The XCircuit Tutorial

The XCircuit Tutorial Part 1: Drawing with XCircuit


Table of Contents

Notes

  1. This tutorial assumes the use of a 3-button mouse. Users of 2-button mice can do one of three things:
    1. If the X server supports 3-button emulation, the middle mouse button can be selected by simulataneously pressing the left and right mouse buttons.
    2. XCircuit defines the key sequence Shift-Button1 as an alternative to the middle mouse button.
    3. XCircuit started with the option "-2" remaps the button and key bindings. In this case, all bindings for "mouse button 2" or the "middle mouse button" will be remapped to the right mouse button, and all bindings for the right mouse button will be remapped to the backspace key.

Task 1: Change an option from the menu

Acquaint yourself with the arrangement of menu buttons and pulldown menus.
  1. Press the button labeled "Options" with mouse button 1 and hold down the button while you drag the cursor aroundwith the mouse (the Tcl/Tk version does not require the button to be held down).
  2. Keeping the mouse button pressed down, move down to the "Elements" button. Each button will highlight as you pass through it.
  3. Put the cursor on top of the arrow icon at the right side of the "Elements" button. You should see a secondary menu titled "Elements" pop up. The title is the topmost entry of the menu. It has no function and does not highlight when the cursor is overtop it.
  4. Keep moving down to the "Color" button and again move the cursor over the arrow icon. The third and final menu of colors will pop up. Note that one item, "Inherit Color" has a check mark on it (a filled checkbox in the Tcl/Tk version). The check mark denotes that this entry is the current default color.
  5. Move down to the purple color button and release the mouse button there. The menus will disappear. You have just changed the default drawing color to purple. The color button on the toolbar should be purple now, reflecting the change in default drawing color.
  6. Repeat the procedure up to step 4. When you enter the "color" menu you will see that the purple color button is now checked, showing that purple is the default drawing color.
  7. The toolbar duplicates many of the actions available from the pull-down menus. Press the color button on the toolbar. You will see the same menu that you saw in step 4 above, only now it is a pop-up, rather than a pull-down, menu. The toolbar button is a convenient way to get to the same menu, faster.
Throughout the tutorial I will refer to the menu items using the pulldown hierarchy, with an arrow ("->") wherever you need to go to a submenu. So the "Inherit Color" menu item would be referred to as "Options->Elements->Color->Inherit Color".

Task 2: Draw a line

Now that you understand the function of the menu buttons, it's time to learn how to draw something. The simplest and most common thing to draw in xcircuit is a series of connected line segments (unclosed polygon), otherwise know for purposes of schematic drawings as a "wire".
  1. Make sure that the toolbar "Wire Button" is highlighted. This toolbar button binds the left mouse button tap to the wire drawing function.
  2. Tap mouse button 1 anywhere in the drawing area and release it immediately. If you wait too long to release the button, xcircuit will interpret it as trying to "grab" an element on the screen, and nothing will happen (because there aren't any elements yet to grab). If this is a persistant problem for you (which can happen, for example, if you are working over a network connection or your processor is heavily loaded), you can disable the function from the "Options" menu (see below).
  3. Move the cursor around the screen. A purple line (because you chose purple to be the default color in Task 1) will appear between the origin point and will track with the cursor.
  4. Tap mouse button 1 again to finish a line segment. A new line will begin at the point the first one left off. Do this several times to form a polygon. Finish the polygon by tapping mouse button 2.
  5. Repeat steps 2 through 4 but finish by tapping mouse button 3. The last line you have just created will disappear. You have just canceled the last line segment. You will continue to be in wire drawing mode as long as at least one wire segment exists. Continue tapping mouse button 3. When the last segment disappears, you are no longer in wire drawing mode.
  6. Repeat steps 2 through 4 but finish by tapping the escape key. The entire set of lines you created will disappear. You have just canceled the whole wire drawing operation.
  7. Repeat steps 2 through 4 but start by tapping the w key instead of the left mouse button. The effect is the same. The w key has the same binding as the left mouse button in wire mode. But the w key continues to initiate wire drawing even when XCircuit is in a different drawing mode.
  8. Click on the toolbar "Pan Button" . This takes XCircuit out of "wire drawing mode" Tapping left mouse button will now move the location of the drawing in the window rather than starting a wire. However, the "w" key will continue to create wires.

A purple wire (unclosed polygon), drawn with mouse clicks in XCircuit.


For most operations in xcircuit, tapping mouse button 1 will begin or continue an operation, tapping mouse button 2 will finish it, tapping mouse button 3 will cancel the operation or most recent part of it, and the escape key will cancel the entire operation. The behavior can be slightly different depending on the circumstance, and the behavior for pressing buttons 1 and 2 is very different, as demonstrated in Tasks 3 and 4.

Task 3: Move an element

Mouse button 1 does have one very different function than that described in the last task. It can be used to "grab" hold of an element for moving.
  1. Press mouse button 1 close to a line of the polygon you just drew. Hold down the button. The line should turn a gold color, indicating that it has been "selected". If instead nothing happens, then the cursor is too far away from the line. Releasing the button releases the object.
  2. Try grabbing and releasing the polygon from different distances to get a feel for how close you must be to the object in order to grab it.
  3. Now grab the polygon, and with the mouse button held down, move the cursor across the screen. The polygon will follow the cursor. This is how you move an object in xcircuit.
  4. As mentioned above, not everyone likes this method of pressing and holding down the mouse button to drag, and sometimes a slow processor or network connection can make it difficult to use. In such cases, go to the "Options" menu, and un-check the box by the item "Allow HOLD mode". Once the HOLD mode has been disabled, it will no longer be possible to drag elements around the drawing window as described in Task 3. Instead, click the "Move Button" in the toolbar. This binds the mouse button 1 tap function to the move action. In this mode, you can move an element either by pressing and dragging, as described above, or by tapping and releasing the button, moving the selected element around, then tapping and releasing again to place the element.

Task 4: Change the properties of a polygon

mouse button 2 also has a selection function; in fact, it has two of them. In a normal drawing mode, it can be used to select objects for editing or changing properties. In this task you will use mouse button 2 to select the polygon you just created in order to make it a dashed line.
  1. Select the object by tapping mouse button 2 with the cursor near to the object. The object will turn gold, indicating that it has been selected.
  2. Tap mouse button 3, and the selection will be canceled.
  3. Investigate the other form of selection by pressing mouse button 2 starting below and to the left of the polygon, and dragging the cursor to the top and right of the polygon. A green box will follow the movement of the cursor.
  4. When the box completely surrounds at least one of the endpoints of any line segment of the polygon, release the button. The polygon should be selected.
  5. Click mouse button 3 to deselect the object.
  6. Repeat steps 3 through 5, noting that if no endpoint of the polygon is contained within the select box, then the polygon will not be selected.
  7. Select the polygon but do not deselect it.
  8. Go to the "Options->Elements->Border" submenu and select option "Dashed". Alternately, the same menu can be accessed from the toolbar "Line Style" button . When you release the button, the polygon will be drawn in dashed lines. To unselect the polygon, click the right mouse button, or hit the "escape" key.
  9. Experiment with the different Colors, Fill-styles, and Border-styles available in the menus and toolbar "Line Style" , "Fill" , and "Color" buttons. Some of the many varieties are shown below.

More purple polygons.
Top left: original. Top right: dashed.
Center left: closed. Center right: stippled (50% stipple).
Bottom left: opaque stippled. Bottom right: filled solid.


Task 5: Change the page

Xcircuit has multiple pages. There are three ways to change the current drawing page, from a key binding convenience function, from the menu, or from the toolbar.
  1. Select the menu item "Window->Goto Page->Page 2". The polygon you just drew on Page 1 will disappear, and you will be on a clean page, with the bottom left-hand window saying that you are editing "Page 2".
  2. Go back to Page 1 using the key binding: With the cursor in the drawing area, press the "1" key. You will be back on page one.
  3. Key "Page Down" will increment the page number. Try this to move up from page one to page ten (TCL version only).
  4. Key "Page Up" will decrement the page number. Try this to move down from page ten to page one (TCL version only).
  5. Keys "1" through "9" and "0" will get you instantly to pages 1 through 10, respectively. There are no keys for changing to pages higher than 10; to do so, either use the menu, the page directory (see below), or the "Page Up" and "Page Down" keys.
  6. Click on the toolbar "Page Directory" button . This will give you a view of all the pages currently in XCircuit. Page 1 is initialized on startup and so is always present in the page directory. Pages 2 through 10 have placeholders in the page directory, even if the pages have not yet been created for drawing. If more than ten pages are created, they will all be displayed in the page directory. From the directory page, click on the top of any page to go directly to that page.
  7. End this task on Page 2, which is currently empty.

Task 6: Select an object from the user library

Another common task in xcircuit is to grab an object from the object library and place it on the drawing.
  1. Select the "Window->Show Library" button from the menu, or press the "l" (that's "ell" as in "library") key in the drawing window, or select the "Library" button in the toolbar. I cannot over-stress that keyboard bindings, once memorized, are more convenient to use than their menu button counterparts. Almost always, the letter or symbol used for the macro is meaningful and easy to remember (like "a" for "arc", "s" for "spline", "p" for "pan", "c" for "copy", etc.).
  2. A page will appear, showing a number of circuit objects in the built-in object library.
  3. Grab one object by moving the cursor over top it and pressing and holding mouse button 1 (you may also just tap and release; this is similar to the "move" operations described in Task 3). As soon as the button is pressed, the object library will disappear, and you will be dragging the object around Page 2, from which you called up the library. When you release the button, the object will be placed and deselected. Place it away from the polygon you drew in the previous tasks.
  4. Select the object by tapping on it with mouse button 2. Try changing the border style to dashed. You will see that nothing happens. This is because object instances from the library are made up of basic elements like polygons, arcs, and splines, but they are composite objects which do not have properties like "Fill-style" and "Border-style". However, object instances do have the property of color, and also the property "size" which simple elements like the polygon do not have (aside comment: The color property only works for elements of the object instance that are marked with "inherit color". Elements in an object with specifically set colors remain that color regardless of what color is chosen for the object instance as a whole).
  5. Select the object again (if you have not already done so), and then select the menu item "Options->Elements->Object Size" (an easier way to get there is the "Rescale Mode" button in the toolbar).
  6. A window will pop up asking you for an object size. Place the cursor somewhere inside the popup window and change the default size of "1.00" to "1.5".
  7. Press the "Okay" button. The popup window will disappear and the object will now be 1.5 times its original size (that is to say, its length and width will each be 1.5 times their previous value. In the interest of not distorting schematic drawings, it is not allowed to separately rescale width and height).

Part of the default circuits built-in library.

Task 7: Create an arc

Every basic element in XCircuit (wires, arcs, curves, labels, paths, and object instances) can be created in the same way by any of four basic methods: 1) menu item selection, 2) toolbar mode selection, 3) key binding, and 4) command-line entry. The menu selections simply invoke the toolbar button, so these will be treated as the same method. Command-line entry is not treated in this tutorial. As mentioned above, keyboard macros are the quickest method. In this task, you will create an arc by both the toolbar and key binding to show the difference.
  1. Select the menu item "Edit->Make Arc", or, equivalently, the toolbar "Arc" button The button will be highlighted to indicate that arc drawing mode is in effect.
  2. Place the cursor where you want the arc center to be and tap and release the left mouse button. Drag the cursor around the screen. An arc will follow the cursor, its center at the original position and the diameter determined by the current mouse position.
  3. Tap and release mouse button 2 to finish.
  4. Begin a new arc (repeat step 2).
  5. This time, instead of ending with the middle mouse button, tap and release the left mouse button again. The arc diameter will now be fixed, and you will be editing the angle of the first endpoint. If you keep pressing mouse button 1, you will be able to edit, in turn, both endpoint positions and the ellipse axis. Whenever the circle/arc/ellipse is the way you want it, tap mouse button 2 to finish. At any point in this operation, if you tap mouse button 3, you will cancel the last edit (all changes since the last tap of the left mouse button). Tapping key "escape" will cancel everything and remove the arc, the same behavior as tapping mouse button 3 multiple times until all edit operations have been canceled.
  6. Now, create an arc by tapping the "a" key while the cursor is in the drawing area. This works exactly like the method described above, except that it can be used in any mode, not just arc drawing mode.
  7. Note that ellipses in XCircuit can be rotated to arbitrary angles. However, this cannot be done by editing the ellipse itself. If the ellipse is placed in an object (see Task 15, below), and the object instance is rotated, then the ellipse will be rotated with it. To rotate a single ellipse, make an object out of (just) the ellipse, then rotate the object instance.

Some differenct arcs.
Top left: linewidth of 1.5, first endpoint at 90 degrees. Top right: closed arc.
Bottom left: red circle. Bottom right: blue ellipse.


Task 8: Zooming and panning

  1. Pan the screen to be centered on the arc by placing the cursor close to the center of the arc and tapping the "p" key.
  2. Pan the screen by selecting menu item "Window->Pan" or clicking the toolbar "Pan" button . This will put XCircuit in "pan mode", with a picture of a hand as the cursor. Tap mouse button 1 to begin repositioning the screen, and tap it again to fix the position.
  3. Pan the screen by half-window amounts using the keyboard arrow keys.
  4. Pan the screen up or down using the mouse scroll wheel.
  5. Tap the "Z" and "z" keys to zoom in and out, or select the menu items "Window->Zoom In" and "Window->Zoom Out", or equivalently, the toolbar "Zoom In" and "Zoom Out" buttons. Note how the scrollbars on the side and bottom of the screen change with the scale of the drawing.
  6. Pan the screen by tapping any mouse button on either of the scrollbars, or pressing and dragging the scrollbar.
  7. Zoom to a selected area of the screen by making a green selection box like you did in Task 4, step 3. However, instead of releasing the button in order to make the selection, type the "Z" key (shift-z) while the mouse button is still pressed down. The screen area will zoom to the area of the green box. If you instead press the "z" key (no shift), the screen area will zoom out such that the previous window boundaries fit in the area of the box.
  8. Click on the black square at the point where the scrollbars meet to center and expand the view of the current drawing to fit and fill the window. This is equivalent to the menu item "Window->Full View".

Task 9: Selection of multiple elements

Note: The selection mechanism for multiple elements changed in XCircuit version 3.3.7. For a description of the mechanism used prior to this version, click here.
  1. Clear the current page by choosing the menu item "File->Clear Page". There is no keyboard macro for this command, to prevent accidental erasure of the screen (which cannot be undone with the "Undo" command).
  2. Grab several objects from the library (see Task 6) and place them on top of each other in the middle of the page.
  3. Decide on one object which you will move, leaving the others where they are.
  4. Now press mouse button 1 as if you were going to select the object you want to move. Because the command is ambiguous---the program doesn't know which one or ones of the objects you really want to select---the program will arbitrarily choose one of them.
  5. If the object highlighted (gold) is the one that you want to select, you're done. If not, then release the mouse button, and press it again. XCircuit will select a different element this time. Repeat until you have the object instance you want to move.
There are various ways to pick and choose a collection of elements at one time. Each of the selection mechanisms in XCircuit behaves differently in this respect. The different mechanisms are outlined below. Some combination of them can always get the selection you want.
Selection and move with mouse button 1 press-and-drag
This method selects exactly one element, but if more than one element meets the selection criteria, a different element will be picked on each successive button press. The criteria for picking elements is for the pointer to be "near" a line, arc, curve, or path, or inside the bounding box of a label or object instance. Object instances are recursively searched for pointer being "near" an element internal to the instance. The definition of "near" has a wider sense for the recursive search, so that, for example, the center of a NAND gate satisfies the search. This method is only used for grabbing and moving elements. If elements are selected prior to using this selection method, no new selections will be made, and these elements will be moved. All elements are unselected when the button is released.
Single selection with mouse button 2 click
This method adds another selection to the existing set. The criteria for picking elements are the same as for the button-1 selection. Elements remain selected after the button release, until one of the methods for selection removal (see below) is invoked.
Area selection with mouse button 2 press-and-drag
This method selects all elements that match the selection criteria. The criteria are slightly different from those for the single-button selections. Labels and object instances are selected if the area rectangle covers one or more corners of the label or instance bounding box. Polygons and curves are selected if an endpoint or breakpoint is within the area box. Arcs are selected if the center point is within the area box (which is usually a poor criterion for very large circles).
Undo selection with mouse button 3 click
Mouse button 3 unselects all elements.
Undo selection with "undo"
The "undo" function (key macro "u") undoes the last selection event. It will remove a single item from a set incrementally selected using mouse button 2, or restore one or more items unselected using the "x" key macro (see below).
Remove selection with "x"
The "x" key macro removes individual elements from the current selection set. The criteria for picking elements are the same as for the button-1 and button-2 selection methods. Only one element is deselected, in the same manner as the selection. If more than one element is near the pointer, and the element picked by the unselection mechanism is restored using undo, the subsequent use of "x" will unselect a different item.

Task 10: Saving a file

Since the main purpose of xcircuit is to create publishable-quality picutures, it is necessary to understand a little bit about the PostScript output which it writes. First I will show you how to save and load a file.
  1. Choose a page which you have been drawing on, or create a drawing to save.
  2. Select the menu item "File->Write Xcircuit PS". You will get a popup window that looks like the figure below.


    The file properties popup window.


  3. If you tap the button labeled "Write File". You will get a message in the bottom message window saying "Warning: Enter a new name". Nothing has been written at this point.
  4. Change the filename. Move the cursor over the window containing the filename. Delete the current file name and type in a new one. When you are done, either hit the RETURN key or tap the button labeled "Okay" (both actions have the same effect).
  5. Important note: If the name has no extension, an extension ".ps" will automatically be added when the file is written. If an extension, for instance ".eps", is written in the filename, then it will be used. XCircuit does not differentiate between encapsulated and non-encapsulated files by the file extension, but rather by the contents of the file.
  6. When you change the filename, the page label will be changed to match the filename, and the bottom left-hand message window will now say "Editing: " followed by the page label name, followed by the page number in parentheses.


    Changes to the filename, orientation, output type, and to the scale using the "auto-fit" function.


  7. If the filename you chose already exists on the disk, the button which previously was labeled "Write File" will now say "Overwrite File", the computer will beep, and the bottom message window will say "Warning: File exists".
  8. Tap the button labeled "Cancel". The window disappears; because you did not tap the "Write File" button, nothing was written, although the filename change has been registered.
  9. Select "File->Write Xcircuit PS" again to bring the window back. This time, tap the "Write File" button. The file will be written to the disk current directory, and the button which previously said "Close" will now say "Done".
  10. The file which has just been saved is already in a PostScript format. You may view it with any PostScript previewer (ghostview is recommended). Look at the file in the previewer. Note that the drawing has been centered on the page. The size of the drawing should be exactly the width and length reported in the window prior to saving.
  11. Now, click on the button labeled "Embedded (EPS)". You will get two choices, "Embedded" or "Full Page". Choose "Full Page". Now, you will see an additional window showing the page size (default letter when units are in inches, or A4 when units are in centimeters). There is a button labeled "Auto-fit" (unselected). In the TCL version, there is another button labeled "Sizes". Select a Tabloid size either by selecting "Tabloid" from the "Sizes" menu (TCL version only), or by editing the page size window and replacing "8.5 x 11.0" with "11.0 x 17.0", and hitting return to accept. Note the scale, width, and height entries. Now, select the "Auto-fit" button. The scale of the drawing changes such that the drawing fits in the selected page size, with minimum 1-inch margins.
  12. Note: Margins can be changed by selecting a scale which fits the drawing to the selected page size with the proper margins. For example, "Auto-fit" on a letter-size paper will rescale the drawing such that the width is 6.5 inches (assuming that the width is the limiting dimension), leaving 1 inch on either side. However, you can reduce the margins to one-half inch by changing the "Width" entry from "6.5" to "7.5". Height will scale accordingly. XCircuit always maintains aspect ratio, and will never scale the axes by different amounts.
  13. Another note: Generally, the page object will be exactly centered on the output. If this is not the desired behavior, a bounding box may be explicitly drawn on the page. To do this, draw a box anywhere on the page. Then, select the box, and choose menu selection "Options->Elements->Border->Bounding Box". When this is selected, the rectangle turns light green, indicating that it is a bounding box. This rectangle will not appear in the output (however, it is saved and will be reloaded with the rest of the drawing). With the bounding box present, all output will be centered on the box, not on the drawing as a whole. Note that by itself, the box does not "bound" anything. However, if the bounding box rectangle is present and "Auto-fit" is selected in the output properties window, then the drawing will be scaled such that the bounding box fits the output page with 1-inch margins. This allows a convenient way to either place a drawing in a specific position on the output page, or to create an output which "zooms in" on a portion of a large, detailed drawing.

Task 11: Loading a file

  1. Go to a new, unused page.
  2. Select menu item "File->Read Xcircuit File". You will get a screen that looks something like the following:


    The load-file popup window.


    Make sure that you use the function "Read", not "Import". The import function loads an xcircuit file, merging with any existing schematic. Importing onto a blank page is essentially the same as loading, but may end up displaying a different page than that intended for the tutorial.
  3. If the file list is larger than the window, you may scroll up and down the list by clicking mouse button 1 or 2 on the scrollbar at the right side of the window and dragging it up and down, or by using the mouse scroll wheel.
  4. A green box will be drawn around each filename as your cursor passes over it.
  5. Find the file that you just saved in the last task. When the green box is over this filename, tap mouse button 1. The filename will turn green, and at the same time will be copied into the text edit box.
  6. Tap the "Okay" button to load the file.
  7. If you do not wish to use the scrolling menu, you may type the filename, with or without the ".ps" extension, in the text edit box, followed by the RETURN key or tapping the "Okay" button.
  8. Selecting a directory name in the file list box, including "../" for the directory one level up, will go to that directory. Entering a directory name in the text edit box followed by the RETURN key will also go to that directory.
  9. If you know where the xcircuit source is kept, then select the "File->Read Xcircuit File", go to the source directory, go to the "examples" directory, and load one of the example files, such as "vcoblock.ps".
  10. Note: The "Filter" button filters a directory by file extension. For file loads, this shows only files with the extension ".ps". If valid XCircuit files have other extensions, such as ".eps", the filter needs to be disabled to view them.
  11. The "Target Library" button selects the library page onto which any new objects found in the file will be placed. By default, new objects go in the "User Library". Pushing the button will generate a pull-down menu from which a different library page can be chosen as the target page for new objects.
  12. The "Replace from" button selects which, if any, technology will replace conflicting objects (objects with the same technology name and same object name) in the file with the version already in the library. Normally, "Replace from" is either "none", for which no replacement occurs (conflicting objects are renamed to avoid problems), or "all", in which case all conflicting objects are replaced by the existing library version. Typically, this feature is only needed when a schematic hierarchy is split into multiple files and an associated project library, and each file should update its local version of objects (symbols) whenever a change made to another file has been written back to the project library file.

Task 12: Recovering From A Crash

System crashes, hangs, power outages, tripped-over power cords, and program segmentation faults all happen, and many programs are loved or hated according to their ability to recover from such mishaps. In this task we investigate the all-important problem of recovering your work after a crash.
  1. Draw something on a page, anything at all. You need to spend at least one minute on the drawing or make at least 20 modifications to the drawing before a backup will be made.
  2. From the terminal or window manager, kill the XCircuit program with an explicit kill signal ("killall wish" will do for the Tcl/Tk version of XCircuit under UNIX).
  3. Do "ls /tmp" from the UNIX command line. Among the entries, you should see something like "XC4NoVXK", a file name beginning with "XC" and followed by six random characters. Your work is in there!
  4. To access this crash recovery file, simply type "xcircuit" at the UNIX command line, without any filename. Specifically, don't enter, e.g., "xcircuit /tmp/XC4NoVXK", because then all pages will have the temporary crash recovery filename rather than the original filename(s).
  5. XCircuit should then start up with a prompt such as (in the example above) "Recover file 'Page 1 (Tue Oct 4 14:07:24 2005)'?". Select "Okay".
  6. You should get back your lost file, or at least the better portion of it. XCircuit by default saves once per minute, or after every 20 modifications to a drawing.
  7. Note that once the backup is read in, the temporary file is removed. It is possible to completely lose a file by responding "Okay" to the "Recover file" prompt, and then quitting without saving. Unlike most programs, XCircuit assumes that end-users are not stupid, but on the other hand, quitting without saving means exactly that.

Task 13: Entering Text

Xcircuit has a very complicated interface for entering text, which allows you to change fonts and font styles within a string, make overlines and underlines, and subscripts and superscripts.

  1. Go to a new, unused page.
  2. Let's say you want to type in a fairly complicated expression, like
    "f(x) = sin(2*pi*omega_c*t)" (except with Greek letters, of course).
  3. If you've read your TeX manual thoroughly, and understand all the finer points of mathematical equation typesetting (if you haven't, you should), then you know that all the variables should be in italic type.
  4. Select menu item "Text->Style->Italic". The default text font is now italic style.
  5. Select menu item "Text->Font->Times Roman" if it is not checked already. The default text font is now Times Italic (Times font + Italic style).
  6. Select menu item "Text->Make Label" or (equivalently) click on the "Text" button in the toolbar. Both actions bind the mouse left button tap to the creation of text labels. Tap the left mouse button while the cursor is anywhere on the drawing.
  7. Alternately, you can just tap the "t" key in the drawing area.
  8. The green line marks the pointer position, and the "x" marks the origin (justification) of the text.
  9. Select menu item "Text->Justification->Middle Justified". You will see the green "x" move to the center of the line, showing that the text is vertically centered on its point of origin.
  10. Alternately, you could type keypad key "6" (on some systems, Shift-keypad 6) to get center-left justified text.
  11. Type "f". In the bottom message window, the letter "f" and a vertical bar "|" appear, showing what's in the string relative to the text cursor.
  12. Select menu item "Text->Insert->1/4 Space". This is the proper thing to do for "italic correction", an extra bit of space necessary after an italic character followed by an upright character, particularly tall ones such as "f" and "t" which lean leans rather far to the right of their character bounding boxes. Alternately, type key combination "Alt-q" to get the quarter space.
  13. Select menu item "Text->Style->Normal" (key "Alt-n").
  14. Type "("
  15. Select menu item "Text->Style->Italic" (key "Alt-i").
  16. Type "x"
  17. Select menu item "Text->Style->Normal" (key "Alt-n").
  18. Type ") = sin(2"
  19. Select menu item "Text->Style->Italic" (key "Alt-i").
  20. Select menu item "Text->Font->Symbol" (key "Alt-f" until font Symbol is chosen).
  21. Type "\". A page with the 256 character encodings for the Symbol font will appear, replacing the current page, as shown in the figure below.
  22. Click on the "pi" symbol. The screen will immediately return to the original page, with the "pi" added to the text line.
  23. Type "\", then click on the "omega" symbol in the encoding vector.
  24. Select menu item "Text->Font->Times-Roman" (key "Alt-f")
  25. Select menu item "Text->Style->Subscript" (or keypad-minus)
  26. Type "c"
  27. Select menu item "Text->Style->Normalscript" (or keypad-enter)
  28. Type "t"
  29. Select menu item "Text->Insert->1/4 Space" for another italic correction (key "Alt-q").
  30. Select menu item "Text->Style->Normal" (key "Alt-n").
  31. Type ")"
  32. Before typing <RETURN> to complete the text, use the left- and right-arrow keys to move the cursor around inside the text string. Note how font- and style- changing commands embedded in the text string can be seen in the message window. Their position relative to the text cursor is important when anticipating the effect of deleting (<DELETE> key) a text command.
  33. Yes, this is very complicated, but it is also very powerful.

Above: The text figure created in the task.
Below: The PostScript output of the same text from xcircuit.


Typographical Note: ISO-Latin1 encodings define the Greek character "mu" () to be used for the symbol "micro", which naturally is used often in circuit schematics. This differs from the Symbol font "mu" in that it matches the style and properties of the font in which it is defined. Thus, it is possible to get a Helvetica "mu", a Times-BoldItalic "mu", etc., something which is virtually impossible to do even in LaTeX(*). Due to the font size and style matching, this is always preferable to the Symbol font "mu". To get the ISO-Latin1 "mu" character, (while entering or editing text) choose Text->Encoding->ISO-Latin1 from the menu, then either choose Text->Insert->Character or type "\" at the text cursor, then select the "mu" character from the character array.

Task 14: Making curves and paths

Curve drawing is a useful feature of most capable drawing programs. The concept of paths is a powerful aspect of PostScript which is not usually found elsewhere. Path definitions are used to create a single entity out of a string of curves, arc segments, and lines. The resulting entity has its own color, fill styles, and border styles.
  1. Go to a new, unused page.
  2. Click on the toolbar "Curve" button to enable curve drawing mode, and then tap the left mouse button to start the curve. Alternatively, type "s" in any drawing mode to start a curve (you can think of "s" as standing for "spline", although these are Bezier curves, not splines, or you can just think of the curvy "s" shape. The key "c" is reserved for copying).
  3. The first thing you will see is two dotted lines ending in little "x" marks. These are the curve control points.
  4. Move the cursor around. Right now you are positioning the end of the curve but have no control over the control points.
  5. Place the curve endpoint. If you are satisfied with the shape of this curve, you can tap mouse button 2 to finish the curve and quit. However, we'll say that you have more to do to this curve, so tap mouse button 1 instead.
  6. You get a message saying "Adjust control point", and the cursor moves overtop the nearest "x" mark. Now when you move the cursor, you change the shape of the curve between the fixed endpoints.
  7. Move the control point two grid blocks to the left of where it started (make the control line horizontal with a length of 4 grid blocks).
  8. Click mouse button 2 to finish the curve.
  9. Simlarly to arc generation, mouse button 1 moves the edit point between control points, mouse button 3 undoes the last point edit, and the escape key cancels the curve creation and deletes the curve, as does clicking the right mouse button until all edits have been canceled.
  10. Now we will make a simple path. But it takes more than one element to form a path. Put the cursor over the curve and tap the "c" key.
  11. When you move the cursor, a copy of the curve will follow you.
  12. While you are dragging the curve copy, flip it by tapping the "f" key and then the "F" key (one horizontal plus one vertical flip).
  13. Place the curve with its endpoints overtop the original curve. The result should look like the figure below.
  14. Select both curves by tapping mouse button 2 on top of each one, or by forming a selection box (see Task 4).
  15. Tap the "j" key in order to "join" the two curves into a single path.
  16. If you now move or select the path, you will find that both curves act as a single entity.
  17. Select the path and then select menu item "Options->Elements->Fill->(black box)". The path will then become solid black. If you color it blue, it will look something like the right side of the figure below.

Curves and paths. Left: The curve has been copied and flipped. Center: The two curves are placed together and joined into a path. Right: The path is filled and colored as a single entity.

XCircuit from stable version 3.7.27 (April 2011) has another convenient way to create a curved path, convenient for drawing complicated curve shapes requiring the curvature to be continuous (no kinks) over the length of the path. Draw a polygon outline of the curved path you want. Then, select the polygon and click on menu item "Edit->Make Spline". The polygon will be converted into a smooth-outline curved path.

XCircuit 3.7 also adds new ways to edit paths to maintain curvature. This is covered below in Task 17.

Task 15: Dealing with over/under arrangement of elements

Otherwise known as the "stacking order" of the drawing.
  1. Clear the current page (menu option "File->Clear Page") or go to a new, unused page.
  2. Start a box with the "b" key (this is a convenience for drawing rectangles and squares).
  3. Click mouse button 2 to finish the box.
  4. Select the box and choose menu item "Options->Elements->Fill->(black box)", where the "black box" is the first menu item in the list. You will now have a black box. (note that to select the box, the cursor must be near the edge of the box, not in the middle).
  5. Select the box again and choose menu item "Options->Elements->Color->(orange box)". You will now have a solid, orange box.
  6. Go to the built-in library ("l" key) and bring back a circuit object (say, a "nand" gate).
  7. Place the gate on top of the orange box.
  8. Make a copy the box ("c" key) and place it beside the first. mouse button 2 ends the copy command.
  9. You will notice that the library object suddenly disappeared. This is because the "copy" command moved the orange box to the end of the drawing list. Because it is drawn after the library object, the library object is hidden underneath.
  10. To get the library object on top again, select everything in the area of the orange box by forming a selection box around the orange box (mouse button 2). Tap the "X" key (Shift-X) to exchange the drawing order of the two elements. The library object will now be visible on top of the orange box.

Over- and Under- arrangements (stacking order) of elements.

Note that the "exchange" function has a different use when applied to only one selected element. A single element will be brought to the top of the drawing stack, unless it is already at the top, in which case it will be sent to the bottom. If you have an obscured element that needs to be shown (such as the "nand" gate in the example above), just select the element by itself and tap the (Shift-) "X" key, and it will be brought to the top (made visible).

XCircuit version 3.7 (April 2011) has more features for handling the stacking order of elements than just the "exchange" function. In particular, the Tcl/Tk script defines the "[" and "]" keys to move one or more selected elements up or down one position in the stacking order, respectively.

Task 16: Making user-defined objects

One of the most powerful aspects of xcircuit is its ability to deal with objects on a hierarchical level. Circuits in particular are highly structured. Often it is desirable to draw a subcircuit and use it several times. It is much more efficient to draw the subcircuit and create a user object from it rather than to copy all the separate elements of the subcircuit every time you want a copy. This is also true of new circuit components.

Say we wish to create a new circuit component, a dependent current source.

  1. Clear the current page or go to a new page.
  2. We want the dependent current source to look something like the independent current source (isource) in the built-in library file. Go to the library and bring back an "isource" object for reference.
  3. Draw a polygon, as in Task 2. Make it diamond-shaped and three grid spaces high, two wide (see the figure below).
  4. Add a line of height one-half-grid space on the top and bottom of the diamond.
  5. Now we will do something unusual. We will grab the arrow from inside the isource object. Edit the original "isource" object by placing the cursor over it and typing the ">" key (push object). The page you were on will disappear, and you will see only the object "isource".
  6. Using the multiple-selection mechanism described in Task 9, select the arrowhead and line in the middle of "isource", but not the surrounding object.
  7. Make a copy of these two elements with the "c" key.
  8. While still dragging around the copy of the arrow, return to the main page by typing the "<" key (pop object). You will be returned to the original drawing, still dragging the arrow with you.
  9. Place the arrow inside the diamond.
  10. Using a selection box, select all of the components of the "dependent current source" object you have just constructed.
  11. Type the "m" key to make the object out of the selected components.
  12. You will get a popup box asking for a name for the object. Type something obvious like "depsource" or "disource". Spaces are not allowed (if you use them, they will be converted to underscores).
  13. Tap the "Okay" button. Now, if you click on the dependent source, it will be treated just like one of the built-in objects.
  14. Type the "L" key to go to the library directory. You will see that the new object you created is now located in the User Library. You can click on the User Library page to go to the User Library, and then click on the "depsource" object to bring back another instance of it, just like the built-in objects.
  15. It is important to be aware of the difference between an object and an object instance. An object is a collection of elements that have been collected together and placed in a library, like the depsource object created in this task. There is only one such object. However, many instances of this object may be created. Each instance may have its own position, scale, and color but may not otherwise change the contents of the object, which are shared by all instances (the method of parameters is the exception to this; see the discussion of parameters in the schematic capture tutorial).

Steps in creating a new user-defined object.

Task 17: Editing objects and elements

You briefly edited the built-in "isource" object in the last task, but did not change anything. In this task, suppose we want to change the appearance of the "dependent current source" object we made in the previous task.
  1. To edit the object, "push" into it using the ">" key, as you did for the "isource" in the last task.
  2. Make the polygon shorter. Put the cursor close to the top of the diamond and type "e" for "edit".
  3. Test which element is being edited by moving the cursor around. If the line, not the polygon, is being edited, then click the right mouse button or the escape key to cancel the edit operation, and repeat from step 2.
  4. Now you will be editing the point position of the polygon. Move the point down one-half grid space, and tap mouse button 2 to complete the edit.
  5. Do the same for the bottom point, moving it up one-half grid space. Where the two ends of the polygon meet, you will need to adjust both of the points.
  6. Extend the lines on the top and bottom to meet the diamond by editing the endpoints just like you did for the diamond.
  7. When you are done, return to the main page by "popping" out of the object page, using the "<" key.

Steps in editing the user-defined object.
XCircuit from version 3.7 makes editing elements, especially polygons, splines, and paths, much simpler. If you select only a portion of any of those type elements using an area select box, the points that fall within the box will be remembered for editing. The whole element will be shown selected; specific subsets of selected points are irrelevant if the selection is followed by a function that acts on the whole element, such as a move or copy function. However, if you follow the area selection with the "edit" (key "e") function, you can edit all the selected points as a group. The figures below show how a section of a path element can be stretched using an area box selection (recall that the area selection box is generated using the middle mouse button and a press-and-drag motion).




Editing a path object by grouped points (XCircuit 3.7). From top left, going clockwise:
(1) A path shape made from lines and arcs using the "join" (key "j") function.
(2) Area select on a portion of the path.
(3) The whole path is shown selected, but the points in the area box are grouped for editing.
(4) The grouped points are moved to the right.
(5) More grouped editing.

Also in version 3.7, paths containing adjacent spline curves by default are edited in a way that keeps the curvature smooth across the boundary between curves. The figure below shows a polygon (left) that has been converted to a smooth curve (center) by selecting the polygon and using the "Edit->Make Spline" menu function to generate the curve. On the right, the curve is being edited point-by-point (key "e"). Control points of adjacent curves change together, keeping the curve smooth across the boundary between the two curves. If you need to subvert this behavior to create a kink at the boundary between two curves, unselect menu item "Options->Elements->Link Curve Tangents".


Creating and editing a smooth path.

Task 18: Generating complex geometric shapes

This can be an incredibly useful feature for general drawing. A wholesale use of it is necessary to create such extravaganzas as this rendition of the JHU Applied Physics Lab's logo. I have made use of something in PostScript known as a "path", that is, a linked set of lines, arcs, and splines which together form the boundary of a single object which can be bordered, filled, colored, etc. In this task, I will show you how to generate a picture of a solid cylinder, by making a path consisting of both ellipses and lines.
  1. Start with a clean page.
  2. Create an ellipse as follows:
    1. Type macro a to start an arc.
    2. Drag the arc out to some desired size.
    3. Click the first mouse button three times (to bypass endpoint editing and go to ellipse axis editing). The position of the cursor will move from the side of the circle to the top.
    4. Drag the ellipse minor axis to the desired size and click the second mouse button to end.

  3. Creating a path object (solid cylinder): top ellipse.
  4. The whole ellipse becomes the top of the "cylinder". To make the bottom of the cylinder:
    1. Copy the first arc and place it well below the first.
    2. Type macro e to edit (or select edit from the menu and click on the lower ellipse).
    3. Immediately type e again or click on the first mouse button to go to endpoint editing mode.
    4. Drag the endpoint around to the other side until the result is the bottom half of an ellipse. Click the second mouse button to finish.

  5. Creating a path object (solid cylinder): bottom (half) ellipse.
  6. Draw two lines to create the sides of the cylinder.
  7. Select the bottom and sides of the cylinder, and type the j key to "join" these segments into a single "path".
  8. Select everything. If you (individually) select any component of the path (either the side lines or the bottom ellipse), the whole path will be highlighted.
  9. Copy (with the c macro) and place the copy to the side.

  10. Creating a path object (solid cylinder): Two cylinder frames.
  11. Select the path (lower part) of the rightmost cylinder.
  12. Choose menu item "Options->Elements->Fill->(black box)". Now you can see how to create arbitrary filled shapes.

  13. Creating a path object (solid cylinder): Two cylinders, the right one consisting of a filled path.
  14. Finish the cylinder in the following manner:
    1. Color the path shape dark gray.
    2. Select the ellipse located above the colored cylinder and perform the same steps to make it filled solid and colored light gray.
    3. Use the X keyboard macro to correctly arrange the elements, with the light gray ellipse on top of the dark gray path object.
    4. Place the black wire frame cylinder on the left on top of the solid cylinder on the right. Hint: Move the wire frame halfway on top of the solid cylinder, then arrange the top-to-bottom order of the elements so that the wire frame ends up on top, then move the wire frame the rest of the way.

Creating a path object (solid cylinder): Finished cylinder.

Xcircuit version 3.7 has several other ways to make even more complex geometric shapes. The use of clipmasks and gradients fields is advanced but can make nice visual effects. A gradient field can be made only from the command line in the Tcl/Tk version. Use menu item "File->Tcl Console" (key "%") to bring up the command window, and type the command into it. The command to create the gradient field in the figure below is:

graphic make gradient {0 0} 5 red gray50
You will need to press the space bar after entering the command to see the new graphic element, because the command does not automatically refresh the window view. You can also generate any graphic image using other graphics programs, export them as GIF or JPG images, and import them into XCircuit using menu item "File->Import->Import Graphic Image".

To get the series of images in the figure below, do the following steps:

  1. Create the gradient field graphic as described above.
  2. Select the graphic element and rotate it 90 degrees ("r" key).
  3. Draw a cylinder front as a path. This is the same as the series of steps above, except that a second half-ellipse was added to the top before creating the path by joining the elements ("j" key).
  4. Turn the path into a clipmask by selecting menu item "Options->Elements->Border->Clipmask" (or click the toolbar Border tool icon, and select the pop-up menu item "Clipmask"). The color of the path will turn to light blue, showing that it is now a clipmask (the light blue border will not appear in the final printed output. If you wish to remove the outline, deselect global option "Options->Show Clipmask Outlines". However, when clipmask outlines are not shown, it is very easy to lose track of the (invisible!) clipmasks!
  5. The graphics rendering engine must first apply a clipmask and then render other items through that clipmask, so somewhat counterintuively, the element that is clipped by the clipmask must be the element above the clipmask in the drawing stacking order. The clipmask will always apply to the single element above it in the stacking order. If you have followed the steps above, then the new clipmask was the last element created, and so is on the top of the stack, and on top of the gradient field we want to clip. So select both the clipmask outline and the gradient field, and type key "X" (exchange), or else click on just the clipmask outline and type key "]" (lower stacking order) to put the gradient field above the clipmask. You should end up with the figure on the right of the drawing.
  6. If you want to clip multiple elements with the same clipmask, you can gather all of those elements into a user object, then clip the user object instance. You should also be aware that clipmasks can be hierarchically nested, for even more complicated clipping effects.

Creating a clip path and gradient field.

Task 19: Investigating other xcircuit commands

By now you should understand the basic user interface of xcircuit and be able to get around the menus, the drawing area, be able to handle the popup prompting windows, load and save files, write text, and create polygons, arcs, curves, paths, and user objects. Of course, we have just touched the surface of xcircuit capabilities. A list of features can be found on the XCircuit Reference web page and will help you find out all the things that can be done with the program. Also, don't miss the Schematic Capture Tutorial. If you have the TCL-enabled version of XCircuit, you may also want to look at the XCircuit TCL Reference page for a listing of command-line commands.


Back to the xcircuit home page. . .

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Last updated: June 26, 2017 at 8:06am