DrawSketchHandler: refactor crosshairCursor

======================================================

-DrawSketchHandler manages both cursor bitmap setting and unsetting

src/Mod/Sketcher/Gui/DrawSketchHandler.cpp

@@ -221,10 +221,20 @@ DrawSketchHandler::DrawSketchHandler() : sketchgui(nullptr) {}
 
 DrawSketchHandler::~DrawSketchHandler() {}
 
+QString DrawSketchHandler::getCrosshairCursorString() const
+{
+    return QString::fromLatin1("None");
+}
+
 void DrawSketchHandler::activate(ViewProviderSketch * vp)
 {
     sketchgui = vp;
 
+    auto cursorstring = getCrosshairCursorString();
+
+    if(cursorstring != QString::fromLatin1("None"))
+        setCrosshairCursor(cursorstring);
+
     this->preActivated();
     this->activated();
 }
@@ -280,8 +290,7 @@ unsigned long DrawSketchHandler::getCrosshairColor()
     return color;
 }
 
-void DrawSketchHandler::setCrosshairCursor(const char* svgName) {
-    QString cursorName = QString::fromLatin1(svgName);
+void DrawSketchHandler::setCrosshairCursor(const QString & svgName) {
     const unsigned long defaultCrosshairColor = 0xFFFFFF;
     unsigned long color = getCrosshairColor();
     auto colorMapping = std::map<unsigned long, unsigned long>();
@@ -289,7 +298,12 @@ void DrawSketchHandler::setCrosshairCursor(const char* svgName) {
     // hot spot of all SVG icons should be 8,8 for 32x32 size (16x16 for 64x64)
     int hotX = 8;
     int hotY = 8;
-    setSvgCursor(cursorName, hotX, hotY, colorMapping);
+    setSvgCursor(svgName, hotX, hotY, colorMapping);
+}
+
+void DrawSketchHandler::setCrosshairCursor(const char* svgName) {
+    QString cursorName = QString::fromLatin1(svgName);
+    setCrosshairCursor(cursorName);
 }
 
 void DrawSketchHandler::setSvgCursor(const QString & cursorName, int x, int y, const std::map<unsigned long, unsigned long>& colorMapping)

src/Mod/Sketcher/Gui/DrawSketchHandler.h

@@ -148,6 +148,7 @@ private:
     virtual void activated(){}
     virtual void deactivated(){}
     virtual void postDeactivated(){}
+    virtual void onWidgetChanged(){}
 
 protected:
     // helpers
@@ -166,6 +167,7 @@ protected:
     void applyCursor(QCursor &newCursor);
     unsigned long getCrosshairColor();
     qreal devicePixelRatio();
+    void setCrosshairCursor(const QString & svgName);
     void setCrosshairCursor(const char* svgName);
 
     void drawEdit(const std::vector<Base::Vector2d> &EditCurve);
@@ -178,6 +180,7 @@ protected:
     int getPreselectCurve(void) const;
     int getPreselectCross(void) const;
 
+    virtual QString getCrosshairCursorString() const;
 
     /**
      * Returns constraints icons scaled to width.