From e55f2daf9075e567b8287ddb0ba049712731ff1d Mon Sep 17 00:00:00 2001
From: Qwerasd <qwerasd205@users.noreply.github.com>
Date: Fri, 29 Mar 2024 13:08:38 -0400
Subject: [PATCH] perf(terminal): clear unprotected cells in spans

Previous behavior of clearing one at a time hit a page integrity assertion after clearing a wide character but not its tail. This fixes that and should also be - in theory - significantly more performant as well by identifying spans of unprotected cells and clearing them in bulk.
---
 src/terminal/Screen.zig   | 18 ++++++++++++++----
 src/terminal/Terminal.zig | 33 ++++++++++-----------------------
 2 files changed, 24 insertions(+), 27 deletions(-)

diff --git a/src/terminal/Screen.zig b/src/terminal/Screen.zig
index a94a24c7a..61af34338 100644
--- a/src/terminal/Screen.zig
+++ b/src/terminal/Screen.zig
@@ -891,10 +891,20 @@ pub fn clearUnprotectedCells(
     row: *Row,
     cells: []Cell,
 ) void {
-    for (cells) |*cell| {
-        if (cell.protected) continue;
-        const cell_multi: [*]Cell = @ptrCast(cell);
-        self.clearCells(page, row, cell_multi[0..1]);
+    var x0: usize = 0;
+    var x1: usize = 0;
+
+    while (x0 < cells.len) clear: {
+        while (cells[x0].protected) {
+            x0 += 1;
+            if (x0 >= cells.len) break :clear;
+        }
+        x1 = x0 + 1;
+        while (x1 < cells.len and !cells[x1].protected) {
+            x1 += 1;
+        }
+        self.clearCells(page, row, cells[x0..x1]);
+        x0 = x1;
     }
 
     page.assertIntegrity();
diff --git a/src/terminal/Terminal.zig b/src/terminal/Terminal.zig
index 2c17c051a..0c91cb428 100644
--- a/src/terminal/Terminal.zig
+++ b/src/terminal/Terminal.zig
@@ -1793,19 +1793,11 @@ pub fn eraseChars(self: *Terminal, count_req: usize) void {
         return;
     }
 
-    // SLOW PATH
-    // We had a protection mode at some point. We must go through each
-    // cell and check its protection attribute.
-    for (0..end) |x| {
-        const cell_multi: [*]Cell = @ptrCast(cells + x);
-        const cell: *Cell = @ptrCast(&cell_multi[0]);
-        if (cell.protected) continue;
-        self.screen.clearCells(
-            &self.screen.cursor.page_pin.page.data,
-            self.screen.cursor.page_row,
-            cell_multi[0..1],
-        );
-    }
+    self.screen.clearUnprotectedCells(
+        &self.screen.cursor.page_pin.page.data,
+        self.screen.cursor.page_row,
+        cells[0..end],
+    );
 }
 
 /// Erase the line.
@@ -1878,16 +1870,11 @@ pub fn eraseLine(
         return;
     }
 
-    for (start..end) |x| {
-        const cell_multi: [*]Cell = @ptrCast(cells + x);
-        const cell: *Cell = @ptrCast(&cell_multi[0]);
-        if (cell.protected) continue;
-        self.screen.clearCells(
-            &self.screen.cursor.page_pin.page.data,
-            self.screen.cursor.page_row,
-            cell_multi[0..1],
-        );
-    }
+    self.screen.clearUnprotectedCells(
+        &self.screen.cursor.page_pin.page.data,
+        self.screen.cursor.page_row,
+        cells[start..end],
+    );
 }
 
 /// Erase the display.