fix: handling of active ruler

- make UBDrawingController::mActiveRuler private
- use guarded pointer to avoid dangling pointer dereferencing
- provide public accessor functions
- consider a ruler active only if it is visible

src/board/UBBoardView.cpp

@@ -1104,7 +1104,7 @@ void UBBoardView::mousePressEvent (QMouseEvent *event)
             break;
 
         default:
-            if(UBDrawingController::drawingController()->mActiveRuler==NULL) {
+            if (UBDrawingController::drawingController()->activeRuler() == nullptr) {
                 viewport()->setCursor (QCursor (Qt::BlankCursor));
             }
             if (scene () && !mTabletStylusIsPressed) {

src/board/UBDrawingController.cpp

@@ -34,6 +34,7 @@
 
 #include "domain/UBGraphicsScene.h"
 #include "board/UBBoardController.h"
+#include "tools/UBAbstractDrawRuler.h"
 
 #include "gui/UBMainWindow.h"
 #include "core/memcheck.h"
@@ -58,7 +59,6 @@ void UBDrawingController::destroy()
 
 UBDrawingController::UBDrawingController(QObject * parent)
     : QObject(parent)
-    , mActiveRuler(NULL)
     , mStylusTool((UBStylusTool::Enum)-1)
     , mLatestDrawingTool((UBStylusTool::Enum)-1)
     , mIsDesktopMode(false)
@@ -322,6 +322,23 @@ void UBDrawingController::setMarkerAlpha(qreal alpha)
     emit colorPaletteChanged();
 }
 
+void UBDrawingController::setActiveRuler(UBAbstractDrawRuler* ruler)
+{
+    mActiveRuler = ruler;
+}
+
+UBAbstractDrawRuler* UBDrawingController::activeRuler() const
+{
+    QGraphicsItem* item = dynamic_cast<QGraphicsItem*>(mActiveRuler.data());
+
+    if (item && item->isVisible())
+    {
+        return mActiveRuler;
+    }
+
+    return nullptr;
+}
+
 
 void UBDrawingController::penToolSelected(bool checked)
 {

src/board/UBDrawingController.h

@@ -64,7 +64,8 @@ class UBDrawingController : public QObject
         void setMarkerColor(bool onDarkBackground, const QColor& color, int pIndex);
         void setMarkerAlpha(qreal alpha);
 
-        UBAbstractDrawRuler* mActiveRuler;
+        void setActiveRuler(UBAbstractDrawRuler* ruler);
+        UBAbstractDrawRuler* activeRuler() const;
 
         void setInDesktopMode(bool mode){
             mIsDesktopMode = mode;
@@ -89,6 +90,7 @@ class UBDrawingController : public QObject
         void colorIndexChanged(int index);
 
     private:
+        QPointer<UBAbstractDrawRuler> mActiveRuler;
         UBStylusTool::Enum mStylusTool;
         UBStylusTool::Enum mLatestDrawingTool;
         bool mIsDesktopMode;

src/domain/UBGraphicsScene.cpp

@@ -451,8 +451,8 @@ bool UBGraphicsScene::inputDevicePress(const QPointF& scenePos, const qreal& pre
             mAddedItems.clear();
             mRemovedItems.clear();
 
-            if (UBDrawingController::drawingController()->mActiveRuler)
-                UBDrawingController::drawingController()->mActiveRuler->StartLine(scenePos, width);
+            if (UBDrawingController::drawingController()->activeRuler())
+                UBDrawingController::drawingController()->activeRuler()->StartLine(scenePos, width);
             else {
                 moveTo(scenePos);
                 drawLineTo(scenePos, width, UBDrawingController::drawingController()->stylusTool() == UBStylusTool::Line);
@@ -539,7 +539,7 @@ bool UBGraphicsScene::inputDeviceMove(const QPointF& scenePos, const qreal& pres
             width /= UBApplication::boardController->systemScaleFactor();
             width /= UBApplication::boardController->currentZoom();
 
-            if (currentTool == UBStylusTool::Line || dc->mActiveRuler)
+            if (currentTool == UBStylusTool::Line || dc->activeRuler())
             {
                 if (UBDrawingController::drawingController()->stylusTool() != UBStylusTool::Marker)
                 if(NULL != mpLastPolygon && NULL != mCurrentStroke && mAddedItems.size() > 0){
@@ -573,8 +573,8 @@ bool UBGraphicsScene::inputDeviceMove(const QPointF& scenePos, const qreal& pres
             if (!mCurrentStroke)
                 mCurrentStroke = new UBGraphicsStroke(this);
 
-            if(dc->mActiveRuler){
-                dc->mActiveRuler->DrawLine(position, width);
+            if(dc->activeRuler()){
+                dc->activeRuler()->DrawLine(position, width);
             }
 
             else if (currentTool == UBStylusTool::Line) {
@@ -859,7 +859,7 @@ void UBGraphicsScene::drawPenCircle(const QPointF &pPoint)
         cursor = UBResources::resources()->penCursor;
     }
 
-    if (!UBDrawingController::drawingController()->mActiveRuler)
+    if (!UBDrawingController::drawingController()->activeRuler())
     {
         // set cursor only if no active ruler
         if (controlView() && controlView()->viewport())

src/tools/UBGraphicsRuler.cpp

@@ -450,7 +450,7 @@ void UBGraphicsRuler::hoverEnterEvent(QGraphicsSceneHoverEvent *event)
     else if (UBDrawingController::drawingController()->isDrawingTool())
     {
         setCursor(drawRulerLineCursor());
-        UBDrawingController::drawingController()->mActiveRuler = this;
+        UBDrawingController::drawingController()->setActiveRuler(this);
         event->accept();
     }
 }
@@ -462,7 +462,7 @@ void UBGraphicsRuler::hoverLeaveEvent(QGraphicsSceneHoverEvent *event)
     mCloseSvgItem->setVisible(mShowButtons);
     mResizeSvgItem->setVisible(mShowButtons);
     mRotateSvgItem->setVisible(mShowButtons);
-    UBDrawingController::drawingController()->mActiveRuler = nullptr;
+    UBDrawingController::drawingController()->setActiveRuler(nullptr);
     event->accept();
     update();
 }

src/tools/UBGraphicsTriangle.cpp

@@ -886,7 +886,7 @@ void UBGraphicsTriangle::hoverEnterEvent(QGraphicsSceneHoverEvent *event)
 
     } else if (UBDrawingController::drawingController()->isDrawingTool())  {
             setCursor(drawRulerLineCursor());
-            UBDrawingController::drawingController()->mActiveRuler = this;
+            UBDrawingController::drawingController()->setActiveRuler(this);
             event->accept();
     }
 
@@ -904,7 +904,7 @@ void UBGraphicsTriangle::hoverLeaveEvent(QGraphicsSceneHoverEvent *event)
     mVFlipSvgItem->setVisible(false);
     mHFlipSvgItem->setVisible(false);
     mRotateSvgItem->setVisible(false);
-    UBDrawingController::drawingController()->mActiveRuler = NULL;
+    UBDrawingController::drawingController()->setActiveRuler(nullptr);
     event->accept();
     update();
 }