Keep the wheel off the boxes and a floor under the window

Two things the scrolling tabs brought with them.

A combo box and a spin box read the wheel as a change of value, and Qt
hands them the focus before delivering it. Now that every tab scrolls,
rolling down the API tab with the pointer over the model box picks a
different model on the way past, and Save writes it down. The boxes take
the focus by click or by tab only, and a wheel that arrives at one
without the focus is refused rather than swallowed, so it carries on up
to the scroll area and the page moves instead.

A tab that scrolls also asks for no height of its own, which left
nothing to stop the window being dragged down to a tab bar and half a
button. It has a floor now, and the floor never asks for more room than
the screen was just found to have.

settings_ui.py

@@ -4,12 +4,12 @@ import os
 import shutil
 import threading
 
-from PyQt6.QtCore import QRect, Qt, QUrl, pyqtSignal
+from PyQt6.QtCore import QEvent, QObject, QRect, Qt, QUrl, pyqtSignal
 from PyQt6.QtGui import QDesktopServices, QGuiApplication, QKeySequence, QShortcut
 from PyQt6.QtWidgets import (
-    QAbstractItemView, QCheckBox, QComboBox, QDialog, QDialogButtonBox,
-    QFileDialog, QFormLayout, QGroupBox, QHBoxLayout, QLabel, QLineEdit,
-    QListWidget, QListWidgetItem, QMenu, QMessageBox, QPlainTextEdit,
+    QAbstractItemView, QAbstractSpinBox, QCheckBox, QComboBox, QDialog,
+    QDialogButtonBox, QFileDialog, QFormLayout, QGroupBox, QHBoxLayout, QLabel,
+    QLineEdit, QListWidget, QListWidgetItem, QMenu, QMessageBox, QPlainTextEdit,
     QPushButton, QScrollArea, QSpinBox, QTabWidget, QVBoxLayout, QWidget,
 )
 
@@ -159,6 +159,26 @@ class WrappedLabel(QLabel):
                 self.fontMetrics().boundingRect(box, wrap, self.text()).height())
 
 
+class WheelGuard(QObject):
+    """Keeps a rolled wheel off the box the pointer only passed over.
+
+    A combo box and a spin box both read the wheel as a change of value, and
+    every tab scrolls now: rolling down the API tab with the pointer over the
+    model box would pick a different model on the way past, and the setting is
+    saved without anybody having chosen it. The wheel counts once the box has
+    been clicked into; before that it is handed back to the page underneath,
+    which is what the roll was for.
+    """
+
+    def eventFilter(self, box, event):
+        if event.type() == QEvent.Type.Wheel and not box.hasFocus():
+            # Refused rather than swallowed. An unaccepted wheel event carries
+            # on up the parents to the scroll area, so the page still moves.
+            event.ignore()
+            return True
+        return super().eventFilter(box, event)
+
+
 class LocalModelBox(QGroupBox):
     """The program, the model, and the two downloads that put them there.
 
@@ -516,6 +536,10 @@ class SettingsWindow(QDialog):
         self.transcriber = FileTranscriber(conf, self)
         self.setWindowTitle(t("Dikte Settings"))
 
+        # One for the whole window, parented to it so it outlives the boxes it
+        # watches and goes when they do.
+        self._wheel_guard = WheelGuard(self)
+
         tabs = self.tabs = QTabWidget(self)
         tabs.addTab(self._scrolled(self._general_tab()), t("General"))
         self.api_tab_index = tabs.addTab(
@@ -560,8 +584,7 @@ class SettingsWindow(QDialog):
         if not conf.transcribe_ready():
             self.tabs.setCurrentIndex(self.api_tab_index)
 
-    @staticmethod
-    def _scrolled(page):
+    def _scrolled(self, page):
         """A tab that scrolls instead of growing the window to fit."""
         # Every tab goes through here. A page kept at its full height passes
         # that height on as the window's minimum, and a tall one (the API tab
@@ -571,6 +594,12 @@ class SettingsWindow(QDialog):
         area.setWidgetResizable(True)
         area.setFrameShape(QScrollArea.Shape.NoFrame)
         area.setWidget(page)
+        for box in page.findChildren((QComboBox, QAbstractSpinBox)):
+            # Focus by click or by tab, not by wheel. Qt hands the focus over
+            # before it delivers the wheel, so a box left on the default policy
+            # would have it by the time the guard below asked.
+            box.setFocusPolicy(Qt.FocusPolicy.StrongFocus)
+            box.installEventFilter(self._wheel_guard)
         return area
 
     def _size_to_screen(self, width, height):
@@ -582,6 +611,11 @@ class SettingsWindow(QDialog):
             # and the buttons along the bottom stay on screen.
             width = min(width, room.width() - 40)
             height = min(height, room.height() - 80)
+        # Scrolling tabs ask for no height of their own, which leaves nothing to
+        # stop the window being dragged down to a tab bar and half a button. The
+        # floor is a floor and not a demand: it never asks for more room than
+        # the screen has just been found to have.
+        self.setMinimumSize(min(520, width), min(380, height))
         self.resize(width, height)
 
     # ---- tabs ----------------------------------------------------------