Merge pull request #1955 from ghostty-org/ibsr

terminal: implement in-band size reports (Mode 2048)

src/terminal/modes.zig

@@ -216,6 +216,7 @@ const entries: []const ModeEntry = &.{
     .{ .name = "synchronized_output", .value = 2026 },
     .{ .name = "grapheme_cluster", .value = 2027 },
     .{ .name = "report_color_scheme", .value = 2031 },
+    .{ .name = "in_band_size_reports", .value = 2048 },
 };
 
 test {

src/termio/Termio.zig

@@ -344,6 +344,7 @@ pub fn changeConfig(self: *Termio, td: *ThreadData, config: *DerivedConfig) !voi
 /// Resize the terminal.
 pub fn resize(
     self: *Termio,
+    td: *ThreadData,
     grid_size: renderer.GridSize,
     screen_size: renderer.ScreenSize,
     padding: renderer.Padding,
@@ -377,7 +378,37 @@ pub fn resize(
 
         // Wake up our renderer so any changes will be shown asap
         self.renderer_wakeup.notify() catch {};
+
+        // If we have size reporting enabled we need to send a report.
+        if (self.terminal.modes.get(.in_band_size_reports)) {
+            try self.sizeReportLocked(td);
         }
+    }
+}
+
+/// Make a mode 2048 in-band size report.
+pub fn sizeReport(self: *Termio, td: *ThreadData) !void {
+    self.renderer_state.mutex.lock();
+    defer self.renderer_state.mutex.unlock();
+    try self.sizeReportLocked(td);
+}
+
+fn sizeReportLocked(self: *Termio, td: *ThreadData) !void {
+    // 1024 bytes should be enough for size report since report
+    // in columns and pixels.
+    var buf: [1024]u8 = undefined;
+    const message = try std.fmt.bufPrint(
+        &buf,
+        "\x1B[48;{};{};{};{}t",
+        .{
+            self.grid_size.rows,
+            self.grid_size.columns,
+            self.terminal.height_px,
+            self.terminal.width_px,
+        },
+    );
+
+    try self.queueWrite(td, message, false);
 }
 
 /// Reset the synchronized output mode. This is usually called by timer

src/termio/Thread.zig

@@ -267,6 +267,7 @@ fn drainMailbox(
             },
             .inspector => |v| self.flags.has_inspector = v,
             .resize => |v| self.handleResize(cb, v),
+            .size_report => try io.sizeReport(data),
             .clear_screen => |v| try io.clearScreen(data, v.history),
             .scroll_viewport => |v| try io.scrollViewport(v),
             .jump_to_prompt => |v| try io.jumpToPrompt(v),
@@ -369,7 +370,12 @@ fn coalesceCallback(
 
     if (cb.self.coalesce_data.resize) |v| {
         cb.self.coalesce_data.resize = null;
-        cb.io.resize(v.grid_size, v.screen_size, v.padding) catch |err| {
+        cb.io.resize(
+            &cb.data,
+            v.grid_size,
+            v.screen_size,
+            v.padding,
+        ) catch |err| {
             log.warn("error during resize err={}", .{err});
         };
     }

src/termio/message.zig

@@ -42,6 +42,10 @@ pub const Message = union(enum) {
     /// Resize the window.
     resize: Resize,
 
+    /// Request a size report is sent to the pty (in-band size report,
+    /// mode 2048: https://gist.github.com/rockorager/e695fb2924d36b2bcf1fff4a3704bd83)
+    size_report: void,
+
     /// Clear the screen.
     clear_screen: struct {
         /// Include clearing the history

src/termio/stream_handler.zig

@@ -597,6 +597,10 @@ pub const StreamHandler = struct {
                 self.messageWriter(.{ .linefeed_mode = enabled });
             },
 
+            .in_band_size_reports => if (enabled) self.messageWriter(.{
+                .size_report = {},
+            }),
+
             .mouse_event_x10 => {
                 if (enabled) {
                     self.terminal.flags.mouse_event = .x10;