Symbol editor: fix issues related to axis not shown.

In Symbol editor, axis are always shown. However after switching the backend, axis were no longer drawn.
In Cairo engine, fix a bug preventing axis to be shown.

common/gal/cairo/cairo_gal.cpp

@@ -904,14 +904,16 @@ void CAIRO_GAL_BASE::resetContext()
 void CAIRO_GAL_BASE::drawAxes( const VECTOR2D& aStartPoint, const VECTOR2D& aEndPoint )
 {
     syncLineWidth();
+
     auto p0 = roundp( xform( aStartPoint ) );
     auto p1 = roundp( xform( aEndPoint ) );
+    auto org = roundp( xform( VECTOR2D( 0.0, 0.0 ) ) );     // Axis origin = 0,0 coord
 
-    cairo_move_to( currentContext, p0.x, 0.0);
-    cairo_line_to( currentContext, p1.x, 0.0 );
-    cairo_move_to( currentContext, 0.0, p0.y );
-    cairo_line_to( currentContext, 0.0, p1.y );
     cairo_set_source_rgba( currentContext, axesColor.r, axesColor.g, axesColor.b, axesColor.a );
+    cairo_move_to( currentContext, p0.x, org.y);
+    cairo_line_to( currentContext, p1.x, org.y );
+    cairo_move_to( currentContext, org.x, p0.y );
+    cairo_line_to( currentContext, org.x, p1.y );
     cairo_stroke( currentContext );
 }
 

eeschema/libedit/lib_edit_frame.cpp

@@ -1840,3 +1840,13 @@ void LIB_EDIT_FRAME::KiwayMailIn( KIWAY_EXPRESS& mail )
         ;
     }
 }
+
+
+void LIB_EDIT_FRAME::OnSwitchCanvas( wxCommandEvent& aEvent )
+{
+    // switches currently used canvas ( Cairo / OpenGL):
+    SCH_BASE_FRAME::OnSwitchCanvas( aEvent );
+
+    // Set options specific to symbol editor (axies are always enabled):
+    GetGalCanvas()->GetGAL()->SetAxesEnabled( true );
+}

eeschema/libedit/lib_edit_frame.h

@@ -154,6 +154,11 @@ public:
 
     ~LIB_EDIT_FRAME();
 
+    /**
+     * switches currently used canvas ( Cairo / OpenGL).
+     */
+    void OnSwitchCanvas( wxCommandEvent& aEvent ) override;
+
     /** The nickname of the current library being edited and empty string if none. */
     wxString GetCurLib() const;
 

eeschema/sch_base_frame.h

@@ -112,7 +112,7 @@ public:
     /**
      * switches currently used canvas ( Cairo / OpenGL).
      */
-    void OnSwitchCanvas( wxCommandEvent& aEvent );
+    virtual void OnSwitchCanvas( wxCommandEvent& aEvent );
 
     /**
      * Update UI called when switches currently used canvas (Cairo / OpenGL).