1 files changed, 85 insertions, 0 deletions
diff --git a/src/gui/vulkan/qvulkandefaultinstance.cpp b/src/gui/vulkan/qvulkandefaultinstance.cpp
new file mode 100644
index 0000000000..b4f343cf17
--- /dev/null
+++ b/src/gui/vulkan/qvulkandefaultinstance.cpp
@@ -0,0 +1,85 @@
+// Copyright (C) 2022 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
+
+#include "qvulkandefaultinstance_p.h"
+#include <rhi/qrhi.h>
+#include <QLoggingCategory>
+
+QT_BEGIN_NAMESPACE
+
+Q_LOGGING_CATEGORY(lcGuiVk, "qt.vulkan")
+
+static QVulkanInstance *s_vulkanInstance;
+Q_CONSTINIT static QVulkanDefaultInstance::Flags s_vulkanInstanceFlags;
+
+QVulkanDefaultInstance::Flags QVulkanDefaultInstance::flags()
+{
+    return s_vulkanInstanceFlags;
+}
+
+// As always, calling this when hasInstance() is already true has no effect. (unless cleanup() is called)
+void QVulkanDefaultInstance::setFlag(Flag flag, bool on)
+{
+    s_vulkanInstanceFlags.setFlag(flag, on);
+}
+
+bool QVulkanDefaultInstance::hasInstance()
+{
+    return s_vulkanInstance != nullptr;
+}
+
+QVulkanInstance *QVulkanDefaultInstance::instance()
+{
+    if (s_vulkanInstance)
+        return s_vulkanInstance;
+
+    s_vulkanInstance = new QVulkanInstance;
+
+    // With a Vulkan implementation >= 1.1 we can check what
+    // vkEnumerateInstanceVersion() says and request 1.3/1.2/1.1 based on the
+    // result. To prevent future surprises, be conservative and ignore any > 1.3
+    // versions for now. For 1.0 implementations nothing will be requested, the
+    // default 0 in VkApplicationInfo means 1.0.
+    //
+    // Vulkan 1.0 is actually sufficient for 99% of Qt Quick (3D)'s
+    // functionality. In addition, Vulkan implementations tend to enable 1.1+
+    // functionality regardless of the VkInstance API request. However, the
+    // validation layer seems to take this fairly seriously, so we should be
+    // prepared for using 1.1+ features in a fully correct manner. This also
+    // helps custom Vulkan code in applications, which is not under out
+    // control; it is ideal if Vulkan 1.1+ versions are usable without
+    // requiring such applications to create their own QVulkanInstance just to
+    // be able to make an appropriate setApiVersion() call on it.
+
+    const QVersionNumber supportedVersion = s_vulkanInstance->supportedApiVersion();
+    if (supportedVersion >= QVersionNumber(1, 3))
+        s_vulkanInstance->setApiVersion(QVersionNumber(1, 3));
+    else if (supportedVersion >= QVersionNumber(1, 2))
+        s_vulkanInstance->setApiVersion(QVersionNumber(1, 2));
+    else if (supportedVersion >= QVersionNumber(1, 1))
+        s_vulkanInstance->setApiVersion(QVersionNumber(1, 1));
+    qCDebug(lcGuiVk) << "QVulkanDefaultInstance: Creating Vulkan instance"
+                     << "Requesting Vulkan API" << s_vulkanInstance->apiVersion()
+                     << "Instance-level version was reported as" << supportedVersion;
+
+    if (s_vulkanInstanceFlags.testFlag(EnableValidation))
+        s_vulkanInstance->setLayers({ "VK_LAYER_KHRONOS_validation" });
+
+    s_vulkanInstance->setExtensions(QRhiVulkanInitParams::preferredInstanceExtensions());
+
+    if (!s_vulkanInstance->create()) {
+        qWarning("QVulkanDefaultInstance: Failed to create Vulkan instance");
+        delete s_vulkanInstance;
+        s_vulkanInstance = nullptr;
+    }
+
+    return s_vulkanInstance;
+}
+
+void QVulkanDefaultInstance::cleanup()
+{
+    delete s_vulkanInstance;
+    s_vulkanInstance = nullptr;
+}
+
+QT_END_NAMESPACE