Merge pull request 'dpi_scaling_round2: a bit of research on `Qt6`'s hiDPI support' (#49) from dpi_scaling_round2 into dpi-font-auto-calc

Reviewed-on: #49

piker/ui/_style.py

@@ -184,22 +184,25 @@ class DpiAwareFont:
         self._font_inches = inches
         font_size = math.floor(inches * pdpi)
 
-        log.debug(
+        ftype: str = f'{type(self)!r}'
-            f"screen:{screen.name()}\n"
+        log.info(
-            f"pDPI: {pdpi}, lDPI: {ldpi}, scale: {scale}\n"
+            f'screen: {screen.name()}\n'
-            f"\nOur best guess font size is {font_size}\n"
+            f'pDPI: {pdpi!r}\n'
+            f'lDPI: {ldpi!r}\n'
+            f'scale: {scale!r}\n'
+            f'{ftype}._font_inches={self._font_inches!r}\n'
+            f'\n'
+            f"Our best guess for an auto-font-size is,\n"
+            f'font_size: {font_size!r}\n'
         )
         # apply the size
         self._set_qfont_px_size(font_size)
 
     def boundingRect(self, value: str) -> QtCore.QRectF:
-
+        if (screen := self.screen) is None:
-        screen = self.screen
-        if 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,

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' _size: {size}\n'
-        f' _screen geometry: {geo}\n'
+        f' _geometry: {geo}\n'
-        f' _devicePixelRationF(): {pxr}\n'
+        f' _devicePixelRatio(): {pxr}\n'
-        f' _physical dpi: {phydpi}\n'
+        f' _unscaled-size: {unscaled_size!r}\n'
-        f' _logical dpi: {logdpi}\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 dpi: {fontdpi!r}\n'
-    f'font height: {font_h}\n'
+    f'font height: {font_h!r}\n'
-    f'string bounding rect: {str_br}\n'
+    f'string bounding rect: {str_br!r}\n'
-    f'string width : {str_w}\n'
+    f'string width : {str_w!r}\n'
 )