C/C++ Users Group Library 1996 July

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MICROCAD is a very small drawing program (less than 12k!) It has commands for drawing/erasing/moving/copying such things as lines, boxes, circles, arcs, graphical text and other drawings as "group" objects. It also features a "display" mode, where it can be used as a simple viewer, and includes an MCPRINT utility to print your drawings. This is not intended as a serious drafting package, however it is useful as a means of transmitting simple drawings via diskette, or modem. MICROCAD is "free", and may be used and distributed without payment or royalty. The complete MICRO-C source code to MICROCAD is available free of charge from our BBS, and may prove useful to anyone wishing to experiment with a drawing editor, or add support for other devices. In its current form, MICROCAD requires a mouse, a VGA display (it works at 640x480), and either an HP LASERJET or EPSON DOT-MATRIX printer. It should be fairly easy to modify it for compatibility with other devices. The MICROCAD command: -------------------- The MICROCAD command has the following syntax: MICROCAD [drawing file] [F=font file] [/Display] [drawing file] is the name of a file containing a drawing that you wish to edit. The extension '.DWG' is assumed. If you do not specify a file name, MICROCAD assumes its default name MICROCAD.DWG. This default drawing file normally contains a blank drawing, and is used only to establish the default settings for the "S)etup" values. [font file] is the name of a file containing a character set font that will be used to display any text in the drawing file. If you do not specify a font file, The default MICROCAD.FNT is assumed. [/Display] causes MICROCAD to act as a viewer. The mouse is not activated, the grid is disabled (even if it is turned on in the drawing), and the drawing is displayed. Pressing any key will terminate the MICROCAD at this point. Mouse: ----- MICROCAD uses only the LEFT and RIGHT mouse buttons, allowing it to be used with either a two or three button pointing device. When sitting at the top command level (no command text visible at the top of the screen), the mouse buttons function as follows: LEFT - Brings up the command menu at the top of the screen. Pressing the key corrsponding to a command will active that command. RIGHT - Activates the last command that you executed. This is a useful way to perform multiple operations, such as drawing multiple box's etc. Unless noted otherwise, the mouse buttons behave as follows once a command has been activated: LEFT - Performs an operation for which you are being prompted at the top of the screen. Some commands may have several locations that have to be selected. For each location, you will receive a prompt at the top of the screen. Simply move the mouse pointer to the desired location, and press the LEFT button. RIGHT - Cancels the operation. In most cases this will return you directly to the top command level (no command active). In some cases, this will cancel a sub-function, and permit you to continue with the command. Main COMMANDS: ------------- The following commands are available from within MICROCAD at the top command level. A)rc Prompts you for a "center" point, a starting point, and an ending point. Draws an arc clockwise from the starting point to the ending point, which would be a portion of a circle centered about the center point. B)ox This command prompts you to select two corners, and after the second one is selected, MICROCAD will draw a BOX with diagonal corners on those points. C)ircle Prompts you to select a center point, and then a second point. MICROCAD will draw a circle about the center point, which includes the second point in its circumference. D)up Prompts you to select an object, and then for a new insertion point. The object is copied to the new point. Most useful for duplicating a "group" that you have included from another file, or insuring that you get a circle of exactly the same size etc. Duplicating an object takes only 7 bytes in the drawing file, no matter how large or complicated the object is. See the E)rase command below for details on selecting an object. E)rase Prompts you to select an object. To select an object, you must position the cursor over the BASE POINT of that object. In general, the base point will be the first point that you selected when defining the object. To make it easier for you, MICROCAD constantly watches the cursor position when this command is executed, and selects any object who's base point comes in contact with the cursor. Once an object is selected, MICROCAD indicates so, by temporarily removing it from the screen. Press the LEFT button to accept this, and permanently erase the object. If you accidently select an object that you don't want to erase, just move the cursor away from it, and press the RIGHT button. MICROCAD will restore it to the screen, and continue to search for other objects. If more than one object has its base point at the same location, MICROCAD will select the one which was defined first. You may accept this with the LEFT button, or press the RIGHT button to switch to the next oldest one. If you wish to cancel the selection in this case, you must keep pressing the RIGHT button until all objects at that location have been skipped. You may use the S)etup / B)ase-markers command to cause the base points of all objects in the drawing to be made visible. F)unc This command brings up menu of misc. functions: F)ont Prompts you for a new character font file, and if given, loads it, and re-draws the drawing, using the new font. I)nsert Prompts you for a drawing filename, and then an insertion point. Inserts the contents of that drawing into the current drawing as a single object. The base point of the new object is the upper left corner of an invisible box, just large enough to include all object base points in the included drawing. This point will be shown by the cursor while selecting the new object location. If you wish to insert the same drawing several times, it takes much less space in the drawing file if you insert it once, and then use the duplicate function to create the other instances. L)oad Prompts for a filename, and loads a drawing from that file. Any unsaved changes to the current drawing are lost. Q)uit Terminates MICROCAD. S)ave Prompts for a filename, and saves the current drawing to that file. L)ine Prompts for a starting point, and then a series of end points. Each time you select a new point, a line is drawn to it from the previous point. Press the RIGHT button to stop drawing lines. M)ove Prompts you to select an object, and then for its new base point. The object is then repositioned in the drawing. See the 'E)rase' command for details on selecting an object. R)edraw Redisplays the drawing. This is useful to see any objects which are overwritten by the text line at the top of the screen, and to "fix" any breaks in lines, or missing grid markers causes by erasing of overlaid objects. S)etup Brings up a menu of setup subcommands: B)ase-markers This command toggles ON/OFF the display of base points. See E)rase command for a description of base points. When ON, the base point for each object in the drawing will appear surrounded by a tiny box. C)urser-base Prompts you to select a base point for the cursor. After you select one, the cursor position shown in the upper right corner of the screen, will be relative to this position. G)rid Prompts for the spacing (in pixels) of the grid markers. Entering a blank line, or a value of zero turns off grid markers. Grid markers are simply "dots" placed at regular intervals, which you can use as a reference for aligning objects etc. S)nap Prompt for the spacing of "snap stops". When snap is enabled, the cursor is forced to "snap" into a grid of evenly placed stops. This makes it MUCH easier to align objects that you create. The "snap" grid should normally be set to some even fraction of the "G)rid" markers, although this is not enforced. Entering a blank line, or a value of zero turns off "snap", allowing the cursor to roam free. T)ext-scale This defines the size of text characters. Only affects text created after this command is used, allowing you to have several different sizes of text in the same drawing. The character set fonts used by MICROCAD are built on a matrix which is 16 pixels wide, by 24 pixels high. A scale value of 100 indicates that this original size will be used. A value of 50 would result in characters half as high and wide, while 200 would double the height and width. NOTE: All of the above settings are saved in the drawing file, and will therefore be restored when you subsequently edit the drawing. T)ext Inserts a text string into the drawing. You will be prompted for the string to be inserted, and then for the position in the drawing. U)ndo Erases the last object which was created. Undo may be repeated, and each time the youngest living object is removed. NOTE that U)ndo cannot reverse operations like M)ove or E)rase. MCPRINT Utility: --------------- MICROCAD includes MCPRINT, which will print your drawing on an HP LaserJet series or EPSON dot-matrix printer. MCPRINT works by building a raster bitmap from your drawing, and then sending it to the printer. It should be fairly easy to modify MCPRINT to work with other printers. The syntax of the MCPRINT command is: MCPRINT <drawing file> <printer type> [F=font file] [D=device] <drawing file> is the name of a file containing the drawing that you wish to print. The extension '.DWG' is assumed. <printer type> indicates which kind of printer you have. It should be either LASERJET or EPSON. [font file] is the name of a file containing a character set font that will be used to display any text in the drawing file. If you do not specify a font file, The default MICROCAD.FNT is assumed. [device] is the DOS device to which the printer output will be written. If you do not specify one, "LPT1" is assumed. You may also use this option to direct the output to a file. Misc. Notes: ----------- MICROCAD does all of its internal calculations using 16 bit arithmetic. Bacause of this, circles or arcs having a very large radius may not display correctly. This is because these objects require manipulation of squares of values, which may overflow 16 bits. The GRID markers are not recorded as part of the object, and will "disappear" if you M)ove, E)rase or U)ndo something that was on top of them. They will be restored any time the screen is redrawn. Character Fonts: --------------- The following characters font files are included with MICROCAD: MICROCAD.FNT - This is the default MICROCAD font. It is a reasonable quality font, which scales fairly well. HIGHRES.FNT - This is a higher quality font, however it does not scale to small sizes quite as well as MICROCAD.FNT. MATRIX.FNT - A low (8x8) resolution font which looks like the output from a dot matrix printer. THINLINE.FNT - A thin spidery font. MICROCAD also includes a "font editor" (FE.COM) which allows you to create and edit your own font files. The program is fairly self explainatory, just run it and specify the name of the font file as an argument. Drawing File Format: ------------------- All entries in the drawing files produced by MICROCAD consist of 8 bit bytes and 16 bit words. Word values are stored with the most significant byte first. The first few bytes of the drawing file contain the "S)etup" values: Word = Grid spacing (0 = disable) Word = Snap spacing (0 = disable) Word = Text scale (100 = 1:1) Word = Cursor base X position Word = Cursor base Y position Byte = Basepoint display: 0 = ON, 1=OFF Following the settings, the file will contain zero or more "objects", representing lines, circles etc. The form of each type of object is: END: Byte = 0x00 This is not required by MICROCAD, and is not normally produced by the program, however, an object consisting of a single 0x00 byte causes MICROCAD to stop drawing. This has two effects: 1- If you are going to transmit the file using a protocol such as XMODEM which adds garbage to the end of the file, you could first append an END object to avoid "Corrupt drawing file". 2- Once the END object is encountered, further additions to the drawing although recorded, are not displayed when the file is redrawn or reloaded. LINE: Byte = 0x01 Word = Absolute X position of first point Word = Absolute Y position of first point Word = Relative X position of second point Word = Relative Y position of second point BOX: Byte = 0x02 Word = Absolute X position of first point Word = Absolute Y position of first point Word = Relative X position of second point Word = Relative Y position of second point CIRCLE: Byte = 0x03 Word = Absolute X position of center point Word = Absolute Y position of center point Word = Radius of circle TEXT: Byte = 0x04 Word = Absolute X position of text Word = Absolute Y position of text Word = Scale of text (100 = 1:1 = 16x24) Bytes= Text string Byte = 0 (zero termination) ARC: Byte = 0x05 Word = Absolute X position of center point Word = Absolute Y position of center point Word = Radius of arc Word = Angle (0-255) to starting point. Word = Angle (0-255) to ending point. Angle: 0 | 192 --+-- 64 | 128 GROUP: Byte = 0x06 Word = Abolute X position of group Word = Abolute Y position of group Word = Size of following objects (in bytes) ... Zero of more objects follow... X/Y positions are relative to group start. ACOPY: Byte = 0x07 Word = Absolute X position of copy Word = Absolute Y position of copy Word = Byte offset of copied object from first object in file RCOPY: Byte = 0x08 Word = Absolute X position of copy Word = Absolute Y position of copy Word = Byte offset of copied object from beginning of this object The absolute copy is used whenever an object is duplicated via the D)up function in MICROCAD. This form is more easy to manipulate when dealing with discrete objects. When objects are "grouped" (a drawing is inserted), any ACOPY objects are changed to the relative RCOPY, so that we do not have to worry about them shifting due to E)rase etc. This makes it much easier to treat the entire group as a single object. This is safe to do, since the ACOPY must reference an object in the same group, and the contents of a group are never altered. This drawing file format is hearby placed in the public domain. Finally: ------- If anyone significantly enhances MICROCAD, or does something else truly useful with it, I'd like to see the results. Dave Dunfield Dunfield Development Systems P.O. Box 31044 Nepean, Ontario Canada K2B 8S8 TEL: (613) 256-5820 BBS: Dial '2' at voice prompt FAX: (613) 256-5821 eg: atdt16132565820,,,,,,,2222 MICROCAD and its related utilities are compiled using the PC version of my MICRO-C compiler. For more information on MICRO-C and my other products, see the CATALOG file in this archive.