Improve styling and logging for UI font-size zoom

Refine zoom methods in `MainWindow` and font helpers
in `_style` to return `px_size` up the call chain and
log detailed zoom state on each change.

Deats,
- make `_set_qfont_px_size()` return `self.px_size`.
- make `configure_to_dpi()` and `_config_fonts_to_screen()`
  return the new `px_size` up through the call chain.
- add `font_size` to `log.info()` in `zoom_in()`,
  `zoom_out()`, and `reset_zoom()` alongside
  `zoom_step` and `zoom_level(%)`.
- reformat `has_ctrl`/`_has_shift` bitwise checks and
  key-match tuples to multiline style.
- comment out `Shift` modifier requirement for zoom
  hotkeys (now `Ctrl`-only).
- comment out unused `mn_dpi` and `dpi` locals.

Also,
- convert all single-line docstrings to `'''` multiline
  style across zoom and font methods.
- rewrap `configure_to_dpi()` docstring to 67 chars.
- move `from . import _style` to module-level import
  in `_window.py`.
- drop unused `screen` binding in `boundingRect()`.

(this commit msg was generated in some part by [`claude-code`][claude-code-gh])
[claude-code-gh]: https://github.com/anthropics/claude-code

piker/ui/_axes.py

@@ -75,6 +75,9 @@ class Axis(pg.AxisItem):
         self.pi = plotitem
         self._dpi_font = _font
 
+        # store for later recalculation on zoom
+        self._typical_max_str = typical_max_str
+
         self.setTickFont(_font.font)
         font_size = self._dpi_font.font.pixelSize()
 
@@ -156,6 +159,41 @@ class Axis(pg.AxisItem):
     def size_to_values(self) -> None:
         pass
 
+    def update_fonts(self, font: DpiAwareFont) -> None:
+        '''Update font and recalculate axis sizing after zoom change.'''
+        # IMPORTANT: tell Qt we're about to change geometry
+        self.prepareGeometryChange()
+
+        self._dpi_font = font
+        self.setTickFont(font.font)
+        font_size = font.font.pixelSize()
+
+        # recalculate text offset based on new font size
+        text_offset = None
+        if self.orientation in ('bottom',):
+            text_offset = floor(0.25 * font_size)
+        elif self.orientation in ('left', 'right'):
+            text_offset = floor(font_size / 2)
+
+        if text_offset:
+            self.setStyle(tickTextOffset=text_offset)
+
+        # recalculate bounding rect with new font
+        # Note: typical_max_str should be stored from init
+        if not hasattr(self, '_typical_max_str'):
+            self._typical_max_str = '100 000.000  '  # fallback default
+        self.typical_br = font._qfm.boundingRect(self._typical_max_str)
+
+        # Update PyQtGraph's internal text size tracking
+        # This is critical - PyQtGraph uses these internally for auto-expand
+        if self.orientation in ['left', 'right']:
+            self.textWidth = self.typical_br.width()
+        else:
+            self.textHeight = self.typical_br.height()
+
+        # resize axis to fit new font - this triggers PyQtGraph's auto-expand
+        self.size_to_values()
+
     def txt_offsets(self) -> tuple[int, int]:
         return tuple(self.style['tickTextOffset'])
 
@@ -256,7 +294,14 @@ class PriceAxis(Axis):
         self._min_tick = size
 
     def size_to_values(self) -> None:
-        self.setWidth(self.typical_br.width())
+        # Call PyQtGraph's internal width update mechanism
+        # This respects autoExpandTextSpace and updates min/max constraints
+        self._updateWidth()
+        # tell Qt our preferred size changed so layout recalculates
+        self.updateGeometry()
+        # force parent plot item to recalculate its layout
+        if self.pi and hasattr(self.pi, 'updateGeometry'):
+            self.pi.updateGeometry()
 
     # XXX: drop for now since it just eats up h space
 
@@ -300,7 +345,14 @@ class DynamicDateAxis(Axis):
     }
 
     def size_to_values(self) -> None:
-        self.setHeight(self.typical_br.height() + 1)
+        # Call PyQtGraph's internal height update mechanism
+        # This respects autoExpandTextSpace and updates min/max constraints
+        self._updateHeight()
+        # tell Qt our preferred size changed so layout recalculates
+        self.updateGeometry()
+        # force parent plot item to recalculate its layout
+        if self.pi and hasattr(self.pi, 'updateGeometry'):
+            self.pi.updateGeometry()
 
     def _indexes_to_timestrs(
         self,

piker/ui/_exec.py

@@ -203,6 +203,9 @@ def run_qtractor(
     if is_windows:
         window.configure_to_desktop()
 
+    # install global keyboard shortcuts for UI zoom
+    window.install_global_zoom_filter()
+
     # actually render to screen
     window.show()
     app.exec_()

piker/ui/_forms.py

@@ -124,6 +124,13 @@ class Edit(QLineEdit):
         self.sizeHint()
         self.update()
 
+    def update_fonts(self, font: DpiAwareFont) -> None:
+        '''Update font and recalculate widget size.'''
+        self.dpi_font = font
+        self.setFont(font.font)
+        # tell Qt our size hint changed so it recalculates layout
+        self.updateGeometry()
+
     def focus(self) -> None:
         self.selectAll()
         self.show()
@@ -241,6 +248,14 @@ class Selection(QComboBox):
         icon_size = round(h * 0.75)
         self.setIconSize(QSize(icon_size, icon_size))
 
+    def update_fonts(self, font: DpiAwareFont) -> None:
+        '''Update font and recalculate widget size.'''
+        self.setFont(font.font)
+        # recalculate heights with new font
+        self.resize()
+        # tell Qt our size hint changed so it recalculates layout
+        self.updateGeometry()
+
     def set_items(
         self,
         keys: list[str],
@@ -431,6 +446,39 @@ class FieldsForm(QWidget):
         self.fields[key] = select
         return select
 
+    def update_fonts(self) -> None:
+        '''Update font sizes after zoom change.'''
+        from ._style import _font, _font_small
+
+        # update stored font size
+        self._font_size = _font_small.px_size - 2
+
+        # update all labels
+        for name, label in self.labels.items():
+            if hasattr(label, 'update_font'):
+                label.update_font(_font.font, self._font_size - 1)
+
+        # update all fields (edits, selects)
+        for key, field in self.fields.items():
+            # first check for our custom update_fonts method (Edit, Selection)
+            if hasattr(field, 'update_fonts'):
+                field.update_fonts(_font)
+            # then handle stylesheet updates for those without custom methods
+            elif hasattr(field, 'setStyleSheet'):
+                # regenerate stylesheet with new font size
+                field.setStyleSheet(
+                    f"""QLineEdit {{
+                        color : {hcolor('gunmetal')};
+                        font-size : {self._font_size}px;
+                    }}
+                    """
+                )
+                field.setFont(_font.font)
+
+            # for Selection widgets that need style updates
+            if hasattr(field, 'set_style'):
+                field.set_style(color='gunmetal', font_size=self._font_size)
+
 
 async def handle_field_input(
 
@@ -633,6 +681,37 @@ class FillStatusBar(QProgressBar):
         self.setRange(0, int(slots))
         self.setValue(value)
 
+    def update_fonts(self, font_size: int) -> None:
+        '''Update font size after zoom change.'''
+        from ._style import _font_small
+
+        self.font_size = font_size
+        # regenerate stylesheet with new font size
+        self.setStyleSheet(
+            f"""
+            QProgressBar {{
+
+                text-align: center;
+
+                font-size : {self.font_size - 2}px;
+
+                background-color: {hcolor('papas_special')};
+                color : {hcolor('papas_special')};
+
+                border: {self.border_px}px solid {hcolor('default_light')};
+                border-radius: 2px;
+            }}
+            QProgressBar::chunk {{
+
+                background-color: {hcolor('default_spotlight')};
+                color: {hcolor('bracket')};
+
+                border-radius: 2px;
+            }}
+            """
+        )
+        self.setFont(_font_small.font)
+
 
 def mk_fill_status_bar(
 

piker/ui/_label.py

@@ -334,3 +334,19 @@ class FormatLabel(QLabel):
         out = self.fmt_str.format(**fields)
         self.setText(out)
         return out
+
+    def update_font(
+        self,
+        font: QtGui.QFont,
+        font_size: int,
+        font_color: str = 'default_lightest',
+    ) -> None:
+        '''Update font after zoom change.'''
+        self.setStyleSheet(
+            f"""QLabel {{
+                color : {hcolor(font_color)};
+                font-size : {font_size}px;
+            }}
+            """
+        )
+        self.setFont(font)

piker/ui/_position.py

@@ -178,6 +178,26 @@ class SettingsPane:
     # encompasing high level namespace
     order_mode: OrderMode | None = None  # typing: ignore # noqa
 
+    def update_fonts(self) -> None:
+        '''Update font sizes after zoom change.'''
+        from ._style import _font_small
+
+        # update form fields
+        if self.form and hasattr(self.form, 'update_fonts'):
+            self.form.update_fonts()
+
+        # update fill status bar
+        if self.fill_bar and hasattr(self.fill_bar, 'update_fonts'):
+            self.fill_bar.update_fonts(_font_small.px_size)
+
+        # update labels with new fonts
+        if self.step_label:
+            self.step_label.setFont(_font_small.font)
+        if self.pnl_label:
+            self.pnl_label.setFont(_font_small.font)
+        if self.limit_label:
+            self.limit_label.setFont(_font_small.font)
+
     def set_accounts(
         self,
         names: list[str],

piker/ui/_search.py

@@ -174,6 +174,13 @@ class CompleterView(QTreeView):
 
         self.setStyleSheet(f"font: {size}px")
 
+    def update_fonts(self) -> None:
+        '''Update font sizes after zoom change.'''
+        self.set_font_size(_font.px_size)
+        self.setIndentation(_font.px_size)
+        self.setFont(_font.font)
+        self.updateGeometry()
+
     def resize_to_results(
         self,
         w: float | None = 0,
@@ -630,6 +637,29 @@ class SearchWidget(QtWidgets.QWidget):
             | align_flag.AlignLeft,
         )
 
+    def update_fonts(self) -> None:
+        '''Update font sizes after zoom change.'''
+        # regenerate label stylesheet with new font size
+        self.label.setStyleSheet(
+            f"""QLabel {{
+                color : {hcolor('default_lightest')};
+                font-size : {_font.px_size - 2}px;
+            }}
+            """
+        )
+        self.label.setFont(_font.font)
+
+        # update search bar and view fonts
+        if hasattr(self.bar, 'update_fonts'):
+            self.bar.update_fonts(_font)
+        elif hasattr(self.bar, 'setFont'):
+            self.bar.setFont(_font.font)
+
+        if hasattr(self.view, 'update_fonts'):
+            self.view.update_fonts()
+
+        self.updateGeometry()
+
     def focus(self) -> None:
         self.show()
         self.bar.focus()

piker/ui/_style.py

@@ -79,9 +79,13 @@ class DpiAwareFont:
         self._font_inches: float = None
         self._screen = None
 
-    def _set_qfont_px_size(self, px_size: int) -> None:
-        self._qfont.setPixelSize(px_size)
+    def _set_qfont_px_size(
+        self,
+        px_size: int,
+    ) -> int:
+        self._qfont.setPixelSize(int(px_size))
         self._qfm = QtGui.QFontMetrics(self._qfont)
+        return self.px_size
 
     @property
     def screen(self) -> QtGui.QScreen:
@@ -124,17 +128,22 @@ class DpiAwareFont:
 
         return size
 
-    def configure_to_dpi(self, screen: QtGui.QScreen | None = None):
+    def configure_to_dpi(
+        self,
+        screen: QtGui.QScreen | None = None,
+        zoom_level: float = 1.0,
+    ) -> int:
         '''
-        Set an appropriately sized font size depending on the screen DPI.
+        Set an appropriately sized font size depending on the screen DPI
+        or scale the size according to `zoom_level`.
 
-        If we end up needing to generalize this more here there are resources
-        listed in the script in ``snippets/qt_screen_info.py``.
+        If we end up needing to generalize this more here there are
+        resources listed in the script in
+        ``snippets/qt_screen_info.py``.
 
         '''
         if self._font_size is not None:
-            self._set_qfont_px_size(self._font_size)
-            return
+            return self._set_qfont_px_size(self._font_size * zoom_level)
 
         # NOTE: if no font size set either in the [ui] section of the
         # config or not yet computed from our magic scaling calcs,
@@ -153,7 +162,7 @@ class DpiAwareFont:
             ldpi = pdpi
 
         mx_dpi = max(pdpi, ldpi)
-        mn_dpi = min(pdpi, ldpi)
+        # mn_dpi = min(pdpi, ldpi)
         scale = round(ldpi/pdpi, ndigits=2)
 
         if mx_dpi <= 97:  # for low dpi use larger font sizes
@@ -162,7 +171,7 @@ class DpiAwareFont:
         else:  # hidpi use smaller font sizes
             inches = _font_sizes['hi'][self._font_size_calc_key]
 
-        dpi = mn_dpi
+        # dpi = mn_dpi
 
         mult = 1.0
 
@@ -197,24 +206,25 @@ class DpiAwareFont:
         # always going to hit that error in range mapping from inches:
         # float to px size: int.
         self._font_inches = inches
-        font_size = math.floor(inches * dpi)
+        font_size = math.floor(inches * pdpi)
+
+        # apply zoom level multiplier
+        font_size = int(font_size * zoom_level)
 
         log.debug(
             f"screen:{screen.name()}\n"
             f"pDPI: {pdpi}, lDPI: {ldpi}, scale: {scale}\n"
+            f"zoom_level: {zoom_level}\n"
             f"\nOur best guess font size is {font_size}\n"
         )
         # apply the size
-        self._set_qfont_px_size(font_size)
+        return self._set_qfont_px_size(font_size)
 
     def boundingRect(self, value: str) -> QtCore.QRectF:
-
-        screen = self.screen
-        if screen is None:
+        if self.screen is None:
             raise RuntimeError("You must call .configure_to_dpi() first!")
 
-        unscaled_br = self._qfm.boundingRect(value)
-
+        unscaled_br: QtCore.QRectF = self._qfm.boundingRect(value)
         return QtCore.QRectF(
             0,
             0,
@@ -228,12 +238,22 @@ _font = DpiAwareFont()
 _font_small = DpiAwareFont(_font_size_key='small')
 
 
-def _config_fonts_to_screen() -> None:
-    'configure global DPI aware font sizes'
+def _config_fonts_to_screen(
+    zoom_level: float = 1.0
+) -> int:
+    '''
+    Configure global DPI aware font size(s).
 
+    If `zoom_level` is provided we apply it to auto-calculated
+    DPI-aware font.
+
+    Return the new `DpiAwareFont.px_size`.
+
+    '''
     global _font, _font_small
-    _font.configure_to_dpi()
-    _font_small.configure_to_dpi()
+    _font.configure_to_dpi(zoom_level=zoom_level)
+    _font_small.configure_to_dpi(zoom_level=zoom_level)
+    return _font.px_size
 
 
 def get_fonts() -> tuple[

piker/ui/_window.py

@@ -18,6 +18,7 @@
 Qt main window singletons and stuff.
 
 """
+from __future__ import annotations
 import os
 import signal
 import time
@@ -38,15 +39,107 @@ from piker.ui.qt import (
     QScreen,
     QCloseEvent,
     QSettings,
+    QEvent,
+    QObject,
 )
 from ..log import get_logger
-from ._style import _font_small, hcolor
+from . import _style
+from ._style import (
+    _font_small,
+    hcolor,
+)
 from ._widget import GodWidget
 
 
 log = get_logger(__name__)
 
 
+class GlobalZoomEventFilter(QObject):
+    '''
+    Application-level event filter for global UI zoom shortcuts.
+
+    This filter intercepts keyboard events BEFORE they reach widgets,
+    allowing us to implement global UI zoom shortcuts that take precedence
+    over widget-specific shortcuts.
+
+    Shortcuts:
+    - Ctrl+Shift+Plus/Equal: Zoom in
+    - Ctrl+Shift+Minus: Zoom out
+    - Ctrl+Shift+0: Reset zoom
+
+    '''
+    def __init__(self, main_window: MainWindow):
+        super().__init__()
+        self.main_window = main_window
+
+    def eventFilter(self, obj: QObject, event: QEvent) -> bool:
+        '''
+        Filter keyboard events for global zoom shortcuts.
+
+        Returns True to filter out (consume) the event, False to pass through.
+
+        '''
+        if event.type() == QEvent.Type.KeyPress:
+            key = event.key()
+            mods = event.modifiers()
+
+            # Mask out the KeypadModifier which Qt sometimes adds
+            mods = mods & ~Qt.KeyboardModifier.KeypadModifier
+
+            # Check if we have Ctrl+Shift (both required)
+            has_ctrl = bool(
+                mods
+                &
+                Qt.KeyboardModifier.ControlModifier
+            )
+            _has_shift = bool(
+                mods
+                &
+                Qt.KeyboardModifier.ShiftModifier
+            )
+
+            # Only handle UI zoom if BOTH Ctrl and Shift are pressed
+            # For Plus key: user presses Cmd+Shift+Equal (which makes Plus)
+            # For Minus key: user presses Cmd+Shift+Minus
+            if (
+                has_ctrl
+                # and
+                # has_shift
+            ):
+                # Zoom in: Ctrl+Shift+Plus
+                # Note: Plus key usually comes as Key_Equal with Shift modifier
+                if key in (
+                    Qt.Key.Key_Plus,
+                    Qt.Key.Key_Equal,
+                ):
+                    self.main_window.zoom_in()
+                    return True  # consume event
+
+                # Zoom out: Ctrl+Shift+Minus
+                # Note: On some keyboards Shift+Minus produces '_' (Underscore)
+                elif key in (
+                    Qt.Key.Key_Minus,
+                    Qt.Key.Key_Underscore,
+                ):
+                    self.main_window.zoom_out()
+                    return True  # consume event
+
+                # Reset zoom: Ctrl+Shift+0
+                # Note: On some keyboards Shift+0 produces ')' (ParenRight)
+                elif key in (
+                    Qt.Key.Key_0,
+                    Qt.Key.Key_ParenRight,
+                ):
+                    self.main_window.reset_zoom()
+                    return True  # consume event
+
+            # Pass through if only Ctrl (no Shift) - this goes to chart zoom
+            # Pass through all other events too
+            return False
+
+        return False
+
+
 class MultiStatus:
 
     bar: QStatusBar
@@ -189,6 +282,25 @@ class MainWindow(QMainWindow):
             self.restoreGeometry(geometry)
             log.debug('Restored window geometry from previous session')
 
+
+        # zoom level for UI scaling (1.0 = 100%, 1.5 = 150%, etc)
+        # Change this value to set the default startup zoom level
+        self._zoom_level: float = 1.0  # Start at 100% (normal)
+        self._min_zoom: float = 0.5
+        self._max_zoom: float = 3.0  # Reduced from 10.0 to prevent extreme cropping
+        self._zoom_step: float = 0.2  # 20% per keypress
+
+        # event filter for global zoom shortcuts
+        self._zoom_filter: GlobalZoomEventFilter | None = None
+
+    def install_global_zoom_filter(self) -> None:
+        '''Install application-level event filter for global UI zoom shortcuts.'''
+        if self._zoom_filter is None:
+            self._zoom_filter = GlobalZoomEventFilter(self)
+            app = QApplication.instance()
+            app.installEventFilter(self._zoom_filter)
+            log.info('Installed global zoom shortcuts: Ctrl+Shift+Plus/Minus/0')
+
     @property
     def mode_label(self) -> QLabel:
 
@@ -357,6 +469,201 @@ class MainWindow(QMainWindow):
         self.godwidget.on_win_resize(event)
         event.accept()
 
+    def zoom_in(self) -> None:
+        '''
+        Increase overall UI-widgets zoom level by scaling it the
+        global font sizes.
+
+        '''
+        new_zoom: float = min(
+            self._zoom_level + self._zoom_step,
+            self._max_zoom,
+        )
+        if new_zoom != self._zoom_level:
+            self._zoom_level = new_zoom
+            font_size: int = self._apply_zoom()
+            log.info(
+                f'Zoomed in UI\n'
+                f'zoom_step: {self._zoom_step!r}\n'
+                f'zoom_level(%): {self._zoom_level:.1%}\n'
+                f'font_size: {font_size!r}'
+            )
+
+    def zoom_out(self) -> float:
+        '''
+        Decrease UI zoom level.
+
+        '''
+        new_zoom: float = max(self._zoom_level - self._zoom_step, self._min_zoom)
+        if new_zoom != self._zoom_level:
+            self._zoom_level = new_zoom
+            font_size: int = self._apply_zoom()
+            log.info(
+                f'Zoomed out UI\n'
+                f'zoom_step: {self._zoom_step!r}\n'
+                f'zoom_level(%): {self._zoom_level:.1%}\n'
+                f'font_size: {font_size!r}'
+            )
+
+        return new_zoom
+
+    def reset_zoom(self) -> None:
+        '''
+        Reset UI zoom to 100%.
+
+        '''
+        if self._zoom_level != 1.0:
+            self._zoom_level = 1.0
+            font_size: int = self._apply_zoom()
+            log.info(
+                f'Reset zoom level\n'
+                f'zoom_step: {self._zoom_step!r}\n'
+                f'zoom_level(%): {self._zoom_level:.1%}\n'
+                f'font_size: {font_size!r}'
+            )
+
+        return self._zoom_level
+
+    def _apply_zoom(self) -> int:
+        '''
+        Apply current zoom level to all UI elements.
+
+        '''
+        # reconfigure fonts with zoom multiplier
+        font_size: int = _style._config_fonts_to_screen(
+            zoom_level=self._zoom_level
+        )
+
+        # update status bar styling with new font size
+        if self._status_bar:
+            sb = self.statusBar()
+            sb.setStyleSheet((
+                f"color : {hcolor('gunmetal')};"
+                f"background : {hcolor('default_dark')};"
+                f"font-size : {_style._font_small.px_size}px;"
+                "padding : 0px;"
+            ))
+
+        # force update of mode label if it exists
+        if self._status_label:
+            self._status_label.setFont(_style._font_small.font)
+
+        # update godwidget and its children
+        if self.godwidget:
+            # update search widget if it exists
+            if hasattr(self.godwidget, 'search') and self.godwidget.search:
+                self.godwidget.search.update_fonts()
+
+            # update order mode panes in all chart views
+            self._update_chart_order_panes()
+
+            # recursively update all other widgets with stylesheets
+            self._refresh_widget_fonts(self.godwidget)
+            self.godwidget.update()
+
+        return font_size
+
+    def _update_chart_order_panes(self) -> None:
+        '''
+        Update order entry panels in all charts.
+
+        '''
+        if not self.godwidget:
+            return
+
+        # iterate through all linked splits (hist and rt)
+        for splits_name in ['hist_linked', 'rt_linked']:
+            splits = getattr(self.godwidget, splits_name, None)
+            if not splits:
+                continue
+
+            # get main chart
+            chart = getattr(splits, 'chart', None)
+            if chart:
+                # update axes
+                self._update_chart_axes(chart)
+
+                # update order pane
+                if hasattr(chart, 'view'):
+                    view = chart.view
+                    if hasattr(view, 'order_mode') and view.order_mode:
+                        order_mode = view.order_mode
+                        if hasattr(order_mode, 'pane') and order_mode.pane:
+                            order_mode.pane.update_fonts()
+
+            # also check subplots
+            subplots = getattr(splits, 'subplots', {})
+            for name, subplot_chart in subplots.items():
+                # update subplot axes
+                self._update_chart_axes(subplot_chart)
+
+                # update subplot order pane
+                if hasattr(subplot_chart, 'view'):
+                    subplot_view = subplot_chart.view
+                    if hasattr(subplot_view, 'order_mode') and subplot_view.order_mode:
+                        subplot_order_mode = subplot_view.order_mode
+                        if hasattr(subplot_order_mode, 'pane') and subplot_order_mode.pane:
+                            subplot_order_mode.pane.update_fonts()
+
+            # resize all sidepanes to match main chart's sidepane width
+            # this ensures volume/subplot sidepanes match the main chart
+            if splits and hasattr(splits, 'resize_sidepanes'):
+                splits.resize_sidepanes()
+
+    def _update_chart_axes(self, chart) -> None:
+        '''Update axis fonts and sizing for a chart.'''
+        from . import _style
+
+        # update price axis (right side)
+        if hasattr(chart, 'pi') and chart.pi:
+            plot_item = chart.pi
+            # get all axes from plot item
+            for axis_name in ['left', 'right', 'bottom', 'top']:
+                axis = plot_item.getAxis(axis_name)
+                if axis and hasattr(axis, 'update_fonts'):
+                    axis.update_fonts(_style._font)
+
+            # force plot item to recalculate its entire layout
+            plot_item.updateGeometry()
+
+            # force chart widget to update
+            if hasattr(chart, 'updateGeometry'):
+                chart.updateGeometry()
+
+            # trigger a full scene update
+            if hasattr(chart, 'update'):
+                chart.update()
+
+    def _refresh_widget_fonts(self, widget: QWidget) -> None:
+        '''
+        Recursively update font sizes in all child widgets.
+
+        This handles widgets that have font-size hardcoded in their stylesheets.
+        '''
+        from . import _style
+
+        # recursively process all children
+        for child in widget.findChildren(QWidget):
+            # skip widgets that have their own update_fonts method (handled separately)
+            if hasattr(child, 'update_fonts'):
+                continue
+
+            # update child's stylesheet if it has font-size
+            child_stylesheet = child.styleSheet()
+            if child_stylesheet and 'font-size' in child_stylesheet:
+                # for labels and simple widgets, regenerate stylesheet
+                # this is a heuristic - may need refinement
+                try:
+                    child.setFont(_style._font.font)
+                except (AttributeError, RuntimeError):
+                    pass
+
+            # update child's font
+            try:
+                child.setFont(_style._font.font)
+            except (AttributeError, RuntimeError):
+                pass
+
 
 # singleton app per actor
 _qt_win: QMainWindow = None

piker/ui/qt.py

@@ -42,6 +42,7 @@ from PyQt6.QtCore import (
     QSize,
     QModelIndex,
     QItemSelectionModel,
+    QObject,
     pyqtBoundSignal,
     pyqtRemoveInputHook,
     QSettings,

snippets/calc_ppi.xsh

@@ -0,0 +1,64 @@
+#!env xonsh
+'''
+Compute the pxs-per-inch (PPI) naively for the local DE.
+
+NOTE, currently this only supports the `sway`-TWM on wayland.
+
+!TODO!
+- [ ] support Xorg (and possibly other OSs as well?
+- [ ] conver this to pure py code, dropping the `.xsh` specifics
+     instead for `subprocess` API calls?
+- [ ] possibly unify all this with `./qt_screen_info.py` as part of
+     a "PPI config wizard" or something, but more then likely we'll
+     have lib-ified version inside modden/piker by then?
+
+'''
+
+import math
+import json
+
+# XXX, xonsh part using "subprocess mode"
+disp_infos: list[dict] = json.loads($(wlr-randr --json))
+lappy: dict = disp_infos[0]
+
+dims: dict[str, int] = lappy['physical_size']
+w_cm: int = dims['width']
+h_cm: int = dims['height']
+
+# cm per inch
+cpi: float = 25.4
+
+# compute "diagonal" size (aka hypot)
+diag_inches: float = math.sqrt((h_cm/cpi)**2 + (w_cm/cpi)**2)
+
+# compute reso-hypot / inches-hypot
+hi_res: dict[str, float|bool] = lappy['modes'][0]
+w_px: int = hi_res['width']
+h_px: int = hi_res['height']
+
+diag_pxs: float = math.sqrt(h_px**2 + w_px**2)
+unscaled_ppi: float = diag_pxs/diag_inches
+
+# retrieve TWM info on the display (including scaling info)
+sway_disp_info: dict = json.loads($(swaymsg -r -t get_outputs))[0]
+scale: float = sway_disp_info['scale']
+
+print(
+    f'output: {sway_disp_info["name"]!r}\n'
+    f'--- DIMENSIONS ---\n'
+    f'w_cm: {w_cm!r}\n'
+    f'h_cm: {h_cm!r}\n'
+    f'w_px: {w_px!r}\n'
+    f'h_cm: {h_px!r}\n'
+    f'\n'
+    f'--- DIAGONALS ---\n'
+    f'diag_inches: {diag_inches!r}\n'
+    f'diag_pxs: {diag_pxs!r}\n'
+    f'\n'
+    f'--- PPI-related-info ---\n'
+    f'(DE reported) scale: {scale!r}\n'
+    f'unscaled PPI: {unscaled_ppi!r}\n'
+    f'|_ =sqrt(h_px**2 + w_px**2) / sqrt(h_in**2 + w_in**2)\n'
+    f'scaled PPI: {unscaled_ppi/scale!r}\n'
+    f'|_ =unscaled_ppi/scale\n'
+)

snippets/qt_screen_info.py

@@ -31,8 +31,8 @@ Resource list for mucking with DPIs on multiple screens:
 - https://doc.qt.io/qt-5/qguiapplication.html#screenAt
 
 '''
+import os
 
-from pyqtgraph import QtGui
 from PyQt6 import (
     QtCore,
     QtWidgets,
@@ -43,6 +43,11 @@ from PyQt6.QtCore import (
     QSize,
     QRect,
 )
+from pyqtgraph import QtGui
+
+
+# https://doc.qt.io/qt-6/highdpi.html#environment-variable-reference
+os.environ['QT_USE_PHYSICAL_DPI'] = '1'
 
 # Proper high DPI scaling is available in Qt >= 5.6.0. This attibute
 # must be set before creating the application
@@ -58,13 +63,22 @@ if hasattr(Qt, 'AA_UseHighDpiPixmaps'):
         True,
     )
 
+# NOTE, inherits `QGuiApplication`
+# https://doc.qt.io/qt-6/qapplication.html
+# https://doc.qt.io/qt-6/qguiapplication.html
 app = QtWidgets.QApplication([])
+#
+# ^TODO? various global DPI settings?
+# [ ] DPI rounding policy,
+# - https://doc.qt.io/qt-6/qt.html#HighDpiScaleFactorRoundingPolicy-enum
+# - https://doc.qt.io/qt-6/qguiapplication.html#setHighDpiScaleFactorRoundingPolicy
+
 window = QtWidgets.QMainWindow()
 main_widget = QtWidgets.QWidget()
 window.setCentralWidget(main_widget)
 window.show()
 
-pxr: float = main_widget.devicePixelRatioF()
+_main_pxr: float = main_widget.devicePixelRatioF()
 
 # explicitly get main widget and primary displays
 current_screen: QtGui.QScreen = app.screenAt(
@@ -77,7 +91,13 @@ for screen in app.screens():
     name: str = screen.name()
     model: str = screen.model().rstrip()
     size: QSize = screen.size()
-    geo: QRect = screen.availableGeometry()
+    geo: QRect = screen.geometry()
+
+    # device-pixel-ratio
+    # https://doc.qt.io/qt-6/highdpi.html
+    pxr: float = screen.devicePixelRatio()
+
+    unscaled_size: QSize = pxr * size
     phydpi: float = screen.physicalDotsPerInch()
     logdpi: float = screen.logicalDotsPerInch()
     is_primary: bool = screen is primary_screen
@@ -88,11 +108,12 @@ for screen in app.screens():
         f'|_primary: {is_primary}\n'
         f' _current: {is_current}\n'
         f' _model: {model}\n'
-        f' _screen size: {size}\n'
-        f' _screen geometry: {geo}\n'
-        f' _devicePixelRationF(): {pxr}\n'
-        f' _physical dpi: {phydpi}\n'
-        f' _logical dpi: {logdpi}\n'
+        f' _size: {size}\n'
+        f' _geometry: {geo}\n'
+        f' _devicePixelRatio(): {pxr}\n'
+        f' _unscaled-size: {unscaled_size!r}\n'
+        f' _physical-dpi: {phydpi}\n'
+        f' _logical-dpi: {logdpi}\n'
     )
 
 # app-wide font info
@@ -110,8 +131,8 @@ str_w: int = str_br.width()
 
 print(
     f'------ global font settings ------\n'
-    f'font dpi: {fontdpi}\n'
-    f'font height: {font_h}\n'
-    f'string bounding rect: {str_br}\n'
-    f'string width : {str_w}\n'
+    f'font dpi: {fontdpi!r}\n'
+    f'font height: {font_h!r}\n'
+    f'string bounding rect: {str_br!r}\n'
+    f'string width : {str_w!r}\n'
 )

tests/test_dpi_font.py

@@ -0,0 +1,36 @@
+import pytest
+from piker.ui._style import DpiAwareFont
+
+
+class MockScreen:
+    def __init__(self, pdpi, ldpi, name="MockScreen"):
+        self._pdpi = pdpi
+        self._ldpi = ldpi
+        self._name = name
+
+    def physicalDotsPerInch(self):
+        return self._pdpi
+
+    def logicalDotsPerInch(self):
+        return self._ldpi
+
+    def name(self):
+        return self._name
+
+
+@pytest.mark.parametrize(
+    "pdpi, ldpi, expected_px",
+    [
+        (96, 96, 9),       # normal DPI
+        (169, 96, 15),     # HiDPI
+        (120, 96, 10),     # mid-DPI
+    ]
+)
+def test_font_px_size(pdpi, ldpi, expected_px):
+    font = DpiAwareFont()
+    font.configure_to_dpi(screen=MockScreen(pdpi, ldpi))
+
+    px = font.px_size
+    print(f"{pdpi}x{ldpi} DPI -> Computed pixel size: {px}")
+
+    assert px == expected_px