Fix QTreeView item hover shift and excessive row padding (#1218)

* Fix QTreeView item hover shift and excessive row padding

Replace mixed margin/padding stylesheet with consistent padding across
all item states, and suppress Qt's focus rectangle with outline: 0.

Fixes #1217.

* Use palette(highlight) borders for hover/selection instead of overriding status colours

Replace static dimgrey/grey background on hover and selected states with
top/bottom borders using the system palette highlight colour. This keeps
the alert status colour (CRITICAL, WARNING, etc.) visible at all times
and works correctly in both dark and light themes.

Fixes #1219.

* Fix unreadable hover/selection on Windows dark mode

Explicitly set background-color and color using palette(highlight) and
palette(highlighted-text) on hover and selected states. Without this,
Windows' native style engine paints its own dark selection background
on top of the model's status colour, making text unreadable.

* Reverse-video hover/selection using each row's own status colours

Replace palette(highlight) with a custom delegate that swaps the row's
foreground and background colours on hover and selection, preserving the
alert status context (CRITICAL red, WARNING yellow, etc.) while still
providing clear visual feedback. Works across all themes and platforms.

* Use reverse-video delegate for status-aware hover and selection

Replace palette(highlight) CSS with a QStyledItemDelegate that swaps
each row's foreground and background colours on hover and selection.
A trivial CSS :hover rule is retained solely to opt Qt into per-item
hover tracking.

The delegate calls super().paint() first, then overdraws background and
text to guarantee the result is never overwritten by native OS styles
(QWindowsVistaStyle, QMacStyle) which ignore option.backgroundBrush.

Includes PyQt5/PyQt6 compatibility guards for QPalette.ColorRole and
Qt.AlignmentFlag enum access.

Tested on KDE Neon, Ubuntu 26.04 (GNOME), and Windows 11.

Fixes #1219.

* Fix delegate text shift on macOS by removing manual text drawing

Replace the post-paint overdraw approach (fillRect + drawText) with
colour swapping in initStyleOption instead. By stripping hover/selected
state flags there, super().paint() draws the item as a plain item,
letting each platform's native style handle text layout with its own
margins. Eliminates the leftward text shift on macOS caused by the
hardcoded adjusted(4, 0, -4, 0) text rect.

---------

Co-authored-by: Dino Korah <691011+codemedic@users.noreply.github.com>

Author: codemedic

Nagstamon/qui/qt.py

@@ -142,6 +142,7 @@
     from PyQt5.QtWidgets import QAbstractItemView, \
         QAction, \
         QApplication, \
+        QStyledItemDelegate, \
         QColorDialog, \
         QComboBox, \
         QDialog, \
@@ -283,6 +284,7 @@ def get_sort_order_value(sort_order):
     from PyQt6.QtWebEngineWidgets import QWebEngineView as WebEngineView
     from PyQt6.QtWidgets import (QAbstractItemView,
                                  QApplication,
+                                 QStyledItemDelegate,
                                  QColorDialog,
                                  QComboBox,
                                  QDialog,

Nagstamon/qui/widgets/treeview.py

@@ -39,25 +39,84 @@
 from Nagstamon.qui.qt import (get_sort_order_value,
                               QAbstractItemView,
                               QAction,
+                              QBrush,
                               QColor,
                               QHeaderView,
                               QKeySequence,
                               QMenu,
                               QObject,
+                              QPalette,
                               QSignalMapper,
                               QSizePolicy,
+                              QStyle,
+                              QStyledItemDelegate,
                               Qt,
                               QThread,
                               QTimer,
                               QTreeView,
                               Signal,
                               Slot)
+
+try:
+    _STATE_HOVER = QStyle.StateFlag.State_MouseOver
+    _STATE_SELECTED = QStyle.StateFlag.State_Selected
+except AttributeError:
+    _STATE_HOVER = QStyle.State_MouseOver
+    _STATE_SELECTED = QStyle.State_Selected
 from Nagstamon.qui.widgets.app import app
 from Nagstamon.qui.widgets.menu import MenuAtCursor
 from Nagstamon.qui.widgets.model import Model
 from Nagstamon.servers import SERVER_TYPES, servers
 
 
+class StatusAwareDelegate(QStyledItemDelegate):
+    """
+    Renders hover and selection as reverse video using each row's own
+    status colours, so the alert context is always visible.
+
+    Colours are swapped in initStyleOption and the hover/selected state flags
+    are stripped there too, so super().paint() draws the item as a plain
+    (non-selected) item. Native OS styles (Windows, macOS) respect
+    backgroundBrush and palette.Text for normal items, so no manual
+    text drawing or post-paint overdraw is needed.
+    """
+
+    # QPalette colour role access differs between PyQt5 (<5.15) and PyQt6
+    try:
+        _ROLE_TEXT = QPalette.ColorRole.Text
+        _ROLE_WINDOW_TEXT = QPalette.ColorRole.WindowText
+    except AttributeError:
+        _ROLE_TEXT = QPalette.Text
+        _ROLE_WINDOW_TEXT = QPalette.WindowText
+
+    def initStyleOption(self, option, index):
+        super().initStyleOption(option, index)
+
+        is_hovered = bool(option.state & _STATE_HOVER)
+        is_selected = bool(option.state & _STATE_SELECTED)
+
+        if not (is_hovered or is_selected):
+            return
+
+        # BackgroundRole and ForegroundRole both return QColor (qbrushes naming is misleading)
+        bg_color = index.data(Qt.ItemDataRole.BackgroundRole)
+        fg_color = index.data(Qt.ItemDataRole.ForegroundRole)
+
+        if bg_color is None or fg_color is None:
+            return
+
+        # Reverse video: swap foreground and background
+        option.backgroundBrush = QBrush(fg_color)
+        option.palette.setColor(self._ROLE_TEXT, bg_color)
+        option.palette.setColor(self._ROLE_WINDOW_TEXT, bg_color)
+
+        # Strip hover/selected so the style engine treats this as a plain item
+        # and uses our backgroundBrush and Text palette colour rather than
+        # the system selection highlight
+        option.state &= ~_STATE_SELECTED
+        option.state &= ~_STATE_HOVER
+
+
 class TreeView(QTreeView):
     """
     attempt to get a less resource-hungry table/tree
@@ -142,17 +201,16 @@ def __init__(self, columncount, rowcount, sort_column, sort_order, server, paren
         self.header().sortIndicatorChanged.connect(self.sort_columns)
 
         # set overall margin and hover colors - to be refined
-        self.setStyleSheet('''QTreeView::item {margin: 5px;}
-                              QTreeView::item:hover {margin: 0px;
-                                                     padding: 5px;
-                                                     color: white;
-                                                     background-color: dimgrey;}
-                              QTreeView::item:selected {margin: 0px;
-                                                        padding: 5px;
-                                                        color: white;
-                                                        background-color: grey;}
+        # The :hover and :selected rules here contain no visual changes — their sole purpose
+        # is to make Qt enable per-item hover tracking so State_MouseOver is set in the delegate.
+        self.setStyleSheet('''QTreeView {outline: 0;}
+                              QTreeView::item {padding: 3px;}
+                              QTreeView::item:hover {padding: 3px;}
+                              QTreeView::item:selected {padding: 3px;}
                             ''')
 
+        self.setItemDelegate(StatusAwareDelegate(self))
+
         # set application font
         self.set_font()