From e2e37cf9b212bc30277b00503c7c01c149428500 Mon Sep 17 00:00:00 2001
From: osy <50960678+osy@users.noreply.github.com>
Date: Tue, 1 Sep 2026 13:20:55 -0700
Subject: [PATCH] config: use linear upscaling except on classic guests

The nearest-neighbour default (ba5f7f7f, #3371) was chosen for
low-resolution guests, where linear washes out already-chunky text. It is
the wrong choice everywhere else: a modern guest rarely upscales by an
integer ratio, so nearest duplicates source pixels unevenly and looks
blocky rather than sharp -- the complaint behind #6209 and #6572.

Default to linear and let the wizard select nearest for the guests the
original change was about: Classic Mac OS, Windows 7 and below, and any OS
configured for legacy hardware. Legacy hardware is checked on its own
rather than folded into the Windows case so that choosing a legacy machine
opts in under any OS, and because the summary page can enable it after the
Windows page has already latched isWindows10OrHigher.

Existing VMs are unaffected: upscalingFilter is a required coding key, so
a saved configuration always carries its own value. The UTM 2.x migration
path is likewise unchanged, since an absent displayUpscaler already
defaulted to linear.

Assisted-by: Claude:claude-opus-5
---
 Configuration/UTMQemuConfigurationDisplay.swift |  7 ++++++-
 Platform/Shared/VMWizardState.swift             | 11 +++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/Configuration/UTMQemuConfigurationDisplay.swift b/Configuration/UTMQemuConfigurationDisplay.swift
index 822c354d6b..894e97ae0c 100644
--- a/Configuration/UTMQemuConfigurationDisplay.swift
+++ b/Configuration/UTMQemuConfigurationDisplay.swift
@@ -28,7 +28,12 @@ struct UTMQemuConfigurationDisplay: Codable, Identifiable {
     var isDynamicResolution: Bool = true
     
     /// Filter to use when upscaling.
-    var upscalingFilter: QEMUScaler = .nearest
+    ///
+    /// Nearest neighbour is only a good fit for low-resolution guests, where it keeps the image
+    /// sharp instead of washing it out (#3371); the wizard selects it for those. For a modern
+    /// guest the upscale is rarely an integer ratio, so nearest duplicates source pixels
+    /// unevenly and looks blocky rather than sharp.
+    var upscalingFilter: QEMUScaler = .linear
     
     /// Filter to use when downscaling.
     var downscalingFilter: QEMUScaler = .linear
diff --git a/Platform/Shared/VMWizardState.swift b/Platform/Shared/VMWizardState.swift
index 53f96f2ec4..f4547a9ace 100644
--- a/Platform/Shared/VMWizardState.swift
+++ b/Platform/Shared/VMWizardState.swift
@@ -475,6 +475,17 @@ struct AlertMessage: Identifiable {
                 config.displays[0].hardware = AnyQEMUConstant(rawValue: newCard)!
             }
         }
+        // Low-resolution guests upscale better with nearest neighbour: linear washes out
+        // their already-chunky text (#3371). Legacy hardware is checked on its own rather
+        // than folded into the Windows case so that picking a legacy machine opts in under
+        // any OS, and because the summary page can enable it after the Windows page has
+        // latched isWindows10OrHigher. Modern guests keep the linear default, where the
+        // upscale is a non-integer ratio and nearest looks blocky instead of sharp.
+        if operatingSystem == .ClassicMacOS || legacyHardware || (operatingSystem == .Windows && !isWindows10OrHigher) {
+            for i in config.displays.indices {
+                config.displays[i].upscalingFilter = .nearest
+            }
+        }
         if operatingSystem == .Linux && !isDisplayEnabled {
             config.displays = []
             let newSerial = UTMQemuConfigurationSerial(forArchitecture: systemArchitecture, target: systemTarget)!