config: Introduce "blink-interval" config

The interval at which text and cursor blink can now be configured by
setting "blink-interval" to an arbitrary time.

Code originally written by @pluiedev and adapted for this patch.

Signed-off-by: Charlie Jenkins <thecharlesjenkins@gmail.com>

src/config/Config.zig

@@ -478,6 +478,41 @@ foreground: Color = .{ .r = 0xFF, .g = 0xFF, .b = 0xFF },
 /// This value does not apply to Emoji or images.
 @"minimum-contrast": f64 = 1,
 
+/// The amount of time it takes for blinking text and cursors to toggle between
+/// being invisible and visible.
+/// Any cell on the screen could be set to blink by setting SGR attribute 5,
+/// while cursor blinking is controlled by the `cursor-style-blink` setting.
+///
+/// The interval is specified as a series of numbers followed by time units.
+/// Whitespace is allowed between numbers and units. Each number and unit will
+/// be added together to form the total interval.
+///
+/// Blinking is disabled when the interval is set to zero.
+///
+/// The allowed time units are as follows:
+///
+///   * `y` - 365 SI days, or 8760 hours, or 31536000 seconds. No adjustments
+///     are made for leap years or leap seconds.
+///   * `d` - one SI day, or 86400 seconds.
+///   * `h` - one hour, or 3600 seconds.
+///   * `m` - one minute, or 60 seconds.
+///   * `s` - one second.
+///   * `ms` - one millisecond, or 0.001 second.
+///   * `us` or `µs` - one microsecond, or 0.000001 second.
+///   * `ns` - one nanosecond, or 0.000000001 second.
+///
+/// Examples:
+///   * `1h30m`
+///   * `45s`
+///
+/// Units can be repeated and will be added together. This means that
+/// `1h1h` is equivalent to `2h`. This is confusing and should be avoided.
+/// A future update may disallow this.
+///
+/// The maximum value is `584y 49w 23h 34m 33s 709ms 551µs 615ns`. Any
+/// value larger than this will be clamped to the maximum value.
+@"blink-interval": Duration = .{ .duration = 600 * std.time.ns_per_ms },
+
 /// Color palette for the 256 color form that many terminal applications use.
 /// The syntax of this configuration is `N=COLOR` where `N` is 0 to 255 (for
 /// the 256 colors in the terminal color table) and `COLOR` is a typical RGB

src/renderer/Thread.zig

@@ -18,7 +18,6 @@ const Allocator = std.mem.Allocator;
 const log = std.log.scoped(.renderer_thread);
 
 const DRAW_INTERVAL = 8; // 120 FPS
-const BLINK_INTERVAL = 600;
 
 /// The type used for sending messages to the IO thread. For now this is
 /// hardcoded with a capacity. We can make this a comptime parameter in
@@ -112,10 +111,18 @@ flags: packed struct {
 
 pub const DerivedConfig = struct {
     custom_shader_animation: configpkg.CustomShaderAnimation,
+    blink_interval: u64,
 
     pub fn init(config: *const configpkg.Config) DerivedConfig {
+        const blink_interval = std.math.divTrunc(
+            u64,
+            config.@"blink-interval".duration,
+            std.time.ns_per_ms,
+        ) catch std.math.maxInt(u64);
+
         return .{
             .custom_shader_animation = config.@"custom-shader-animation",
+            .blink_interval = blink_interval,
         };
     }
 };
@@ -238,14 +245,16 @@ fn threadMain_(self: *Thread) !void {
     try self.wakeup.notify();
 
     // Start the blinking timer.
-    self.blink_h.run(
-        &self.loop,
-        &self.blink_c,
-        BLINK_INTERVAL,
-        Thread,
-        self,
-        blinkTimerCallback,
-    );
+    if (self.config.blink_interval > 0) {
+        self.blink_h.run(
+            &self.loop,
+            &self.blink_c,
+            self.config.blink_interval,
+            Thread,
+            self,
+            blinkTimerCallback,
+        );
+    }
 
     // Start the draw timer
     self.startDrawTimer();
@@ -385,14 +394,16 @@ fn drainMailbox(self: *Thread) !void {
                     self.startDrawTimer();
 
                     // If we're focused, we immediately start blinking again
-                    self.blink_h.run(
-                        &self.loop,
-                        &self.blink_c,
-                        BLINK_INTERVAL,
-                        Thread,
-                        self,
-                        blinkTimerCallback,
-                    );
+                    if (self.blink_c.state() != .active and self.config.blink_interval > 0) {
+                        self.blink_h.run(
+                            &self.loop,
+                            &self.blink_c,
+                            self.config.blink_interval,
+                            Thread,
+                            self,
+                            blinkTimerCallback,
+                        );
+                    }
                 }
             },
 
@@ -632,7 +643,8 @@ fn blinkTimerCallback(
 
     t.wakeup.notify() catch {};
 
-    t.blink_h.run(&t.loop, &t.blink_c, BLINK_INTERVAL, Thread, t, blinkTimerCallback);
+    t.blink_h.run(&t.loop, &t.blink_c, t.config.blink_interval, Thread, t, blinkTimerCallback);
+
     return .disarm;
 }