feat: Smooth cursor blink animation option

[agraven]

Add a new g:neovide_cursor_smooth_blink setting which will make the cursor smoothly transition between its on and off state when enabled.

Screencast.from.2024-03-16.16-33-33.webm

What kind of change does this PR introduce?

• Feature

Did this PR introduce a breaking change?

• No

[MultisampledNight]

Thank you!!

[MultisampledNight]

When testing, I've found that the new option causes the cursor to disappear when configured to be non-blinking/static. Minimal repro is

1. Launch neovide -- --clean
2. :let neovide_cursor_smooth_blink=v:true

Causing the cursor to disappear.

This is an issue, since in some configurations, it might be desirable to have the cursor static in one mode but not in another.

self.get_delay() in src/renderer/cursor_renderer/blink.rs:93 seems to return 0 in that case, causing remaining / total to be actually 0 / 0 ⇒ NaN. I'd guess it might make sense to add a guard condition for is_static in fn opacity?

[agraven]

The change

@@ -63,7 +63,7 @@ impl BlinkStatus {
         let current_cursor = self.current_cursor.as_ref().unwrap();
 
         if is_static(current_cursor) {
-            self.state = BlinkState::On;
+            self.state = BlinkState::Waiting;
             ShouldRender::Wait
         } else {
             if self.transition_time <= now {

i.e. setting the BlinkState for when blinking is disabled to BlinkState::Waiting. This doesn't seem to cause any issue after some quick testing, and it would integrate better with the changes to the update loop, on top of feeling more semantically correct to me in general, since BlinkState::On implies there is an ongoing blinking process, while BlinkState::Waiting more accurately represents that blinking is inactive, just indefinitely instead of for blinkwait milliseconds

[MultisampledNight]

Looks good to me, thank you again!! Merging...

[hudgins]

I love this, but I've noticed it causes Neovide to report 15% CPU usage, where it is normally at about 1%.

[agraven]

@hudgins That does seem like a bit much. Could you check if you get the same CPU usage when running neovide with --no-idle and smooth blink disabled?