Added a live logging window

res/design.ui

@@ -8,19 +8,19 @@
     <x>0</x>
     <y>0</y>
     <width>786</width>
-    <height>426</height>
+    <height>598</height>
    </rect>
   </property>
   <property name="minimumSize">
    <size>
     <width>786</width>
-    <height>426</height>
+    <height>450</height>
    </size>
   </property>
   <property name="maximumSize">
    <size>
     <width>786</width>
-    <height>426</height>
+    <height>598</height>
    </size>
   </property>
   <property name="font">
@@ -35,7 +35,22 @@
    <iconset resource="resources.qrc">
     <normaloff>:/resources/icon.ico</normaloff>:/resources/icon.ico</iconset>
   </property>
+  <property name="styleSheet">
+   <string notr="true">QMainWindow::separator { height: 0px; width: 0px; }</string>
+  </property>
   <widget class="QWidget" name="central_widget">
+   <property name="minimumSize">
+    <size>
+     <width>0</width>
+     <height>404</height>
+    </size>
+   </property>
+   <property name="maximumSize">
+    <size>
+     <width>16777215</width>
+     <height>404</height>
+    </size>
+   </property>
    <widget class="QLabel" name="x_label">
     <property name="geometry">
      <rect>
@@ -930,9 +945,105 @@
     <addaction name="action_save_profile_as"/>
     <addaction name="action_load_profile"/>
    </widget>
+   <widget class="QMenu" name="menu_view">
+    <property name="title">
+     <string>View</string>
+    </property>
+    <addaction name="action_toggle_logs"/>
+   </widget>
    <addaction name="menu_file"/>
+   <addaction name="menu_view"/>
    <addaction name="menu_help"/>
   </widget>
+  <widget class="QStatusBar" name="status_bar">
+   <property name="styleSheet">
+    <string notr="true">QStatusBar { border-top: 1px solid palette(mid); }
+ClickableLabel { padding: 1px 16px 1px 6px; }
+ClickableLabel:hover { background-color: palette(midlight); }</string>
+   </property>
+   <property name="sizeGripEnabled">
+    <bool>false</bool>
+   </property>
+   <widget class="ClickableLabel" name="log_footer_label">
+    <property name="geometry">
+     <rect>
+      <x>0</x>
+      <y>0</y>
+      <width>100</width>
+      <height>30</height>
+     </rect>
+    </property>
+    <property name="sizePolicy">
+     <sizepolicy hsizetype="Expanding" vsizetype="Preferred">
+      <horstretch>1</horstretch>
+      <verstretch>0</verstretch>
+     </sizepolicy>
+    </property>
+    <property name="toolTip">
+     <string>Last log message. Click to show the full log.</string>
+    </property>
+    <property name="text">
+     <string/>
+    </property>
+   </widget>
+  </widget>
+  <widget class="QDockWidget" name="log_dock">
+   <property name="styleSheet">
+    <string notr="true">QDockWidget::title { padding: 6px;  }</string>
+   </property>
+   <property name="features">
+    <set>QDockWidget::DockWidgetFeature::NoDockWidgetFeatures</set>
+   </property>
+   <property name="windowTitle">
+    <string>1 (docker header can't be hidden in editor, removed at runtime)
+2 (line count height is approximate, making header appear about 2 lines)</string>
+   </property>
+   <attribute name="dockWidgetArea">
+    <number>8</number>
+   </attribute>
+   <widget class="QWidget" name="log_dock_contents">
+    <layout class="QVBoxLayout" name="log_dock_layout">
+     <property name="leftMargin">
+      <number>3</number>
+     </property>
+     <property name="topMargin">
+      <number>0</number>
+     </property>
+     <property name="rightMargin">
+      <number>3</number>
+     </property>
+     <property name="bottomMargin">
+      <number>0</number>
+     </property>
+     <item>
+      <widget class="QPlainTextEdit" name="log_history_view">
+       <property name="font">
+        <font>
+         <family>monospace</family>
+        </font>
+       </property>
+       <property name="readOnly">
+        <bool>true</bool>
+       </property>
+       <property name="plainText">
+        <string>3
+4
+5
+6
+7
+8
+9
+10
+11</string>
+       </property>
+       <property name="textInteractionFlags">
+        <set>Qt::TextInteractionFlag::TextSelectableByKeyboard|Qt::TextInteractionFlag::TextSelectableByMouse</set>
+       </property>
+      </widget>
+     </item>
+    </layout>
+   </widget>
+  </widget>
   <action name="action_view_help">
    <property name="text">
     <string>View Help</string>
@@ -1031,7 +1142,25 @@
     <enum>QAction::MenuRole::AboutQtRole</enum>
    </property>
   </action>
+  <action name="action_toggle_logs">
+   <property name="text">
+    <string>Toggle Logs</string>
+   </property>
+   <property name="shortcut">
+    <string>Ctrl+L</string>
+   </property>
+   <property name="shortcutContext">
+    <enum>Qt::ShortcutContext::ApplicationShortcut</enum>
+   </property>
+  </action>
  </widget>
+ <customwidgets>
+  <customwidget>
+   <class>ClickableLabel</class>
+   <extends>QLabel</extends>
+   <header>log_capture</header>
+  </customwidget>
+ </customwidgets>
  <tabstops>
   <tabstop>split_image_folder_input</tabstop>
   <tabstop>x_spinbox</tabstop>

src/AutoSplit.py

@@ -1,6 +1,7 @@
 #!/usr/bin/env python3
 
 import os
+import re
 import sys
 import warnings
 
@@ -33,6 +34,13 @@ def do_nothing(*_): ...
     # os.environ.setdefault("QT_DEBUG_PLUGINS", "1")
 
 # ruff: disable[E402] # https://github.com/astral-sh/ruff/issues/21423
+
+# Tee stdout/stderr as soon as possible, so import-time warnings and errors are also caught.
+# This must run after the platform-specific setup above (which has to happen before any Qt import).
+import log_capture
+
+log_capture.install()
+
 import signal
 from collections.abc import Callable
 from copy import deepcopy
@@ -43,7 +51,7 @@ def do_nothing(*_): ...
 import cv2
 from PySide6 import QtCore, QtGui
 from PySide6.QtTest import QTest
-from PySide6.QtWidgets import QApplication, QFileDialog, QLabel, QMainWindow, QMessageBox
+from PySide6.QtWidgets import QApplication, QFileDialog, QLabel, QMainWindow, QMessageBox, QWidget
 
 import error_messages
 import user_profile
@@ -100,6 +108,12 @@ def do_nothing(*_): ...
 
 CHECK_FPS_ITERATIONS = 10
 
+LOG_STDERR_COLOR = QtGui.QColor("#c0392b")
+"""Color for log lines that came from stderr (warnings, errors, tracebacks).
+Source: Pomegranate from https://flatuicolors.com/palette/defo"""
+LOG_LOCATION_PREFIX_RE = re.compile(r"^\S+:\d+:\s+")
+"""Matches a leading `path:lineno:` (e.g. from a warning) to drop it from the footer preview."""
+
 
 class AutoSplit(QMainWindow, design.Ui_MainWindow):
     # Parse command line args
@@ -173,6 +187,7 @@ def _show_error_signal_slot(error_message_box: Callable[..., object]):
             f"AutoSplit v{AUTOSPLIT_VERSION}"
             + (" (externally controlled)" if self.is_auto_controlled else "")
         )
+        self._setup_log_footer()
 
         # Hotkeys need to be initialized to be passed as thread arguments in hotkeys.py
         for hotkey in HOTKEYS:
@@ -197,6 +212,7 @@ def _show_error_signal_slot(error_message_box: Callable[..., object]):
             self.update_auto_control.start()
 
         # Connecting menu actions
+        self.action_toggle_logs.triggered.connect(self._toggle_log_panel)
         self.action_view_help.triggered.connect(view_help)
         self.action_about.triggered.connect(lambda: open_about(self))
         self.action_about_qt.triggered.connect(about_qt)
@@ -283,6 +299,98 @@ def _update_checker_widget_signal_slot(latest_version: str, check_on_open: bool)
 
     # FUNCTIONS
 
+    # region Log footer panel
+    _last_log_footer_entry: log_capture.LogLine | None = None
+    """Last (timestamp, text, is_stderr) shown in the footer, kept so it can be re-rendered."""
+
+    _collapsed_height = 0
+    """
+    Window height with the log panel collapsed; captured from the .ui to fix the height per state.
+    """
+
+    _log_panel_height = 0
+    """Window growth when the panel opens; derived from the .ui (expanded - collapsed height)."""
+
+    def _setup_log_footer(self):
+        """Wire up the clickable log footer and the expandable log history panel."""
+        # Both come from the .ui: collapsed = minimumSize height, panel = designed (expanded)
+        # geometry height minus that. Captured before setFixedHeight() overwrites minimumHeight().
+        self._collapsed_height = self.minimumHeight()
+        self._log_panel_height = self.height() - self._collapsed_height
+        # The status bar doesn't add() its .ui child, and stretch isn't expressible there.
+        self.status_bar.addWidget(self.log_footer_label, 1)
+        self.status_bar.setContentsMargins(0, 0, 0, 0)  # Let the label's padding define the insets.
+        # An empty title bar (collapses to no height) makes the dock read as an inline panel.
+        self.log_dock.setTitleBarWidget(QWidget())
+        self.log_history_view.setFont(  # Use the system's monospace font.
+            QtGui.QFontDatabase.systemFont(QtGui.QFontDatabase.SystemFont.FixedFont)
+        )
+        # Drop the .ui's Designer-only placeholders (kept there as layout/line-count notes).
+        self.log_history_view.clear()
+        self.log_dock.setWindowTitle("")
+        self.log_footer_label.clicked.connect(self._toggle_log_panel)
+
+        # Include logs already emitted before connecting live.
+        history = log_capture.LOG_EMITTER.history()
+        for log_line in history:
+            self._append_log_line(log_line)
+        if history:
+            self._update_log_footer(history[-1])
+        # Each live line goes into the panel and updates the footer
+        # (append first, so the footer's single-line preview reflects the line that was just added).
+        log_capture.LOG_EMITTER.line_logged.connect(self._append_log_line)
+        log_capture.LOG_EMITTER.line_logged.connect(self._update_log_footer)
+
+        # Restore the panel's last expanded/collapsed state.
+        self._set_log_panel_visible(
+            show=cast("bool", user_profile.QT_SETTINGS.value("log_panel_visible", False, type=bool))
+        )
+
+    def _set_log_panel_visible(self, show: bool):  # noqa: FBT001 # boolean value setter, not an arbitrary flag
+        self.log_dock.setVisible(show)
+        # Fix the height per state so it can't be dragged to over-expand or hide content.
+        self.setFixedHeight(self._collapsed_height + (self._log_panel_height if show else 0))
+        self._refresh_log_footer()  # Flip the chevron to match the new state.
+
+    def _toggle_log_panel(self):
+        self._set_log_panel_visible(not self.log_dock.isVisible())
+        user_profile.QT_SETTINGS.setValue("log_panel_visible", self.log_dock.isVisible())
+
+    def _append_log_line(self, log_line: log_capture.LogLine):
+        timestamp, text, is_stderr = log_line
+        cursor = self.log_history_view.textCursor()
+        cursor.movePosition(QtGui.QTextCursor.MoveOperation.End)
+        char_format = QtGui.QTextCharFormat()
+        if is_stderr:
+            char_format.setForeground(LOG_STDERR_COLOR)
+        # Newline before each entry (not after) so there is no trailing blank line.
+        prefix = "" if self.log_history_view.document().isEmpty() else "\n"
+        # Align a multi-line entry's continuation lines under the text (past the timestamp).
+        body = text.replace("\n", "\n" + " " * (len(timestamp) + 1))
+        cursor.insertText(f"{prefix}{timestamp} {body}", char_format)
+        scrollbar = self.log_history_view.verticalScrollBar()
+        scrollbar.setValue(scrollbar.maximum())
+
+    def _update_log_footer(self, log_line: log_capture.LogLine):
+        self._last_log_footer_entry = log_line
+        self._refresh_log_footer()
+
+    def _refresh_log_footer(self):
+        if self._last_log_footer_entry is None:
+            return
+        timestamp, text, is_stderr = self._last_log_footer_entry
+        # Footer is single-line and shows the message directly (no path prefix).
+        # First line of an (already-relativized) entry; drops a leading `path:lineno:` prefix.
+        first_line = LOG_LOCATION_PREFIX_RE.sub("", text.split("\n", 1)[0])
+        # Footer affordances hinting it expands a log panel: a chevron and hover/border styling.
+        # Not using isVisible()) as it's incorrect during startup restore, before window is shown
+        chevron = "▶" if self.log_dock.isHidden() else "▲"
+        stderr_color = f"color: {LOG_STDERR_COLOR.name()};" if is_stderr else ""
+        self.log_footer_label.setStyleSheet(stderr_color)
+        self.log_footer_label.set_elided_text(f"{chevron}  {timestamp} {first_line}")
+
+    # endregion
+
     def __browse(self):
         # User selects the file with the split images in it.
         new_split_image_directory = QFileDialog.getExistingDirectory(

src/error_messages.py

@@ -9,7 +9,7 @@
 from types import TracebackType
 from typing import TYPE_CHECKING, NoReturn
 
-from PySide6 import QtCore, QtWidgets
+from PySide6 import QtCore, QtGui, QtWidgets
 
 from utils import FROZEN, GITHUB_REPOSITORY
 
@@ -41,6 +41,10 @@ def _set_text_message(
     kill_button: str = "",
     accept_button: str = "",
 ):
+    # Also surface the error message in the logs
+    plain_message = QtGui.QTextDocumentFragment.fromHtml(message).toPlainText()
+    sys.stderr.write(f"{plain_message}\n{details}\n" if details else f"{plain_message}\n")
+
     message_box = QtWidgets.QMessageBox()
     message_box.setWindowTitle("Error")
     message_box.setTextFormat(QtCore.Qt.TextFormat.RichText)