From 901515fe03ec2a8613cbb721625f382d9271bcc7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Morten=20S=C3=B8rvig?= <morten.sorvig@qt.io>
Date: Tue, 7 Nov 2023 14:44:13 +0100
Subject: [PATCH] Fix off-by-one surface pixel size on Android
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

m_window->size() may have been rounded for devices
with DPI which results in a fractional DPR (e.g.
650 DPI / 160 DPI = 3.5 DPR). In this case scaling
by devicePixelRatio does not give the correct result.

Instead, use QPlatformWindow geometry and DPR to determine
the device size, without using the (possibly) rounded
device independent window size.

Fixes: QTBUG-87334
Pick-to: 6.5 6.2
Change-Id: I280236a06516cdb2a1a259fd0cfa8084c1ce7f46
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Jøger Hansegård <joger.hansegard@qt.io>
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>
(cherry picked from commit 96d0f2af75aa069f2b6973a621b3bf6ebaafc9a5)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
---
 src/gui/rhi/qrhigles2.cpp | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/gui/rhi/qrhigles2.cpp b/src/gui/rhi/qrhigles2.cpp
index 02138d7fb77..371abe89f36 100644
--- a/src/gui/rhi/qrhigles2.cpp
+++ b/src/gui/rhi/qrhigles2.cpp
@@ -7,6 +7,7 @@
 #include <QtCore/qmap.h>
 #include <QtGui/private/qopenglextensions_p.h>
 #include <QtGui/private/qopenglprogrambinarycache_p.h>
+#include <QtGui/private/qwindow_p.h>
 #include <qpa/qplatformopenglcontext.h>
 #include <qmath.h>
 
@@ -6116,7 +6117,12 @@ QRhiRenderTarget *QGles2SwapChain::currentFrameRenderTarget(StereoTargetBuffer t
 QSize QGles2SwapChain::surfacePixelSize()
 {
     Q_ASSERT(m_window);
-    return m_window->size() * m_window->devicePixelRatio();
+    if (QPlatformWindow *platformWindow = m_window->handle())
+        // Prefer using QPlatformWindow geometry and DPR in order to avoid
+        // errors due to rounded QWindow geometry.
+        return platformWindow->geometry().size() * platformWindow->devicePixelRatio();
+    else
+        return m_window->size() * m_window->devicePixelRatio();
 }
 
 bool QGles2SwapChain::isFormatSupported(Format f)