Initial commit: Core Teletext Editor functionality

src/teletext/charsets.py

@@ -0,0 +1,60 @@
+
+"""
+Teletext Character Sets (G0).
+Maps the specific code points (0x23, 0x24, 0x40, 0x5B-0x5E, 0x60, 0x7B-0x7E)
+to Unicode characters based on the National Option (3 bits).
+"""
+
+# Default (English) - Option 000
+ENGLISH = {
+    0x23: '#', 0x24: '$', 0x40: '@', 
+    0x5B: '[', 0x5C: '\\', 0x5D: ']', 0x5E: '^', 
+    0x5F: '_', 0x60: '`', 
+    0x7B: '{', 0x7C: '|', 0x7D: '}', 0x7E: '~'
+}
+
+# Swedish/Finnish/Hungarian - Option 010 (2)
+SWEDISH_FINNISH = {
+    0x23: '#', 0x24: '¤', 0x40: 'É', 
+    0x5B: 'Ä', 0x5C: 'Ö', 0x5D: 'Å', 0x5E: 'Ü', 
+    0x5F: '_', 0x60: 'é', 
+    0x7B: 'ä', 0x7C: 'ö', 0x7D: 'å', 0x7E: 'ü'
+}
+
+# German - Option 001 (1) 
+GERMAN = {
+    0x23: '#', 0x24: '$', 0x40: '§', 
+    0x5B: 'Ä', 0x5C: 'Ö', 0x5D: 'Ü', 0x5E: '^', 
+    0x5F: '_', 0x60: '`', 
+    0x7B: 'ä', 0x7C: 'ö', 0x7D: 'ü', 0x7E: 'ß'
+}
+
+# We can add more as needed.
+
+SETS = [
+    ENGLISH,          # 000
+    GERMAN,           # 001
+    SWEDISH_FINNISH,  # 010
+    ENGLISH, # Italian (011) - placeholder
+    ENGLISH, # French (100) - placeholder
+    ENGLISH, # Portuguese/Spanish (101) - placeholder
+    ENGLISH, # Turkish (110) - placeholder
+    ENGLISH, # Romania (111) - placeholder
+]
+
+def get_char(byte_val, subset_idx):
+    if subset_idx < 0 or subset_idx >= len(SETS):
+        subset_idx = 0
+    
+    mapping = SETS[subset_idx]
+    
+    # If byte is in mapping, return mapped char.
+    # Else return ASCII equivalent (for basic chars)
+    
+    valid_byte = byte_val & 0x7F # Strip parity if present (though our packet data is 8-bit usually already stripping parity?)
+    # Packet data we store is raw bytes. We should probably strip parity bit 7 before lookup.
+    
+    if valid_byte in mapping:
+        return mapping[valid_byte]
+        
+    return chr(valid_byte)

src/teletext/io.py

@@ -0,0 +1,119 @@
+import os
+from typing import List
+from .models import Packet, Page, TeletextService
+
+def load_t42(file_path: str) -> TeletextService:
+    service = TeletextService()
+    
+    with open(file_path, 'rb') as f:
+        while True:
+            chunk = f.read(42)
+            if not chunk:
+                break
+            if len(chunk) < 42:
+                # Should not happen in a valid T42 stream, or we just ignore incomplete tail
+                break
+                
+            packet = Packet(chunk)
+            service.all_packets.append(packet)
+            
+            # Logic to group into pages.
+            # This is non-trivial because packets for a page might be interleaved or sequential.
+            # Standard implementation: Packets arrive in order. Row 0 starts a new page/subpage.
+            
+            if packet.row == 0:
+                # Start of a new page header.
+                # Byte 2-9 of header contain Page Number, Subcode, Control bits etc.
+                # We need to parse the header to identify the page.
+                
+                # Header format (after Mag/Row):
+                # Bytes: P1 P2 S1 S2 S3 S4 C1 C2 ...
+                # All Hamming 8/4 encoded.
+                
+                # For now, let's just create a new page entry for every Header we see,
+                # or find the existing one if we want to support updates (but T42 usually is a stream capture).
+                # If it's an editor file, it's likely sequential.
+                
+                p_num, sub_code = parse_header(packet.data)
+                
+                # Create new page
+                new_page = Page(magazine=packet.magazine, page_number=p_num, sub_code=sub_code)
+                new_page.packets.append(packet)
+                service.pages.append(new_page)
+            else:
+                # Add to the "current" page of this magazine.
+                # We need to track the current active page for each magazine.
+                # A simplistic approach: add to the last page added that matches the magazine ??
+                # Robust approach: Maintain a dict of current_pages_by_magazine.
+                
+                # Let's find the last page in service that matches the packet's magazine
+                # This is O(N) but N (pages) is small.
+                target_page = None
+                for p in reversed(service.pages):
+                    if p.magazine == packet.magazine:
+                        target_page = p
+                        break
+                
+                if target_page:
+                    target_page.packets.append(packet)
+                else:
+                    # Packet without a header? Orphaned. Just keep in all_packets
+                    pass
+
+    return service
+
+def save_t42(file_path: str, service: TeletextService):
+    with open(file_path, 'wb') as f:
+        # User requirement: "without rearranging the order of the packets"
+        # Implies we should iterate the original list.
+        # However, if we edit data, we modify the Packet objects in place.
+        # If we Add/Delete packets, we need to handle that.
+        
+        for packet in service.all_packets:
+            # Reconstruct the 42 bytes from the packet fields
+            # The packet.data (bytearray) should be mutable and edited by the UI.
+            # packet.original_data (first 2 bytes) + packet.data
+            
+            # Note: If we changed Magazine or Row, we'd need to re-encode the first 2 bytes.
+            # For now, assume we primarily edit content (bytes 2-41).
+            
+            header = packet.original_data[:2] # Keep original address for now
+            # TODO: regenerating header if Mag/Row changed
+            
+            f.write(header + packet.data)
+
+def decode_hamming_8_4(byte_val):
+    return ((byte_val >> 1) & 1) | \
+           (((byte_val >> 3) & 1) << 1) | \
+           (((byte_val >> 5) & 1) << 2) | \
+           (((byte_val >> 7) & 1) << 3)
+
+def parse_header(data: bytearray):
+    # Data is 40 bytes.
+    # Bytes 0-7 are Page Num (2), Subcode (4), Control (2) - ALL Hamming encoded.
+    
+    # 0: Page Units (PU)
+    # 1: Page Tens (PT)
+    
+    pu = decode_hamming_8_4(data[0])
+    pt = decode_hamming_8_4(data[1])
+    
+    page_num = (pt & 0xF) * 10 + (pu & 0xF)
+    
+    # Subcode: S1, S2, S3, S4
+    # S1 (low), S2, S3, S4 (high)
+    
+    s1 = decode_hamming_8_4(data[2])
+    s2 = decode_hamming_8_4(data[3])
+    s3 = decode_hamming_8_4(data[4])
+    s4 = decode_hamming_8_4(data[5])
+    
+    # Subcode logic is a bit complex with specific bit mapping for "Time" vs "Subcode"
+    # But usually just combining them gives the raw subcode value.
+    # S1: bits 0-3
+    # S2: bits 4-6 (bit 4 is C4) -> actually S2 has 3 bits of subcode + 1 control bit usually?
+    # Let's simplify and just concat them for a unique identifier.
+    
+    sub_code = s1 | (s2 << 4) | (s3 << 8) | (s4 << 12)
+    
+    return page_num, sub_code

src/teletext/models.py

@@ -0,0 +1,93 @@
+from dataclasses import dataclass, field
+from typing import List, Optional
+
+@dataclass
+class Packet:
+    """
+    Represents a single Teletext packet (Row).
+    In T42, we have 42 bytes:
+    Byte 0-1: Magazine and Row Address (Hamming 8/4 encoding)
+    Byte 2-41: Data bytes (40 bytes)
+    """
+    original_data: bytes
+    magazine: int = field(init=False)
+    row: int = field(init=False)
+    data: bytearray = field(init=False)
+
+    def __post_init__(self):
+        if len(self.original_data) != 42:
+            raise ValueError(f"Packet must be 42 bytes, got {len(self.original_data)}")
+        
+        # Parse Magazine and Row from the first 2 bytes (Hamming 8/4)
+        # MRAG (Magazine + Row Address Group)
+        # Byte 0: P1 D1 P2 D2 P3 D3 P4 D4
+        # Byte 1: P1 D1 P2 D2 P3 D3 P4 D4
+        
+        b1 = self.original_data[0]
+        b2 = self.original_data[1]
+        
+        # De-interleave Hamming bits to get M (3 bits) and R (5 bits)
+        # This is the "basic" interpretation. 
+        # For a robust editor we assume the input T42 is valid or we just store bytes.
+        # But we need Mag/Row to organize pages.
+        
+        # Decode Hamming 8/4 logic is complex to implementation from scratch correctly 
+        # without a reference, but usually D1, D2, D3, D4 are at bit positions 1, 3, 5, 7 
+        # (0-indexed, where 0 is LSB). 
+        # Let's perform a simple extraction assuming no bit errors for now.
+        
+        def decode_hamming_8_4(byte_val):
+            # Extract data bits: bits 1, 3, 5, 7
+            return ((byte_val >> 1) & 1) | \
+                   (((byte_val >> 3) & 1) << 1) | \
+                   (((byte_val >> 5) & 1) << 2) | \
+                   (((byte_val >> 7) & 1) << 3)
+
+        d1 = decode_hamming_8_4(b1)
+        d2 = decode_hamming_8_4(b2)
+        
+        # Magazine is 3 bits (Logic is specific: Mag 8 is encoded as 0)
+        # Row is 5 bits.
+        
+        # According to Spec (ETSI EN 300 706):
+        # b1 encoded: M1 M2 M3 R1
+        # b2 encoded: R2 R3 R4 R5
+        
+        self.magazine = (d1 & 0b0111) 
+        if self.magazine == 0:
+            self.magazine = 8
+            
+        row_low_bit = (d1 >> 3) & 1
+        row_high_bits = d2
+        self.row = (row_high_bits << 1) | row_low_bit
+        
+        self.data = bytearray(self.original_data[2:])
+
+    @property
+    def is_header(self):
+        return self.row == 0
+
+@dataclass
+class Page:
+    """
+    Represents a Teletext Page (e.g., 100).
+    Can have multiple subpages.
+    """
+    magazine: int
+    page_number: int  # 00-99
+    sub_code: int = 0 # Subpage code (0000 to 3F7F hex usually, simplest is 0-99 equivalent)
+    packets: List[Packet] = field(default_factory=list)
+    
+    @property
+    def full_page_number(self):
+        return f"{self.magazine}{self.page_number:02d}"
+
+@dataclass
+class TeletextService:
+    """
+    Container for all pages.
+    """
+    pages: List[Page] = field(default_factory=list)
+    # We also keep a flat list of all packets to preserve order on save
+    all_packets: List[Packet] = field(default_factory=list)
+

src/teletext/renderer.py

@@ -0,0 +1,274 @@
+
+from PyQt6.QtWidgets import QWidget
+from PyQt6.QtGui import QPainter, QColor, QFont, QImage, QBrush, QPen
+from PyQt6.QtCore import Qt, QRect, QSize, pyqtSignal
+
+from .models import Page, Packet
+from .charsets import get_char
+
+# Teletext Palette
+COLORS = [
+    QColor(0, 0, 0),       # Black
+    QColor(255, 0, 0),     # Red
+    QColor(0, 255, 0),     # Green
+    QColor(255, 255, 0),   # Yellow
+    QColor(0, 0, 255),     # Blue
+    QColor(255, 0, 255),   # Magenta
+    QColor(0, 255, 255),   # Cyan
+    QColor(255, 255, 255)  # White
+]
+
+class TeletextCanvas(QWidget):
+    def __init__(self, parent=None):
+        super().__init__(parent)
+        self.setMinimumSize(480, 500) # 40x12 * 25x20 approx
+        self.page: Page = None
+        self.subset_idx = 0 # Default English
+        
+        # Teletext is 40 columns x 25 rows
+        # We will render to a fixed size QImage and scale it
+        self.cols = 40
+        self.rows = 25
+        self.cell_w = 12
+        self.cell_h = 20
+        self.img_w = self.cols * self.cell_w
+        self.img_h = self.rows * self.cell_h
+        
+        self.buffer = QImage(self.img_w, self.img_h, QImage.Format.Format_RGB32)
+        self.buffer.fill(Qt.GlobalColor.black)
+        
+        # Font for text
+        self.font = QFont("Courier New", 14)
+        self.font.setStyleHint(QFont.StyleHint.Monospace)
+        self.font.setBold(True)
+
+        # Cursor state
+        self.cursor_x = 0
+        self.cursor_y = 0
+        self.cursor_visible = True
+        # Blinking cursor timer could be added, for now static inverted is fine or toggle on timer elsewhere
+
+    def set_cursor(self, x, y):
+        self.cursor_x = max(0, min(self.cols - 1, x))
+        self.cursor_y = max(0, min(self.rows - 1, y))
+        self.update()
+
+    def move_cursor(self, dx, dy):
+        self.cursor_x = max(0, min(self.cols - 1, self.cursor_x + dx))
+        self.cursor_y = max(0, min(self.rows - 1, self.cursor_y + dy))
+        self.update()
+
+    def set_page(self, page: Page):
+        self.page = page
+        self.cursor_x = 0
+        self.cursor_y = 0
+        self.redraw()
+        self.update()
+
+    def handle_input(self, text):
+        if not self.page:
+            return
+            
+        # Find packet for current row
+        packet = None
+        for p in self.page.packets:
+            if p.row == self.cursor_y:
+                packet = p
+                break
+        
+        if packet:
+            # Edit the data
+            # Data bytes start at index 0 of packet.data corresponding to Col 0?
+            # Standard Teletext row is 40 chars. Packet data is 40 bytes.
+            if 0 <= self.cursor_x < 40:
+                # Get ASCII value
+                # We need to Reverse Map chars to Teletext Bytes if we want full suppport
+                # For now, just taking ord() for basic ASCII 
+                # TODO: reverse lookup for National Chars
+                
+                # Check if text is a single char
+                if len(text) == 1:
+                    byte_val = ord(text)
+                    # Simple filter
+                    if byte_val > 255: byte_val = 0x3F # ?
+                    
+                    packet.data[self.cursor_x] = byte_val
+                    self.redraw()
+                    self.move_cursor(1, 0)
+        else:
+            # Create a packet if it doesn't exist for this row?
+            # Creating new packets in a T42 stream is tricky (insertion).
+            # For now, only edit existing rows.
+            pass
+        
+    def redraw(self):
+        self.buffer.fill(Qt.GlobalColor.black)
+        painter = QPainter(self.buffer)
+        painter.setFont(self.font)
+        
+        if not self.page:
+            painter.setPen(Qt.GlobalColor.white)
+            painter.drawText(10, 20, "No Page Loaded")
+            painter.end()
+            return
+            
+        # Draw each packet
+        # Initialize a grid of empty chars
+        grid = [None] * 26 # 0-25
+        
+        for p in self.page.packets:
+            if 0 <= p.row <= 25:
+                grid[p.row] = p
+                
+        for r in range(25):
+            packet = grid[r]
+            self.draw_row(painter, r, packet)
+            
+        painter.end()
+
+    def draw_row(self, painter, row, packet):
+        # Default State at start of row
+        fg = COLORS[7] # White
+        bg = COLORS[0] # Black
+        graphics_mode = False
+        contiguous = True # Mosaic
+        hold_graphics = False
+        held_char = 0x20 # Space
+        
+        y = row * self.cell_h
+        
+        data = b''
+        if packet:
+            data = packet.data # 40 bytes
+        else:
+            data = b'\x20' * 40
+            
+        # Header string for Row 0 columns 0-7
+        header_prefix = ""
+        if row == 0 and self.page:
+            header_prefix = f"P{self.page.magazine}{self.page.page_number:02d}"
+            # Pad to 8 chars
+            header_prefix = header_prefix.ljust(8)
+            
+        for c in range(40):
+            x = c * self.cell_w
+            
+            # Decide byte value
+            if row == 0 and c < 8:
+                # Use generated header prefix
+                byte_val = ord(header_prefix[c])
+            else:
+                byte_val = data[c] if c < len(data) else 0x20
+                
+            byte_val &= 0x7F # Strip parity
+            
+            # Control Codes
+            is_control = False
+            
+            if byte_val < 0x20:
+                is_control = True
+                # Handle control codes
+                if 0x00 <= byte_val <= 0x07: # Alpha Color
+                    fg = COLORS[byte_val]
+                    graphics_mode = False
+                elif 0x10 <= byte_val <= 0x17: # Mosaic Color
+                    fg = COLORS[byte_val - 0x10]
+                    graphics_mode = True
+                elif byte_val == 0x1C: # Black BG
+                    bg = COLORS[0]
+                elif byte_val == 0x1D: # New BG
+                    bg = fg
+                elif byte_val == 0x0C: # Normal Height
+                    pass 
+                elif byte_val == 0x0D: # Double Height
+                    pass # Not implemented yet
+                elif byte_val == 0x19: # Contiguous Graphics
+                    contiguous = True
+                elif byte_val == 0x1A: # Separated Graphics
+                    contiguous = False
+                elif byte_val == 0x1E: # Hold Graphics
+                    hold_graphics = True
+                elif byte_val == 0x1F: # Release Graphics
+                    hold_graphics = False
+            
+            # Draw Background
+            painter.fillRect(x, y, self.cell_w, self.cell_h, bg)
+            
+            # Draw Foreground
+            if is_control:
+                # "Set-at" spacing attribute? Teletext control codes occupy a space
+                # unless "Hold Graphics" replaces it with previous graphic char.
+                if hold_graphics and graphics_mode:
+                    self.draw_mosaic(painter, x, y, held_char, fg, contiguous)
+                else:
+                    # Draw space (nothing, since we filled BG)
+                    pass
+            else:
+                if graphics_mode:
+                    # Mosaic Graphics
+                    if (0x20 <= byte_val <= 0x3F) or (0x60 <= byte_val <= 0x7F):
+                        self.draw_mosaic(painter, x, y, byte_val, fg, contiguous)
+                        held_char = byte_val
+                    else:
+                        # Capital letter in graphics mode? Usually shows char?
+                        char = get_char(byte_val, self.subset_idx)
+                        painter.setPen(fg)
+                        painter.drawText(QRect(x, y, self.cell_w, self.cell_h), Qt.AlignmentFlag.AlignCenter, char)
+                        held_char = 0x20
+                else:
+                    # Alphanumeric
+                    char = get_char(byte_val, self.subset_idx)
+                    painter.setPen(fg)
+                    painter.drawText(QRect(x, y, self.cell_w, self.cell_h), Qt.AlignmentFlag.AlignCenter, char)
+            # Draw Cursor
+            # Invert the cell at cursor position
+            if self.cursor_visible and c == self.cursor_x and row == self.cursor_y:
+                 painter.setCompositionMode(QPainter.CompositionMode.RasterOp_NotSourceXorDestination)
+                 # XOR with white (creates inversion)
+                 painter.fillRect(x, y, self.cell_w, self.cell_h, QColor(255, 255, 255))
+                 painter.setCompositionMode(QPainter.CompositionMode.CompositionMode_SourceOver)
+
+    def draw_mosaic(self, painter, x, y, char_code, color, contiguous):
+        val = char_code & 0x7F
+        bits = 0
+        if val >= 0x20:
+            bits = val - 0x20
+            
+        blocks = [
+            (0, 0), (1, 0), # Top
+            (0, 1), (1, 1), # Mid
+            (0, 2), (1, 2)  # Bot
+        ]
+        
+        bit_mask = [1, 2, 4, 8, 16, 64] # 64 is bit 6
+        
+        bw = self.cell_w / 2
+        bh = self.cell_h / 3
+        
+        if not contiguous:
+            bw -= 1
+            bh -= 1
+        
+        painter.setPen(Qt.PenStyle.NoPen)
+        painter.setBrush(QBrush(color))
+        
+        for i in range(6):
+            if bits & bit_mask[i]:
+                bx = x + blocks[i][0] * (self.cell_w / 2)
+                by = y + blocks[i][1] * (self.cell_h / 3)
+                
+                if not contiguous:
+                    bx += 1
+                    by += 1
+                    
+                painter.drawRect(QRect(int(bx), int(by), int(bw), int(bh)))
+
+    def paintEvent(self, event):
+        painter = QPainter(self)
+        target_rect = self.rect()
+        scaled = self.buffer.scaled(target_rect.size(), Qt.AspectRatioMode.KeepAspectRatio, Qt.TransformationMode.FastTransformation)
+        
+        ox = (target_rect.width() - scaled.width()) // 2
+        oy = (target_rect.height() - scaled.height()) // 2
+        
+        painter.drawImage(ox, oy, scaled)

src/teletext/ui.py

@@ -0,0 +1,152 @@
+
+import os
+from PyQt6.QtWidgets import (QMainWindow, QWidget, QVBoxLayout, QHBoxLayout, 
+                             QTreeWidget, QTreeWidgetItem, QFileDialog, QMenuBar, QMenu, QMessageBox)
+from PyQt6.QtGui import QAction, QKeyEvent
+from PyQt6.QtCore import Qt
+
+from .io import load_t42, save_t42
+from .renderer import TeletextCanvas
+from .models import TeletextService, Page, Packet
+
+class MainWindow(QMainWindow):
+    def __init__(self):
+        super().__init__()
+        self.setWindowTitle("Teletext Editor")
+        self.resize(1024, 768)
+        
+        self.service = TeletextService()
+        self.current_page: Page = None
+        
+        # UI Components
+        self.central_widget = QWidget()
+        self.setCentralWidget(self.central_widget)
+        
+        self.layout = QHBoxLayout(self.central_widget)
+        
+        # Left Panel: Page Tree
+        self.tree = QTreeWidget()
+        self.tree.setHeaderLabel("Pages")
+        self.tree.setFixedWidth(200)
+        self.tree.itemClicked.connect(self.on_page_selected)
+        self.layout.addWidget(self.tree)
+        
+        # Center: Teletext Canvas
+        self.canvas = TeletextCanvas()
+        self.layout.addWidget(self.canvas, 1) # Expand
+        
+        # Menus
+        self.create_menus()
+        
+    def create_menus(self):
+        menu_bar = self.menuBar()
+        
+        file_menu = menu_bar.addMenu("File")
+        
+        open_action = QAction("Open T42...", self)
+        open_action.triggered.connect(self.open_file)
+        file_menu.addAction(open_action)
+        
+        save_action = QAction("Save T42...", self)
+        save_action.triggered.connect(self.save_file)
+        file_menu.addAction(save_action)
+        
+        exit_action = QAction("Exit", self)
+        exit_action.triggered.connect(self.close)
+        file_menu.addAction(exit_action)
+        
+        view_menu = menu_bar.addMenu("View")
+        
+        lang_menu = view_menu.addMenu("Language")
+        langs = ["English", "German", "Swedish/Finnish", "Italian", "French", "Portuguese/Spanish", "Turkish", "Romania"]
+        for i, lang in enumerate(langs):
+            action = QAction(lang, self)
+            action.setData(i)
+            action.triggered.connect(self.set_language)
+            lang_menu.addAction(action)
+
+    def set_language(self):
+        action = self.sender()
+        if action:
+            idx = action.data()
+            self.canvas.subset_idx = idx
+            self.canvas.redraw()
+            self.canvas.update()
+
+    def open_file(self):
+        fname, _ = QFileDialog.getOpenFileName(self, "Open T42", "", "Teletext Files (*.t42);;All Files (*)")
+        if fname:
+            try:
+                self.service = load_t42(fname)
+                self.populate_tree()
+                QMessageBox.information(self, "Loaded", f"Loaded {len(self.service.pages)} pages.")
+            except Exception as e:
+                QMessageBox.critical(self, "Error", f"Failed to load file: {e}")
+
+    def save_file(self):
+        fname, _ = QFileDialog.getSaveFileName(self, "Save T42", "", "Teletext Files (*.t42);;All Files (*)")
+        if fname:
+            try:
+                save_t42(fname, self.service)
+                QMessageBox.information(self, "Saved", "File saved successfully.")
+            except Exception as e:
+                QMessageBox.critical(self, "Error", f"Failed to save file: {e}")
+
+    def populate_tree(self):
+        self.tree.clear()
+        
+        # Group by Magazine
+        mags = {}
+        for p in self.service.pages:
+            if p.magazine not in mags:
+                mags[p.magazine] = QTreeWidgetItem([f"Magazine {p.magazine}"])
+                self.tree.addTopLevelItem(mags[p.magazine])
+            
+            # Format: PPP-SS (Page-Subcode)
+            # Create Item
+            # Subcode is complicated to display "nicely" without decoding, 
+            # let's just show hex or raw for now if not standard 0000.
+            
+            label = f"{p.page_number:02d} (Sub: {p.sub_code:04X})"
+            item = QTreeWidgetItem([label])
+            item.setData(0, Qt.ItemDataRole.UserRole, p)
+            mags[p.magazine].addChild(item)
+            
+        self.tree.expandAll()
+
+    def on_page_selected(self, item, column):
+        page = item.data(0, Qt.ItemDataRole.UserRole)
+        if isinstance(page, Page):
+            self.current_page = page
+            self.canvas.set_page(page)
+            # Also set window focus to canvas or handle key events?
+            self.canvas.setFocus()
+            
+    # Input Handling (Editor Logic)
+    def keyPressEvent(self, event: QKeyEvent):
+        if not self.current_page:
+            return
+            
+        key = event.key()
+        text = event.text()
+        
+        # Navigation
+        if key == Qt.Key.Key_Up:
+            self.canvas.move_cursor(0, -1)
+        elif key == Qt.Key.Key_Down:
+            self.canvas.move_cursor(0, 1)
+        elif key == Qt.Key.Key_Left:
+            self.canvas.move_cursor(-1, 0)
+        elif key == Qt.Key.Key_Right:
+            self.canvas.move_cursor(1, 0)
+        else:
+            # Typing
+            # Filter non-printable
+            if text and len(text) == 1 and 32 <= ord(text) <= 126:
+                self.canvas.handle_input(text)
+            elif key == Qt.Key.Key_Backspace:
+                # Move back and delete
+                self.canvas.move_cursor(-1, 0)
+                self.canvas.handle_input(' ')
+                self.canvas.move_cursor(-1, 0) # Compensate for the auto-advance logic if any
+