. A timer will start when the list is executed and then stop when the list is finished. The total running time of the list will be printed. The output will be whatever the list outputs, if anything.

MARK:

This is for debugging memory management. MARK will take one parameter, set a flag on it, and output that parameter. At the moment it is marked, a debugging message will be printed out. Later, if/when the item is deleted, another debugging message will be printed.

CURSORINSERT:

Sets cursor to insert mode in QLogo. This is the default.

CURSOROVERWRITE:

Sets cursor to overwrite mode in QLogo.

CURSORMODE:

Outputs either INSERT or OVERWRITE.

STANDOUT:

This works in the QLogo GUI by switching the font's foreground and background colors. It isn't implemented for text terminals.

SETBOUNDS:

The drawing canvas in the QLogo GUI is designed to be device and resolution independent. The user can stretch and resize the GUI window and its components without needing interaction or permission from the QLogo program. Therefore, the best way for the programmer to have control and the GUI to have responsiveness is to set the bounds programatically. The GUI then can squeeze or stretch the canvas to fit the window as needed.

The coordinate system of the drawing canvas is Cartesian: the Origin [0,0] is always in the center. The range of the X-coordinate is between -boundX and boundX. The range of the Y-coordinate is between -boundY and boundY. For example, a bound set at [350 150] means that the turtle is visible if its X-coordinate is between -350 and 350 and its Y-coordinate is between -150 and 150. See also BOUNDS.

BOUNDS:

Outputs a list of two numbers giving the maximum bounds (x,y) of the canvas.

FILEDIALOG:

Provides the user with a file dialog to select a file. The file name is returned as a string.