Take ‘\E(#0’ for example - this is *not* the same as ‘\E(0’.
Up until now, foot has however treated them as the same escape,
because the handler for ‘\E(0’ didn’t verify there weren’t any _other_
private characters present.
Fix this by turning the ‘private’ array into a single 4-byte
integer. This allows us to match *all* privates with a single
comparison.
Private characters are added to the LSB first, and MSB last. This
means we can check for single privates in pretty much the same way as
before:
switch (term->vt.private) {
case ‘?’:
...
break;
}
Checking for two (or more) is much uglier, but foot only supports
a *single* escape with two privates, and no escapes with three or
more:
switch (term->vt.private) {
case 0x243f: /* ‘?$’ */
...
break;
}
The ‘clear’ action remains simple (and fast), with a single write
operation.
Collecting privates is potentially _slightly_ more complex than
before; we now need mask and compare, instead of simply comparing,
when checking how many privates we already have.
We _could_ add a counter, which would make collecting privates easier,
but this would add an additional write to the ‘clean’ action which is
really bad since it’s in the hot path.
This implements basic parsing of sixel data. Lots of limitations and
temporary solutions as this is still work-in-progress:
* Maximum image size hardcoded to 800x800
* No HLS color format support
* Image is always rendered at 0x0 in the terminal
Add data structure to term->vt. This structure tracks the free-form
data that is passed-through, and the handler to call at the end.
Intermediates and parameters are collected by the normal VT
parser. Then, when we enter the passthrough state, we call dcs_hook().
This function checks the intermediate(s) and parameters, and selects
the appropriate unhook handler (and optionally does some execution
already).
In passthrough mode, we simply append strings to an internal
buffer. This might have to be changed in the future, if we need to
support a DCS that needs to execute as we go.
In unhook (i.e. when the DCS is terminated), we execute the unhook
handler.
As a proof-of-concept, handlers for BSU/ESU (Begin/End Synchronized
Update) has been added (but are left unimplemented).
