ttx::terminal::ScrollBack Class Reference

Represents the terminal scroll back. More...

#include <ttx/terminal/scroll_back.h>

Public Member Functions
auto	absolute_row_start () const -> u64
auto	absolute_row_end () const -> u64
auto	total_rows () const -> usize
void	clear ()
	Clear the scroll back history.
void	add_rows (RowGroup &from, usize row_index, usize row_count)
	Add rows to the scroll back buffer.
void	take_rows (RowGroup &to, u32 desired_cols, usize row_index, usize row_count)
	Remove rows from the scroll back buffer.
auto	take_rows_for_reflow (RowGroup &to) -> u64
	Take rows so that to.reflow() will produce correct results.
auto	reflow_visual_rows (u64 absolute_row_start, usize row_count, u32 desired_cols) -> di::Optional< ReflowResult >
	Reflow scroll back for displaying a range of visual lines.
auto	find_row (u64 row) const -> di::Tuple< u32, RowGroup const & >

Detailed Description

Represents the terminal scroll back.

The scroll back is effectively immutable and optimized to minimize the memory needed per cell. Blank cells are not stored but still accessible when iterating over a row.

The scroll back is unaffected by resize operations (until rewrap is supported), so rows can be over or under sized depending on the actual screen size when the scroll back is being rendered.

For efficiency, the scroll back is divided into chunks which target a particular number of cells, and represent a collection of visual terminal lines. The memory limit for the scroll back buffer is specified by the total number of cells allowed, which is used to determine the number of chunks.

Member Function Documentation

absolute_row_end()

auto ttx::terminal::ScrollBack::absolute_row_end ( ) const -> u64

inline

absolute_row_start()

auto ttx::terminal::ScrollBack::absolute_row_start ( ) const -> u64

inline

add_rows()

void ttx::terminal::ScrollBack::add_rows	(	RowGroup &	from,
		usize	row_index,
		usize	row_count )

Add rows to the scroll back buffer.

Parameters

from	Row group to take from
row_index	Row index within the group to take from
row_count	Number of rows to take

The taken rows will be deleted after this call.

clear()

void ttx::terminal::ScrollBack::clear

(

)

Clear the scroll back history.

find_row()

auto ttx::terminal::ScrollBack::find_row

(

u64

row

)

const -> di::Tuple<u32, RowGroup const&>

reflow_visual_rows()

auto ttx::terminal::ScrollBack::reflow_visual_rows	(	u64	absolute_row_start,
		usize	row_count,
		u32	desired_cols ) -> di::Optional<ReflowResult>

Reflow scroll back for displaying a range of visual lines.

Parameters

absolute_row_start	The absolute for of the first visible row
row_count	The number of visible rows
desired_cols	The desired display width

Returns

The result of the reflow operation (nullopt if no reflow is needed)

Rather than reflow the entire scrollback all at once, reflowing happens lazily during render based on what part of the screen is visible. The scrollback remembers the last size each row group was reflowed to in order to avoid redundant computation. Depending the the absolute row start, it may be required to reflow more than 1 row group, in which case all reflow results are merged together.

take_rows()

void ttx::terminal::ScrollBack::take_rows	(	RowGroup &	to,
		u32	desired_cols,
		usize	row_index,
		usize	row_count )

Remove rows from the scroll back buffer.

Parameters

from	Row group to tranfer to
desired_cols	Number of columns to force in the output
row_index	Row index within the group to insert
row_count	Number of rows to take

This function requires: row_count >= total rows in scroll back.

The desired_cols value ensures that the inserted rows will have the correct number of cells per row. The row from scrollback will either be truncated or padded with empty cells to meet this constraint.

take_rows_for_reflow()

auto ttx::terminal::ScrollBack::take_rows_for_reflow

(

RowGroup &

to

)

-> u64

Take rows so that to.reflow() will produce correct results.

Parameters

to	Row group to transfer to

Returns

The number of rows transferred

This function takes as many rows as necessary from the scrollback so that the last row in the scrollback buffer wasn't overflowed. This means that calling reflow() on the resulting group produces the correct results. Note that because row group boundaries should already be segmented into such boundaries, this function is only best effort. In extreme cases where we have 10 of thousands of lines of next that have overflowed reflow() everything isn't computationally practical, so we impose a limit on how far back we go.

total_rows()

auto ttx::terminal::ScrollBack::total_rows ( ) const -> usize

inline

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The documentation for this class was generated from the following files:

• ttx/terminal/scroll_back.h
• lib/src/terminal/scroll_back.cpp