This document covers the technical aspects of Eterm, including escape sequences it supports, "under-the-hood" descriptions of certain Eterm features, etc. Portions of this document were taken from the XTerm documentation.
| Convention | Meaning |
| c | A literal. It should be typed as shown. |
| SYM | A symbol. Replace with the proper character. See the symbol table below for a listing of the symbols used and their meanings. |
| text | A parameter. Replace the italicized text with a parameter. The text itself generally describes the type of parameter needed. |
| [ ... ] | Items enclosed in brackets are optional. |
| { ... | ... } | Items enclosed in braces and separated by pipes indicate that exactly one of the items should be chosen. |
| Symbol | Meaning |
| BEL | Bell (Ctrl-G) |
| BS | Backspace (Ctrl-H) |
| CR | Carriage Return (Ctrl-M) |
| ENQ | Enquiry (Ctrl-E), Send Device Attributes (DA). Eterm ignores ENQ if NO_ENQ_ANS is defined, which it is by default in src/feature.h. |
| ESC | Escape (Ctrl-[) |
| FF or NP | Form Feed or New Page(Ctrl-L) |
| LF or NL | Line Feed or New Line (Ctrl-J) |
| SO | Shift Out (Ctrl-N), invokes the G1 (alternate) character set |
| SI | Shift In (Ctrl-O), invokes the G0 (default) character set |
| SPC | Space |
| TAB or HT | Horizontal Tab (Ctrl-I) |
| VT | Vertical Tab (Ctrl-K) |
| Sequence | Function |
| ESC { ( | ) | * | + | $ } { 0 | A | B } | Select ISO 2022 character sets.
|
| ESC 7 | Save cursor (SC) |
| ESC 8 | Restore cursor (RC) |
| ESC = | Application Keypad (SMKX) |
| ESC > | Numeric Keypad (RMKX) |
| ESC @ | Discards the subsequent character |
| ESC D | Index (IND) |
| ESC E | Next Line (NEL) |
| ESC G | Graphics (an rxvt extension). Eterm replies to ESC G Q (query graphics) with ESC G 0 (no graphics available) and ignores all other graphics sequences. |
| ESC H | Tab Set (HTS) |
| ESC M | Reverse Index (RI) |
| ESC Z | Obsolete form of Send Device Attributes (DA), which is ESC [ c |
| ESC [ [ n ] @ | Insert n blank Characters (ICH). Default for n is 1. |
| ESC [ [ n ] A | Cursor Up n times (CUU), default 1 |
| ESC [ [ n ] B | Cursor Down n times (CUD), default 1 |
| ESC [ [ n ] C | Cursor Forward n times (CUF), default 1 |
| ESC [ [ n ] D | Cursor Backward n times (CUB), default 1 |
| ESC [ [ n ] E | Cursor Down n times and to first column, default 1 |
| ESC [ [ n ] F | Cursor Up n times and to first column, default 1 |
| ESC [ [ n ] G | Cursor to Column n (HPA) |
| ESC [ [ r ; c ] H | Cursor Position [row;column] (CUP), default 1;1 |
| ESC [ [ n ] I | Move forward n tab stops, default 1 |
| ESC [ [ n ] J | Erase in Display (ED)
|
| ESC [ [ n ] K | Erase in Line (EL)
|
| ESC [ [ n ] L | Insert n lines (IL), default 1 |
| ESC [ [ n ] M | Delete n lines (DL), default 1 |
| ESC [ [ n ] P | Delete n characters (DCH), default 1 |
| ESC [ [ n ] W | Tabulator functions
|
| ESC [ [ n ] X | Erase n characters (ECH), default 1 |
| ESC [ [ n ] Z | Move backward n tabstops, default 1 |
| ESC [ [ n ] ` | Same as ESC [ n G (HPA) |
| ESC [ [ n ] a | Same as ESC [ n C (CUF) |
| ESC [ [ n ] c | Send Device Attributes (DA), default of 0 returns "ESC[?1;2c" indicating a VT100 with advanced video option |
| ESC [ [ n ] d | Cursor to line n (VPA) |
| ESC [ [ n ] e | Same as ESC [ n A (CUU) |
| ESC [ [ r ; c ] f | Horizontal and Vertical Position (HVP), default 1;1 |
| ESC [ [ n ] g | Tab Clear
|
| ESC [ [ n ] i | Printing
|
| ESC [ n [ ; n ... ] { h | l } |
|
| ESC [ n [ ; n ... ] m | Character Attributes (SGR)
|
| ESC [ [ n ] n | Device Status Report (DSR)
|
| ESC [ [ t ; b ] r | Set Scrolling Region (CSR), where t is the top row and b is the bottom row, defaults to the full screen |
| ESC [ ? n [ ; n ... ] { h | l | s | r | t } | DEC Private Modes (shown as set/reset)
|
| ESC [ n [ ; n [ ... ] ] t | Window Operations
|
| ESC ] n ; string BEL | Set X Terminal Parameters
|
| ESC ] { l | L | I } string ESC \ |
|
| ESC ] P n rr gg bb | Changes terminal color n ('0' through 'f') to the color represented by the RGB values rr, gg, and bb. (Compatible with Linux console.) |
| ESC ] R | Restores the original palette. (Compatible with Linux console.) |
| ESC c | Full Reset (RIS) |
| ESC n | Invoke the G2 character set (LS2) |
| ESC o | Invoke the G3 character set (LS3) |
| Escaped String | Meaning |
| Backslash-Escaped Characters (case is ignored) | |
| \a | BEL (Alert) |
| \b | BS |
| \cX | Interpreted as Ctrl-X. Analogous to ^X. |
| \e | ESC |
| \f | FF |
| \n | LF |
| \r | CR |
| \t | TAB |
| \v | VT |
| \nnn | nnn is interpreted as an octal number, and the corresponding character is inserted. |
| Convenience Shortcuts | |
| ^X | Interpreted as Ctrl-X. X can be any character between @ and _. Case is ignored. |
| C-X | Interpreted as Ctrl-X. Analogous to ^X. |
| M-X | Interpreted as ESC followed by X. Analogous to \eX. If the string begins with M-, a CR is automatically appended to the end of the string if not already present. |
The string supplied to the image escape sequence (above) consists of a filename (which can be empty) followed by a semicolon, then one or more geometry strings. Each geometry string contains zero or one scale/position adjustment and may optionally be followed by a colon and one or more colon-delimited pixmap operations. The following table shows the valid geometry strings and their affects on the background image:
| String | Function |
| Adjusting scaling and position | |
| WxH+X+Y | Set scaling to W% by H%, and position to X% by Y%. W and H are percentages of the terminal window size. X and Y are also percentages; e.g., +50+50 centers the image in the window. |
| WxH+X | Assumes Y == X |
| WxH | Assumes Y == X == 50 (centers the image) |
| W+X+Y | Assumes H == W |
| W+X | Assumes H == W and Y == X |
| W | Assumes H == W and Y == X == 50 |
| Adjusting position only | |
| =+X+Y | Set position to X% by Y% (absolute). |
| =+X | Set position to X% by X%. |
| +X+Y | Adjust position horizontally X% and vertically Y% from current position (relative). |
| +X+X | Adjust position horizontally X% and vertically X% from current position. |
| Adjusting scale only | |
| Wx0 | Multiply horizontal scaling factor by W% |
| 0xH | Multiply vertical scaling factor by H% |
| 0x0 | No scaling (show image at normal size). |
| Pixmap Operations | |
| tile | Tile image. Scaling/position modifiers above will affect the tile size and origin. |
| propscale | When scaling, scale proportionally. That is, maintain the proper aspect ratio for the image. Any portion of the background not covered by the image is filled with the current background color. |
Examples:
When Eterm receives a mouse reporting request (and if mouse reporting is currently enabled), it replies with the sequence "ESC[Mbxy". The values for b, x, and y are as follows (subtract the value of space ' ' first):
| Cursor Keys | ||||
| Key Pressed | What Eterm Sends | |||
| Normal | Shift | Control | Application | |
| Up | ESC [ A | ESC [ a | ESC O a | ESC O A |
| Down | ESC [ B | ESC [ b | ESC O b | ESC O B |
| Right | ESC [ C | ESC [ c | ESC O c | ESC O C |
| Left | ESC [ D | ESC [ d | ESC O d | ESC O D |
| Special Keys | ||||
| Key Pressed | Normal | Shift | Control | Control+Shift |
| Tab | ^I | ESC [ Z | ^I | |
| Backspace | ^H | ^? | ^? | |
| Home (Find) | ESC [ 1 ~ | ESC [ 1 $ | ESC [ 1 ^ | ESC [ 1 @ |
| End (Select) | ESC [ 4 ~ | ESC [ 4 $ | ESC [ 4 ^ | ESC [ 4 @ |
| Insert | ESC [ 2 ~ | Paste mouse selection | ESC [ 2 ^ | ESC [ 2 @ |
| Delete (Execute) | ESC [ 3 ~ | ESC [ 3 $ | ESC [ 3 ^ | ESC [ 3 @ |
| PageUp (Prior) | ESC [ 5 ~ | Scroll up one page | ESC [ 5 ^ | ESC [ 5 @ |
| PageDown (Next) | ESC [ 6 ~ | Scroll down one page | ESC [ 6 ^ | ESC [ 6 @ |
| Function Keys (Note: Shift-F1 through F10 sends F11-F20) | ||||
| Key Pressed | Normal | Shift | Control | Control+Shift |
| F1 | ESC [ 11 ~ | ESC [ 23 ~ | ESC [ 11 ^ | ESC [ 23 ^ |
| F2 | ESC [ 12 ~ | ESC [ 24 ~ | ESC [ 12 ^ | ESC [ 24 ^ |
| F3 | ESC [ 13 ~ | ESC [ 25 ~ | ESC [ 13 ^ | ESC [ 25 ^ |
| F4 | ESC [ 14 ~ | ESC [ 26 ~ | ESC [ 14 ^ | ESC [ 26 ^ |
| F5 | ESC [ 15 ~ | ESC [ 28 ~ | ESC [ 15 ^ | ESC [ 28 ^ |
| F6 | ESC [ 17 ~ | ESC [ 29 ~ | ESC [ 17 ^ | ESC [ 29 ^ |
| F7 | ESC [ 18 ~ | ESC [ 31 ~ | ESC [ 18 ^ | ESC [ 31 ^ |
| F8 | ESC [ 19 ~ | ESC [ 32 ~ | ESC [ 19 ^ | ESC [ 32 ^ |
| F9 | ESC [ 20 ~ | ESC [ 33 ~ | ESC [ 20 ^ | ESC [ 33 ^ |
| F10 | ESC [ 21 ~ | ESC [ 34 ~ | ESC [ 21 ^ | ESC [ 34 ^ |
| F11 | ESC [ 23 ~ | ESC [ 23 $ | ESC [ 23 ^ | ESC [ 23 @ |
| F12 | ESC [ 24 ~ | ESC [ 24 $ | ESC [ 24 ^ | ESC [ 24 @ |
| F13 | ESC [ 25 ~ | ESC [ 25 $ | ESC [ 25 ^ | ESC [ 25 @ |
| F14 | ESC [ 26 ~ | ESC [ 26 $ | ESC [ 26 ^ | ESC [ 26 @ |
| F15 (Help) | ESC [ 28 ~ | ESC [ 28 $ | ESC [ 28 ^ | ESC [ 28 @ |
| F16 (Menu) | ESC [ 29 ~ | ESC [ 29 $ | ESC [ 29 ^ | ESC [ 29 @ |
| F17 | ESC [ 31 ~ | ESC [ 31 $ | ESC [ 31 ^ | ESC [ 31 @ |
| F18 | ESC [ 32 ~ | ESC [ 32 $ | ESC [ 32 ^ | ESC [ 32 @ |
| F19 | ESC [ 33 ~ | ESC [ 33 $ | ESC [ 33 ^ | ESC [ 33 @ |
| F20 | ESC [ 34 ~ | ESC [ 34 $ | ESC [ 34 ^ | ESC [ 34 @ |
| Keypad | ||||
| Key Pressed | Normal | Application | ||
| KP_Enter | ^M | ESC O M | ||
| KP_F1 | ESC O P | ESC O P | ||
| KP_F2 | ESC O Q | ESC O Q | ||
| KP_F3 | ESC O R | ESC O R | ||
| KP_F4 | ESC O S | ESC O S | ||
| XK_KP_Multiply | * | ESC O j | ||
| XK_KP_Add | + | ESC O k | ||
| XK_KP_Separator | , | ESC O l | ||
| XK_KP_Subtract | - | ESC O m | ||
| XK_KP_Decimal | . | ESC O n | ||
| XK_KP_Divide | / | ESC O o | ||
| XK_KP_0 | 0 | ESC O p | ||
| XK_KP_1 | 1 | ESC O q | ||
| XK_KP_2 | 2 | ESC O r | ||
| XK_KP_3 | 3 | ESC O s | ||
| XK_KP_4 | 4 | ESC O t | ||
| XK_KP_5 | 5 | ESC O u | ||
| XK_KP_6 | 6 | ESC O v | ||
| XK_KP_7 | 7 | ESC O w | ||
| XK_KP_8 | 8 | ESC O x | ||
| XK_KP_9 | 9 | ESC O y | ||
The table below contains a listing of all the Eterm-specific escape sequences that Eterm supports. These sequences were created by the Eterm authors. Please note the following conventions used in this table:
When an escape sequence is said to "set/toggle" an option, this means that the boolean parameter of the sequence is optional. If given, it will either set or unset the option. If omitted, the current state of that option will be reversed (i.e., turned off if on, or on if off). Acceptable values for "true" are: 1, on, yes, or (of course) true. Likewise, acceptable values for "false" are: 0, off, no, or false.
| Sequence | Function |
| ESC [ 9 n | Titlebar Status. This places Eterm's current status in the titlebar. The status information includes the application name and version number, as well as the shading/tinting state if transparent, the path to the background image if there is one, or "No Pixmap" if neither of these is true. |
| ESC ] 5 ; BEL | Steal Focus. Eterm will raise itself to the top and steal keyboard/mouse focus. This is useful in case your window manager dies or has trouble starting up. By default, this is activated by holding the Ctrl key and clicking on the Eterm window with the left mouse button (Button1). |
| ESC ] 6 ; 0 [ ; boolean ] BEL | Set/toggle transparency state. This affects all images for which transparency is an allowed mode. |
| ESC ] 6 ; 1 ; [ class ; ] color ; attribute ; value BEL | Adjusts a color modifier. class determines which image class will have its color modifier altered: bg (background, the default), up (up arrow), down (down arrow), sb (scrollbar trough), sa (scrollbar anchor), st (scrollbar thumb), menu (popup menu background), menuitem (popup menu items), submenu (menu items which represent submenus), button (buttons on the buttonbar), or bbar (buttonbar). Next comes the color which determines how pixels are modified. This is either image, red, green, or blue. attribute is one of brightness, contrast, or gamma, and value is the actual integer value (>= 0). As stated in the man page, 256 (0x100) is 100%. |
| ESC ] 6 ; 2 ; { shade | tint } [ class ; ] value BEL | Shade/tint the specified class (see above). For shading, value is the shade percentage. For tinting, it is the tint color or mask. |
| ESC ] 6 ; 3 ; BEL | Force an update the of transparency background. |
| ESC ] 6 ; 10 ; [ type ] [ ; width ] BEL | Set scrollbar style to type and scrollbar width to width. If specified, type must be one of motif, xterm, or next. If you omit the type parameter and only wish to set the width, take care not to omit the extra semicolon. width is an integer. Its value is fairly wide-open, but should be something reasonable. |
| ESC ] 6 ; 11 [ ; boolean ] BEL | Set/toggle right-side scrollbar. |
| ESC ] 6 ; 12 [ ; boolean ] BEL | Set/toggle floating scrollbar (i.e., one with no trough). |
| ESC ] 6 ; 13 [ ; boolean ] BEL | Set/toggle popup scrollbar (i.e., one that appears when the window has focus and disappears when it does not). |
| ESC ] 6 ; 14 [ ; boolean ] BEL | Set/toggle display of buttonbars. |
| ESC ] 6 ; 20 [ ; boolean ] BEL | Set/toggle visual bell. |
| ESC ] 6 ; 21 [ ; boolean ] BEL | Set/toggle map alert. |
| ESC ] 6 ; 22 [ ; boolean ] BEL | Set/toggle xterm's cutchar selection behavior. |
| ESC ] 6 ; 23 [ ; boolean ] BEL | Set/toggle selection of the whole line by triple-click. |
| ESC ] 6 ; 24 [ ; boolean ] BEL | Set/toggle viewport mode for all images that have allowed viewport mode. |
| ESC ] 6 ; 25 [ ; boolean ] BEL | Set/toggle selection trailing spaces. |
| ESC ] 6 ; 26 [ ; boolean ] BEL | Set/toggle reporting as keysyms. See the man page for details. |
| ESC ] 6 ; 27 [ ; boolean ] BEL | Set/toggle the refusal of keyboard input and focus. |
| ESC ] 6 ; 50 ; desktop BEL | Move Eterm to desktop desktop and make it the current desktop. This requires a compliant Window Manager, such as Enlightenment. |
| ESC ] 6 ; 72 [ ; string ] BEL | Search for and highlight any occurrences of string in the scrollback buffer. |
| ESC ] 6 ; 80 ; level BEL | Set the debugging level to level. |
| ESC ] 18 ; string BEL | Set bold color to string. |
| ESC ] 19 ; string BEL | Set underline color to string. |
The standard for implementing transparency was a mutual effort between myself, Carsten Haitzler <raster@rasterman.com>, Gerald Britton <gbritton@mit.edu>, and Nat Friedman <nat@nat.org>, based off of an original idea by Nat. First I'll define the standard, then I'll discuss its justification.
There are two separate procedures for setting the transparency property (the _XROOTPMAP_ID atom in X). The first is for persistent X clients such as window managers. These clients should proceed through their normal mechanism for setting the desktop image. Once the finalized pixmap has been created, the _XROOTPMAP_ID property should be set on the desktop window (the same window which will receive the pixmap...note that this is not necessarily the root window), and its value should be set to the Pixmap ID. The following sample code (taken from Enlightenment) demonstrates this:
/* disp is the Display, win is the desktop Window, pmap is the pixmap */
static Atom prop = 0;
if (!prop) {
prop = XInternAtom(disp, "_XROOTPMAP_ID", False);
}
XChangeProperty(disp, win, prop, XA_PIXMAP, 32, PropModeReplace,
(unsigned char *)&pmap, 1);
XSetWindowBackgroundPixmap(disp, win, pmap);
XClearWindow(disp, win);
The second procedure is for temporary clients; i.e., clients who set the desktop pixmap and then exit. An example of this type of client would be Esetroot, the transparency utility provided with Eterm. These clients should set the _XROOTPMAP_ID property just like the persistent client does. They should also set a companion property as well, ESETROOT_PMAP_ID. Both are set to the same pixmap ID. When a temporary client runs, it checks to see if _XROOTPMAP_ID and ESETROOT_PMAP_ID have the same value. If so, the client knows that it can safely do an XKillClient() on the pixmap ID. This will save memory, as the old pixmap can be removed. If they are not equal, however, calling XKillClient() would kill the persistent client which did set it, most likely the user's window manager. This would be a Bad Ideatm. The following code fragment (taken from Esetroot) illustrates this process:
/* disp is the Display, win is the desktop Window, pmap is the pixmap */
Atom prop_root, prop_esetroot, type;
int format;
unsigned long length, after;
unsigned char *data_root, *data_esetroot;
/* First check to see if the properties already exist, and if they are equal */
prop_root = XInternAtom(disp, "_XROOTPMAP_ID", True);
prop_esetroot = XInternAtom(disp, "ESETROOT_PMAP_ID", True);
if (prop_root != None && prop_esetroot != None) {
XGetWindowProperty(disp, win, prop_root, 0L, 1L, False, AnyPropertyType,
&type, &format, &length, &after, &data_root);
if (type == XA_PIXMAP) {
XGetWindowProperty(disp, win, prop_esetroot, 0L, 1L, False, AnyPropertyType,
&type, &format, &length, &after, &data_esetroot);
if (data_root && data_esetroot && type == XA_PIXMAP && *((Pixmap *) data_root) == *((Pixmap *) data_esetroot)) {
/* It's safe. Kill the pixmap. */
XKillClient(disp, *((Pixmap *) data_root));
}
}
}
/* This will locate the property, creating it if it doesn't exist */
prop_root = XInternAtom(disp, "_XROOTPMAP_ID", False);
prop_esetroot = XInternAtom(disp, "ESETROOT_PMAP_ID", False);
/* The call above should have created it. If that failed, we can't continue. */
if (prop_root == None || prop_esetroot == None) {
fprintf(stderr, "Error: Creation of pixmap property failed.\n");
exit(1);
}
XChangeProperty(disp, win, prop_root, XA_PIXMAP, 32, PropModeReplace,
(unsigned char *) &pmap, 1);
XChangeProperty(disp, win, prop_esetroot, XA_PIXMAP, 32, PropModeReplace,
(unsigned char *) &pmap, 1);
XSetCloseDownMode(disp, RetainPermanent);
When the client runs, it looks for the _XROOTPMAP_ID property on the desktop window. (The client searches through all its parent windows until it either finds one with this property set, or hits the root window without finding it.) If the client finds this property, it can then use the pixmap directly, or make a copy of the pixmap in order to perform additional operations on it (such as brightening, shading, tinting, etc.).
So why use this technique? Why require such support from the window manager and other external applications? Why not simply set the background to ParentRelative and be done with it? let X handle everything? This seems to be a point of great confusion lately. Those who have taken the time to put the other terminal emulators who have chosen the latter route through their paces already know the answer: Power. Very simply, you have *much* greater power and flexibility with this technique than any other. X only permits a limited amount of flexibility when copying the background directly (basically just bitwise logical operations). The above technique allows programs to tint, shade, brighten, or otherwise manipulate the image in *any* way they see fit. Want a 10% shade? A 30% shade? Maybe a light cyan tint? Or perhaps you prefer a midnight blue tint.... With this technique, you can have it *your* way, not their way.