piker/snippets/qt_screen_info.py

# piker: trading gear for hackers
# Copyright (C) Tyler Goodlet (in stewardship for pikers)

# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.

# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Affero General Public License for more details.

# You should have received a copy of the GNU Affero General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.

'''
A per-display, DPI (scaling) info dumper.

Resource list for mucking with DPIs on multiple screens:

- https://stackoverflow.com/questions/42141354/convert-pixel-size-to-point-size-for-fonts-on-multiple-platforms
- https://stackoverflow.com/questions/25761556/qt5-font-rendering-different-on-various-platforms/25929628#25929628
- https://doc.qt.io/qt-5/highdpi.html
- https://stackoverflow.com/questions/20464814/changing-dpi-scaling-size-of-display-make-qt-applications-font-size-get-rendere
- https://stackoverflow.com/a/20465247
- https://doc.qt.io/archives/qt-4.8/qfontmetrics.html#width
- https://forum.qt.io/topic/54136/how-do-i-get-the-qscreen-my-widget-is-on-qapplication-desktop-screen-returns-a-qwidget-and-qobject_cast-qscreen-returns-null/3
- https://forum.qt.io/topic/43625/point-sizes-are-they-reliable/4
- https://stackoverflow.com/questions/16561879/what-is-the-difference-between-logicaldpix-and-physicaldpix-in-qt
- https://doc.qt.io/qt-5/qguiapplication.html#screenAt

'''
import os

from PyQt6 import (
    QtCore,
    QtWidgets,
)
from PyQt6.QtCore import (
    Qt,
    QCoreApplication,
    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
if hasattr(Qt, 'AA_EnableHighDpiScaling'):
    QCoreApplication.setAttribute(
        Qt.AA_EnableHighDpiScaling,
        True,
    )

if hasattr(Qt, 'AA_UseHighDpiPixmaps'):
    QCoreApplication.setAttribute(
        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()

_main_pxr: float = main_widget.devicePixelRatioF()

# explicitly get main widget and primary displays
current_screen: QtGui.QScreen = app.screenAt(
    main_widget.geometry().center()
)
primary_screen: QtGui.QScreen = app.primaryScreen()

screen: QtGui.QScreen
for screen in app.screens():
    name: str = screen.name()
    model: str = screen.model().rstrip()
    size: QSize = screen.size()
    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
    is_current: bool = screen is current_screen

    print(
        f'------ screen name: {name} ------\n'
        f'|_primary: {is_primary}\n'
        f' _current: {is_current}\n'
        f' _model: {model}\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
font = QtGui.QFont("Hack")
# use pixel size to be cross-resolution compatible?
font.setPixelSize(6)

fm = QtGui.QFontMetrics(font)
fontdpi: float = fm.fontDpi()
font_h: int = fm.height()

string: str = '10000'
str_br: QtCore.QRect = fm.boundingRect(string)
str_w: int = str_br.width()

print(
    f'------ global font settings ------\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'
)