[TOC]

# (Not used) Approach 1: Adaption from TanChord 41 Bopomofo

Master Forge (M4G), the successor of CC1, will not have the thumb3 switches, so it's impossible to directly use TanChord 41 Bopomofo on M4G. And to have all the Bopomofo symbols placed on the home row of M4G, some more non-character keys on the home row have to be sacrificed, or we need to use a whole layer (such as the functional layer) for Bopomofo input.

Adapted from the [TC41.V5](/@andy23512/HJRUbUH4n#V5-Latest), here is a possible Bopomofo layout design on M4G.


But as you see, some keys on pinky switches would be occupied by the Bopomofo symbols. It means that num-shift, shift, and mirror keys would lose their original position. It makes this layout difficult to coexist with the English layout.

Moreover, on TC41.V5, I can access all the rhyme keys (except ㄦ) with my right thumb only. But on M4G, I will need an additional finger for them.

Due to the mentioned drawbacks, I think that CC1 is much better for my usage (English + Chinese Bopomofo), so I am not going to switch to M4G for now unless I find a better solution for this.

# (Used) Approach 2: Multiple Symbols per Key

Another possible way is to map multiple Bopomofo symbols on some keys. Some existing Bopomofo IMEs or layouts, like Hsu Bopomofo layout ([許氏鍵盤](https://zh.m.wikipedia.org/wiki/%E8%87%AA%E7%84%B6%E8%BC%B8%E5%85%A5%E6%B3%95#%E8%A8%B1%E6%B0%8F%E9%8D%B5%E7%9B%A4)) and Sound Chaser input method ([追音輸入法](https://www.text.tw/chasew)), also have this kind of design to reduce the amount of required keys, and users would have shorter and less hand movements when using them.

But a possible drawback is that the number of possible Chinese words of a set of keystrokes might increase. In other word, we would get more possible to do word selection.

## Analysis for Bopomofo combinations

To decide which Bopomofo symbols to put together in a key, I used a list of all Bopomofo combinations from [this Chinese dictionary](https://www.zdic.net/zd/zy/), and calculated the overlap counts in every two consonants and every two rhymes, respectively. For example, both `ㄅ` and `ㄐ` have combinations with `ㄧ`, `ㄧㄝ`, `ㄧㄠ`, `ㄧㄢ`, `ㄧㄣ` and `ㄧㄥ`, so their overlap count is 6. Then I plotted the counts on contingency tables as below.



## Progress of designing layout

### 1st iteration

Then I could choose groups with smaller overlap count and put them on the same key respectively.

I chose:
1. `ㄍ-ㄐ`, `ㄎ-ㄑ`, `ㄏ-ㄒ` and `ㄥ-ㄦ`, since they don't have any overlap.
2. `ㄛ-ㄜ-ㄝ`, since they have little overlaps with each other (3,0,1).

and I modified the layout as the image below.


I tried to implement this at my fork of McBopomofo IME, and would reconsider about ordering M4G if this works well finally.

### 2nd iteration - TanChord 36 Bopomofo (TC36) V1

After I implemented it, I found that McBopomofo seemed to have problems with `ㄛ-ㄜ-ㄝ` group since they have some overlaps between them, so I changed the layout as below.


The right mirror key was replaced with `/` key.


After some more tests on this, it seems that this layout and McBopomofo don't work well together for Bopomofo chords, since McBopomofo expects the symbols to be input with correct order to correctly choose which symbol to use for a keystroke. So I modify the logic to make it works. I name this layout as TanChord 36 Bopomofo to distinguish with the TanChord 41 Bopomofo layout.

([See Appendix A for the details about the logic for choosing symbols](#A-TanChord-36-symbol-choosing-rules).)

## Drawbacks

### Hard to type Bopomofo password

For TanChord 41 layout, I could make an additional OS layout for the Bopomofo password, because a key is only mapping to a symbol and it's easy to make a layout to map between CC1's output and Bopomofo password of a symbol.

But for TanChord 36 layout, since there's multiple symbols on a keys, it's far more complex to deal with it. So I may just type it on QWERTY keyboard, or use a password manager for it.

### Might be confusing at first

This layout has multiple symbols on a key, and the final symbol of a keystroke is decided by some rules accroding to all the possible combinations of Bopomofo symbols ([details in appendix A](#A-TanChord-36-symbol-choosing-rules)), so the displayed symbols in buffer may be changed during typing.
For example, when I want to type `ㄐㄧ`, I may first hit the `ㄍ/ㄐ` key and then the `ㄧ` key. Because of the rule, first symbol in the buffer would be changed from `ㄍ` to `ㄐ` after hitting the `ㄧ` key.

|Keystroke|Symbol in buffer|
|-|-|
|`ㄍ/ㄐ`|ㄍ|
|`ㄧ`|ㄐㄧ|

That's why it is confusing first, but it can be gotten used to with practice.

## Updates

### V2

After some tests, I found that words with `ㄩㄝ` are hard to type under the V1 layout, so I adjusted the layout like this.


The `ㄩ` and `ㄝ` are at the same direction so it's easier to type `ㄩㄝ`. I seldom use `ㄧㄛ` words so it's okay to let `ㄧ` and `ㄛ` at opposite directions.

#### V2.1

I may have to use a notebook from my company to work in the future, but my McBopomofo can't be installed on it due to the information security policy of my company. To type Chinese with the built-in standard Bopomofo IME with CC1 or M4G, I remapped the A3 layer according to the layout shown in [Approach 1](#Approach-1-Adaption-from-TanChord-41-Bopomofo) and the mapping of [Standard Bopomofo layout](https://zh.wikipedia.org/zh-tw/%E6%B3%A8%E9%9F%B3%E8%BC%B8%E5%85%A5%E6%B3%95#/media/File:Keyboard_layout_Zhuyin.svg). Although I have to use two keystrokes to switch between Chinese and English, (one for switching the layer of device between A3 and A1, another for switching the input source on the OS.) this is the only way I can think of under this condition.

The following is that Bopomofo layout and the corresponding A3 layer.


#### V2.2

To balance the workload of both hands when do mouse click on CC1, I decided to remap all the mouse click actions (left click, middle click, and right click) on both thumb 2 switches of numeric layer.

The following is the numeric layer after changes.


- ②: numeric layer key
- M(arrow): mouse move
- S(arrow): mouse scroll
- LC, MC, RC: mouse left, middle, right click

#### V2.3

1. I add back the missing F11 and F12 keys.
2. I find that I can use the original num-shift key to unlock numeric layer so I drop the numeric layer key on the left thumb middle switch.

(Numeric layer)

# (Not used) Approach 3: Try the 3D presses on M4G

I can't use 3D presses on CC1 because they require much force to use and my weak fingers can't deal with it. But if the 3D presses on M4G don't require that much force, I could move some keys like tones to the 3D presses and leave more spaces to other Bopomofo symbols. But I need to wait until I try the 3D presses directly on M4G to ensure if this is a possible approach for me.

# Appendix

## A. TanChord 36 symbol choosing rules

The five pairs of Bopomofo symbols which are at the same keys on TanChord 36 layout are:

`ㄍ-ㄐ`, `ㄎ-ㄑ`, `ㄏ-Ｔ`, `ㄜ-ㄝ`, `ㄥ-ㄦ`

IME needs to have a rule to decide which symbol to use in these pairs.

### Rule for `ㄍ-ㄐ`, `ㄎ-ㄑ`, `ㄏ-Ｔ`, `ㄜ-ㄝ`

If we look into the combination of the first four pairs, we would discover that:

1. For `ㄐ`, `ㄑ`, `ㄒ` and `ㄝ`, the medial of all combinations of each of them only can be `ㄧ` or `ㄩ`.
2. For `ㄍ`, `ㄎ`, `ㄏ` and `ㄜ`, the medial of all combinations of each of them only can be `ㄨ` or `(no medial)`.

So the IME can be choosed the symbols in these pairs by the rule: When `ㄧ` or `ㄩ` is in buffer, choose `ㄐ`, `ㄑ`, `ㄒ` or `ㄝ`. Otherwise, choose `ㄍ`, `ㄎ`, `ㄏ` or `ㄜ`.

### Rule for `ㄥ-ㄦ`

`ㄥ-ㄦ` pair is relatively simple. Since `ㄦ` doesn't have any combinations with any medial and consonant, the rule of IME is: When any medial or consonant exists in buffer, choose `ㄥ`. Otherwise, choose `ㄦ`.