From 9448d193c914f0d1398e8618f85790645fdefb66 Mon Sep 17 00:00:00 2001
From: John Papale <jpapale@vitamin-te.ch>
Date: Fri, 16 Oct 2020 11:43:51 +0200
Subject: [PATCH 1/8] Optimized performance while zooming complex pdf.

---
 src/pdf/XPDFRenderer.cpp | 110 +++++++++++++++++++++++++++++++++++++--
 src/pdf/XPDFRenderer.h   |  33 +++++++++++-
 2 files changed, 136 insertions(+), 7 deletions(-)

diff --git a/src/pdf/XPDFRenderer.cpp b/src/pdf/XPDFRenderer.cpp
index f7769f4b..b2a3fbe8 100644
--- a/src/pdf/XPDFRenderer.cpp
+++ b/src/pdf/XPDFRenderer.cpp
@@ -38,13 +38,22 @@
 
 #include "core/memcheck.h"
 
+#ifdef XPDFRENDERER_CACHE_ZOOM_WITH_LOSS
+double const XPDFRenderer::sRatioZoomRendering[] = { 3.0 };
+#else //XPDFRENDERER_CACHE_ZOOM_WITH_LOSS
+double const XPDFRenderer::sRatioZoomRendering[] = { 2.5, 5, 10.0 };
+#endif //XPDFRENDERER_CACHE_ZOOM_WITH_LOSS
+
 QAtomicInt XPDFRenderer::sInstancesCount = 0;
 
 XPDFRenderer::XPDFRenderer(const QString &filename, bool importingFile)
     : mDocument(0)
-    , mpSplashBitmap(0)
-    , mSplash(0)
 {
+    for (int i = 0; i < NbrZoomCache; i++)
+    {
+        m_cache.push_back(TypeCacheData(sRatioZoomRendering[i]));
+    }
+
     Q_UNUSED(importingFile);
     if (!globalParams)
     {
@@ -67,9 +76,14 @@ XPDFRenderer::XPDFRenderer(const QString &filename, bool importingFile)
 
 XPDFRenderer::~XPDFRenderer()
 {
-    if(mSplash){
-        delete mSplash;
-        mSplash = NULL;
+    for(int i = 0; i < m_cache.size(); i++)
+    {
+        TypeCacheData &cacheData = m_cache[i];
+        if(cacheData.splash != nullptr){
+            cacheData.cachedImage = QImage(); // The 'cachedImage' uses a buffer from 'splash'.
+            delete cacheData.splash;
+            cacheData.splash = nullptr;
+        }
     }
 
     if (mDocument)
@@ -175,6 +189,7 @@ int XPDFRenderer::pageRotation(int pageNumber) const
         return 0;
 }
 
+#ifndef XPDFRENDERER_CACHE_ZOOM_IMAGE
 void XPDFRenderer::render(QPainter *p, int pageNumber, const QRectF &bounds)
 {
     if (isValid())
@@ -231,3 +246,88 @@ QImage* XPDFRenderer::createPDFImage(int pageNumber, qreal xscale, qreal yscale,
     }
     return new QImage(mpSplashBitmap->getDataPtr(), mpSplashBitmap->getWidth(), mpSplashBitmap->getHeight(), mpSplashBitmap->getWidth() * 3, QImage::Format_RGB888);
 }
+#else
+
+
+void XPDFRenderer::render(QPainter *p, int pageNumber, const QRectF &bounds)
+{
+    Q_UNUSED(bounds);
+    if (isValid())
+    {
+        qreal xscale = p->worldTransform().m11();
+        qreal yscale = p->worldTransform().m22();
+        Q_ASSERT(qFuzzyCompare(xscale, yscale)); // Zoom equal in all axes expected.
+        Q_ASSERT(xscale > 0.0); // Potential Div0 later if this assert fail.
+
+        int zoomIndex = 0;
+        bool foundIndex = false;
+        for (; zoomIndex < NbrZoomCache && !foundIndex;)
+        {
+            if (xscale <= m_cache[zoomIndex].ratio) {
+                foundIndex = true;
+            } else {
+                zoomIndex++;
+            }
+        }
+
+        if (!foundIndex) // Use the previous one.
+            zoomIndex--;
+
+        QImage const &pdfImage = createPDFImage(pageNumber, m_cache[zoomIndex]);
+        QTransform savedTransform = p->worldTransform();
+
+        double const ratioDifferenceBetweenWorldAndImage = 1.0/m_cache[zoomIndex].ratio;
+        // The 'pdfImage' is rendered with a quality equal or superior. We adjust the 'transform' to zoom it
+        // out the required ratio.
+        QTransform newTransform = savedTransform.scale(ratioDifferenceBetweenWorldAndImage, ratioDifferenceBetweenWorldAndImage);
+        p->setWorldTransform(newTransform);
+        p->drawImage(QPointF( mSliceX,  mSliceY), pdfImage);
+
+        p->setWorldTransform(savedTransform);
+    }
+}
+
+QImage& XPDFRenderer::createPDFImage(int pageNumber, TypeCacheData &cacheData)
+{
+    if (isValid())
+    {      
+        SplashColor paperColor = {0xFF, 0xFF, 0xFF}; // white
+        bool const requireUpdateImage = (pageNumber != cacheData.cachedPageNumber) || (cacheData.splash == nullptr);
+        if (requireUpdateImage)
+        {
+            if(cacheData.splash != nullptr)
+            {
+                cacheData.cachedImage = QImage(); // The 'm_cachedImage' uses a buffer from 'mSplash'.
+                delete cacheData.splash;
+            }
+            cacheData.splash = new SplashOutputDev(splashModeRGB8, 1, false, paperColor);
+            cacheData.cachedPageNumber = pageNumber;
+
+#ifdef USE_XPDF
+            cacheData.splash->startDoc(mDocument->getXRef());
+#else
+            cacheData.splash->startDoc(mDocument);
+#endif
+            int rotation = 0; // in degrees (get it from the worldTransform if we want to support rotation)
+            bool useMediaBox = false;
+            bool crop = true;
+            bool printing = false;
+            mSliceX = 0.;
+            mSliceY = 0.;
+
+            mDocument->displayPage(cacheData.splash, pageNumber, this->dpiForRendering * cacheData.ratio, this->dpiForRendering * cacheData.ratio,
+                                   rotation, useMediaBox, crop, printing);
+            cacheData.splashBitmap = cacheData.splash->getBitmap();
+        }
+
+        // Note this uses the 'mSplash->getBitmap()->getDataPtr()' as data buffer.
+        cacheData.cachedImage = QImage(cacheData.splashBitmap->getDataPtr(), cacheData.splashBitmap->getWidth(), cacheData.splashBitmap->getHeight(),
+                               cacheData.splashBitmap->getWidth() * 3 /* bytesPerLine, 24 bits for RGB888, = 3 bytes */,
+                               QImage::Format_RGB888);
+    } else {
+        cacheData.cachedImage = QImage();
+    }
+
+    return cacheData.cachedImage;
+}
+#endif
diff --git a/src/pdf/XPDFRenderer.h b/src/pdf/XPDFRenderer.h
index c668515b..37387dc6 100644
--- a/src/pdf/XPDFRenderer.h
+++ b/src/pdf/XPDFRenderer.h
@@ -51,6 +51,9 @@
 
 class PDFDoc;
 
+#define XPDFRENDERER_CACHE_ZOOM_IMAGE
+//#define XPDFRENDERER_CACHE_ZOOM_WITH_LOSS
+
 class XPDFRenderer : public PDFRenderer
 {
     Q_OBJECT
@@ -74,15 +77,41 @@ class XPDFRenderer : public PDFRenderer
 
     private:
         void init();
+#ifdef XPDFRENDERER_CACHE_ZOOM_IMAGE
+
+        enum {
+#ifndef XPDFRENDERER_CACHE_ZOOM_WITH_LOSS
+            NbrZoomCache = 3
+#else //XPDFRENDERER_CACHE_ZOOM_WITH_LOSS
+            NbrZoomCache = 1
+#endif //XPDFRENDERER_CACHE_ZOOM_WITH_LOSS
+        };
+
+        class TypeCacheData {
+        public:
+            TypeCacheData(double const a_ratio) : splashBitmap(nullptr), cachedPageNumber(-1), splash(nullptr), ratio(a_ratio) {};
+            ~TypeCacheData() {};
+            SplashBitmap* splashBitmap;
+            QImage cachedImage;
+            int cachedPageNumber;
+            SplashOutputDev* splash;
+            double const ratio;
+        };
+
+        QImage &createPDFImage(int pageNumber, TypeCacheData &cacheData);
+#else
         QImage* createPDFImage(int pageNumber, qreal xscale = 0.5, qreal yscale = 0.5, const QRectF &bounds = QRectF());
+#endif
 
         PDFDoc *mDocument;
         static QAtomicInt sInstancesCount;
+        //! The image is rendered with a quality above normal, so we can use that same
+        //! image while zooming.
+        static const double sRatioZoomRendering[NbrZoomCache];
         qreal mSliceX;
         qreal mSliceY;
 
-        SplashBitmap* mpSplashBitmap;
-        SplashOutputDev* mSplash;
+        QVector<TypeCacheData> m_cache;
 };
 
 #endif // XPDFRENDERER_H

From c860e0b0b765f4ead74cd532fc3347836bb84cbc Mon Sep 17 00:00:00 2001
From: John Papale <jpapale@vitamin-te.ch>
Date: Fri, 16 Oct 2020 12:07:14 +0200
Subject: [PATCH 2/8] Made work the (inactive) case !defined
 XPDFRENDERER_CACHE_ZOOM_IMAGE.

---
 src/pdf/XPDFRenderer.cpp | 13 +++++++++++--
 src/pdf/XPDFRenderer.h   |  9 ++++++---
 2 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/src/pdf/XPDFRenderer.cpp b/src/pdf/XPDFRenderer.cpp
index b2a3fbe8..e0ee4ac3 100644
--- a/src/pdf/XPDFRenderer.cpp
+++ b/src/pdf/XPDFRenderer.cpp
@@ -38,21 +38,28 @@
 
 #include "core/memcheck.h"
 
+#ifdef XPDFRENDERER_CACHE_ZOOM_IMAGE
 #ifdef XPDFRENDERER_CACHE_ZOOM_WITH_LOSS
 double const XPDFRenderer::sRatioZoomRendering[] = { 3.0 };
 #else //XPDFRENDERER_CACHE_ZOOM_WITH_LOSS
 double const XPDFRenderer::sRatioZoomRendering[] = { 2.5, 5, 10.0 };
 #endif //XPDFRENDERER_CACHE_ZOOM_WITH_LOSS
+#endif //XPDFRENDERER_CACHE_ZOOM_IMAGE
 
 QAtomicInt XPDFRenderer::sInstancesCount = 0;
 
-XPDFRenderer::XPDFRenderer(const QString &filename, bool importingFile)
-    : mDocument(0)
+XPDFRenderer::XPDFRenderer(const QString &filename, bool importingFile) :
+#ifndef XPDFRENDERER_CACHE_ZOOM_IMAGE
+    mSplash(nullptr),
+#endif //XPDFRENDERER_CACHE_ZOOM_IMAGE
+    mDocument(0)
 {
+#ifdef XPDFRENDERER_CACHE_ZOOM_IMAGE
     for (int i = 0; i < NbrZoomCache; i++)
     {
         m_cache.push_back(TypeCacheData(sRatioZoomRendering[i]));
     }
+#endif //XPDFRENDERER_CACHE_ZOOM_IMAGE
 
     Q_UNUSED(importingFile);
     if (!globalParams)
@@ -76,6 +83,7 @@ XPDFRenderer::XPDFRenderer(const QString &filename, bool importingFile)
 
 XPDFRenderer::~XPDFRenderer()
 {
+#ifdef XPDFRENDERER_CACHE_ZOOM_IMAGE
     for(int i = 0; i < m_cache.size(); i++)
     {
         TypeCacheData &cacheData = m_cache[i];
@@ -85,6 +93,7 @@ XPDFRenderer::~XPDFRenderer()
             cacheData.splash = nullptr;
         }
     }
+#endif //XPDFRENDERER_CACHE_ZOOM_IMAGE
 
     if (mDocument)
     {
diff --git a/src/pdf/XPDFRenderer.h b/src/pdf/XPDFRenderer.h
index 37387dc6..fef8b411 100644
--- a/src/pdf/XPDFRenderer.h
+++ b/src/pdf/XPDFRenderer.h
@@ -99,19 +99,22 @@ class XPDFRenderer : public PDFRenderer
         };
 
         QImage &createPDFImage(int pageNumber, TypeCacheData &cacheData);
+
+        static const double sRatioZoomRendering[NbrZoomCache];
+        QVector<TypeCacheData> m_cache;
 #else
         QImage* createPDFImage(int pageNumber, qreal xscale = 0.5, qreal yscale = 0.5, const QRectF &bounds = QRectF());
+
+        SplashBitmap* mpSplashBitmap;
+        SplashOutputDev* mSplash;
 #endif
 
         PDFDoc *mDocument;
         static QAtomicInt sInstancesCount;
         //! The image is rendered with a quality above normal, so we can use that same
         //! image while zooming.
-        static const double sRatioZoomRendering[NbrZoomCache];
         qreal mSliceX;
         qreal mSliceY;
-
-        QVector<TypeCacheData> m_cache;
 };
 
 #endif // XPDFRENDERER_H

From 8ba6d1b7b21496793e035472bc961855fae740bb Mon Sep 17 00:00:00 2001
From: John Papale <jpapale@vitamin-te.ch>
Date: Tue, 27 Oct 2020 19:05:40 +0100
Subject: [PATCH 3/8] Made zoom cache behavior configurable with var
 'ZoomBehavior' (0 =no cache, 1 =x3 zoom cache, 2 = 2.5/5/10 cache). Cleanup.

---
 src/core/UBSettings.cpp  |   1 +
 src/core/UBSettings.h    |   1 +
 src/pdf/XPDFRenderer.cpp | 142 +++++++++++++++++++--------------------
 src/pdf/XPDFRenderer.h   |  37 ++++------
 4 files changed, 83 insertions(+), 98 deletions(-)

diff --git a/src/core/UBSettings.cpp b/src/core/UBSettings.cpp
index 80e14677..b83d5f88 100644
--- a/src/core/UBSettings.cpp
+++ b/src/core/UBSettings.cpp
@@ -408,6 +408,7 @@ void UBSettings::init()
     pdfMargin = new UBSetting(this, "PDF", "Margin", "20");
     pdfPageFormat = new UBSetting(this, "PDF", "PageFormat", "A4");
     pdfResolution = new UBSetting(this, "PDF", "Resolution", "300");
+    pdfZoomBehavior = new UBSetting(this, "PDF", "ZoomBehavior", "1");
 
     podcastFramesPerSecond = new UBSetting(this, "Podcast", "FramesPerSecond", 10);
     podcastVideoSize = new UBSetting(this, "Podcast", "VideoSize", "Medium");
diff --git a/src/core/UBSettings.h b/src/core/UBSettings.h
index c79e4f95..5b287354 100644
--- a/src/core/UBSettings.h
+++ b/src/core/UBSettings.h
@@ -359,6 +359,7 @@ class UBSettings : public QObject
         UBSetting* pdfMargin;
         UBSetting* pdfPageFormat;
         UBSetting* pdfResolution;
+        UBSetting* pdfZoomBehavior;
 
         UBSetting* podcastFramesPerSecond;
         UBSetting* podcastVideoSize;
diff --git a/src/pdf/XPDFRenderer.cpp b/src/pdf/XPDFRenderer.cpp
index e0ee4ac3..410739fc 100644
--- a/src/pdf/XPDFRenderer.cpp
+++ b/src/pdf/XPDFRenderer.cpp
@@ -37,29 +37,27 @@
 #endif
 
 #include "core/memcheck.h"
+#include "core/UBSettings.h"
 
-#ifdef XPDFRENDERER_CACHE_ZOOM_IMAGE
-#ifdef XPDFRENDERER_CACHE_ZOOM_WITH_LOSS
-double const XPDFRenderer::sRatioZoomRendering[] = { 3.0 };
-#else //XPDFRENDERER_CACHE_ZOOM_WITH_LOSS
-double const XPDFRenderer::sRatioZoomRendering[] = { 2.5, 5, 10.0 };
-#endif //XPDFRENDERER_CACHE_ZOOM_WITH_LOSS
-#endif //XPDFRENDERER_CACHE_ZOOM_IMAGE
 
 QAtomicInt XPDFRenderer::sInstancesCount = 0;
 
 XPDFRenderer::XPDFRenderer(const QString &filename, bool importingFile) :
-#ifndef XPDFRENDERER_CACHE_ZOOM_IMAGE
-    mSplash(nullptr),
-#endif //XPDFRENDERER_CACHE_ZOOM_IMAGE
-    mDocument(0)
+    mpSplashBitmapHistorical(nullptr), mSplashHistorical(nullptr), mDocument(nullptr)
 {
-#ifdef XPDFRENDERER_CACHE_ZOOM_IMAGE
-    for (int i = 0; i < NbrZoomCache; i++)
-    {
-        m_cache.push_back(TypeCacheData(sRatioZoomRendering[i]));
+    switch (UBSettings::settings()->pdfZoomBehavior->get().toUInt()) {
+        case 0: // Render each time (historical initial implementation).
+        break;
+        case 1: // Render a single image, degradated quality when zoomed big.
+        default:
+            m_pdfZoomCache.push_back(3.0);
+        break;
+        case 2: // Render three images, optimal quality all the time.
+            m_pdfZoomCache.push_back(2.5);
+            m_pdfZoomCache.push_back(5.0);
+            m_pdfZoomCache.push_back(10.0);
+        break;
     }
-#endif //XPDFRENDERER_CACHE_ZOOM_IMAGE
 
     Q_UNUSED(importingFile);
     if (!globalParams)
@@ -83,17 +81,18 @@ XPDFRenderer::XPDFRenderer(const QString &filename, bool importingFile) :
 
 XPDFRenderer::~XPDFRenderer()
 {
-#ifdef XPDFRENDERER_CACHE_ZOOM_IMAGE
-    for(int i = 0; i < m_cache.size(); i++)
+    for(int i = 0; i < m_pdfZoomCache.size(); i++)
     {
-        TypeCacheData &cacheData = m_cache[i];
+        TypePdfZoomCacheData &cacheData = m_pdfZoomCache[i];
         if(cacheData.splash != nullptr){
             cacheData.cachedImage = QImage(); // The 'cachedImage' uses a buffer from 'splash'.
             delete cacheData.splash;
             cacheData.splash = nullptr;
         }
     }
-#endif //XPDFRENDERER_CACHE_ZOOM_IMAGE
+
+    if(mSplashHistorical)
+        delete mSplashHistorical;
 
     if (mDocument)
     {
@@ -198,33 +197,17 @@ int XPDFRenderer::pageRotation(int pageNumber) const
         return 0;
 }
 
-#ifndef XPDFRENDERER_CACHE_ZOOM_IMAGE
-void XPDFRenderer::render(QPainter *p, int pageNumber, const QRectF &bounds)
-{
-    if (isValid())
-    {
-        qreal xscale = p->worldTransform().m11();
-        qreal yscale = p->worldTransform().m22();
-
-        QImage *pdfImage = createPDFImage(pageNumber, xscale, yscale, bounds);
-        QTransform savedTransform = p->worldTransform();
-        p->resetTransform();
-        p->drawImage(QPointF(savedTransform.dx() + mSliceX, savedTransform.dy() + mSliceY), *pdfImage);
-        p->setWorldTransform(savedTransform);
-        delete pdfImage;
-    }
-}
 
-QImage* XPDFRenderer::createPDFImage(int pageNumber, qreal xscale, qreal yscale, const QRectF &bounds)
+QImage* XPDFRenderer::createPDFImageHistorical(int pageNumber, qreal xscale, qreal yscale, const QRectF &bounds)
 {
     if (isValid())
     {
         SplashColor paperColor = {0xFF, 0xFF, 0xFF}; // white
-        if(mSplash)
-            delete mSplash;
-        mSplash = new SplashOutputDev(splashModeRGB8, 1, false, paperColor);
+        if(mSplashHistorical)
+            delete mSplashHistorical;
+        mSplashHistorical = new SplashOutputDev(splashModeRGB8, 1, false, paperColor);
 #ifdef USE_XPDF
-        mSplash->startDoc(mDocument->getXRef());
+        mSplashHistorical->startDoc(mDocument->getXRef());
 #else
         mSplash->startDoc(mDocument);
 #endif
@@ -237,7 +220,7 @@ QImage* XPDFRenderer::createPDFImage(int pageNumber, qreal xscale, qreal yscale,
 
         if (bounds.isNull())
         {
-            mDocument->displayPage(mSplash, pageNumber, this->dpiForRendering * xscale, this->dpiForRendering *yscale,
+            mDocument->displayPage(mSplashHistorical, pageNumber, this->dpiForRendering * xscale, this->dpiForRendering *yscale,
                                    rotation, useMediaBox, crop, printing);
         }
         else
@@ -247,56 +230,68 @@ QImage* XPDFRenderer::createPDFImage(int pageNumber, qreal xscale, qreal yscale,
             qreal sliceW = bounds.width() * xscale;
             qreal sliceH = bounds.height() * yscale;
 
-            mDocument->displayPageSlice(mSplash, pageNumber, this->dpiForRendering * xscale, this->dpiForRendering * yscale,
+            mDocument->displayPageSlice(mSplashHistorical, pageNumber, this->dpiForRendering * xscale, this->dpiForRendering * yscale,
                 rotation, useMediaBox, crop, printing, mSliceX, mSliceY, sliceW, sliceH);
         }
 
-        mpSplashBitmap = mSplash->getBitmap();
+        mpSplashBitmapHistorical = mSplashHistorical->getBitmap();
     }
-    return new QImage(mpSplashBitmap->getDataPtr(), mpSplashBitmap->getWidth(), mpSplashBitmap->getHeight(), mpSplashBitmap->getWidth() * 3, QImage::Format_RGB888);
+    return new QImage(mpSplashBitmapHistorical->getDataPtr(), mpSplashBitmapHistorical->getWidth(), mpSplashBitmapHistorical->getHeight(), mpSplashBitmapHistorical->getWidth() * 3, QImage::Format_RGB888);
 }
-#else
-
 
 void XPDFRenderer::render(QPainter *p, int pageNumber, const QRectF &bounds)
 {
     Q_UNUSED(bounds);
     if (isValid())
     {
-        qreal xscale = p->worldTransform().m11();
-        qreal yscale = p->worldTransform().m22();
-        Q_ASSERT(qFuzzyCompare(xscale, yscale)); // Zoom equal in all axes expected.
-        Q_ASSERT(xscale > 0.0); // Potential Div0 later if this assert fail.
-
-        int zoomIndex = 0;
-        bool foundIndex = false;
-        for (; zoomIndex < NbrZoomCache && !foundIndex;)
+        if (m_pdfZoomCache.size() > 0)
         {
-            if (xscale <= m_cache[zoomIndex].ratio) {
-                foundIndex = true;
-            } else {
-                zoomIndex++;
+            qreal xscale = p->worldTransform().m11();
+            qreal yscale = p->worldTransform().m22();
+            Q_ASSERT(qFuzzyCompare(xscale, yscale)); // Zoom equal in all axes expected.
+            Q_ASSERT(xscale > 0.0); // Potential Div0 later if this assert fail.
+
+            int zoomIndex = 0;
+            bool foundIndex = false;
+            for (; zoomIndex < m_pdfZoomCache.size() && !foundIndex;)
+            {
+                if (xscale <= m_pdfZoomCache[zoomIndex].ratio) {
+                    foundIndex = true;
+                } else {
+                    zoomIndex++;
+                }
             }
-        }
 
-        if (!foundIndex) // Use the previous one.
-            zoomIndex--;
+            if (!foundIndex) // Use the previous one.
+                zoomIndex--;
 
-        QImage const &pdfImage = createPDFImage(pageNumber, m_cache[zoomIndex]);
-        QTransform savedTransform = p->worldTransform();
 
-        double const ratioDifferenceBetweenWorldAndImage = 1.0/m_cache[zoomIndex].ratio;
-        // The 'pdfImage' is rendered with a quality equal or superior. We adjust the 'transform' to zoom it
-        // out the required ratio.
-        QTransform newTransform = savedTransform.scale(ratioDifferenceBetweenWorldAndImage, ratioDifferenceBetweenWorldAndImage);
-        p->setWorldTransform(newTransform);
-        p->drawImage(QPointF( mSliceX,  mSliceY), pdfImage);
+            QImage const &pdfImage = createPDFImageCached(pageNumber, m_pdfZoomCache[zoomIndex]);
+            QTransform savedTransform = p->worldTransform();
 
-        p->setWorldTransform(savedTransform);
+            double const ratioDifferenceBetweenWorldAndImage = 1.0/m_pdfZoomCache[zoomIndex].ratio;
+            // The 'pdfImage' is rendered with a quality equal or superior. We adjust the 'transform' to zoom it
+            // out the required ratio.
+            QTransform newTransform = savedTransform.scale(ratioDifferenceBetweenWorldAndImage, ratioDifferenceBetweenWorldAndImage);
+            p->setWorldTransform(newTransform);
+            p->drawImage(QPointF( mSliceX,  mSliceY), pdfImage);
+
+            p->setWorldTransform(savedTransform);
+        } else {
+            qreal xscale = p->worldTransform().m11();
+            qreal yscale = p->worldTransform().m22();
+
+            QImage *pdfImage = createPDFImageHistorical(pageNumber, xscale, yscale, bounds);
+            QTransform savedTransform = p->worldTransform();
+            p->resetTransform();
+            p->drawImage(QPointF(savedTransform.dx() + mSliceX, savedTransform.dy() + mSliceY), *pdfImage);
+            p->setWorldTransform(savedTransform);
+            delete pdfImage;
+        }
     }
 }
 
-QImage& XPDFRenderer::createPDFImage(int pageNumber, TypeCacheData &cacheData)
+QImage& XPDFRenderer::createPDFImageCached(int pageNumber, TypePdfZoomCacheData &cacheData)
 {
     if (isValid())
     {      
@@ -306,7 +301,7 @@ QImage& XPDFRenderer::createPDFImage(int pageNumber, TypeCacheData &cacheData)
         {
             if(cacheData.splash != nullptr)
             {
-                cacheData.cachedImage = QImage(); // The 'm_cachedImage' uses a buffer from 'mSplash'.
+                cacheData.cachedImage = QImage(); // The 'm_pdfZoomCachedImage' uses a buffer from 'mSplash'.
                 delete cacheData.splash;
             }
             cacheData.splash = new SplashOutputDev(splashModeRGB8, 1, false, paperColor);
@@ -339,4 +334,3 @@ QImage& XPDFRenderer::createPDFImage(int pageNumber, TypeCacheData &cacheData)
 
     return cacheData.cachedImage;
 }
-#endif
diff --git a/src/pdf/XPDFRenderer.h b/src/pdf/XPDFRenderer.h
index fef8b411..61dc323a 100644
--- a/src/pdf/XPDFRenderer.h
+++ b/src/pdf/XPDFRenderer.h
@@ -51,9 +51,6 @@
 
 class PDFDoc;
 
-#define XPDFRENDERER_CACHE_ZOOM_IMAGE
-//#define XPDFRENDERER_CACHE_ZOOM_WITH_LOSS
-
 class XPDFRenderer : public PDFRenderer
 {
     Q_OBJECT
@@ -77,20 +74,10 @@ class XPDFRenderer : public PDFRenderer
 
     private:
         void init();
-#ifdef XPDFRENDERER_CACHE_ZOOM_IMAGE
-
-        enum {
-#ifndef XPDFRENDERER_CACHE_ZOOM_WITH_LOSS
-            NbrZoomCache = 3
-#else //XPDFRENDERER_CACHE_ZOOM_WITH_LOSS
-            NbrZoomCache = 1
-#endif //XPDFRENDERER_CACHE_ZOOM_WITH_LOSS
-        };
 
-        class TypeCacheData {
-        public:
-            TypeCacheData(double const a_ratio) : splashBitmap(nullptr), cachedPageNumber(-1), splash(nullptr), ratio(a_ratio) {};
-            ~TypeCacheData() {};
+        struct TypePdfZoomCacheData {
+            TypePdfZoomCacheData(double const a_ratio) : splashBitmap(nullptr), cachedPageNumber(-1), splash(nullptr), ratio(a_ratio) {};
+            ~TypePdfZoomCacheData() {};
             SplashBitmap* splashBitmap;
             QImage cachedImage;
             int cachedPageNumber;
@@ -98,16 +85,18 @@ class XPDFRenderer : public PDFRenderer
             double const ratio;
         };
 
-        QImage &createPDFImage(int pageNumber, TypeCacheData &cacheData);
+        QImage &createPDFImageCached(int pageNumber, TypePdfZoomCacheData &cacheData);
+        QImage* createPDFImageHistorical(int pageNumber, qreal xscale, qreal yscale, const QRectF &bounds);
 
-        static const double sRatioZoomRendering[NbrZoomCache];
-        QVector<TypeCacheData> m_cache;
-#else
-        QImage* createPDFImage(int pageNumber, qreal xscale = 0.5, qreal yscale = 0.5, const QRectF &bounds = QRectF());
+        // Used when 'ZoomBehavior == 1 or 2'.
+        // =1 has only x3 zoom in cache (= loss if user zoom > 3.0).
+        // =2, has 2.5, 5 and 10 (= no loss, but a bit slower).
+        QVector<TypePdfZoomCacheData> m_pdfZoomCache;
 
-        SplashBitmap* mpSplashBitmap;
-        SplashOutputDev* mSplash;
-#endif
+        // Used when 'ZoomBehavior == 0' (no cache).
+        SplashBitmap* mpSplashBitmapHistorical;
+        // Used when 'ZoomBehavior == 0' (no cache).
+        SplashOutputDev* mSplashHistorical;
 
         PDFDoc *mDocument;
         static QAtomicInt sInstancesCount;

From e5377891edeb6124109c8df61f88af7d7685bfe6 Mon Sep 17 00:00:00 2001
From: John Papale <jpapale@vitamin-te.ch>
Date: Tue, 27 Oct 2020 19:05:53 +0100
Subject: [PATCH 4/8] Removed MSVC debug warning.

---
 OpenBoard.pro | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/OpenBoard.pro b/OpenBoard.pro
index da285a9b..f36bf9fe 100644
--- a/OpenBoard.pro
+++ b/OpenBoard.pro
@@ -126,7 +126,11 @@ win32 {
    CONFIG += axcontainer
    exists(console):CONFIG += console
    QMAKE_CXXFLAGS += /MP
-   QMAKE_CXXFLAGS += /MD
+   CONFIG( debug, debug|release ) {
+      QMAKE_CXXFLAGS += /MDd
+   } else {
+      QMAKE_CXXFLAGS += /MD
+   }
    QMAKE_CXXFLAGS_RELEASE += /Od /Zi
    QMAKE_LFLAGS += /VERBOSE:LIB
    UB_LIBRARY.path = $$DESTDIR

From 0cf3bdde1aab882c59b12589a9df056146422cec Mon Sep 17 00:00:00 2001
From: John Papale <jpapale@vitamin-te.ch>
Date: Tue, 27 Oct 2020 19:13:52 +0100
Subject: [PATCH 5/8] Cleanup comments.

---
 src/pdf/XPDFRenderer.cpp | 2 +-
 src/pdf/XPDFRenderer.h   | 2 --
 2 files changed, 1 insertion(+), 3 deletions(-)

diff --git a/src/pdf/XPDFRenderer.cpp b/src/pdf/XPDFRenderer.cpp
index 410739fc..ef6ede30 100644
--- a/src/pdf/XPDFRenderer.cpp
+++ b/src/pdf/XPDFRenderer.cpp
@@ -301,7 +301,7 @@ QImage& XPDFRenderer::createPDFImageCached(int pageNumber, TypePdfZoomCacheData
         {
             if(cacheData.splash != nullptr)
             {
-                cacheData.cachedImage = QImage(); // The 'm_pdfZoomCachedImage' uses a buffer from 'mSplash'.
+                cacheData.cachedImage = QImage();
                 delete cacheData.splash;
             }
             cacheData.splash = new SplashOutputDev(splashModeRGB8, 1, false, paperColor);
diff --git a/src/pdf/XPDFRenderer.h b/src/pdf/XPDFRenderer.h
index 61dc323a..105c574e 100644
--- a/src/pdf/XPDFRenderer.h
+++ b/src/pdf/XPDFRenderer.h
@@ -100,8 +100,6 @@ class XPDFRenderer : public PDFRenderer
 
         PDFDoc *mDocument;
         static QAtomicInt sInstancesCount;
-        //! The image is rendered with a quality above normal, so we can use that same
-        //! image while zooming.
         qreal mSliceX;
         qreal mSliceY;
 };

From d5988f979ca8a873696a11fc38670d739980e889 Mon Sep 17 00:00:00 2001
From: John Papale <jpapale@vitamin-te.ch>
Date: Wed, 28 Oct 2020 10:56:19 +0100
Subject: [PATCH 6/8] Cleanup. Fixed 'Poppler' compile error, since previous
 commit.

---
 src/pdf/XPDFRenderer.cpp | 34 +++++++++++++++++-----------------
 src/pdf/XPDFRenderer.h   | 25 ++++++++++++++++++++-----
 2 files changed, 37 insertions(+), 22 deletions(-)

diff --git a/src/pdf/XPDFRenderer.cpp b/src/pdf/XPDFRenderer.cpp
index ef6ede30..92a6e1e6 100644
--- a/src/pdf/XPDFRenderer.cpp
+++ b/src/pdf/XPDFRenderer.cpp
@@ -42,6 +42,13 @@
 
 QAtomicInt XPDFRenderer::sInstancesCount = 0;
 
+namespace constants{
+   const double mode1_zoomFactor = 3.0;
+   const double mode2_zoomFactorStage1 = 2.5;
+   const double mode2_zoomFactorStage2 = 5.0;
+   const double mode2_zoomFactorStage3 = 10.0;
+}
+
 XPDFRenderer::XPDFRenderer(const QString &filename, bool importingFile) :
     mpSplashBitmapHistorical(nullptr), mSplashHistorical(nullptr), mDocument(nullptr)
 {
@@ -50,12 +57,12 @@ XPDFRenderer::XPDFRenderer(const QString &filename, bool importingFile) :
         break;
         case 1: // Render a single image, degradated quality when zoomed big.
         default:
-            m_pdfZoomCache.push_back(3.0);
+            m_pdfZoomCache.push_back(constants::mode1_zoomFactor);
         break;
         case 2: // Render three images, optimal quality all the time.
-            m_pdfZoomCache.push_back(2.5);
-            m_pdfZoomCache.push_back(5.0);
-            m_pdfZoomCache.push_back(10.0);
+            m_pdfZoomCache.push_back(constants::mode2_zoomFactorStage1);
+            m_pdfZoomCache.push_back(constants::mode2_zoomFactorStage2);
+            m_pdfZoomCache.push_back(constants::mode2_zoomFactorStage3);
         break;
     }
 
@@ -83,7 +90,7 @@ XPDFRenderer::~XPDFRenderer()
 {
     for(int i = 0; i < m_pdfZoomCache.size(); i++)
     {
-        TypePdfZoomCacheData &cacheData = m_pdfZoomCache[i];
+        PdfZoomCacheData &cacheData = m_pdfZoomCache[i];
         if(cacheData.splash != nullptr){
             cacheData.cachedImage = QImage(); // The 'cachedImage' uses a buffer from 'splash'.
             delete cacheData.splash;
@@ -209,7 +216,7 @@ QImage* XPDFRenderer::createPDFImageHistorical(int pageNumber, qreal xscale, qre
 #ifdef USE_XPDF
         mSplashHistorical->startDoc(mDocument->getXRef());
 #else
-        mSplash->startDoc(mDocument);
+        mSplashHistorical->startDoc(mDocument);
 #endif
         int rotation = 0; // in degrees (get it from the worldTransform if we want to support rotation)
         bool useMediaBox = false;
@@ -291,21 +298,14 @@ void XPDFRenderer::render(QPainter *p, int pageNumber, const QRectF &bounds)
     }
 }
 
-QImage& XPDFRenderer::createPDFImageCached(int pageNumber, TypePdfZoomCacheData &cacheData)
+QImage& XPDFRenderer::createPDFImageCached(int pageNumber, PdfZoomCacheData &cacheData)
 {
     if (isValid())
     {      
         SplashColor paperColor = {0xFF, 0xFF, 0xFF}; // white
-        bool const requireUpdateImage = (pageNumber != cacheData.cachedPageNumber) || (cacheData.splash == nullptr);
-        if (requireUpdateImage)
+        if (cacheData.requireUpdateImage(pageNumber))
         {
-            if(cacheData.splash != nullptr)
-            {
-                cacheData.cachedImage = QImage();
-                delete cacheData.splash;
-            }
-            cacheData.splash = new SplashOutputDev(splashModeRGB8, 1, false, paperColor);
-            cacheData.cachedPageNumber = pageNumber;
+            cacheData.prepareNewSplash(pageNumber, paperColor);
 
 #ifdef USE_XPDF
             cacheData.splash->startDoc(mDocument->getXRef());
@@ -324,7 +324,7 @@ QImage& XPDFRenderer::createPDFImageCached(int pageNumber, TypePdfZoomCacheData
             cacheData.splashBitmap = cacheData.splash->getBitmap();
         }
 
-        // Note this uses the 'mSplash->getBitmap()->getDataPtr()' as data buffer.
+        // Note this uses the 'cacheData.splash->getBitmap()->getDataPtr()' as data buffer.
         cacheData.cachedImage = QImage(cacheData.splashBitmap->getDataPtr(), cacheData.splashBitmap->getWidth(), cacheData.splashBitmap->getHeight(),
                                cacheData.splashBitmap->getWidth() * 3 /* bytesPerLine, 24 bits for RGB888, = 3 bytes */,
                                QImage::Format_RGB888);
diff --git a/src/pdf/XPDFRenderer.h b/src/pdf/XPDFRenderer.h
index 105c574e..43357b01 100644
--- a/src/pdf/XPDFRenderer.h
+++ b/src/pdf/XPDFRenderer.h
@@ -75,23 +75,38 @@ class XPDFRenderer : public PDFRenderer
     private:
         void init();
 
-        struct TypePdfZoomCacheData {
-            TypePdfZoomCacheData(double const a_ratio) : splashBitmap(nullptr), cachedPageNumber(-1), splash(nullptr), ratio(a_ratio) {};
-            ~TypePdfZoomCacheData() {};
+        struct PdfZoomCacheData {
+            PdfZoomCacheData(double const a_ratio) : splashBitmap(nullptr), cachedPageNumber(-1), splash(nullptr), ratio(a_ratio) {};
+            ~PdfZoomCacheData() {};
             SplashBitmap* splashBitmap;
             QImage cachedImage;
             int cachedPageNumber;
             SplashOutputDev* splash;
             double const ratio;
+
+            bool requireUpdateImage(int const pageNumber) const {
+                return (pageNumber != cachedPageNumber) || (splash == nullptr);
+            }
+
+            void prepareNewSplash(int const pageNumber, SplashColor &paperColor)
+            {
+                if(splash != nullptr)
+                {
+                    cachedImage = QImage();
+                    delete splash;
+                }
+                splash = new SplashOutputDev(splashModeRGB8, 1, false, paperColor);
+                cachedPageNumber = pageNumber;
+            }
         };
 
-        QImage &createPDFImageCached(int pageNumber, TypePdfZoomCacheData &cacheData);
+        QImage &createPDFImageCached(int pageNumber, PdfZoomCacheData &cacheData);
         QImage* createPDFImageHistorical(int pageNumber, qreal xscale, qreal yscale, const QRectF &bounds);
 
         // Used when 'ZoomBehavior == 1 or 2'.
         // =1 has only x3 zoom in cache (= loss if user zoom > 3.0).
         // =2, has 2.5, 5 and 10 (= no loss, but a bit slower).
-        QVector<TypePdfZoomCacheData> m_pdfZoomCache;
+        QVector<PdfZoomCacheData> m_pdfZoomCache;
 
         // Used when 'ZoomBehavior == 0' (no cache).
         SplashBitmap* mpSplashBitmapHistorical;

From 505ca347afe1aca13e68823df05322364150f81e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Cl=C3=A9ment=20Fauconnier?= <fc86@outlook.fr>
Date: Mon, 2 Nov 2020 11:05:10 +0100
Subject: [PATCH 7/8] renamed and moved XPDF zoom constants to make them more
 readable and open to further development

---
 src/pdf/XPDFRenderer.cpp | 15 ++++-----------
 src/pdf/XPDFRenderer.h   |  9 +++++++++
 2 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/src/pdf/XPDFRenderer.cpp b/src/pdf/XPDFRenderer.cpp
index 92a6e1e6..e128b33b 100644
--- a/src/pdf/XPDFRenderer.cpp
+++ b/src/pdf/XPDFRenderer.cpp
@@ -42,13 +42,6 @@
 
 QAtomicInt XPDFRenderer::sInstancesCount = 0;
 
-namespace constants{
-   const double mode1_zoomFactor = 3.0;
-   const double mode2_zoomFactorStage1 = 2.5;
-   const double mode2_zoomFactorStage2 = 5.0;
-   const double mode2_zoomFactorStage3 = 10.0;
-}
-
 XPDFRenderer::XPDFRenderer(const QString &filename, bool importingFile) :
     mpSplashBitmapHistorical(nullptr), mSplashHistorical(nullptr), mDocument(nullptr)
 {
@@ -57,12 +50,12 @@ XPDFRenderer::XPDFRenderer(const QString &filename, bool importingFile) :
         break;
         case 1: // Render a single image, degradated quality when zoomed big.
         default:
-            m_pdfZoomCache.push_back(constants::mode1_zoomFactor);
+            m_pdfZoomCache.push_back(XPDFRendererZoomFactor::mode1_zoomFactor);
         break;
         case 2: // Render three images, optimal quality all the time.
-            m_pdfZoomCache.push_back(constants::mode2_zoomFactorStage1);
-            m_pdfZoomCache.push_back(constants::mode2_zoomFactorStage2);
-            m_pdfZoomCache.push_back(constants::mode2_zoomFactorStage3);
+            m_pdfZoomCache.push_back(XPDFRendererZoomFactor::mode2_zoomFactorStage1);
+            m_pdfZoomCache.push_back(XPDFRendererZoomFactor::mode2_zoomFactorStage2);
+            m_pdfZoomCache.push_back(XPDFRendererZoomFactor::mode2_zoomFactorStage3);
         break;
     }
 
diff --git a/src/pdf/XPDFRenderer.h b/src/pdf/XPDFRenderer.h
index 43357b01..4ac3f9aa 100644
--- a/src/pdf/XPDFRenderer.h
+++ b/src/pdf/XPDFRenderer.h
@@ -51,6 +51,15 @@
 
 class PDFDoc;
 
+
+namespace XPDFRendererZoomFactor
+{
+    const double mode1_zoomFactor = 3.0;
+    const double mode2_zoomFactorStage1 = 2.5;
+    const double mode2_zoomFactorStage2 = 5.0;
+    const double mode2_zoomFactorStage3 = 10.0;
+}
+
 class XPDFRenderer : public PDFRenderer
 {
     Q_OBJECT

From 6716e031fd3ad1b568ef6c61b1a2c106bf019343 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Cl=C3=A9ment=20Fauconnier?= <fc86@outlook.fr>
Date: Mon, 2 Nov 2020 11:08:55 +0100
Subject: [PATCH 8/8] added pdf zoom behavior default value to config file

---
 resources/etc/OpenBoard.config | 1 +
 1 file changed, 1 insertion(+)

diff --git a/resources/etc/OpenBoard.config b/resources/etc/OpenBoard.config
index 06c81ef6..c85c025e 100644
--- a/resources/etc/OpenBoard.config
+++ b/resources/etc/OpenBoard.config
@@ -123,6 +123,7 @@ RefreshRateInFramePerSecond=2
 Margin=20
 PageFormat=A4
 Resolution=300
+ZoomBehavior=1
 
 [Podcast]
 AudioRecordingDevice=Default