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E.9.2 Window Internals

The fields of a window (for a complete list, see the definition of struct window in window.h) include:

frame

The frame that this window is on, as a Lisp object.

mini

Non-zero if this window is a minibuffer window, a window showing the minibuffer or the echo area.

pseudo_window_p

Non-zero if this window is a pseudo window. A pseudo window is either a window used to display the menu bar or the tool bar (when Emacs uses toolkits that don’t display their own menu bar and tool bar) or the tab bar or a window showing a tooltip on a tooltip frame. Pseudo windows are in general not accessible from Lisp code.

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 the window’s parent in that tree, as a Lisp object. For the root window of the tree and a minibuffer window this is always nil.

Parent windows do not display buffers, and play little role in display except to shape their child windows. Emacs Lisp programs cannot directly manipulate parent windows; they operate on the windows at the leaves of the tree, which actually display buffers.

contents

For a leaf window and windows showing a tooltip, this is the buffer, as a Lisp object, that the window is displaying. For an internal (“parent") window, this is its first child window. For a pseudo window showing a menu or tool bar this is nil. It is also nil for a window that has been deleted.

next

prev

The next and previous sibling of this window as Lisp objects. next is nil if the window is the right-most or bottom-most in its group; prev is nil if it is the left-most or top-most in its group. Whether the sibling is left/right or up/down is determined by the horizontal field of the sibling’s parent: if it’s non-zero, the siblings are arranged horizontally.

As a special case, next of a frame’s root window points to the frame’s minibuffer window, provided this is not a minibuffer-only or minibuffer-less frame. On such frames prev of the minibuffer window points to that frame’s root window. In any other case, the root window’s next and the minibuffer window’s (if present) prev fields are nil.

left_col

The left-hand edge of the window, measured in columns, relative to the leftmost column (column 0) of the window’s native frame.

top_line

The top edge of the window, measured in lines, relative to the topmost line (line 0) of the window’s native frame.

pixel_left

pixel_top

The left-hand and top edges of this window, measured in pixels, relative to the top-left corner (0, 0) of the window’s native frame.

total_cols

total_lines

The total width and height of the window, measured in columns and lines respectively. The values include scroll bars and fringes, dividers and/or the separator line on the right of the window (if any).

pixel_width;

pixel_height;

The total width and height of the window measured in pixels.

start

A marker pointing to the position in the buffer that is the first character (in the logical order, see Bidirectional Display) 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.

old_pointm

The value of pointm at the last redisplay time.

force_start

If this flag is non-nil, it says that the window has been scrolled explicitly by the Lisp program, and the value of the window’s start was set for redisplay to honor. 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.

optional_new_start

This is similar to force_start, but the next redisplay will only obey it if point stays visible.

start_at_line_beg

Non-nil means current value of start was the beginning of a line when it was chosen.

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-zero value means the window’s buffer was modified when the window was last updated.

vertical_scroll_bar_type

horizontal_scroll_bar_type

The types of this window’s vertical and horizontal scroll bars.

scroll_bar_width

scroll_bar_height

The width of this window’s vertical scroll bar and the height of this window’s horizontal scroll bar, in pixels.

left_margin_cols

right_margin_cols

The widths of the left and right margins in this window. A value of zero means no margin.

left_fringe_width

right_fringe_width

The pixel widths of the left and right fringes in this window. A value of -1 means use the values of the frame.

fringes_outside_margins

A non-zero value means the fringes outside the display margins; othersize they are between the margin and the text.

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 non-zero.

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-zero value if window_end_pos and window_end_vpos are truly valid. This is zero if nontrivial redisplay is pre-empted, since in that case the display that window_end_pos was computed for did not get onto the screen.

cursor

A structure describing where the cursor is in this window.

last_cursor_vpos

The window-relative vertical position of the line showing the cursor as of the last redisplay that finished.

phys_cursor

A structure describing where the cursor of this window physically is.

phys_cursor_type

phys_cursor_height

phys_cursor_width

The type, height, and width of the 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 off. This is used for blinking the cursor.

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. When only the current line is hscrolled, this describes how much the current line is scrolled.

min_hscroll

Minimum value of hscroll, set by the user via set-window-hscroll (see Horizontal Scrolling). When only the current line is hscrolled, this describes the horizontal scrolling of lines other than the current one.

vscroll

Vertical scroll amount, in pixels. Normally, this is 0.

dedicated

Non-nil if this window is dedicated to its buffer.

combination_limit

This window’s combination limit, meaningful only for a parent window. If this is t, then it is not allowed to delete this window and recombine its child windows with other siblings of this window.

window_parameters

The alist of this window’s parameters.

display_table

The window’s display table, or nil if none is specified for it.

update_mode_line

Non-zero means this window’s mode line needs to be updated.

mode_line_height

header_line_height

The height in pixels of the mode line and the header line, or -1 if not known.

base_line_number

The line number of a certain position in the buffer, or zero. 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 zero meaning none is known. If it is -1, don’t display the line number as long as the window shows that buffer.

column_number_displayed

The column number currently displayed in this window’s mode line, or -1 if column numbers are not being displayed.

current_matrix

desired_matrix

Glyph matrices describing the current and desired display of this window.