[Add] Added zoom and pan for preview widget.

src/pdf_page_widget.cpp

@@ -9,7 +9,6 @@ PDFPageWidget::PDFPageWidget(QWidget* parent) :
   selected = false;
   setAcceptDrops(true);
 
-  /* Resize widget. */
   this->resize(150, 150);
   this->setMinimumSize(150, 150);
   this->setMaximumSize(150, 150);

src/pdf_preview_widget.cpp

@@ -1,7 +1,9 @@
 #include <QtWidgets>
 #include "pdf_preview_widget.h"
 
-PDFPreviewWidget::PDFPreviewWidget(QWidget* parent) : QWidget(parent) {
+PDFPreviewWidget::PDFPreviewWidget(QWidget* parent) : QFrame(parent) {
+  setCursor(Qt::OpenHandCursor);
+  setFrameStyle(QFrame::StyledPanel | QFrame::Plain);
   pPage = NULL;
   currentPixmapSize = QSize(0,0);
 }
@@ -23,14 +25,35 @@ void PDFPreviewWidget::regenImage(void) {
   previewImage = pPage->renderToImage(dpi, dpi);
 }
 
+void PDFPreviewWidget::regenPixmap(void) {
+  pixmap = QPixmap::fromImage(previewImage);
+  pixmap = pixmap.scaled(currentPixmapSize, Qt::KeepAspectRatioByExpanding);
+  currentPixmapSize = pixmap.size();
+}
+
+void PDFPreviewWidget::repositionPixmap(void) {
+  currentPixmapPos = QPoint((size().width() - pixmap.width()) / 2,
+                     (size().height() - pixmap.height()) / 2);
+}
+
 void PDFPreviewWidget::previewUpdate(Poppler::Page* pp) {
   pPage = pp;
   regenImage();
+  regenPixmap();
+  repositionPixmap();
   update();
 }
 
+void PDFPreviewWidget::resizeEvent(QResizeEvent* event) {
+  if(pPage != NULL) {
+    repositionPixmap();
+    update();
+  }
+}
+
 void PDFPreviewWidget::wheelEvent(QWheelEvent* event) {
   if(pPage != NULL) {
+    qDebug() << currentPixmapSize;
     if(event->delta() > 0)
       currentPixmapSize += QSize(30, 30);
     else if(event->delta() < 0)
@@ -41,20 +64,59 @@ void PDFPreviewWidget::wheelEvent(QWheelEvent* event) {
     }
 
     regenImage();
+    regenPixmap();
+    repositionPixmap();
     update();
   }
 }
 
+void PDFPreviewWidget::mousePressEvent(QMouseEvent* event) {
+  if(pPage != NULL) {
+    setCursor(Qt::ClosedHandCursor);
+
+    if(event->button() == Qt::LeftButton) {
+      dragStartPos = event->pos();
+      lastPixmapPos = currentPixmapPos;
+    }
+  }
+}
+
+void PDFPreviewWidget::mouseMoveEvent(QMouseEvent* event) {
+  if(pPage != NULL) {
+    if(!(event->buttons() & Qt::LeftButton)) {
+      return;
+    }
+
+    QPoint currentPos = event->pos();
+    QPoint vector     = currentPos - dragStartPos;
+    QPoint newPos     = lastPixmapPos + vector;
+
+    if(pixmap.width() > size().width()) {
+      if(newPos.x() <= 0 && newPos.x() >= size().width() - pixmap.width())
+        currentPixmapPos.setX(newPos.x());
+    }
+
+    if(pixmap.height() > size().height()) {
+      if(newPos.y() <= 0 && newPos.y() >= size().height() - pixmap.height())
+        currentPixmapPos.setY(newPos.y());
+    }
+
+    update();
+  }
+}
+
+void PDFPreviewWidget::mouseReleaseEvent(QMouseEvent* event) {
+  setCursor(Qt::OpenHandCursor);
+}
+
 void PDFPreviewWidget::paintEvent(QPaintEvent* event) {
   if(pPage != NULL) {
 
     QPainter painter(this);
-    QPixmap pixmap = QPixmap::fromImage(previewImage);
-    pixmap = pixmap.scaled(currentPixmapSize, Qt::KeepAspectRatio);
-    currentPixmapSize = pixmap.size();
-    painter.drawPixmap(QRect((size().width() - pixmap.width()) / 2,
-                      (size().height() - pixmap.height()) / 2,
+    painter.drawPixmap(QRect(currentPixmapPos.x(), currentPixmapPos.y(),
           pixmap.width(), pixmap.height()), pixmap);
+
+    QFrame::paintEvent(event);
   }
 }
 

src/pdf_preview_widget.h

@@ -1,33 +1,44 @@
 #pragma once
-#include <QWidget>
+#include <QFrame>
 #include <poppler-qt5.h>
 
 class QImage;
+class QPixmap;
 class QSize;
 class QPoint;
+class QResizeEvent;
 class QWheelEvent;
 class QPaintEvent;
 class QMouseEvent;
 
-class PDFPreviewWidget : public QWidget {
+class PDFPreviewWidget : public QFrame {
   Q_OBJECT
 public:
   explicit PDFPreviewWidget(QWidget* parent = 0);
 
 public slots:
   void regenImage(void);
+  void regenPixmap(void);
+  void repositionPixmap(void);
   void previewUpdate(Poppler::Page*);
 
 protected:
   void wheelEvent(QWheelEvent* event);
   void paintEvent(QPaintEvent* event);
+  void resizeEvent(QResizeEvent* event);
+  void mousePressEvent(QMouseEvent* event);
+  void mouseMoveEvent(QMouseEvent* event);
+  void mouseReleaseEvent(QMouseEvent* event);
 
 private:
   QImage previewImage;
+  QPixmap pixmap;
   Poppler::Page* pPage;
  
   QSize   currentPixmapSize;
   QPoint  currentPixmapPos;
+  QPoint  lastPixmapPos;
+  QPoint  dragStartPos;
 
 signals:
   void updatePreview(QImage);