From 245b9642f932124294012754bae61f26e3db3b69 Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <mitchell.hashimoto@gmail.com>
Date: Sat, 25 Jun 2022 10:56:41 -0700
Subject: [PATCH] save and restore cursor

---
 src/Window.zig            |  8 ++++++++
 src/terminal/Terminal.zig | 27 ++++++++++++++++++++++++---
 src/terminal/stream.zig   | 15 +++++++++++++++
 3 files changed, 47 insertions(+), 3 deletions(-)

diff --git a/src/Window.zig b/src/Window.zig
index 46b4780e2..8f85a4b3d 100644
--- a/src/Window.zig
+++ b/src/Window.zig
@@ -781,3 +781,11 @@ pub fn tabClear(self: *Window, cmd: terminal.TabClear) !void {
 pub fn tabSet(self: *Window) !void {
     self.terminal.tabSet();
 }
+
+pub fn saveCursor(self: *Window) !void {
+    self.terminal.saveCursor();
+}
+
+pub fn restoreCursor(self: *Window) !void {
+    self.terminal.restoreCursor();
+}
diff --git a/src/terminal/Terminal.zig b/src/terminal/Terminal.zig
index 0f8695c9c..3e3c8c6a1 100644
--- a/src/terminal/Terminal.zig
+++ b/src/terminal/Terminal.zig
@@ -28,6 +28,9 @@ screen: Screen,
 /// Cursor position.
 cursor: Cursor,
 
+/// Saved cursor saved with DECSC (ESC 7).
+saved_cursor: Cursor,
+
 /// Where the tabstops are.
 tabstops: Tabstops,
 
@@ -53,8 +56,8 @@ const ScrollingRegion = struct {
 /// Cursor represents the cursor state.
 const Cursor = struct {
     // x, y where the cursor currently exists (0-indexed).
-    x: usize,
-    y: usize,
+    x: usize = 0,
+    y: usize = 0,
 
     // pen is the current cell styling to apply to new cells.
     pen: Screen.Cell = .{ .char = 0 },
@@ -66,7 +69,8 @@ pub fn init(alloc: Allocator, cols: usize, rows: usize) !Terminal {
         .cols = cols,
         .rows = rows,
         .screen = try Screen.init(alloc, rows, cols),
-        .cursor = .{ .x = 0, .y = 0 },
+        .cursor = .{},
+        .saved_cursor = .{},
         .tabstops = try Tabstops.init(alloc, cols, TABSTOP_INTERVAL),
         .scrolling_region = .{
             .top = 0,
@@ -119,6 +123,23 @@ pub fn plainString(self: Terminal, alloc: Allocator) ![]const u8 {
     return try self.screen.testString(alloc);
 }
 
+/// Save cursor position and further state.
+///
+/// The primary and alternate screen have distinct save state. One saved state
+/// is kept per screen (main / alternative). If for the current screen state
+/// was already saved it is overwritten.
+pub fn saveCursor(self: *Terminal) void {
+    self.saved_cursor = self.cursor;
+}
+
+/// Restore cursor position and other state.
+///
+/// The primary and alternate screen have distinct save state.
+/// If no save was done before values are reset to their initial values.
+pub fn restoreCursor(self: *Terminal) void {
+    self.cursor = self.saved_cursor;
+}
+
 /// TODO: test
 pub fn setAttribute(self: *Terminal, attr: sgr.Attribute) !void {
     switch (attr) {
diff --git a/src/terminal/stream.zig b/src/terminal/stream.zig
index 2958de0c0..b1c6161b3 100644
--- a/src/terminal/stream.zig
+++ b/src/terminal/stream.zig
@@ -379,8 +379,23 @@ pub fn Stream(comptime Handler: type) type {
             action: Parser.Action.ESC,
         ) !void {
             switch (action.final) {
+                // DECSC - Save Cursor
+                '7' => if (@hasDecl(T, "saveCursor")) switch (action.intermediates.len) {
+                    0 => try self.handler.saveCursor(),
+                    else => {
+                        log.warn("invalid command: {}", .{action});
+                        return;
+                    },
+                } else log.warn("unimplemented ESC callback: {}", .{action}),
+
                 '8' => blk: {
                     switch (action.intermediates.len) {
+                        // DECRC - Restore Cursor
+                        0 => if (@hasDecl(T, "restoreCursor")) {
+                            try self.handler.restoreCursor();
+                            break :blk {};
+                        } else log.warn("unimplemented restore cursor callback: {}", .{action}),
+
                         1 => switch (action.intermediates[0]) {
                             // DECALN - Fill Screen with E
                             '#' => if (@hasDecl(T, "decaln")) {