Add preference to disable automatic pen/eraser switching

Fixes the annoyance where Openboard auto-switches to the eraser tool
when a tablet device (like the Promethean Activ Panel) detects the
eraser pointer type. There is now a checkbox in the Pen preferences tab
to turn this off. Defaults to on so nothing changes for existing users.

Closes #1432

Author: SofianElmotiem

resources/forms/preferences.ui

@@ -948,6 +948,13 @@
          </property>
         </widget>
        </item>
+       <item row="1" column="0" colspan="2">
+        <widget class="QCheckBox" name="autoSwitchToEraserCheckBox">
+         <property name="text">
+          <string>Automatically switch to eraser when tablet eraser is detected</string>
+         </property>
+        </widget>
+       </item>
       </layout>
      </widget>
      <widget class="QWidget" name="markerTab">

src/board/UBBoardView.cpp

@@ -350,13 +350,16 @@ void UBBoardView::tabletEvent (QTabletEvent * event)
     UBStylusTool::Enum currentTool = (UBStylusTool::Enum)dc->stylusTool ();
 
     if (event->type () == QEvent::TabletPress || event->type () == QEvent::TabletEnterProximity) {
+        const bool autoSwitch = UBSettings::settings()->boardAutoSwitchToEraser->get().toBool();
 #if (QT_VERSION >= QT_VERSION_CHECK(6, 0, 0))
         if (event->pointerType () == QPointingDevice::PointerType::Eraser) {
 #else
         if (event->pointerType () == QTabletEvent::Eraser) {
 #endif
-            dc->setStylusTool (UBStylusTool::Eraser);
-            mUsingTabletEraser = true;
+            if (autoSwitch) {
+                dc->setStylusTool (UBStylusTool::Eraser);
+                mUsingTabletEraser = true;
+            }
         }
         else {
             if (mUsingTabletEraser && currentTool == UBStylusTool::Eraser)

src/core/UBPreferencesController.cpp

@@ -271,6 +271,8 @@ void UBPreferencesController::wire()
     connect(mPenProperties->circleCheckBox, SIGNAL(clicked(bool)), settings, SLOT(setPenPreviewCircle(bool)));
     connect(mPenProperties->circleSpinBox, SIGNAL(valueChanged(int)), this, SLOT(penPreviewFromSizeChanged(int)));
 
+    connect(mPreferencesUI->autoSwitchToEraserCheckBox, SIGNAL(clicked(bool)), settings->boardAutoSwitchToEraser, SLOT(setBool(bool)));
+
     // marker
     QList<QColor> markerLightBackgroundColors = settings->boardMarkerLightBackgroundColors->colors();
     QList<QColor> markerDarkBackgroundColors = settings->boardMarkerDarkBackgroundColors->colors();
@@ -342,6 +344,7 @@ void UBPreferencesController::init()
     mPenProperties->pressureSensitiveCheckBox->setChecked(settings->boardPenPressureSensitive->get().toBool());
     mPenProperties->circleCheckBox->setChecked(settings->showPenPreviewCircle->get().toBool());
     mPenProperties->circleSpinBox->setValue(settings->penPreviewFromSize->get().toInt());
+    mPreferencesUI->autoSwitchToEraserCheckBox->setChecked(settings->boardAutoSwitchToEraser->get().toBool());
 
     // marker tab
     mMarkerProperties->fineSlider->setValue(settings->boardMarkerFineWidth->get().toDouble() * sSliderRatio);

src/core/UBSettings.cpp

@@ -285,6 +285,7 @@ void UBSettings::init()
     boardMarkerPressureSensitive = new UBSetting(this, "Board", "MarkerPressureSensitive", false);
 
     boardUseHighResTabletEvent = new UBSetting(this, "Board", "UseHighResTabletEvent", true);
+    boardAutoSwitchToEraser = new UBSetting(this, "Board", "AutoSwitchToEraser", true);
 
     boardInterpolatePenStrokes = new UBSetting(this, "Board", "InterpolatePenStrokes", true);
     boardSimplifyPenStrokes = new UBSetting(this, "Board", "SimplifyPenStrokes", true);

src/core/UBSettings.h

@@ -287,6 +287,7 @@ class UBSettings : public QObject
         UBSetting* boardMarkerPressureSensitive;
 
         UBSetting* boardUseHighResTabletEvent;
+        UBSetting* boardAutoSwitchToEraser;
 
         UBSetting* boardInterpolatePenStrokes;
         UBSetting* boardSimplifyPenStrokes;