Before this patch, when the cell dimensions changed (i.e. when the
font size changes), sixel images were either removed (the new cell
dimensions are smaller than the old), or simply kept at their original
size (new cell dimensions are larger).
With this patch, sixels are instead resized. This means a
sixel *always* occupies the same number of rows and columns,
regardless of how much the font size is changed.
This is done by maintaining two sets of image data and pixman images,
as well as their dimensions. These two sets are the new ‘original’ and
‘scaled’ members of the sixel struct.
The "top-level" pixman image pointer, and the ‘width’ and ‘height’
members either point to the "original", or the "scaled" version.
They are invalidated as soon as the cell dimensions change. They, and
the ‘scaled’ image is updated on-demand (when we need to render a
sixel).
Note that the ‘scaled’ image is always NULL when the current cell
dimensions matches the ones used when emitting the sixel (to save
run-time memory).
Closes#1383
Images with an aspect ratio of 1:1 are by far the most common (though
not the default).
It makes a lot of sense, performance wise, to special case
them.
Specifically, the sixel_add() function benefits greatly from this, as
it is the inner most, most heavily executed function when parsing a
sixel image.
sixel_add_many() also benefits, since allows us to drop a
multiplication. Since sixel_add_many() always called first (no other
call sites call sixel_add() directly), this has a noticeable effect on
performance.
Another thing that helps (though not as much), and not specifically
with AR 1:1 images, is special casing DECGRI a bit.
Up until now, it simply updated the current sixel parameter value. The
problem is that the default parameter value is 0. But, a value of 0
should be treated as 1. By adding a special ‘repeat_count’ variable to
the sixel struct, we can initialize it to ‘1’ when we see DECGRI, and
then simply overwrite it as the parameter value gets updated. This
allows us to drop an if..else when emitting the sixel.
This way, the initial frame is more likely to get scaled correctly;
foot will guess the initial (integer) scale from the available
monitors, and use that. By using legacy scaling, we force the
compositor to down-scale the image to the correct scale factor.
If we use the new fraction scaling method with an integer scaling
factor, the initial frame gets rendered way too big.
We now default to scaling fonts using the scaling factor, not monitor
DPI.
The ‘auto’ value for dpi-aware has been removed.
Documentation (man pages and README) have been updated to reflect the
new default.
When the window’s preferred scaling factor is changed (through the
fractional-scaling protocol), update the terminal; resize font, resize
sub-surfaces etc.
Instead of passing a raw wl_surface pointer, pass a wayl_surface
pointer.
This is needed later, when using fractional scaling to scale the
surface (since then we need the surface’s viewport object).
And add a viewport object to accompany the surface (to be used when
scaling the surface).
Also rename the wl_surf_subsurf struct to wayl_sub_surface, and add a
wayl_surface object to it, rather than a plain wl_surface pointer (to
also get the viewport pointer).
* Bind the wp-viewporter and wp-fractional-scale-manager globals.
* Create a viewport and fractional-scale when instantiating a window.
* Add fractional-scale listener (that does nothing at the moment).
* Destroy everything on teardown.
When emitting a sixel, we need to:
a) scroll terminal content to ensure the new image fits
b) position the text cursor
Recent changes in the cursor positioning logic meant we reduced the
number of linefeeds, to ensure 1) sixels could be printed to the
bottom row without scrolling the terminal contents, and 2) the cursor
was positioned on the last sixel row.
Except, we’re not actually positioning the cursor on the last sixel
row. We’re positioning it on the text row that maps to the *upper*
pixel of the last sixel.
In most cases, this _is_ the last row of the sixel. But for certain
combinations of font and image sizes, it may be higher up.
This patch fixes a regression, where the terminal contents weren’t
scrolled up enough for certain images, causing a crash when trying to
dirty a not-yet scrolled in row.
The fix is this:
* Always scroll by the number of rows occupied by the image, minus
one. This ensures the image "fits".
* Adjust the cursor position, if necessary.
* Lazy initialize image height. This is necessary to prevent garbage
from being rendered for "empty" sixels.
* Fix plotting of non-1:1 pixels
* Fix calculation of height in resize(), for non-1:1 aspect ratios
