This is a theorical feature listed in http://st.suckless.org/goals. All the
input/output of the terminal will be written to a file, which can be very
useful for debugging, and also allow interconnect st to other process
through named pipes.
---
 st.1 |    6 ++++++
 st.c |   14 +++++++++++++-
 2 files changed, 19 insertions(+), 1 deletion(-)

Taken from the description:

When tput init is executed the list of task performed are (taken from
terminfo(5)):

              run the program
                     iprog

              output is1 is2

              set the margins using
                     mgc, smgl and smgr

              set tabs using
                     tbc and hts

              print the file
                     if

              and finally
                     output is3.

When reset is executed, a more stronger initialization process is performed,
so the terminal can return from an unknown state. rs1, rs2 and rs3 are used
in this case instead of
using is1, is2 and is3.

This patch makes is2 = rs2, resets insert mode and set normal keypad
mode. For rs1 it performs a full initilization using ^[c.

SM and RM can receive multiple parameters, but the code only was accepting
only one. This patch join the code of set and reset modes (SM and RM) in a
common function and uses a loop which deals with all the arguments of the
sequence. This patch improves xterm and vt100 compability.
---
 st.c |  180 ++++++++++++++++++++++++++++--------------------------------------
 1 file changed, 76 insertions(+), 104 deletions(-)

---
 st.info |    2 ++
 1 file changed, 2 insertions(+)

This will really be needed when there is a full 256 color support.

This sequence performs "Cursor Forward Tabulation <n> tab stops", which
although is not present in vt100 or vt102, xterm accepts it.
---
 st.c |    5 +++++
 1 file changed, 5 insertions(+)

way.

This sequence clears tab stops in the terminal. If the argument is not present
or is zero, then removes the tab stop of the current horizontal position. If
the argument is 3 then removes all the tab stops of the terminal. It was
necessary modify the terminfo entry tbc, because it has \E[2g instead of the
correct \E[3g.

Signed-off-by: Roberto E. Vargas Caballero <k0ga@shike2.com>
---
 st.c    |   12 ++++++++++++
 st.info |    2 +-
 2 files changed, 13 insertions(+), 1 deletion(-)

This sequence adds a new tab stop in the current horizontal position. This
means that tputtab must be look for the next tab stop in the tabs array
instead of using a hard coded value offset. Also, CHT sequence XXX message
is removed because it is not a vt10x sequence (as far as I know it is a
vt50x sequence), and it is not implemented by linux virtual terminal neither
by xterm.

Signed-off-by: Roberto E. Vargas Caballero <k0ga@shike2.com>
---
 st.c |   12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

Tabs stop are simulated in st using a fixed size of 8, always, without be
worried about sequences changing the tab stops. A user can put a tab stop in
each horizontal position of the screen, so we need at least one flag for
each column of the screen. In the same way as dirty flags is used for the
rows, it is used a bool dinamic array.

Signed-off-by: Roberto E. Vargas Caballero <k0ga@shike2.com>
---
 st.c |   22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

* add a timeout value (SELECT_TIMEOUT) of 20ms in the select() call
* wait at least 20ms (DRAW_TIMEOUT) between draw() calls
* only copy dirty lines from the buffer to the screen

what draw() does:
* clears dirty lines in the buffer
* draws the longest same-attributes string of each
  dirty line to the buffer with multiple xdraws() call
* copies the current dirty line from buffer to the screen with a single
  xcopy() call

this changeset makes st run ~10x faster.