From 474e4284d428fa16c20dd3e997a4793c2b363476 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Micha=C3=ABl=20Lemaire?= <michael@thunderk.net>
Date: Wed, 27 Jun 2012 13:05:57 +0000
Subject: [PATCH] paysages : Preview rendering is balanced when two previews
 are visible.

git-svn-id: https://subversion.assembla.com/svn/thunderk/paysages@366 b1fd45b6-86a6-48da-8261-f70d1f35bdcc
---
 TODO                   |  1 -
 gui_qt/basepreview.cpp | 24 +++++++++++++++++++++---
 gui_qt/basepreview.h   |  1 +
 3 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/TODO b/TODO
index 520e9c0..eff4e67 100644
--- a/TODO
+++ b/TODO
@@ -28,7 +28,6 @@ Technology Preview 2 :
 - Fix "RGB parameters out of range" (and segfault) on preview while moving render params fast in render tab.
    => May need to change the updateData system.
    => Previews need to be paused while updating data.
-- When there are two previews in the same view, balance rendering between the two.
 - Lock some previews together (eg: terrain height and colored preview).
 - Find a new licence.
 
diff --git a/gui_qt/basepreview.cpp b/gui_qt/basepreview.cpp
index da70358..9a357cb 100644
--- a/gui_qt/basepreview.cpp
+++ b/gui_qt/basepreview.cpp
@@ -25,6 +25,11 @@ public:
         _alive = true;
     }
     
+    inline BasePreview* preview()
+    {
+        return _preview;
+    }
+    
     inline bool isOnFront()
     {
         return _preview->isVisible() && _preview->window()->isActiveWindow();
@@ -132,6 +137,7 @@ PreviewDrawingManager::PreviewDrawingManager()
     {
         _thread_count = 1;
     }
+    _lastRendered = NULL;
 }
 
 void PreviewDrawingManager::startThreads()
@@ -201,7 +207,7 @@ void PreviewDrawingManager::updateChunks(BasePreview* preview)
             chunk->update();
             _lock.lock();
             if (!_updateQueue.contains(chunk))
-            {   
+            {
                 _updateQueue.prepend(chunk);
             }
             _lock.unlock();
@@ -220,7 +226,7 @@ void PreviewDrawingManager::updateAllChunks()
             chunk->update();
             _lock.lock();
             if (!_updateQueue.contains(chunk))
-            {   
+            {
                 _updateQueue.prepend(chunk);
             }
             _lock.unlock();
@@ -236,12 +242,24 @@ void PreviewDrawingManager::performOneThreadJob()
     _lock.lock();
     if (!_updateQueue.isEmpty())
     {
-        chunk = _updateQueue.takeFirst();
+        for (int i = _updateQueue.size(); i > 0; i--)
+        {
+            chunk = _updateQueue.takeFirst();
+            if (chunk && i > 1 && chunk->preview() == _lastRendered)
+            {
+                _updateQueue.append(chunk);
+            }
+            else
+            {
+                break;
+            }
+        }
     }
     _lock.unlock();
 
     if (chunk)
     {
+        _lastRendered = chunk->preview();
         chunk->render();
     }        
 }
diff --git a/gui_qt/basepreview.h b/gui_qt/basepreview.h
index 52eba54..e5f9d58 100644
--- a/gui_qt/basepreview.h
+++ b/gui_qt/basepreview.h
@@ -136,6 +136,7 @@ private:
     QVector<PreviewDrawingThread*> _threads;
     QVector<PreviewChunk*> _chunks;
     QList<PreviewChunk*> _updateQueue;
+    BasePreview* _lastRendered;
     QMutex _lock;
 };