This implements gamma-correct blending, which mainly affects font
rendering.
The implementation requires compile-time availability of the new
color-management protocol (available in wayland-protocols >= 1.41),
and run-time support for the same in the compositor (specifically, the
EXT_LINEAR TF function and sRGB primaries).
How it works: all colors are decoded from sRGB to linear (using a
lookup table, generated in the exact same way pixman generates it's
internal conversion tables) before being used by pixman. The resulting
image buffer is thus in decoded/linear format. We use the
color-management protocol to inform the compositor of this, by tagging
the wayland surfaces with the 'ext_linear' image attribute.
Sixes: all colors are sRGB internally, and decoded to linear before
being used in any sixels. Thus, the image buffers will contain linear
colors. This is important, since otherwise there would be a
decode/encode penalty every time a sixel is blended to the grid.
Emojis: we require fcft >= 3.2, which adds support for sRGB decoding
color glyphs. Meaning, the emoji pixman surfaces can be blended
directly to the grid, just like sixels.
Gamma-correct blending is enabled by default *when the compositor
supports it*. There's a new option to explicitly enable/disable it:
gamma-correct-blending=no|yes. If set to 'yes', and the compositor
does not implement the required color-management features, warning
logs are emitted.
There's a loss of precision when storing linear pixels in 8-bit
channels. For this reason, this patch also adds supports for 10-bit
surfaces. For now, this is disabled by default since such surfaces
only have 2 bits for alpha. It can be enabled with
tweak.surface-bit-depth=10-bit.
Perhaps, in the future, we can enable it by default if:
* gamma-correct blending is enabled
* the user has not enabled a transparent background
* The toplevel icon is now set to the app-id, unless "overridden" by
OSC-1 or OSC-0.
* Implemented OSC-1
* OSC-0 extended to also set the icon
* Implemented CSI 20 t - report window icon
* Implemented CSI 21 t - report window title
* Implemented CSI 22 ; 1 t - push window icon
* Implemented CS 23 ; 1 t - pop window icon
* Extended CSI 22/23 ; 0 t to also push/pop the icon
* Verify app-id set by OSC-176 is valid UTF-8
* Verify icon set by OSC-0/1 is valid UTF-8
This adds support for a new OSC escape sequence: OSC 176, that lets
terminal programs tell the terminal the name of the app that is
running. foot then sets the app ID of the toplevel to that ID,
which lets the compositor know which app is running, and typically
sets the appropriate icon, window grouping, ...
See: https://gist.github.com/delthas/d451e2cc1573bb2364839849c7117239
POSIX.1-2008 has marked gettimeofday(2) as obsolete, recommending the
use of clock_gettime(2) instead.
CLOCK_MONOTONIC has been used instead of CLOCK_REALTIME because it is
unaffected by manual changes in the system clock. This makes it better
for our purposes, namely, measuring the difference between two points in
time.
tv_sec has been casted to long in most places since POSIX does not
define the actual type of time_t.
* xcursor always set for all pointers
* xcursor sometimes not updated when it should be
* mouse grabbed state wasn't per seat, but global (i.e. "does at least
one seat enable mouse grabbing")
* selection enabled state wasn't per seat
Handle the CSDs and the search box the same way we handle the main
grid; when we need to redraw them, call
render_refresh_{csd,search}(). This sets a flag that is checked after
each FDM iteration. All actual rendering is done here.
This also ties the commits of the Wayland sub-surfaces to the commit
of the main surface.
With a bad behaving client (e.g. 'less' with mouse support enabled),
we can end up with a *lot* of xcursor updates (so much, that we
flooded the wayland socket before we implemented a blocking
wayl_flush()).
Since there's little point in updating the cursor more than once per
frame interval, use frame callbacks to throttle the updates.
This works more or lesslike normal terminal refreshes:
render_xcursor_set() stores the last terminal (window) that had (and
updated) the cursor.
The renderer's FDM hook checks if we have such a pending terminal set,
and if so, tries to refresh the cursor.
This is done by first checking if we're already waiting for a callback
from a previous cursor update, and if so we do nothing; the callback
will update the cursor for the next frame. If we're *not* already
waiting for a callback, we update the cursor immediately.
In some cases, we end up calling render_refresh() multiple times in
the same FDM iteration. This means will render the first update
immediately, and then set the 'pending' flag, causing the updated
content to be rendered in the next frame.
This can cause flicker, or flashes, since we're presenting one or more
intermediate frames until the final content is shown.
Not to mention that it is inefficient to render multiple frames like
this.
Fix by:
* render_refresh() only sets a flag in the terminal
* install an FDM hook; this hook loops all terminals and executes what
render_refresh() _used_ to do (that is, render immediately if we're
not waiting for a frame callback, otherwise set 'pending' flag). for
all terminals that have the 'refresh_needed' flag set.
Our surface may be on multiple outputs at the same time. In this case,
we use the largest scale factor, and let the compositor down scale on
the "other" output(s).
To avoid having to re-generate glyphs, cache the glyphs.
For now, we only cache ASCII characters, as this allows us to lookup
the cache by simply indexing with the character (into a 256-entry
array).
