Convert DesignNotes to Markdown to fix display in GitHub.

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Henry Qin 2019-03-18 11:42:18 -07:00
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= Design Notes =
# Design Notes
This file is meant to document design decisions and algorithms inside vimwiki
which are too large for code comments, and not necessarily interesting to
users. Please create a new section to document each behavior.
== Formatting tables ==
## Formatting tables
In vimwiki, formatting tables occurs dynamically, when navigating between cells
and adding new rows in a table in the Insert mode, or statically, when pressing
@ -14,16 +14,16 @@ leaving Insert mode, provided variable `g:vimwiki_table_auto_fmt` is set. In
this section, the original and the newer optimized algorithms of table
formatting will be described and compared.
=== The older table formatting algorithm and why this is not optimal ===
### The older table formatting algorithm and why this is not optimal
Let's consider a simple example. Open a new file, say _tmp.wiki_, and create a
new table with command `VimwikiTable`. This should create a blank table.
{{{
```
| | | | | |
|---|---|---|---|---|
| | | | | |
}}}
```
Let's put the cursor in the first header column of the table, enter the Insert
mode and type a name, say _Col1_. Then press _Tab_: the cursor will move to the
@ -31,11 +31,11 @@ second column of the header and the table will get aligned (in the context of
the table formatting story, words _aligned_ and _formatted_ are considered as
synonyms). Now the table looks as in the following snippet.
{{{
```
| Col1 | | | | |
|------|---|---|---|---|
| | | | | |
}}}
```
Then, when moving cursor to the first data row (i.e. to the third line of the
table below the separator line) and typing anything here and there while
@ -43,34 +43,34 @@ navigating using _Tab_ or _Enter_ (pressing this creates a new row below the
current row), the table shall keep formatting. Below is a result of such a
random edit.
{{{
```
| Col1 | | | | |
|------|-------|---|-------|----------|
| | Data1 | | Data2 | |
| | | | | New data |
}}}
```
The lowest row gets aligned when leaving the Insert mode. Let's copy _Data1_
(using `viwy` or another keystroke) and paste it (using `p`) in the second data
row of the first column. Now the table looks mis-aligned (as we did not enter
the Insert mode).
{{{
```
| Col1 | | | | |
|------|-------|---|-------|----------|
| | Data1 | | Data2 | |
| Data1 | | | | New data |
}}}
```
This is not a big problem though, because we can put the cursor at _any_ place
in the table and press `gqq`: the table will get aligned.
{{{
```
| Col1 | | | | |
|-------|-------|---|-------|----------|
| | Data1 | | Data2 | |
| Data1 | | | | New data |
}}}
```
Now let's make real problems! Move the cursor to the lowest row and copy it
with `yy`. Then 500-fold paste it with `500p`. Now the table very long. Move
@ -83,7 +83,7 @@ time _Tab_ or _Enter_ get pressed down, all rows in the table get visited to
calculate a new alignment. Moreover, by design it may happen even more than
once per one press!
{{{vim
```vim
function! s:kbd_create_new_row(cols, goto_first)
let cmd = "\<ESC>o".s:create_empty_row(a:cols)
let cmd .= "\<ESC>:call vimwiki#tbl#format(line('.'))\<CR>"
@ -98,7 +98,7 @@ function! s:kbd_create_new_row(cols, goto_first)
return cmd
endfunction
}}}
```
Function `s:kbd_create_new_row()` is called when _Tab_ or _Enter_ get pressed.
Formatting of the whole table happens in function `vimwiki#tbl#format()`. But
@ -107,25 +107,25 @@ variable `g:vimwiki_table_auto_fmt` is set. This means that formatting of the
whole table is called on all those multiple interleaves between the Insert and
the Normal mode in `s:kbd_create_new_row` (notice `\<ESC>`, `o`, etc.).
=== The newer table formating algorithm ===
### The newer table formating algorithm
The newer algorithm was introduced to struggle against performance issues when
formatting large tables.
Let's take the table from the previous example in an intermediate state.
{{{
```
| Col1 | | | | |
|------|-------|---|-------|----------|
| | Data1 | | Data2 | |
| Data1 | | | | New data |
}}}
```
Then move the cursor to the first data row, copy it with `yy`, go down to the
mis-aligned line, and press `5p`. Now we have a slightly bigger mis-aligned
table.
{{{
```
| Col1 | | | | |
|------|-------|---|-------|----------|
| | Data1 | | Data2 | |
@ -135,14 +135,14 @@ table.
| | Data1 | | Data2 | |
| | Data1 | | Data2 | |
| | Data1 | | Data2 | |
}}}
```
Go down to the lowest, the 7th, data row and press `gq1`. Nothing happened.
Let's go to the second or the third data row and press `gq1` once again. Now
the table gets aligned. Let's undo formatting with `u`, go to the fourth row,
and press `gq1`. Now the table should look like in the following snippet.
{{{
```
| Col1 | | | | |
|------|-------|---|-------|----------|
| | Data1 | | Data2 | |
@ -152,7 +152,7 @@ and press `gq1`. Now the table should look like in the following snippet.
| | Data1 | | Data2 | |
| | Data1 | | Data2 | |
| | Data1 | | Data2 | |
}}}
```
What a peculiar command! Does using it make any sense? Not much, honestly.
Except it shows how the newer optimized table formatting algorithm works in the
@ -184,4 +184,3 @@ viewport) until one of the being edited cells grows in length to a value big
enough to trigger the older algorithm and the whole table gets aligned. When
partial formatting is not desirable, the whole table can be formatted by
pressing `gqq` in the Normal mode.