From 1c1886defca5bd7bce495960ffe0d3e34de5c746 Mon Sep 17 00:00:00 2001
From: CJ van den Berg <cj@vdbonline.com>
Date: Tue, 7 Apr 2026 16:17:35 +0200
Subject: [PATCH] feat(gui): add gui cursor blink rendering

---
 src/renderer/gui/renderer.zig   | 61 +++++++++++++++++++++++++++++++--
 src/renderer/vaxis/renderer.zig |  5 +--
 src/tui/tui.zig                 | 12 ++++---
 3 files changed, 69 insertions(+), 9 deletions(-)

diff --git a/src/renderer/gui/renderer.zig b/src/renderer/gui/renderer.zig
index 7d0e53f4..2cc582f2 100644
--- a/src/renderer/gui/renderer.zig
+++ b/src/renderer/gui/renderer.zig
@@ -61,6 +61,15 @@ cursor_color: app.GpuColor = app.GpuColor.initRgb(255, 255, 255),
 secondary_cursors: std.ArrayListUnmanaged(app.CursorInfo) = .{},
 secondary_color: app.GpuColor = app.GpuColor.initRgb(255, 255, 255),
 
+cursor_blink: bool = false,
+blink_on: bool = true,
+blink_epoch: i64 = 0,
+blink_period_us: i64 = 500_000,
+blink_idle_us: i64 = 15_000_000,
+blink_last_change: i64 = 0,
+prev_cursor: app.CursorInfo = .{},
+prev_cursor_blink: bool = false,
+
 const global = struct {
     var init_called: bool = false;
 };
@@ -128,9 +137,47 @@ fn fmtmsg(self: *Self, value: anytype) std.Io.Writer.Error![]const u8 {
     return self.event_buffer.written();
 }
 
-pub fn render(self: *Self) error{}!void {
-    if (!self.window_ready) return;
-    app.updateScreen(&self.vx.screen, self.cursor_info, self.secondary_cursors.items);
+pub fn render(self: *Self) error{}!bool {
+    if (!self.window_ready) return false;
+
+    var cursor = self.cursor_info;
+
+    // Detect changes since the last rendered frame. Reset blink epoch and idle
+    // timer on any meaningful change so the cursor snaps to visible immediately.
+    if (cursor.vis != self.prev_cursor.vis or
+        cursor.row != self.prev_cursor.row or
+        cursor.col != self.prev_cursor.col or
+        cursor.shape != self.prev_cursor.shape or
+        self.cursor_blink != self.prev_cursor_blink)
+    {
+        const now = std.time.microTimestamp();
+        if (cursor.vis) {
+            self.blink_epoch = now;
+            self.blink_on = true;
+        }
+        self.blink_last_change = now;
+    }
+    self.prev_cursor = cursor;
+    self.prev_cursor_blink = self.cursor_blink;
+
+    // Apply blink unless the cursor has been idle for too long.
+    if (cursor.vis and self.cursor_blink) {
+        const now = std.time.microTimestamp();
+        const idle = now - self.blink_last_change;
+        if (idle < self.blink_idle_us) {
+            const elapsed = @mod(now - self.blink_epoch, self.blink_period_us * 2);
+            self.blink_on = elapsed < self.blink_period_us;
+            cursor.vis = self.blink_on;
+        } else {
+            cursor.vis = true; // freeze visible after idle timeout
+        }
+    }
+
+    app.updateScreen(&self.vx.screen, cursor, self.secondary_cursors.items);
+
+    if (!self.cursor_info.vis or !self.cursor_blink) return false;
+    const idle = std.time.microTimestamp() - self.blink_last_change;
+    return idle < self.blink_idle_us;
 }
 
 pub fn sigwinch(self: *Self) !void {
@@ -467,6 +514,7 @@ pub fn request_mouse_cursor_default(self: *Self, push_or_pop: bool) void {
 }
 
 pub fn cursor_enable(self: *Self, y: i32, x: i32, shape: CursorShape) !void {
+    self.cursor_blink = isBlink(shape);
     self.cursor_info = .{
         .vis = true,
         .row = if (y < 0) 0 else @intCast(y),
@@ -503,6 +551,13 @@ fn themeColorToGpu(color: Color) app.GpuColor {
     };
 }
 
+fn isBlink(shape: CursorShape) bool {
+    return switch (shape) {
+        .default, .block_blink, .beam_blink, .underline_blink => true,
+        else => false,
+    };
+}
+
 fn vaxisCursorShape(shape: CursorShape) app.CursorShape {
     return switch (shape) {
         .default, .block, .block_blink => .block,
diff --git a/src/renderer/vaxis/renderer.zig b/src/renderer/vaxis/renderer.zig
index 95025892..30710f43 100644
--- a/src/renderer/vaxis/renderer.zig
+++ b/src/renderer/vaxis/renderer.zig
@@ -219,10 +219,11 @@ pub fn run(self: *Self) Error!void {
     try self.loop.start();
 }
 
-pub fn render(self: *Self) !void {
-    if (in_panic.load(.acquire)) return;
+pub fn render(self: *Self) !bool {
+    if (in_panic.load(.acquire)) return false;
     try self.vx.render(self.tty.writer());
     try self.tty.writer().flush();
+    return false;
 }
 
 pub fn sigwinch(self: *Self) !void {
diff --git a/src/tui/tui.zig b/src/tui/tui.zig
index bc92fa2b..d457819d 100644
--- a/src/tui/tui.zig
+++ b/src/tui/tui.zig
@@ -681,13 +681,17 @@ fn render(self: *Self) void {
         top_layer_.draw(self.rdr_.stdplane());
     }
 
-    {
+    const renderer_more = ret: {
         const frame = tracy.initZone(@src(), .{ .name = renderer.log_name ++ " render" });
         defer frame.deinit();
-        self.rdr_.render() catch |e| self.logger.err("render", e);
+        const m = self.rdr_.render() catch |e| blk: {
+            self.logger.err("render", e);
+            break :blk false;
+        };
         tracy.frameMark();
         self.unrendered_input_events_count = 0;
-    }
+        break :ret m;
+    };
     self.top_layer_reset();
 
     self.idle_frame_count = if (self.unrendered_input_events_count > 0)
@@ -695,7 +699,7 @@ fn render(self: *Self) void {
     else
         self.idle_frame_count + 1;
 
-    if (more or self.idle_frame_count < idle_frames or self.no_sleep) {
+    if (more or renderer_more or self.idle_frame_count < idle_frames or self.no_sleep) {
         if (!self.frame_clock_running) {
             self.frame_clock.start() catch {};
             self.frame_clock_running = true;