From 710da838d8867cacd2427bc0db5e5e914eda628f Mon Sep 17 00:00:00 2001
From: Lubosz Sarnecki <lubosz@gmail.com>
Date: Wed, 4 Sep 2024 21:17:26 +0200
Subject: [PATCH] OpenXr: Use C++20 std::optional.

---
 plugins/openxr/src/OpenXrContext.h         |  5 ++---
 plugins/openxr/src/OpenXrDisplayPlugin.cpp | 17 ++++++++---------
 plugins/openxr/src/OpenXrDisplayPlugin.h   |  4 +---
 plugins/openxr/src/OpenXrInputPlugin.cpp   |  4 ++--
 4 files changed, 13 insertions(+), 17 deletions(-)

diff --git a/plugins/openxr/src/OpenXrContext.h b/plugins/openxr/src/OpenXrContext.h
index eed18eeeb8..82baf098f5 100644
--- a/plugins/openxr/src/OpenXrContext.h
+++ b/plugins/openxr/src/OpenXrContext.h
@@ -9,6 +9,7 @@
 
 #pragma once
 
+#include <optional>
 
 #include <openxr/openxr.h>
 
@@ -58,9 +59,7 @@ public:
     XrPath _handPaths[HAND_COUNT];
 
     controller::Pose _lastHeadPose;
-    XrTime _lastPredictedDisplayTime;
-    // TODO: Enable C++17 and use std::optional
-    bool _lastPredictedDisplayTimeInitialized = false;
+    std::optional<XrTime> _lastPredictedDisplayTime;
 
     bool _shouldQuit = false;
     bool _shouldRunFrameCycle = false;
diff --git a/plugins/openxr/src/OpenXrDisplayPlugin.cpp b/plugins/openxr/src/OpenXrDisplayPlugin.cpp
index fd9177143a..efd8952a7e 100644
--- a/plugins/openxr/src/OpenXrDisplayPlugin.cpp
+++ b/plugins/openxr/src/OpenXrDisplayPlugin.cpp
@@ -67,13 +67,13 @@ inline static glm::mat4 fovToProjection(const XrFovf fov, const float near, cons
 }
 
 glm::mat4 OpenXrDisplayPlugin::getEyeProjection(Eye eye, const glm::mat4& baseProjection) const {
-    if (!_viewsInitialized) {
+    if (!_views.has_value()) {
         return baseProjection;
     }
 
     ViewFrustum frustum;
     frustum.setProjection(baseProjection);
-    return fovToProjection(_views[(eye == Left) ? 0 : 1].fov, frustum.getNearClip(), frustum.getFarClip());
+    return fovToProjection(_views.value()[(eye == Left) ? 0 : 1].fov, frustum.getNearClip(), frustum.getFarClip());
 }
 
 // TODO: This apparently wasn't right in the OpenVR plugin, but this is what it basically did.
@@ -99,9 +99,11 @@ bool OpenXrDisplayPlugin::initViews() {
 
     assert(_viewCount != 0);
 
+    _views = std::vector<XrView>();
+
     for (uint32_t i = 0; i < _viewCount; i++) {
         XrView view = { .type = XR_TYPE_VIEW };
-        _views.push_back(view);
+        _views.value().push_back(view);
 
         XrViewConfigurationView viewConfig = { .type = XR_TYPE_VIEW_CONFIGURATION_VIEW };
         _viewConfigs.push_back(viewConfig);
@@ -363,7 +365,6 @@ bool OpenXrDisplayPlugin::beginFrameRender(uint32_t frameIndex) {
         return false;
 
     _context->_lastPredictedDisplayTime = _lastFrameState.predictedDisplayTime;
-    _context->_lastPredictedDisplayTimeInitialized = true;
 
     std::vector<XrView> eye_views(_viewCount);
     for (uint32_t i = 0; i < _viewCount; i++) {
@@ -399,17 +400,15 @@ bool OpenXrDisplayPlugin::beginFrameRender(uint32_t frameIndex) {
         .space = _context->_stageSpace,
     };
 
-    result = xrLocateViews(_context->_session, &viewLocateInfo, &_lastViewState, _viewCount, &_viewCount, _views.data());
+    result = xrLocateViews(_context->_session, &viewLocateInfo, &_lastViewState, _viewCount, &_viewCount, _views.value().data());
     if (!xrCheck(_context->_instance, result, "Could not locate views"))
         return false;
 
     for (uint32_t i = 0; i < _viewCount; i++) {
-        _projectionLayerViews[i].pose = _views[i].pose;
-        _projectionLayerViews[i].fov = _views[i].fov;
+        _projectionLayerViews[i].pose = _views.value()[i].pose;
+        _projectionLayerViews[i].fov = _views.value()[i].fov;
     }
 
-    _viewsInitialized = true;
-
     XrSpaceLocation headLocation = {
         .type = XR_TYPE_SPACE_LOCATION,
         .pose = XR_INDENTITY_POSE,
diff --git a/plugins/openxr/src/OpenXrDisplayPlugin.h b/plugins/openxr/src/OpenXrDisplayPlugin.h
index ac83c8e094..01df5fcf27 100644
--- a/plugins/openxr/src/OpenXrDisplayPlugin.h
+++ b/plugins/openxr/src/OpenXrDisplayPlugin.h
@@ -66,9 +66,7 @@ private:
     uint32_t _viewCount = 0;
     std::vector<XrCompositionLayerProjectionView> _projectionLayerViews;
 
-    std::vector<XrView> _views;
-    // TODO: Enable C++17 and use std::optional
-    bool _viewsInitialized = false;
+    std::optional<std::vector<XrView>> _views;
 
     std::vector<XrViewConfigurationView> _viewConfigs;
 
diff --git a/plugins/openxr/src/OpenXrInputPlugin.cpp b/plugins/openxr/src/OpenXrInputPlugin.cpp
index c16581efb5..f9823adf70 100644
--- a/plugins/openxr/src/OpenXrInputPlugin.cpp
+++ b/plugins/openxr/src/OpenXrInputPlugin.cpp
@@ -228,8 +228,8 @@ XrSpaceLocation OpenXrInputPlugin::Action::getPose(uint32_t handId) {
         .type = XR_TYPE_SPACE_LOCATION,
     };
 
-    if (_context->_lastPredictedDisplayTimeInitialized) {
-        result = xrLocateSpace(_poseSpaces[handId], _context->_stageSpace, _context->_lastPredictedDisplayTime, &location);
+    if (_context->_lastPredictedDisplayTime.has_value()) {
+        result = xrLocateSpace(_poseSpaces[handId], _context->_stageSpace, _context->_lastPredictedDisplayTime.value(), &location);
         xrCheck(_context->_instance, result, "Failed to locate hand space!");
     }