implement DECSASD by just blackholing the output for now

We don't want to support status lines, and if anything sends us status
line information we don't want it to mess up the main display, so just
drop it.

src/Window.zig

@@ -925,3 +925,10 @@ pub fn restoreCursor(self: *Window) !void {
 pub fn enquiry(self: *Window) !void {
     try self.queueWrite("");
 }
+
+pub fn setActiveStatusDisplay(
+    self: *Window,
+    req: terminal.StatusDisplay,
+) !void {
+    self.terminal.status_display = req;
+}

src/terminal/Terminal.zig

@@ -35,6 +35,11 @@ active_screen: ScreenType,
 screen: Screen,
 secondary_screen: Screen,
 
+/// Whether we're currently writing to the status line (DECSASD and DECSSDT).
+/// We don't support a status line currently so we just black hole this
+/// data so that it doesn't mess up our main display.
+status_display: ansi.StatusDisplay = .main,
+
 /// Where the tabstops are.
 tabstops: Tabstops,
 
@@ -303,6 +308,9 @@ pub fn print(self: *Terminal, c: u21) !void {
     const tracy = trace(@src());
     defer tracy.end();
 
+    // If we're not on the main display, do nothing for now
+    if (self.status_display != .main) return;
+
     // If we're not at the bottom, then we need to move there
     if (!self.screen.displayIsBottom()) self.screen.scroll(.{ .bottom = {} });
 

src/terminal/ansi.zig

@@ -115,3 +115,22 @@ pub const CursorStyle = enum(u16) {
         };
     }
 };
+
+/// The status line type for DECSSDT.
+pub const StatusLineType = enum(u16) {
+    none = 0,
+    indicator = 1,
+    host_writable = 2,
+
+    // Non-exhaustive so that @intToEnum never fails for unsupported values.
+    _,
+};
+
+/// The display to target for status updates (DECSASD).
+pub const StatusDisplay = enum(u16) {
+    main = 0,
+    status_line = 1,
+
+    // Non-exhaustive so that @intToEnum never fails for unsupported values.
+    _,
+};

src/terminal/main.zig

@@ -11,6 +11,8 @@ pub const CursorStyle = ansi.CursorStyle;
 pub const DeviceAttributeReq = ansi.DeviceAttributeReq;
 pub const DeviceStatusReq = ansi.DeviceStatusReq;
 pub const Mode = ansi.Mode;
+pub const StatusLineType = ansi.StatusLineType;
+pub const StatusDisplay = ansi.StatusDisplay;
 pub const EraseDisplay = csi.EraseDisplay;
 pub const EraseLine = csi.EraseLine;
 pub const TabClear = csi.TabClear;

src/terminal/stream.zig

@@ -382,6 +382,26 @@ pub fn Stream(comptime Handler: type) type {
                     1 => try self.handler.insertBlanks(action.params[0]),
                     else => log.warn("invalid ICH command: {}", .{action}),
                 } else log.warn("unimplemented CSI callback: {}", .{action}),
+
+                // DECSASD - Select Active Status Display
+                '}' => {
+                    const success = decsasd: {
+                        // Verify we're getting a DECSASD command
+                        if (action.intermediates.len != 1 or action.intermediates[0] != '$')
+                            break :decsasd false;
+                        if (action.params.len != 1)
+                            break :decsasd false;
+                        if (!@hasDecl(T, "setActiveStatusDisplay"))
+                            break :decsasd false;
+
+                        try self.handler.setActiveStatusDisplay(
+                            @intToEnum(ansi.StatusDisplay, action.params[0]),
+                        );
+                        break :decsasd true;
+                    };
+
+                    if (!success) log.warn("unimplemented CSI callback: {}", .{action});
+                },
             }
         }