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fix: maintain pyte screen state in TerminalSession for accurate screenshots

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Instead of trying to replay a truncated byte buffer through pyte, this
change maintains a pyte Screen object within TerminalSession that gets
updated as terminal data flows through. This provides accurate terminal
state for screenshots without issues from buffer truncation.

Key changes:
- Add pyte Screen and Stream to TerminalSession
- Update screen state as data arrives via _update_screen()
- Add get_screen_lines() to return current screen state
- Resize pyte screen when terminal size changes
- Update local_server to use get_screen_lines() directly
- Remove _apply_carriage_returns() workaround

This properly fixes the tmux status bar 'creeping up' issue by ensuring
the screenshot always reflects the actual terminal state.
This commit is contained in:
GitHub Copilot
2026-01-24 10:33:31 +00:00
parent a58c434eaf
commit 894fb2eaaf
4 changed files with 87 additions and 70 deletions
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tests/test_local_server_unit.py
+10 -44
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@@ -9,7 +9,6 @@ from textual_webterm.config import App, Config
from textual_webterm.local_server import (
LocalClientConnector,
LocalServer,
_apply_carriage_returns,
_rewrite_svg_fonts,
)
@@ -110,26 +109,6 @@ class TestLocalServer:
class TestLocalServerHelpers:
"""Tests for LocalServer helper methods."""
def test_apply_carriage_returns_overwrites_line(self):
text = "hello\rworld\r\nnext"
# pyte terminal emulator interprets CR properly - overwrites hello with world
lines = _apply_carriage_returns(text, width=80, height=24)
# First line should have "world" (overwritten), second line "next"
assert lines[0] == "world"
assert lines[1] == "next"
def test_apply_carriage_returns_handles_cursor_positioning(self):
# Simulate tmux-style cursor positioning to row 5, column 1 (\x1b[5;1H)
# Then clear to end of line (\x1b[K) and write new content
# Use \r\n for proper line endings
text = "line1\r\nline2\r\nline3\r\nline4\r\nline5\x1b[5;1H\x1b[Kupdated"
lines = _apply_carriage_returns(text, width=80, height=10)
# Line 5 (index 4) should be overwritten with "updated"
assert lines[4] == "updated"
# Previous lines should remain
assert lines[0] == "line1"
assert lines[1] == "line2"
@pytest.mark.asyncio
async def test_keyboard_interrupt_closes_sessions_and_websockets(self, server, monkeypatch):
ws1 = MagicMock()
@@ -215,7 +194,7 @@ class TestLocalServerHelpers:
request.query = {"route_key": "rk", "width": "80"}
session = MagicMock()
session.get_replay_buffer = AsyncMock(return_value=b"hello\r\n")
session.get_screen_lines = AsyncMock(return_value=["hello", ""])
monkeypatch.setattr(server.session_manager, "get_session_by_route_key", lambda _rk: session)
@@ -233,7 +212,7 @@ class TestLocalServerHelpers:
request.query = {"route_key": "known", "width": "90"}
session = MagicMock()
session.get_replay_buffer = AsyncMock(return_value=b"world\r\n")
session.get_screen_lines = AsyncMock(return_value=["world", ""])
# Pretend app exists for slug "known"
server.session_manager.apps_by_slug["known"] = App(
@@ -565,7 +544,7 @@ class TestLocalServerMoreCoverage:
request.headers = {}
session = MagicMock()
session.get_replay_buffer = AsyncMock(return_value=b"SHOULD_NOT_BE_READ")
session.get_screen_lines = AsyncMock(return_value=["SHOULD_NOT_BE_READ"])
monkeypatch.setattr(server_with_no_apps.session_manager, "get_session_by_route_key", lambda _rk: session)
server_with_no_apps._screenshot_cache["rk"] = (0.0, "<svg>cached</svg>")
@@ -575,7 +554,7 @@ class TestLocalServerMoreCoverage:
resp = await server_with_no_apps._handle_screenshot(request)
assert "cached" in resp.text
session.get_replay_buffer.assert_not_awaited()
session.get_screen_lines.assert_not_awaited()
@pytest.mark.asyncio
async def test_handle_screenshot_invalid_width_height_defaults(self, server_with_no_apps, monkeypatch):
@@ -584,7 +563,7 @@ class TestLocalServerMoreCoverage:
request.headers = {}
session = MagicMock()
session.get_replay_buffer = AsyncMock(return_value=b"hello\n")
session.get_screen_lines = AsyncMock(return_value=["hello", ""])
monkeypatch.setattr(server_with_no_apps.session_manager, "get_session_by_route_key", lambda _rk: session)
resp = await server_with_no_apps._handle_screenshot(request)
@@ -756,32 +735,19 @@ class TestLocalServerMoreCoverage:
assert created is True
@pytest.mark.asyncio
async def test_handle_screenshot_truncates_replay_buffer_before_decode(self, server_with_no_apps, monkeypatch):
from textual_webterm.local_server import SCREENSHOT_MAX_BYTES
async def test_handle_screenshot_uses_get_screen_lines(self, server_with_no_apps, monkeypatch):
"""Test that screenshot uses get_screen_lines() from terminal session."""
request = MagicMock()
request.query = {"route_key": "rk"}
request.headers = {}
session = MagicMock()
session.get_replay_buffer = AsyncMock(return_value=b"x" * (SCREENSHOT_MAX_BYTES + 10))
session.get_screen_lines = AsyncMock(return_value=["line1", "line2", ""])
monkeypatch.setattr(server_with_no_apps.session_manager, "get_session_by_route_key", lambda _rk: session)
server_with_no_apps._route_last_activity["rk"] = 1.0
captured = {"len": None}
def apply_cr(text: str, width: int = 80, height: int = 24):
captured["len"] = len(text)
return ["x"]
async def fake_to_thread(_fn):
return "<svg></svg>"
monkeypatch.setattr("textual_webterm.local_server._apply_carriage_returns", apply_cr)
monkeypatch.setattr("textual_webterm.local_server.asyncio.to_thread", AsyncMock(side_effect=fake_to_thread))
monkeypatch.setattr("textual_webterm.local_server._rewrite_svg_fonts", lambda s: s)
resp = await server_with_no_apps._handle_screenshot(request)
assert resp.content_type == "image/svg+xml"
assert captured["len"] == SCREENSHOT_MAX_BYTES
assert "<svg" in resp.text
session.get_screen_lines.assert_awaited_once()