From f643e80de77a76e11306605be044e050bb2ee512 Mon Sep 17 00:00:00 2001
From: Bruno <bruno.herbelin@gmail.com>
Date: Sat, 24 Apr 2021 13:14:57 +0200
Subject: [PATCH] Using std future promises to get thumbnail of render view

---
 RenderView.cpp | 35 +++++++++++++++++++++--------------
 RenderView.h   |  8 +++++++-
 Session.cpp    |  1 -
 Session.h      |  4 ++++
 4 files changed, 32 insertions(+), 16 deletions(-)

diff --git a/RenderView.cpp b/RenderView.cpp
index 631549e..267fa6c 100644
--- a/RenderView.cpp
+++ b/RenderView.cpp
@@ -13,6 +13,7 @@
 
 
 RenderView::RenderView() : View(RENDERING), frame_buffer_(nullptr), fading_overlay_(nullptr)
+//  ,thumbnail_(nullptr), thumbnail_ready_(false)
 {
 }
 
@@ -81,26 +82,32 @@ void RenderView::draw()
         fading_overlay_->draw(glm::identity<glm::mat4>(), projection);
         frame_buffer_->end();
     }
-}
 
+    if (thumbnailer_.valid()) {
 
-FrameBufferImage *RenderView::thumbnail () const
-{
-    FrameBufferImage *thumbnail = nullptr;
+        if (frame_buffer_) {
+            FrameBuffer *frame_thumbnail = new FrameBuffer( glm::vec3(SESSION_THUMBNAIL_HEIGHT * frame_buffer_->aspectRatio(), SESSION_THUMBNAIL_HEIGHT, 1.f) );
 
-    if (frame_buffer_) {
-        FrameBufferSurface *thumb = new FrameBufferSurface(frame_buffer_);
-        FrameBuffer *frame_thumbnail = new FrameBuffer( glm::vec3(SESSION_THUMBNAIL_HEIGHT * frame_buffer_->aspectRatio(), SESSION_THUMBNAIL_HEIGHT, 1.f) );
+            FrameBufferSurface *thumb = new FrameBufferSurface(frame_buffer_);
+            frame_thumbnail->begin();
+            thumb->draw(glm::identity<glm::mat4>(), frame_thumbnail->projection());
+            frame_thumbnail->end();
+            delete thumb;
 
-        frame_thumbnail->begin();
-        thumb->draw(glm::identity<glm::mat4>(), frame_thumbnail->projection());
-        frame_thumbnail->end();
+    //        frame_buffer_->blit(frame_thumbnail); // a tester...
 
-        thumbnail = frame_thumbnail->image();
+            thumbnail_.set_value( frame_thumbnail->image() );
 
-        delete thumb;
-        delete frame_thumbnail;
+            delete frame_thumbnail;
+        }
     }
 
-    return thumbnail;
+}
+
+
+FrameBufferImage *RenderView::thumbnail ()
+{
+    thumbnailer_ = thumbnail_.get_future();
+
+    return thumbnailer_.get();
 }
diff --git a/RenderView.h b/RenderView.h
index d235482..add1c62 100644
--- a/RenderView.h
+++ b/RenderView.h
@@ -1,6 +1,9 @@
 #ifndef RENDERVIEW_H
 #define RENDERVIEW_H
 
+#include <mutex>
+#include <future>
+
 #include "View.h"
 
 class RenderView : public View
@@ -8,6 +11,9 @@ class RenderView : public View
     FrameBuffer *frame_buffer_;
     Surface *fading_overlay_;
 
+    std::promise<FrameBufferImage *> thumbnail_;
+    std::future<FrameBufferImage *> thumbnailer_;
+
 public:
     RenderView ();
     ~RenderView ();
@@ -23,7 +29,7 @@ public:
 
     inline FrameBuffer *frame () const { return frame_buffer_; }
 
-    FrameBufferImage *thumbnail () const;
+    FrameBufferImage *thumbnail ();
 };
 
 #endif // RENDERVIEW_H
diff --git a/Session.cpp b/Session.cpp
index a406226..a1ad389 100644
--- a/Session.cpp
+++ b/Session.cpp
@@ -128,7 +128,6 @@ void Session::update(float dt)
 
     // draw render view in Frame Buffer
     render_.draw();
-
 }
 
 SourceList::iterator Session::addSource(Source *s)
diff --git a/Session.h b/Session.h
index a1962be..42f06a4 100644
--- a/Session.h
+++ b/Session.h
@@ -83,6 +83,9 @@ public:
     // get frame result of render
     inline FrameBuffer *frame () const { return render_.frame(); }
 
+    // get thumbnail image
+    inline FrameBufferImage *thumbnail () { return render_.thumbnail(); }
+
     // configure rendering resolution
     void setResolution (glm::vec3 resolution, bool useAlpha = false);
 
@@ -138,6 +141,7 @@ protected:
     SessionSnapshots snapshots_;
     float fading_target_;
     std::mutex access_;
+
 };