GNU Info
(elisp)Window Internals
Window Internals
----------------
Windows have the following accessible fields:
`frame'
The frame that this window is on.
`mini_p'
Non-`nil' if this window is a minibuffer window.
`parent'
Internally, Emacs arranges windows in a tree; each group of
siblings has a parent window whose area includes all the siblings.
This field points to a window's parent.
Parent windows do not display buffers, and play little role in
display except to shape their child windows. Emacs Lisp programs
usually have no access to the parent windows; they operate on the
windows at the leaves of the tree, which actually display buffers.
The following four fields also describe the window tree structure.
`hchild'
In a window subdivided horizontally by child windows, the leftmost
child. Otherwise, `nil'.
`vchild'
In a window subdivided vertically by child windows, the topmost
child. Otherwise, `nil'.
`next'
The next sibling of this window. It is `nil' in a window that is
the rightmost or bottommost of a group of siblings.
`prev'
The previous sibling of this window. It is `nil' in a window that
is the leftmost or topmost of a group of siblings.
`left'
This is the left-hand edge of the window, measured in columns.
(The leftmost column on the screen is column 0.)
`top'
This is the top edge of the window, measured in lines. (The top
line on the screen is line 0.)
`height'
The height of the window, measured in lines.
`width'
The width of the window, measured in columns. This width includes
the scroll bar and fringes, and/or the separator line on the right
of the window (if any).
`buffer'
The buffer that the window is displaying. This may change often
during the life of the window.
`start'
The position in the buffer that is the first character to be
displayed in the window.
`pointm'
This is the value of point in the current buffer when this window
is selected; when it is not selected, it retains its previous
value.
`force_start'
If this flag is non-`nil', it says that the window has been
scrolled explicitly by the Lisp program. This affects what the
next redisplay does if point is off the screen: instead of
scrolling the window to show the text around point, it moves point
to a location that is on the screen.
`frozen_window_start_p'
This field is set temporarily to 1 to indicate to redisplay that
`start' of this window should not be changed, even if point gets
invisible.
`start_at_line_beg'
Non-`nil' means current value of `start' was the beginning of a
line when it was chosen.
`too_small_ok'
Non-`nil' means don't delete this window for becoming "too small".
`height_fixed_p'
This field is temporarily set to 1 to fix the height of the
selected window when the echo area is resized.
`use_time'
This is the last time that the window was selected. The function
`get-lru-window' uses this field.
`sequence_number'
A unique number assigned to this window when it was created.
`last_modified'
The `modiff' field of the window's buffer, as of the last time a
redisplay completed in this window.
`last_overlay_modified'
The `overlay_modiff' field of the window's buffer, as of the last
time a redisplay completed in this window.
`last_point'
The buffer's value of point, as of the last time a redisplay
completed in this window.
`last_had_star'
A non-`nil' value means the window's buffer was "modified" when the
window was last updated.
`vertical_scroll_bar'
This window's vertical scroll bar.
`left_margin_width'
The width of the left margin in this window, or `nil' not to
specify it (in which case the buffer's value of `left-margin-width'
is used.
`right_margin_width'
Likewise for the right margin.
`window_end_pos'
This is computed as `z' minus the buffer position of the last glyph
in the current matrix of the window. The value is only valid if
`window_end_valid' is not `nil'.
`window_end_bytepos'
The byte position corresponding to `window_end_pos'.
`window_end_vpos'
The window-relative vertical position of the line containing
`window_end_pos'.
`window_end_valid'
This field is set to a non-`nil' value if `window_end_pos' is truly
valid. This is `nil' if nontrivial redisplay is preempted since
in that case the display that `window_end_pos' was computed for
did not get onto the screen.
`redisplay_end_trigger'
If redisplay in this window goes beyond this buffer position, it
runs run the `redisplay-end-trigger-hook'.
`cursor'
A structure describing where the cursor is in this window.
`last_cursor'
The value of `cursor' as of the last redisplay that finished.
`phys_cursor'
A structure describing where the cursor of this window physically
is.
`phys_cursor_type'
The type of cursor that was last displayed on this window.
`phys_cursor_on_p'
This field is non-zero if the cursor is physically on.
`cursor_off_p'
Non-zero means the cursor in this window is logically on.
`last_cursor_off_p'
This field contains the value of `cursor_off_p' as of the time of
the last redisplay.
`must_be_updated_p'
This is set to 1 during redisplay when this window must be updated.
`hscroll'
This is the number of columns that the display in the window is
scrolled horizontally to the left. Normally, this is 0.
`vscroll'
Vertical scroll amount, in pixels. Normally, this is 0.
`dedicated'
Non-`nil' if this window is dedicated to its buffer.
`display_table'
The window's display table, or `nil' if none is specified for it.
`update_mode_line'
Non-`nil' means this window's mode line needs to be updated.
`base_line_number'
The line number of a certain position in the buffer, or `nil'.
This is used for displaying the line number of point in the mode
line.
`base_line_pos'
The position in the buffer for which the line number is known, or
`nil' meaning none is known.
`region_showing'
If the region (or part of it) is highlighted in this window, this
field holds the mark position that made one end of that region.
Otherwise, this field is `nil'.
`column_number_displayed'
The column number currently displayed in this window's mode line,
or `nil' if column numbers are not being displayed.
`current_matrix'
A glyph matrix describing the current display of this window.
`desired_matrix'
A glyph matrix describing the desired display of this window.
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