The row numbers in the tracking points are in absolute
numbers. However, when we walk the old grid, we do so starting in the
beginning of the scrollback history.
We must ensure the tracking points are sorted such that the *first*
one we see is the “oldest” one. I.e. the one furthest back in the
scrollback history.
Instead of iterating a linked list of tracking points, for *each and
every* cell in the old grid, use a sorted array.
This allows us to step through the array of tracking points as we walk
the old grid; each time we match a tracking point, we move to the next
one.
This means we only have to check a single tracking point for each cell.
Calling wcwidth() on every character in the entire scrollback history
is slow.
We already have the character width encoded in the grid; it’s in the
CELL_SPACERs following a multi-column character.
Thus, when we see a non-SPACER character, that isn’t in the last
column, peek the next character. If it’s a SPACER, get the current
characters width from it.
The only thing we need the width for, is to be able to print padding
SPACERS in the right margin, if the there isn’t enough space on the
current row for the current character.
Instead of using CELL_SPACER for *all* cells that previously used
CELL_MULT_COL_SPACER, include the remaining number of spacers
following, and including, itself. This is encoded by adding to the
CELL_SPACER value.
So, a double width character will now store the character itself in
the first cell (just like before), and CELL_SPACER+1 in the second
cell.
A three-cell character would store the character itself, then
CELL_SPACER+2, and finally CELL_SPACER+1.
In other words, the last spacer is always CELL_SPACER+1.
CELL_SPACER+0 is used when padding at the right margin. I.e. when
writing e.g. a double width character in the last column, we insert a
CELL_SPACER+0 pad character, and then write the double width character
in the first column on the next row.
Which means, when we match URI start and end points against the
current column index, we must *not* use ‘if...else if’, but two
‘if... if’.
Fixes an assertion when resizing a window with an URI range of just
one cell.
URI ranges are per row. Translate by detecting URI range start/end
coordinates, and opening and closing a corresponding URI range on the
new grid.
We need to take care when line-wrapping the new grid; here we need to
manually close the still-open URI ranges (on the new grid), and
re-opening them on the next row.
This patch adds an ‘extra’ member to the row struct. It is a pointer
to a struct containing extra data to be associated with this row.
Initially, this struct contains a list of URL ranges. These
define (OSC-8) URLs on this row.
The ‘extra’ data is allocated on-demand. I.e. the pointer is NULL by
default; it is *not* allocated by grid_row_alloc().
Alt screen applications normally reflow/readjust themselves on a
window resize.
When we do it too, the result is graphical glitches/flashes since our
re-flowed text is rendered in one frame, and the application re-flowed
text soon thereafter.
We can’t avoid rendering some kind of re-flowed frame, since we don’t
know when, or even if, the application will update itself. To avoid
glitches, we need to render, as closely as possible, what the
application itself will render shortly.
This is actually pretty simple; we just need to copy the visible
content over from the old grid to the new grid. We don’t bother with
text re-flow, but simply truncate long lines.
To simplify things, we simply cancel any active selection (since often
times, it will be corrupted anyway when the application redraws
itself).
Since we’re not reflowing text, there’s no need to translate e.g. the
cursor position - we just keep the current position (but bounded to
the new dimensions).
Fun thing: ‘less’ gets corrupted if we don’t leave the cursor at
the (new) bottom row. To handle this, we check if the cursor (before
resize) is at the bottom row, and if so, we move it to the new bottom
row.
Closes#221
Move sixel reflow from grid_reflow() to sixel_reflow(). This lets us
use internal sixel functions to update the sixels.
Note that grid_reflow() still needs to remap the sixelss coordinates.
Even though we translate the cursor position from the old grid
coordinates to the new, the cursor may _still_ end up outside the
visible area.
Make sure it doesn’t.
Ignore *old* cells containing spacers.
Pad new grid with spacers if a multi-column character doesn't fit at
the end of a line.
Insert spacers after a multi-column character.
Our sixel handling code requires sixels to *not* cross the scrollback
wrap around.
Until we've fixes the reflow code that split up such sixels (much like
we do when we generate a sixel), simply delete it.
Instead of storing combining data per cell, realize that most
combinations are re-occurring and that there's lots of available space
left in the unicode range, and store seen base+combining combinations
chains in a per-terminal array.
When we encounter a combining character, we first try to pre-compose,
like before. If that fails, we then search for the current
base+combining combo in the list of previously seen combinations. If
not found there either, we allocate a new combo and add it to the
list. Regardless, the result is an index into this array. We store
this index, offsetted by COMB_CHARS_LO=0x40000000ul in the cell.
When rendering, we need to check if the cell character is a plain
character, or if it's a composed character (identified by checking if
the cell character is >= COMB_CHARS_LO).
Then we render the grapheme pretty much like before.
We only used utf8proc to try to pre-compose a glyph from a base and
combining character.
We can do this ourselves by using a pre-compiled table of valid
pre-compositions. This table isn't _that_ big, and binary searching it
is fast.
That is, for a very small amount of code, and not too much extra RO
data, we can get rid of the utf8proc dependency.
