From 54839718555c23f11afc322bd9c693844cae97e0 Mon Sep 17 00:00:00 2001
From: Brad Davis <bdavis@saintandreas.org>
Date: Fri, 15 Feb 2019 10:46:08 -0800
Subject: [PATCH] Fix crash in vive and interleaved stereo plugins

---
 .../src/display-plugins/OpenGLDisplayPlugin.cpp              | 2 +-
 .../src/display-plugins/OpenGLDisplayPlugin.h                | 5 +++++
 libraries/oculusMobilePlugin/src/OculusMobileDisplayPlugin.h | 1 +
 3 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/libraries/display-plugins/src/display-plugins/OpenGLDisplayPlugin.cpp b/libraries/display-plugins/src/display-plugins/OpenGLDisplayPlugin.cpp
index e4deaf8f4b..20fc9a2290 100644
--- a/libraries/display-plugins/src/display-plugins/OpenGLDisplayPlugin.cpp
+++ b/libraries/display-plugins/src/display-plugins/OpenGLDisplayPlugin.cpp
@@ -720,7 +720,7 @@ void OpenGLDisplayPlugin::present() {
         }
 
         gpu::Backend::freeGPUMemSize.set(gpu::gl::getFreeDedicatedMemory());
-    } else {
+    } else if (alwaysPresent()) {
         internalPresent();
     }
     _movingAveragePresent.addSample((float)(usecTimestampNow() - startPresent));
diff --git a/libraries/display-plugins/src/display-plugins/OpenGLDisplayPlugin.h b/libraries/display-plugins/src/display-plugins/OpenGLDisplayPlugin.h
index 5c653f8a0a..49a38ecb4c 100644
--- a/libraries/display-plugins/src/display-plugins/OpenGLDisplayPlugin.h
+++ b/libraries/display-plugins/src/display-plugins/OpenGLDisplayPlugin.h
@@ -88,6 +88,11 @@ protected:
 
     glm::uvec2 getSurfaceSize() const;
     glm::uvec2 getSurfacePixels() const;
+    // Some display plugins require us to always execute some present logic,
+    // whether we have a frame or not (Oculus Mobile plugin)
+    // Such plugins must be prepared to do the right thing if the `_currentFrame`
+    // is not populated
+    virtual bool alwaysPresent() const { return false; }
 
     void updateCompositeFramebuffer();
 
diff --git a/libraries/oculusMobilePlugin/src/OculusMobileDisplayPlugin.h b/libraries/oculusMobilePlugin/src/OculusMobileDisplayPlugin.h
index 4a0a21e995..a98989655e 100644
--- a/libraries/oculusMobilePlugin/src/OculusMobileDisplayPlugin.h
+++ b/libraries/oculusMobilePlugin/src/OculusMobileDisplayPlugin.h
@@ -57,6 +57,7 @@ protected:
     void internalPresent() override;
     void hmdPresent() override { throw std::runtime_error("Unused"); }
     bool isHmdMounted() const override;
+    bool alwaysPresent() const override { return true; }
 
     static const char* NAME;
     mutable gl::Context* _mainContext{ nullptr };