File 0001-Use-the-physical-DPI-on-X11-as-logical-DPI... of Package libqt5-qtbase

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File 0001-Use-the-physical-DPI-on-X11-as-logical-DPI-by-defaul.patch of Package libqt5-qtbase

From eb5545318cc8a62750adc9ff6a803d935c832e27 Mon Sep 17 00:00:00 2001
From: Fabian Vogt <fabian@ritter-vogt.de>
Date: Wed, 5 May 2021 11:42:51 +0200
Subject: [PATCH] Use the physical DPI on X11 as logical DPI by default

If Xft.dpi is not set and QT_USE_PHYSICAL_DPI isn't explicitly set to 0, then
use the physical size of the screen to calculate the logical DPI. Apply some
heuristics to catch invalid EDID values and fall back to 96dpi in such cases.

QTBUG-67928
QTBUG-93454
---
 src/plugins/platforms/xcb/qxcbscreen.cpp | 33 ++++++++++++++++++++----
 src/plugins/platforms/xcb/qxcbscreen.h   |  1 +
 2 files changed, 29 insertions(+), 5 deletions(-)

diff --git a/src/plugins/platforms/xcb/qxcbscreen.cpp b/src/plugins/platforms/xcb/qxcbscreen.cpp
index e637ed827c..1932a2716f 100644
--- a/src/plugins/platforms/xcb/qxcbscreen.cpp
+++ b/src/plugins/platforms/xcb/qxcbscreen.cpp
@@ -717,12 +717,18 @@ QDpi QXcbScreen::logicalDpi() const
     if (forcedDpi > 0)
         return QDpi(forcedDpi, forcedDpi);
 
-    // Fall back to physical virtual desktop DPI, but prevent
-    // using DPI values lower than 96. This ensuers that connecting
-    // to e.g. a TV works somewhat predictabilly.
     QDpi virtualDesktopPhysicalDPi = m_virtualDesktop->dpi();
-    return QDpi(std::max(virtualDesktopPhysicalDPi.first, 96.0),
-                std::max(virtualDesktopPhysicalDPi.second, 96.0));
+
+    // By default, X fakes the virtual size to be 96 dpi (+-rounding),
+    // so if it's different the user overwrote it.
+    // Prevent using DPI values lower than 96. This ensuers that connecting
+    // to e.g. a TV works somewhat predictabilly.
+    if (qRound(virtualDesktopPhysicalDPi.first) > 96
+        && qRound(virtualDesktopPhysicalDPi.second) > 96) {
+        return virtualDesktopPhysicalDPi;
+    }
+
+    return QDpi(m_pixelDensity * 96, m_pixelDensity * 96);
 }
 
 QPlatformCursor *QXcbScreen::cursor() const
@@ -788,6 +794,23 @@ void QXcbScreen::updateGeometry(const QRect &geometry, uint8_t rotation)
     if (m_sizeMillimeters.isEmpty())
         m_sizeMillimeters = sizeInMillimeters(geometry.size(), m_virtualDesktop->dpi());
 
+    qreal dpi = geometry.width() / m_sizeMillimeters.width() * qreal(25.4);
+    qreal referenceDpi = physicalSize().width() <= 320 ? 128 : 96;
+    m_pixelDensity = qMax(1, qRound(dpi/referenceDpi));
+
+    bool usePhysicalDpiSet = false;
+    if(qEnvironmentVariableIntValue("QT_USE_PHYSICAL_DPI", &usePhysicalDpiSet) == 0 && usePhysicalDpiSet)
+        m_pixelDensity = 1;
+
+    if(m_pixelDensity > 1) {
+        // If we have no physical size or the resolution is untypical, fall back to 1x
+        if (physicalSize().height() <= 0
+            || geometry.height() < 1440
+            || m_pixelDensity > 3) {
+            m_pixelDensity = 1;
+        }
+    }
+
     m_geometry = geometry;
     m_availableGeometry = geometry & m_virtualDesktop->workArea();
     QWindowSystemInterface::handleScreenGeometryChange(QPlatformScreen::screen(), m_geometry, m_availableGeometry);
diff --git a/src/plugins/platforms/xcb/qxcbscreen.h b/src/plugins/platforms/xcb/qxcbscreen.h
index ad2980b55e..b627006b53 100644
--- a/src/plugins/platforms/xcb/qxcbscreen.h
+++ b/src/plugins/platforms/xcb/qxcbscreen.h
@@ -231,6 +231,7 @@ private:
     QXcbCursor *m_cursor;
     qreal m_refreshRate = 60.0;
     QEdidParser m_edid;
+    int m_pixelDensity = 1;
 };
 
 #ifndef QT_NO_DEBUG_STREAM
-- 
2.25.1

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File 0001-Use-the-physical-DPI-on-X11-as-logical-DPI-by-defaul.patch of Package libqt5-qtbase

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