This reduces the burden on sixel_split_by_rectangle(), which would
otherwise consider the newly added/splitted sixels. Since we already
know they aren't covered by the specified rectangle, we can skip that.
This function splits a sixel image into up to four pieces. The four
pieces correspond to the relative complement (set difference) of the
sixel image and the specified rectangle.
Use this function when (possibly) overwriting existing sixel images
when generating a new one, i.e. in sixel_unhook().
Instead of completely erasing a sixel image when it is being
"overwritten" (text is printed somewhere within the image, or another
sixel image is emitted within the first image), split it up into up to
four pieces: 'above', 'below', 'to-the-left' and 'to-the-right'.
This is currently very un-optimized, but seems to produce correct
results.
We used to auto-resize images to always be a multiple of 6.
This is incorrect. The client may, for example, have specified a size
to align the image to a cell boundary, which may not be a multiple of
6.
Furthermore, in e.g. Jexer, which splits up an image into stripes,
that the next image would "overwrite" the previous one. Since the next
image was started on a cell row that the previous image had overflowed
into.
A client can re-use the palette between images. Resetting the palette
breaks this.
Now we initialize the palette on demand, and resets it when the
palette size is changed (by the client).
Update the sixels' 'row' attribute when re-flowing a grid, to ensure
it is rendered at the correct place.
This should work in most cases, but will break when the cell size has
changed (e.g. font size increase/decrease, or a DPI change).
This patch also moves the sixel image list from the terminal struct
into the grid struct. The sixels are per-grid after all.
In unhook, add the generated image to a list of finished sixel images,
along with positioning and size information.
When rendering, loop this list of images, and render the images (or
parts of) that are visible.
When scrolling, check if any part of the images cover the re-cycled
lines, and if so, remove the *entire* image from the list.
This means we have the following limitations:
* The renderer always renders the whole (visible area of) the
image(s). There are times when this isn't necessary - for example,
when the image is scrolled inside the visible area.
* It would be nice if we could crop the image when parts of it is
scrolled out.
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
