Fix graphprinting example crash

We exceed maximum texture size on certain platforms. Added a check
for it.

Pick-to: 6.9.1
Fixes: QTBUG-135384
Fixes: QTBUG-135386
Change-Id: I0a09337c9c6b831f801df35b5756327f45507237
Reviewed-by: Owais Akhtar <owais.akhtar@qt.io>
Reviewed-by: Tomi Korpipää <tomi.korpipaa@qt.io>
(cherry picked from commit 713a6e0b72)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

examples/graphs/graphprinting/CMakeLists.txt

@@ -40,6 +40,7 @@ target_link_libraries(graphprinting PRIVATE
     Qt::Quick3D
     Qt::Graphs
     Qt::PrintSupport
+    Qt::GuiPrivate
 )
 
 qt6_add_qml_module(graphprinting

examples/graphs/graphprinting/graphprinter.cpp

@@ -1,8 +1,13 @@
 // Copyright (C) 2024 The Qt Company Ltd.
 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
 #include "graphprinter.h"
+#include <QtGui/qtguiglobal.h>
 #include <QtGui/qtransform.h>
 #include <QtPrintSupport/QtPrintSupport>
+#if QT_CONFIG(opengl)
+#include <QtGui/qoffscreensurface.h>
+#endif
+#include <rhi/qrhi.h>
 
 GraphPrinter::GraphPrinter(QObject *parent)
     : QObject(parent)
@@ -10,6 +15,45 @@ GraphPrinter::GraphPrinter(QObject *parent)
 
 GraphPrinter::~GraphPrinter() {}
 
+static qreal s_maxTextureSize = 0.;
+
+qreal GraphPrinter::maxTextureSize()
+{
+    // Query maximum texture size only once
+    if (!s_maxTextureSize) {
+        std::unique_ptr<QRhi> rhi;
+#if defined(Q_OS_WIN)
+        QRhiD3D12InitParams params;
+        rhi.reset(QRhi::create(QRhi::D3D12, &params));
+#elif defined(Q_OS_MACOS) || defined(Q_OS_IOS)
+        QRhiMetalInitParams params;
+        rhi.reset(QRhi::create(QRhi::Metal, &params));
+#elif QT_CONFIG(opengl)
+        QRhiGles2InitParams params;
+        params.fallbackSurface = QRhiGles2InitParams::newFallbackSurface();
+        rhi.reset(QRhi::create(QRhi::OpenGLES2, &params));
+#elif QT_CONFIG(vulkan)
+        if (!qEnvironmentVariable("QSG_RHI_BACKEND").compare("vulkan")) {
+            QVulkanInstance inst;
+            inst.setExtensions(QRhiVulkanInitParams::preferredInstanceExtensions());
+            if (inst.create()) {
+                QRhiVulkanInitParams params;
+                params.inst = &inst;
+                rhi.reset(QRhi::create(QRhi::Vulkan, &params));
+            } else {
+                qWarning("Failed to create Vulkan instance");
+            }
+        }
+#endif
+        if (rhi)
+            s_maxTextureSize = qreal(rhi->resourceLimit(QRhi::TextureSizeMax));
+        else
+            s_maxTextureSize = 4096.; // Use 4096 as the minimum
+    }
+
+    return s_maxTextureSize;
+}
+
 QString GraphPrinter::generatePDF(const QUrl &path, const QImage &image)
 {
     //! [0]

examples/graphs/graphprinting/graphprinter.h

@@ -19,6 +19,7 @@ public:
   Q_INVOKABLE QString generatePDF(const QUrl &path, const QImage &image);
   Q_INVOKABLE QString print(const QImage &image, const QString printerName);
   Q_INVOKABLE QStringList getPrinters();
+  Q_INVOKABLE qreal maxTextureSize();
 };
 
 #endif // GRAPHPRINTER_H

examples/graphs/graphprinting/qml/graphprinting/main.qml

@@ -146,6 +146,8 @@ Rectangle {
     }
     MessageDialog {
         id: message
+        onButtonClicked: mainView.cleanAfterPrint()
+
     }
 
     //! [1.1]
@@ -257,7 +259,20 @@ Rectangle {
     //! [3.3]
     function prepareForPrint() {
         if (stackLayout.currentIndex === 1) {
-            outputsize = Qt.size(bargraph.width * 4, bargraph.height * 4)
+            var newsize = Qt.size(bargraph.width * 4, bargraph.height * 4)
+
+            // check that we do not exceed maximum texture size
+            if (newsize.width * Screen.devicePixelRatio > graphPrinter.maxTextureSize() ) {
+                // scale to 25% under max texture size to be on the safe side; some GPUs seem
+                // to glitch when using the abosulute max
+                var ratio = (newsize.width * Screen.devicePixelRatio * 1.25)
+                        / graphPrinter.maxTextureSize()
+                newsize.width /= ratio
+                newsize.height /= ratio
+            }
+            outputsize.width = Math.round(newsize.width)
+            outputsize.height = Math.round(newsize.height)
+
             // resize the bar graph to match the PDF output size
             item.width = outputsize.width
             item.height = outputsize.height
@@ -269,8 +284,8 @@ Rectangle {
     function cleanAfterPrint() {
         if (stackLayout.currentIndex === 1) {
             // resize the bar graph back to the actual visual size
-            item.width = mainView.width
-            item.height = mainView.height
+            item.width = stackLayout.width
+            item.height = stackLayout.height
         }
     }
     //! [3.3]