A.1 Old Lisp Features in Emacs 20

• The push and pop macros are not defined. Neither are dolist and dotimes.

• You can't display images in buffers. (Emacs is meant for editing text.) With no images, there are no display margins, and no tool bars.

• The display text property has no special meaning; you can use it freely in Lisp programs, with no effects except what you implement for yourself. With no images, who needs the display text property?

• The field text property has no special meaning; buffers are no longer subdivided into fields. (The division of information into fields is always rather arbitrary.)

• Faces have fewer attributes. The attributes :family, :height, :width, :weight, and :slant, have been replaced with a font name, a "bold" flag, and an "italic" flag.

  The attributes :overline, :strike-through and :box have been eliminated too. Underlining now always has the same color as the text--using any other color would be bad taste.

  With fewer font attributes, there are no functions set-face-attribute and face-attribute. Instead, you access these attributes using functions such as face-font, and set them with functions such as set-face-font. (These functions were available in Emacs 21, but are not as useful there.)

• The standard faces scroll-bar, menu, border, cursor, and mouse have been eliminated. They are rather strange, as faces, and therefore shouldn't really exist. You can use set-border-color, set-cursor-color and set-mouse-color to specify the colors for the frame border, the text cursor, and the mouse cursor. To specify menu colors, use X resources.

• Colors and other face attributes are no longer supported on character terminals, so you no longer have to worry about terminals making faces at you.

• Emacs will respect your peace and quiet, aside from occasional beeps, because there are no facilities for playing sounds.

• Emacs 20 provides a complex and badly designed method for handling character composition for languages such as Thai that display several letters as a single combined image. We are too ashamed of it to tell you any more than that.

• delete-and-extract-region has been deleted; instead, use buffer-substring to extract the text, then use delete-region to delete it.

• Regular expressions do not support the POSIX character classes such as `[:alpha:]'. All characters are created equal.

• Hash tables have been eliminated; use alists instead.

• The Lisp printer does not detect and report circular structure. That is ok, because the Lisp reader cannot recreate circular structure anyway. However, there is a library `cust-print.el' which can report circular structure.

• Emacs provides its own implementation of scroll bars, instead of using those of the X toolkit. They always use the frame foreground and background colors, so you cannot specify different colors for the scroll bars.

• For simplicity, all ASCII characters now have the same height and width. (Certain characters, such as Chinese characters, always have twice the standard width.) All characters are created equal.

• You can now resize any Emacs window, and size changes in one window can propagate to all others. Windows can no longer use window-size-fixed to get special privileges.

• The function intern-soft no longer accepts a symbol as argument.

• The function bitmap-spec-p has been renamed to pixmap-spec-p to encourage users to practice Emacs' help system while trying to find it.

• Tooltips operate using ordinary Emacs frames.

• Areas of the mode line are not mouse-sensitive; however, some mouse commands are available for the mode line as a whole.

• Windows cannot have header lines. Conversely, there is no way to turn off the mode line of a window unless it is a minibuffer.

• Plain dashes are the only separators you can use in a menu.

• Vertical fractional scrolling does not exist.

• The functions format and message ignore and discard text properties.

• The function propertize does not exist; you can get the job done using set-text-properties.

• Colors are supported only on window systems, not on text-only terminals. So the support functions for colors on text-only terminals are not needed, and have been eliminated.

• The functions color-values, color-defined-p and defined-colors have been renamed to x-color-values, x-color-defined-p and x-defined-colors.

• Windows cannot be made fixed-width or fixed-height; Emacs will adjust the size of all windows when it needs to.

• The string used as the value of the before-string or after-string property must contain only characters that display as a single column--control characters, including tabs and newlines, will give strange results.

• The minibuffer prompt does not actually appear in content of the minibuffer; it is displayed specially in the minibuffer window.

• The "exclusive open" feature of write-region has been eliminated; any non-nil value for the seventh argument now means to ask the user for confirmation.

• The function buffer-size always reports on the current buffer.

• The function assq-delete-all has itself been deleted. So there!

• The keyword :set-after no longer does anything in defcustom.

• The variable small-temporary-file-directory has no special meaning. There's only one variable for specifying which directory to use for temporary files, temporary-file-directory, but not all Emacs features use it anyway. Some use the TMP environment variable, and some use the TMPDIR environment variable.

• If the second argument of save-some-buffers, pred, is not nil, then the precise value no longer matters. Any non-nil value means the same as t: offer to save each non-file buffer that has a non-nil value for buffer-offer-save.

• The variable inhibit-modification-hooks has no special meaning.

• The hook fontification-functions has been eliminated, but there are other hooks, such as window-scroll-functions, that you can use to do a similar job.

• The variable redisplay-dont-pause has no special meaning.

• The hook calendar-move-hook has been deleted.

• The function move-to-column treats any non-nil second argument just like t.