fix: use pyte+Rich hybrid for colored SVG screenshots

Screenshots now properly preserve terminal colors:
1. Replay buffer provides raw ANSI data with color codes
2. pyte interprets escape sequences for accurate screen state
3. Rich renders the pyte buffer with colors to SVG

This gives us both accurate terminal state (no creeping/wrapping)
and proper color preservation in screenshots.

Bumps version to 0.1.12.

pyproject.toml

@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "textual-webterm"
-version = "0.1.11"
+version = "0.1.12"
 description = "Serve terminal sessions over the web"
 authors = ["Will McGugan <will@textualize.io>"]
 license = "MIT"

src/textual_webterm/local_server.py

@@ -14,9 +14,11 @@ from pathlib import Path
 from typing import TYPE_CHECKING
 
 import aiohttp
+import pyte
 from aiohttp import WSMsgType, web
-from rich.ansi import AnsiDecoder
 from rich.console import Console
+from rich.style import Style
+from rich.text import Text
 
 from . import constants
 from .exit_poller import ExitPoller
@@ -469,11 +471,6 @@ class LocalServer:
             if cached_response is not None:
                 return cached_response
 
-        # Get screen lines directly from the terminal session's pyte screen
-        # This provides accurate terminal state without replay buffer truncation issues
-        lines = await session_process.get_screen_lines()  # type: ignore[union-attr]
-        screen_text = "\n".join(lines)
-
         try:
             width = int(request.query.get("width", "120"))
         except ValueError:
@@ -486,6 +483,18 @@ class LocalServer:
             height = DISCONNECT_RESIZE[1]
         height = max(5, min(200, height))
 
+        # Hybrid approach for colored screenshots:
+        # 1. Get screen dimensions from pyte (accurate viewport)
+        # 2. Get raw ANSI from replay buffer for colors
+        # 3. Use pyte to interpret the ANSI and get proper screen state
+        # 4. Render through Rich for SVG with colors
+        replay_data = await session_process.get_replay_buffer()  # type: ignore[union-attr]
+        # Limit replay data to prevent excessive processing
+        max_replay = 128 * 1024  # 128KB should be plenty for a screen
+        if len(replay_data) > max_replay:
+            replay_data = replay_data[-max_replay:]
+        ansi_text = replay_data.decode("utf-8", errors="replace")
+
         now = asyncio.get_event_loop().time()
         ttl = self._get_screenshot_cache_ttl(route_key, now)
         cached = self._screenshot_cache.get(route_key)
@@ -517,10 +526,41 @@ class LocalServer:
                     return cached_response
 
             def _render_svg() -> str:
+                # Use pyte to interpret ANSI sequences and get accurate screen state
+                screen = pyte.Screen(width, height)
+                stream = pyte.Stream(screen)
+                stream.feed(ansi_text)
+
+                # Convert pyte screen buffer to Rich Text with colors
                 console = Console(record=True, width=width, height=height, file=io.StringIO())
-                decoder = AnsiDecoder()
-                for renderable in decoder.decode(screen_text):
-                    console.print(renderable)
+
+                for row in range(height):
+                    line = Text()
+                    for col in range(width):
+                        char = screen.buffer[row][col]
+                        char_data = char.data if char.data else " "
+
+                        # Build Rich style from pyte character attributes
+                        style_kwargs = {}
+                        if char.fg != "default":
+                            style_kwargs["color"] = char.fg
+                        if char.bg != "default":
+                            style_kwargs["bgcolor"] = char.bg
+                        if char.bold:
+                            style_kwargs["bold"] = True
+                        if char.italics:
+                            style_kwargs["italic"] = True
+                        if char.underscore:
+                            style_kwargs["underline"] = True
+                        if char.reverse:
+                            style_kwargs["reverse"] = True
+
+                        if style_kwargs:
+                            line.append(char_data, Style(**style_kwargs))
+                        else:
+                            line.append(char_data)
+
+                    console.print(line, end="\n", highlight=False)
 
                 return console.export_svg(
                     title="textual-webterm",

tests/test_local_server_unit.py

@@ -195,6 +195,7 @@ class TestLocalServerHelpers:
 
         session = MagicMock()
         session.get_screen_lines = AsyncMock(return_value=["hello", ""])
+        session.get_replay_buffer = AsyncMock(return_value=b"hello\r\n")
 
         monkeypatch.setattr(server.session_manager, "get_session_by_route_key", lambda _rk: session)
 
@@ -213,6 +214,7 @@ class TestLocalServerHelpers:
 
         session = MagicMock()
         session.get_screen_lines = AsyncMock(return_value=["world", ""])
+        session.get_replay_buffer = AsyncMock(return_value=b"world\r\n")
 
         # Pretend app exists for slug "known"
         server.session_manager.apps_by_slug["known"] = App(
@@ -564,6 +566,7 @@ class TestLocalServerMoreCoverage:
 
         session = MagicMock()
         session.get_screen_lines = AsyncMock(return_value=["hello", ""])
+        session.get_replay_buffer = AsyncMock(return_value=b"hello\n")
         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)
@@ -735,14 +738,15 @@ class TestLocalServerMoreCoverage:
         assert created is True
 
     @pytest.mark.asyncio
-    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."""
+    async def test_handle_screenshot_uses_replay_buffer_with_pyte(self, server_with_no_apps, monkeypatch):
+        """Test that screenshot uses replay buffer with pyte for colored rendering."""
         request = MagicMock()
         request.query = {"route_key": "rk"}
         request.headers = {}
 
         session = MagicMock()
         session.get_screen_lines = AsyncMock(return_value=["line1", "line2", ""])
+        session.get_replay_buffer = AsyncMock(return_value=b"line1\r\nline2\r\n")
         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
@@ -750,4 +754,4 @@ class TestLocalServerMoreCoverage:
         resp = await server_with_no_apps._handle_screenshot(request)
         assert resp.content_type == "image/svg+xml"
         assert "<svg" in resp.text
-        session.get_screen_lines.assert_awaited_once()
+        session.get_replay_buffer.assert_awaited_once()