From 1de8b01d2b6db8a4fe2eddd0c595d9e680964db5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Morten=20Johan=20S=C3=B8rvig?= <morten.sorvig@qt.io>
Date: Thu, 10 Nov 2016 14:17:53 +0100
Subject: [PATCH] Deprecate QT_AUTO_SCREEN_SCALE_FACTOR
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Replace by QT_ENABLE_HIGHDPI_SCALING.

QT_AUTO_SCREEN_SCALE_FACTOR has the usability problem that it mixes
enabling the high-DPI scaling mode with the method of getting screen
scale factors (“auto”). Due to this, it ends up with a slightly
strange name.

QT_ENABLE_HIGHDPI_SCALING matches the C++ option
(Qt::AA_EnableHighDPiScaling), and leaves the scale factor acquisition
method unspecified, possibly to be set by some other means (like
QT_SCREEN_SCALE_FACTORS).

Done-with: Friedemann Kleint <Friedemann.Kleint@qt.io>
Task-number: QTBUG-53022
Change-Id: I30033d91175a00db7837efc9c48c33396f5f0449
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
---
 src/gui/kernel/qhighdpiscaling.cpp | 29 +++++++++++++++++++++++------
 1 file changed, 23 insertions(+), 6 deletions(-)

diff --git a/src/gui/kernel/qhighdpiscaling.cpp b/src/gui/kernel/qhighdpiscaling.cpp
index 3de67d5cfa2..4a9c9a99347 100644
--- a/src/gui/kernel/qhighdpiscaling.cpp
+++ b/src/gui/kernel/qhighdpiscaling.cpp
@@ -56,8 +56,10 @@ Q_LOGGING_CATEGORY(lcScaling, "qt.scaling");
 
 #ifndef QT_NO_HIGHDPISCALING
 static const char legacyDevicePixelEnvVar[] = "QT_DEVICE_PIXEL_RATIO";
+static const char legacyAutoScreenEnvVar[] = "QT_AUTO_SCREEN_SCALE_FACTOR";
+
+static const char enableHighDpiScalingEnvVar[] = "QT_ENABLE_HIGHDPI_SCALING";
 static const char scaleFactorEnvVar[] = "QT_SCALE_FACTOR";
-static const char autoScreenEnvVar[] = "QT_AUTO_SCREEN_SCALE_FACTOR";
 static const char screenFactorsEnvVar[] = "QT_SCREEN_SCALE_FACTORS";
 static const char scaleFactorRoundingPolicyEnvVar[] = "QT_SCALE_FACTOR_ROUNDING_POLICY";
 static const char dpiAdjustmentPolicyEnvVar[] = "QT_DPI_ADJUSTMENT_POLICY";
@@ -90,17 +92,24 @@ static inline qreal initialGlobalScaleFactor()
             result = f;
         }
     } else {
+        // Check for deprecated environment variables.
         if (qEnvironmentVariableIsSet(legacyDevicePixelEnvVar)) {
             qWarning("Warning: %s is deprecated. Instead use:\n"
                      "   %s to enable platform plugin controlled per-screen factors.\n"
-                     "   %s to set per-screen factors.\n"
+                     "   %s to set per-screen DPI.\n"
                      "   %s to set the application global scale factor.",
-                     legacyDevicePixelEnvVar, autoScreenEnvVar, screenFactorsEnvVar, scaleFactorEnvVar);
+                     legacyDevicePixelEnvVar, legacyAutoScreenEnvVar, screenFactorsEnvVar, scaleFactorEnvVar);
 
             int dpr = qEnvironmentVariableIntValue(legacyDevicePixelEnvVar);
             if (dpr > 0)
                 result = dpr;
         }
+
+        if (qEnvironmentVariableIsSet(legacyAutoScreenEnvVar)) {
+            qWarning("Warning: %s is deprecated. Instead use:\n"
+                     "   %s to enable platform plugin controlled per-screen factors.",
+                     legacyAutoScreenEnvVar, enableHighDpiScalingEnvVar);
+        }
     }
     return result;
 }
@@ -258,16 +267,24 @@ static inline bool usePixelDensity()
     // Determine if we should set a scale factor based on the pixel density
     // reported by the platform plugin. There are several enablers and several
     // disablers. A single disable may veto all other enablers.
+
+    // First, check of there is an explicit disable.
     if (QCoreApplication::testAttribute(Qt::AA_DisableHighDpiScaling))
         return false;
     bool screenEnvValueOk;
-    const int screenEnvValue = qEnvironmentVariableIntValue(autoScreenEnvVar, &screenEnvValueOk);
+    const int screenEnvValue = qEnvironmentVariableIntValue(legacyAutoScreenEnvVar, &screenEnvValueOk);
     if (screenEnvValueOk && screenEnvValue < 1)
         return false;
+    bool enableEnvValueOk;
+    const int enableEnvValue = qEnvironmentVariableIntValue(enableHighDpiScalingEnvVar, &enableEnvValueOk);
+    if (enableEnvValueOk && enableEnvValue < 1)
+        return false;
+
+    // Then return if there was an enable.
     return QCoreApplication::testAttribute(Qt::AA_EnableHighDpiScaling)
         || (screenEnvValueOk && screenEnvValue > 0)
-        || (qEnvironmentVariableIsSet(legacyDevicePixelEnvVar) &&
-            qgetenv(legacyDevicePixelEnvVar).compare("auto", Qt::CaseInsensitive) == 0);
+        || (enableEnvValueOk && enableEnvValue > 0)
+        || (qEnvironmentVariableIsSet(legacyDevicePixelEnvVar) && qgetenv(legacyDevicePixelEnvVar).toLower() == "auto");
 }
 
 qreal QHighDpiScaling::rawScaleFactor(const QPlatformScreen *screen)