terminal: search should use active area dirty tracking

src/terminal/Terminal.zig

@@ -112,6 +112,16 @@ flags: packed struct {
     /// True if the terminal should perform selection scrolling.
     selection_scroll: bool = false,
 
+    /// Dirty flag used only by the search thread. The renderer is expected
+    /// to set this to true if the viewport was dirty as it was rendering.
+    /// This is used by the search thread to more efficiently re-search the
+    /// viewport and active area.
+    ///
+    /// Since the renderer is going to inspect the viewport/active area ANYWAYS,
+    /// this lets our search thread do less work and hold the lock less time,
+    /// resulting in more throughput for everything.
+    search_viewport_dirty: bool = false,
+
     /// Dirty flags for the renderer.
     dirty: Dirty = .{},
 } = .{},

src/terminal/search/Thread.zig

@@ -419,6 +419,10 @@ const Search = struct {
         var vp: ViewportSearch = try .init(alloc, needle);
         errdefer vp.deinit();
 
+        // We use dirty tracking for active area changes. Start with it
+        // dirty so the first change is re-searched.
+        vp.active_dirty = true;
+
         return .{
             .viewport = vp,
             .screens = .init(.{}),
@@ -553,6 +557,15 @@ const Search = struct {
             }
         }
 
+        // See the `search_viewport_dirty` flag on the terminal to know
+        // what exactly this is for. But, if this is set, we know the renderer
+        // found the viewport/active area dirty, so we should mark it as
+        // dirty in our viewport searcher so it forces a re-search.
+        if (t.flags.search_viewport_dirty) {
+            self.viewport.active_dirty = true;
+            t.flags.search_viewport_dirty = false;
+        }
+
         // Check our viewport for changes.
         if (self.viewport.update(&t.screens.active.pages)) |updated| {
             if (updated) self.stale_viewport_matches = true;

src/terminal/search/viewport.zig

@@ -125,6 +125,10 @@ pub const ViewportSearch = struct {
             self.fingerprint = null;
         }
 
+        // If our active area was set as dirty, we always unset it here
+        // because we're re-searching now.
+        if (self.active_dirty) |*v| v.* = false;
+
         // Clear our previous sliding window
         self.window.clearAndRetainCapacity();