Add CEF embedded browser + win32gui for weblink handling

Windows-specific fixes:
- New cef_browser.py: embedded Chromium via cefpython3, no subprocess
- _bring_kivy_to_front(): uses win32gui.SetForegroundWindow (reliable)
- _windows_kill_weblink_after_frame: kills Chrome IMMEDIATELY
- prewarm_weblink disabled on Windows (desktop launch is fast)
- _windows_play_weblink tries CEF first, falls back to subprocess
- Updated requirements_win.txt (cefpython3, pywin32 confirmed)
- Added development-track.md for change tracking

windows/cef_browser.py

@@ -0,0 +1,246 @@
+"""
+cef_browser.py — Embedded Chromium browser for Kiwy Signage Player (Windows)
+
+Replaces the subprocess-based Chromium launch with an embedded CEF
+browser window.  Eliminates all process-launch / z-order / taskkill bugs.
+
+Usage:
+    from cef_browser import CefBrowser
+    browser = CefBrowser()
+    browser.show("https://example.com")
+    # ... later
+    browser.hide()
+    browser.shutdown()
+"""
+
+import ctypes
+import os
+import sys
+import threading
+import time
+from pathlib import Path
+
+# ── CEF imports (must happen on the main thread) ────────────────────
+try:
+    from cefpython3 import cefpython as cef
+    CEF_AVAILABLE = True
+except ImportError:
+    CEF_AVAILABLE = False
+
+
+class CefBrowser:
+    """Embedded Chromium browser via cefpython3.
+
+    On show(url): creates/hides a borderless fullscreen CEF window.
+    On hide(): destroys the CEF window, brings Kivy to front.
+    On shutdown(): terminates CEF message loop.
+
+    The CEF message loop runs in a background thread so it does not
+    block the Kivy UI thread.
+    """
+
+    def __init__(self):
+        self._browser = None
+        self._cef_initialized = False
+        self._window_info = None
+        self._hwnd = None
+        self._cef_thread = None
+        self._stop_event = threading.Event()
+        self._message_loop_running = False
+
+    # ── Public API ──────────────────────────────────────────────────
+
+    def show(self, url):
+        """Open a fullscreen browser window displaying *url*."""
+        if not CEF_AVAILABLE:
+            return False
+
+        # If already showing, just navigate
+        if self._browser is not None:
+            self._browser.Navigate(url)
+            self._bring_to_front()
+            return True
+
+        self._create_browser_window(url)
+        return True
+
+    def hide(self):
+        """Close the browser window and bring Kivy to front."""
+        if self._browser is not None:
+            try:
+                # Close the browser
+                self._browser.CloseBrowser(True)
+            except Exception:
+                pass
+            self._browser = None
+
+        if self._hwnd:
+            try:
+                ctypes.windll.user32.DestroyWindow(self._hwnd)
+            except Exception:
+                pass
+            self._hwnd = None
+
+        # Bring Kivy to front
+        self._bring_kivy_to_front()
+
+    def shutdown(self):
+        """Shut down the CEF engine entirely."""
+        self.hide()
+        self._stop_event.set()
+        if self._cef_initialized:
+            try:
+                cef.Shutdown()
+            except Exception:
+                pass
+            self._cef_initialized = False
+
+    def navigate(self, url):
+        """Navigate the current browser to *url* (no window changes)."""
+        if self._browser is not None:
+            self._browser.Navigate(url)
+
+    def is_showing(self):
+        """Return True if the browser window is currently visible."""
+        return self._browser is not None
+
+    # ── Internal helpers ────────────────────────────────────────────
+
+    def _create_browser_window(self, url):
+        """Create a borderless fullscreen CEF window."""
+        if not CEF_AVAILABLE:
+            return
+
+        # Initialize CEF once
+        if not self._cef_initialized:
+            self._init_cef()
+
+        # Get screen dimensions
+        user32 = ctypes.windll.user32
+        screen_w = user32.GetSystemMetrics(0)
+        screen_h = user32.GetSystemMetrics(1)
+
+        # Create window info: borderless popup, fullscreen
+        window_info = cef.WindowInfo()
+        rect = [0, 0, screen_w, screen_h]
+        window_info.SetAsChild(0, rect)
+        # Use style: WS_POPUP | WS_VISIBLE | WS_CLIPCHILDREN
+        # We'll create the parent window ourselves for better control
+
+        # Create a borderless parent window
+        hinstance = ctypes.windll.kernel32.GetModuleHandleW(None)
+        self._hwnd = user32.CreateWindowExW(
+            0x00000008,  # WS_EX_TOPMOST | WS_EX_TOOLWINDOW
+            b'#32770',   # Dialog class
+            b'',         # no title
+            0x80000000 | 0x10000000,  # WS_POPUP | WS_VISIBLE
+            0, 0, screen_w, screen_h,
+            0, 0, hinstance, 0
+        )
+
+        if not self._hwnd:
+            return
+
+        # Make it black initially
+        hdc = user32.GetDC(self._hwnd)
+        rect_struct = (ctypes.c_long * 4)(0, 0, screen_w, screen_h)
+        gdi32 = ctypes.windll.gdi32
+        brush = gdi32.CreateSolidBrush(0x00000000)
+        gdi32.FillRect(hdc, ctypes.byref(rect_struct), brush)
+        gdi32.DeleteObject(brush)
+        user32.ReleaseDC(self._hwnd, hdc)
+
+        # Force it to top
+        user32.SetWindowPos(self._hwnd, -1, 0, 0, screen_w, screen_h, 0x0002 | 0x0040)
+        user32.ShowWindow(self._hwnd, 1)
+        user32.UpdateWindow(self._hwnd)
+
+        # Create browser as child of our window
+        window_info.SetAsChild(self._hwnd, [0, 0, screen_w, screen_h])
+
+        # Browser settings
+        browser_settings = {
+            "background_color": 0x00000000,  # Black
+        }
+
+        # Create browser
+        self._browser = cef.CreateBrowserSync(
+            window_info=window_info,
+            settings=browser_settings,
+            url=url
+        )
+
+        # Start message loop if not running
+        self._start_message_loop()
+
+    def _init_cef(self):
+        """Initialize CEF once."""
+        if self._cef_initialized:
+            return
+
+        # CEF settings
+        settings = {
+            "multi_threaded_message_loop": True,  # Required for Kivy integration
+            "log_severity": cef.LOGSEVERITY_WARNING,
+            "user_agent": "Mozilla/5.0 KiwySignage/1.0",
+            "cache_path": str(Path(os.environ.get("KIWY_DATA_DIR", ".")) / ".cef_cache"),
+        }
+
+        cef.Initialize(settings=settings)
+        self._cef_initialized = True
+
+    def _start_message_loop(self):
+        """Start CEF message loop in background thread."""
+        if self._message_loop_running:
+            return
+
+        self._message_loop_running = True
+        self._stop_event.clear()
+
+        def loop():
+            while not self._stop_event.is_set():
+                cef.MessageLoopWork()
+                time.sleep(0.01)
+            self._message_loop_running = False
+
+        self._cef_thread = threading.Thread(target=loop, daemon=True)
+        self._cef_thread.start()
+
+    def _bring_to_front(self):
+        """Bring the CEF window to foreground."""
+        if self._hwnd:
+            ctypes.windll.user32.SetWindowPos(
+                self._hwnd, -1, 0, 0, 0, 0,
+                0x0002 | 0x0001  | 0x0040
+                # SWP_NOSIZE | SWP_NOMOVE | SWP_SHOWWINDOW
+            )
+            ctypes.windll.user32.SetForegroundWindow(self._hwnd)
+
+    def _bring_kivy_to_front(self):
+        """Bring the Kivy/SDL window to foreground using win32gui."""
+        try:
+            import win32gui
+            import win32con
+
+            def enum_callback(hwnd, hwnd_list):
+                """Find Kivy/SDL window by class or title."""
+                class_name = win32gui.GetClassName(hwnd)
+                title = win32gui.GetWindowText(hwnd)
+                # SDL2 window on Windows typically has class "SDL_app"
+                # or title matches our app
+                if class_name == "SDL_app":
+                    hwnd_list.append(hwnd)
+                elif "Kiwy" in title or "Signage" in title:
+                    hwnd_list.append(hwnd)
+
+            hwnd_list = []
+            win32gui.EnumWindows(enum_callback, hwnd_list)
+
+            if hwnd_list:
+                # Bring the last found (most recent) to front
+                kivy_hwnd = hwnd_list[-1]
+                win32gui.ShowWindow(kivy_hwnd, win32con.SW_SHOWNORMAL)
+                win32gui.SetForegroundWindow(kivy_hwnd)
+                win32gui.BringWindowToTop(kivy_hwnd)
+        except Exception:
+            pass