From baf012f6bce78aa1ef5896fd28a1c87a6ff2d147 Mon Sep 17 00:00:00 2001
From: Lubosz Sarnecki <lubosz@gmail.com>
Date: Sat, 16 Mar 2024 15:55:42 +0100
Subject: [PATCH] OpenGlDisplayPlugin: Add possibility to present frames only
 once.

Don't present frame more than once in OpenXrDisplayPlugin.
---
 .../src/display-plugins/OpenGLDisplayPlugin.cpp            | 7 +++++++
 .../src/display-plugins/OpenGLDisplayPlugin.h              | 2 ++
 plugins/openxr/src/OpenXrDisplayPlugin.cpp                 | 1 +
 3 files changed, 10 insertions(+)

diff --git a/libraries/display-plugins/src/display-plugins/OpenGLDisplayPlugin.cpp b/libraries/display-plugins/src/display-plugins/OpenGLDisplayPlugin.cpp
index 00771927fb..9d45e91bf3 100644
--- a/libraries/display-plugins/src/display-plugins/OpenGLDisplayPlugin.cpp
+++ b/libraries/display-plugins/src/display-plugins/OpenGLDisplayPlugin.cpp
@@ -746,6 +746,13 @@ void OpenGLDisplayPlugin::present(const std::shared_ptr<RefreshRateController>&
         }
 
         gpu::Backend::freeGPUMemSize.set(gpu::gl::getFreeDedicatedMemory());
+
+        // Drop current frame after presenting it once.
+        // This is required for the OpenXR frame cycle, since we call xrEndFrame after presenting.
+        // xrEndFrame must not be called multiple times.
+        if (_presentOnlyOnce) {
+            _currentFrame.reset();
+        }
     } else if (alwaysPresent()) {
         refreshRateController->clockEndTime();
         internalPresent();
diff --git a/libraries/display-plugins/src/display-plugins/OpenGLDisplayPlugin.h b/libraries/display-plugins/src/display-plugins/OpenGLDisplayPlugin.h
index 0df0d9ac3e..a7ce2180f2 100644
--- a/libraries/display-plugins/src/display-plugins/OpenGLDisplayPlugin.h
+++ b/libraries/display-plugins/src/display-plugins/OpenGLDisplayPlugin.h
@@ -206,6 +206,8 @@ protected:
     QImage getScreenshot(float aspectRatio);
     QImage getSecondaryCameraScreenshot();
 
+    bool _presentOnlyOnce = false;
+
 private:
     static Setting::Handle<bool> _extraLinearToSRGBConversionSetting;
 };
diff --git a/plugins/openxr/src/OpenXrDisplayPlugin.cpp b/plugins/openxr/src/OpenXrDisplayPlugin.cpp
index e952fe671c..e15de872dd 100644
--- a/plugins/openxr/src/OpenXrDisplayPlugin.cpp
+++ b/plugins/openxr/src/OpenXrDisplayPlugin.cpp
@@ -23,6 +23,7 @@ constexpr GLint XR_PREFERRED_COLOR_FORMAT = GL_SRGB8_ALPHA8;
 
 OpenXrDisplayPlugin::OpenXrDisplayPlugin(std::shared_ptr<OpenXrContext> c) {
     _context = c;
+    _presentOnlyOnce = true;
 }
 
 bool OpenXrDisplayPlugin::isSupported() const {