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.0 &The format for the option into the display parameter is as follows:[host]:[server][:screen]If you are given permission to open a display, you are logged into the remotemachine.You can verify this with the uname command.Check the DISPLAYwith the echo $DISPLAY command.When you log out with the exit command, the remote session and the xtermare terminated.TIP: One of the mostcommon reasons for not being able to open a remote terminal is that the remote hostdoes not allow you to open windows there.Ask the remote users to use the xhostcommand at the remote machine as a part of their login.ColorsAll the colors in the X Window system are located in the /usr/lib/X11/rgb.txtfile.This file consists of four columns.The first three columns specify red, green,and blue values; the last entry specifies the name you can use in your parameters.A partial listing of the rgb.txt file is shown in Listing 23.5.Listing 23.5.Anexcerpt from the rgb.txt file.255 250 250 snow248 248 255 ghost white248 248 255 GhostWhite245 245 245 white smoke245 245 245 WhiteSmoke220 220 220 gainsboro255 250 240 floral white255 250 240 FloralWhite253 245 230 old lace253 245 230 OldLace250 240 230 linen250 235 215 antique white255 239 213 PapayaWhip255 235 205 blanched almond255 235 205 BlanchedAlmond255 218 185 peach puff255 218 185 PeachPuff255 222 173 navajo white255 223 181 moccasin255 248 220 cornsilk255 255 240 ivory255 250 205 lemon chiffon255 250 205 LemonChiffon255 245 238 seashell240 255 240 honeydew245 255 250 mint cream255 240 245 LavenderBlush255 223 225 misty rose255 223 225 MistyRose255 255 255 white0 0 0 black47 79 79 dark slate grey47 79 79 DarkSlateGrey105 105 105 dim gray105 105 105 DimGray105 105 105 dim grey105 105 105 DimGrey112 123 144 slate gray112 123 144 SlateGray112 123 144 slate grey112 123 144 SlateGrey119 136 153 light slate gray119 136 153 LightSlateGray119 136 153 light slate grey119 136 153 LightSlateGrey190 190 190 gray190 190 190 grey211 211 211 light greyBecause red, green, and blue have 256 values each, the number of possible colorsis 16,777,216.Not many workstations can display that many colors at one time.Therefore,X uses a facility to map these colors onto the display, called a colormap.A colordisplay uses several bits for displaying entries from this map.The xdpyinfo programgives you the number of bits for the display.This is a frame buffer.A 1-bit framesignifies a black-and-white display.An 8-bit frame buffer signifies 2 to the powerof 8 entries, or 256 possible colors.Unfortunately, due to different phosphors on different screens, your color specificationon one monitor might be completely different on another monitor.Tektronix providesa tool called xtici, an API, and docs to counter such problems by using the internationalCIEXYZ standard for color specifications.This is called the Color Management System(CMS), which uses a model called HVC (Hue-Value-Chroma).In the X11R5 (or later)release, look for Xcms for more details, or contact Tektronix.FontsFonts in the X Window system are designed for maximum flexibility.These are twogood utilities to help you sift through some of the 400 or so font types on a basicsystem:xlsfontsLists the fonts in your system.xfontselEnables you to interactively see which fonts are available on your system and whatthey look like on the screen.Using xlsfontsFirst, let's examine the font names themselves.Use the xlsfonts commandto list the fonts on your system.Type the command on an xterm, and because the listingfrom xlsfonts is very long, be sure to pipe to a text file for review.You shouldsee a listing in which each line is of this form:-foundry-family-wt-sl-wd-p-pts-hr-vr-sp-ave-charset-styleThe foundry is the company that first developed the font.The most common onesare misc, Adobe, Bitstream, and B&H.Youmight see more on your system from the results of your xlsfonts command.A foundry of misc implies a font with fixed width and height per character;the rest were donated by their respective manufacturers.The family is the general type of font: Courier, Helvetica, New Century Schoolbook,Lucida, and so on.Some families are monospaced, meaning that all their charactershave the same width.The other families are proportionally spaced, meaning that eachcharacter has a separate width.Courier and Lucida are monospaced fonts.New CenturySchoolbook is proportionally spaced.Use monospaced fonts for tabular information or running text.This makes yourtext line up cleanly in running displays.Proportionally spaced fonts are helpfulfor text in buttons or menu items.The wt and sl parameters stand for weights and slants, respectively.The common weights are bold and medium.Bold text is drawn witha thicker pen than the normal pen.The common slants are (r) roman, (o)oblique, and (i) italic.Roman text is drawn upright, and oblique text hascharacters sheared to the right.Italic text is similar to oblique text, but thecharacters are touched up to show a smoother effect.You might also have reverseoblique (ro) and reverse italic (ri), which make the text leanto the left rather than the right.The p stands for the point size, which traditionally is 1/72 of an inch.Most monitors support only 75 or 100 dots per inch (dpi) resolution.Because X fontsare bitmaps, it seems logical that the most common fonts within X are of two types:75dpi and 100dpi.This number is found in the two fields hr and vr, which standfor the horizontal and vertical resolution, respectively.In almost all cases, youspecify either 75 or 100 in each of these fields.The sp refers to the spacing between two characters on the screen.Thiscan be m for monospaced, p for proportional, or c forfixed fonts in which each character occupies a fixed box.The ave is 1/10 of the average width of all the characters in the set.The charset and style are usually set to ISO8859-1.This refers to theISO Latin-1 character set, which includes characters found in ASCII and other Europeancharacter sets.Now that you've seen the large number of options that can define a font, you canrely on using wildcards to specify most of the options for a font.The server matchesthe first font name that matches your specification with a wildcard.In other words,you only have to specify the parameters you want to change, and you can use the asteriskfor the rest.For example, *courier-roman gets the first specification for the roman-weightedCourier font.*Courier, however, gets the bold Courier font.This is becausethe bold specification exists before the roman specification in the fonts file.TIP: Use the xsetfp=fontpath command to set the directory (75 or 100 dpi) you want searched firstin the front of the font path.This guarantees that the correct dpi size directoryis searched first.The font search path is the path used by the server to search for the fonts inyour system [ Pobierz całość w formacie PDF ]
