Vice's Vexing VKM Part 5: Breaking Down the Option Wall

#VICE’s Vexing VKM: Part 5

Breaking Down the Option Wall

When we left off, I had hit a wall.

Using the mac’s (left) option key to map to the Commodore 64’s C= key couldn’t work.

There are two reasons for this:

1. The option key generates a unique KEYCODE for each option-key combination, BUT not every key on the keyboard (not even every letter on the keyboard) has such a KEYCODE.
2. VICE has no way (that I was able to discover) of mapping these “missing” keycodes.

Here is what the option KEYCODEs are for the macbook keyboard’s letter keys:

• A - aring
• B - integral
• C - ccedilla
• D - partialderivative
• E - dead_acute
• F - function
• G - copyright
• H - abovedot
• I - dead _circumflex
• J - n/a
• K - n/a
• L - notsign
• M - mu
• N - dead_perispomeni
• O - ooblique
• P - Greek_pi
• Q - oe
• R - registered
• S - ssharp
• T - dagger
• U - dead_diaeresis
• V - radical
• W - n/a
• X - n/a
• Y - yen
• Z - Greek_OMEGA

A total of four keys don’t have a mapping, but that’s enough to make using the option key to act as the Commodore (C=) key impossible.

Swapping CTRL and C=

Since I am still determined not to use the tab key or a function key to map to the C= key, the best option I have is to swap the mappings of the control and option keys.

This makes the mapping of the CTRL-key combinations for colors and enabling/disabling the REVERSE mode easy enough, as we basically already did that for the “Commodore” colors before.

The only difference is that we need to use a different SHIFTFLAGS value:

# 0x1000 4096 key is combined with ctrl for this keysym/scancode

And we’ll need to add mappings for C= 9 and 0 (RVS ON and RVS OFF). That makes the mappings:

exclamdown      7 0 4096      # CTRL 1 (black) 
trademark       7 3 4096      # CTRL 2 (white) 
sterling        1 0 4096      # CTRL 3 (red) 
cent            1 3 4096      # CTRL 4 (cyan) 
infinity        2 0 4096      # CTRL 5 (purple) 
section         2 3 4096      # CTRL 6 (green) 
paragraph       3 0 4096      # CTRL 7 (blue) 
enfilledcircbullet 3 3 4096   # CTRL 8 (yellow) 
ordfeminine     4 0 4096      # CTRL 9 (reverse on) 
masculine       4 3 4096      # CTRL 0 (reverse off)

And we’ll need to map the option key to CTRL:

Alt_L           7 2 16384

Note that unlike the mapping of option to the C= key before, we can tell VICE that this key is the CTRL key using the SHIFTFLAGS value of 16384.

Making control act like C=

Mapping in the other direction is trickier. As we mentioned before, when using the mac’s control key, the KEYCODE for the key pressed along with control is the same as the “normal” KEYCODE for that key.

We’ve also established that due to some tricky mappings (that I have stubbornly refused to abandon), we can’t simply map the control key to the C64’s C= key, because in some cases it will create a C= SHIFT combination and toggle the character set between uppercase/graphics and lowercase/uppercase.

So that means the control key mapping needs to be:

Control_L       7 5 0

But how do we map the keys themselves?

Walking through the VICE documentation means:

• For each “normal” key we are going to have two definitions:
  • One for the unmodified key
  • One for the C= variant of the key (i.e. pressed along with the control key)
• For the C= variant:
  • The control key on the “host” (the macbook) will be depressed (0x0400 or 1024)
  • In most cases, the mapped (C64) key will need to be combined with the “cbm” (C=) key (0x0800 or 2048)
  • In some cases, the mapped (C64) key will need to be combined with the SHIFT key (0x0001 or 1)

This means that:

• If I am mapping a control-key combination on the mac to a C=-key combination on the C64, the SHIFTFLAGS value will be 1024 + 2048 = 3072.
• If I am mapping a control-key combination to a SHIFT-key combination on the C64, the SHIFTFLAGS value will be 1024 + 1 = 1025.

But I also must set the SHIFTFLAGS value for the unmodified key to 32 (0x0020), which means there are other definitions for this key to follow.

The first time I tried mapping the same key, I assumed it made the most sense to define the most restrictive mapping first and then the more general one. So I mapped the** **control-key combination first, adding 32 to the SHIFTFLAGS (so 3104 instead of 3072). This did not work. For whatever reason, VICE prefers the most general mapping to show up first in the vkm file.

So to map the Commodore color for the 1 key (orange), I need the following pair of lines:

1               7 0 32        # 1 
1               7 0 3072      # control 1 to C= 1 (orange)

This maps the unmodified 1 key to the C64 1 key, indicating another definition of this key will follow. That mapping indicates that it applies to when the control key is pressed along with the 1 key, and this will map to the 1 key combined with the C= key on the C64.

Remapping the Second Row

With this approach, the second row of keys will now map like:

grave           7 1 0      # ` = left arrow 
asciitilde      6 6 1      # ~ = pi 
1               7 0 32     # 1 
1               7 0 3072   # control 1 = c= 1 (orange) 
exclam          7 0 1      # ! 
exclamdown      7 0 4096   # option 1 = ctrl 1 (black) 
2               7 3 32     # 2 
2               7 3 3072   # control 2 = c= 2 (brown) 
at              5 6 16     # @ 
trademark       7 3 4096   # option 2 = ctrl 2 (white) 
3               1 0 32     # 3 
3               1 0 3072   # control 3 = c= 3 (light red) 
numbersign      1 0 1      # # 
sterling        1 0 4096   # option 3 = ctrl 3 (red) 
4               1 3 32     # 4 
4               1 3 3072   # control 4 = c= 4 (dark gray) 
dollar          1 3 1      # $ 
cent            1 3 4096   # option 4 = ctrl 4 (cyan) 
5               2 0 32     # 5 
5               2 0 3072   # control 5 = c= 5 (medium gray) 
percent         2 0 1      # % 
infinity        2 0 4096   # option 5 = ctrl 5 (purple) 
6               2 3 32     # 6 
6               2 3 3072   # control 6 = c= 6 (light green) 
asciicircum     6 6 16     # up arrow 
section         2 3 4096   # option 6 = ctrl 6 (green) 
7               3 0 32     # 7 
7               3 0 3072   # control 7 = c= 7 (light blue) 
ampersand       2 3 1      # & 
paragraph       3 0 4096   # option 7 = ctrl 7 (blue) 
8               3 3 32     # 8 
8               3 3 3072   # control 8 = c= 8 (light gray) 
asterisk        6 1 16     # * 
enfilledcircbullet 3 3 4096 # option 8 = ctrl 8 (yellow) 
9               4 0 0      # 9 
parenleft       3 3 1      # ( 
ordfeminine     4 0 4096   # option 9 = ctrl 9 (rvs on) 
0               4 3 0      # 0 
parenright      4 0 1      # ) 
masculine       4 3 4096   # option 0 = ctrl 0 (rvs off) 
minus           5 3 32     # - 
minus           6 1 1025   # control - = shift * 
underscore      5 6 2064   # option - = c= @ 
equal           6 5 32      # = 
equal           5 0 1025    # control = = shift + 
plus            5 0 16      # +  
BackSpace       0 0 8       # inst/del

The Third Row: Piece of Cake!

The third row on the macbook should be easy, peasy…now. A little shuffling of graphic characters on the last three keys, but we’ve figured out how to do that. And the rest is trivially straightforward mapping.

The mapping for the tab key doesn’t change:

Tab             7 4 0         # space 
ISO_Left_Tab    0 2 1         # shift CRSR LEFT/right

Mapping Letters

Mapping each letter means doing three things:

1. Mapping the “normal” letter (which is the lowercase letter KEYCODE).
2. Mapping the shifted letter (which is the uppercase letter KEYCODE).
3. Mapping the “commodore” (C=) graphic character, which is the option letter combination, which generates a unique KEYCODE.

Start with Q:

q               7 6 32        # Q 
q               7 6 3072      # control Q = c= Q 
Q               7 6 1         # shift Q`

And on through the rest of the letters:

w               1 1 32        # W 
w               1 1 3072      # control W = c= W 
W               1 1 1         # shift W 
e               1 6 32        # E 
e               1 6 3072      # control E = c= E 
E               1 6 1         # shift E 
r               2 1 32        # R 
r               2 1 3072      # control R = c= R 
R               2 1 1         # shift R 
t               2 6 32        # T 
t               2 6 3072      # control T = c= T 
T               2 6 1         # shift T 
y               3 1 32        # Y 
y               3 1 3072      # control Y = c= Y 
Y               3 1 1         # shift Y 
u               3 6 32        # U 
u               3 6 3072      # control U = c= U 
U               3 6 1         # shift U 
i               4 1 32        # I 
i               4 1 3072      # control I = c= I 
I               4 1 1         # shift I 
o               4 6 32        # O 
o               4 6 3072      # control O = c= O 
O               4 6 1         # shift O 
p               5 1 32        # P 
p               5 1 3072      # control P = c= P 
P               5 1 1         # shift P

The Symbol Keys

The last three keys in the third row of the mac are mostly places to put some extra graphic characters.

These all have some new SHIFTFLAGS values:

bracketleft     5 5 33     # [ = SHIFT : 
bracketleft     5 3 3072   # control [ = c= - 
braceleft       6 0 2064   # shift [ = c= pound 
bracketright    6 2 33     # ] = SHIFT ; 
bracketright    6 1 3072   # control ] = c= * 
braceright      6 0 1      # shift ] = shift pound 
backslash       4 4 33     # \ = shift M 
backslash       6 6 1025   # control \ = shift ^ 
bar             5 3 8      # shift \ = shift -` |

Let’s look at what each of these means:

• 33 - combining 1 (map to keysym with SHIFT) and 32 (another mapping available)
• 2064 - combining 2048 (map to keysym with C=) and 16 (de-shift this key)

The Fourth Row: Straightforward

The fourth row on the mac should map pretty much just like the third.

Mostly letters, with a few symbol keys, an action key, and one somewhat unique key…

How to Map Caps Lock

The obvious mapping for the macbook’s caps lock key is the Commodore 64’s SHIFT LOCK key. They do almost the same thing, except that SHIFT LOCK applies to every key on the keyboard, not just the letter keys. But close enough to map.

But what is the mapping? The keyboard debugger tells me the KEYCODE is Caps_Lock. But there is no SHIFT LOCK key mappable in the keyboard matrix.

Enter that block of definitions at the start of the file I ignored back in Part 2.

!CLEAR !LSHIFT 1 7 
!RSHIFT 6 4 
!VSHIFT RSHIFT 
!SHIFTL LSHIFT 
!LCBM 7 5 
!VCBM LCBM 
!LCTRL 7 2 
!VCTRL LCTRL

The !SHIFTL definition tells me that SHIFT LOCK is mapped to the same matrix location as the left SHIFT (LSHIFT) key (which we can see is ROW 1, COLUMN 7).

So we’ve got the KEYCODE, and the ROW and COLUMN. What about the SHIFTFLAGS value? This looks promising:

# 0x0040 64 key is shift-lock on emulated machine

All that put together makes for the following mapping:

Caps_Lock       1 7 64         # shift lock

The Letters

As with the third line, each letter gets three mappings: unmodified, control/C=, and shifted.

a               1 2 32      # A 
a               1 2 3072    # control A = c= A 
A               1 2 1       # shift A 
s               1 5 32      # S 
s               1 5 3072    # control S = c= S 
S               1 5 1       # shift S 
d               2 2 32      # D 
d               2 2 3072    # control D = c= D 
D               2 2 1       # shift D 
f               2 5 32      # F 
f               2 5 3072    # control F = c= F 
F               2 5 1       # shift F 
g               3 2 32      # G 
g               3 2 3072    # control G = c= G 
G               3 2 1       # shift G 
h               3 5 32      # H 
h               3 5 3072    # control H = c= H 
H               3 5 1       # shift H 
j               4 2 32      # J 
j               4 2 3072    # control J = c= J 
J               4 2 1       # shift J 
k               4 5 32      # K 
k               4 5 3072    # control K = c= K 
K               4 5 1       # shift K 
l               5 2 32      # L 
l               5 2 3072    # control L = c= L 
L               5 2 1       # shift L

The Symbols

There are two symbol keys, and only one of them (;) gets a graphic character mapping (to SHIFT @):

semicolon       6 2 32      # ; 
semicolon       5 6 1025    # control ; = shift @ 
colon           5 5 16      # : 
apostrophe      3 0 33      # ' = shift 7
apostrophe      5 0 3072    # control ' = c= + 
quotedbl        7 3 1       # “ = shift 2

The Action

The RETURN key on the Commodore 64 can work either unmodified, where it means “process this line” or SHIFTed where it simply does a carriage return (putting the cursor at the start of the next line). That means a SHIFTFLAGS value of 8 is appropriate.

Return          0 1 8       # Return

We’ll do the last two lines and finish up the mapping of the Commodore 64 in our next installment in this series.