Fix hover when cursor leaves view, fixes #63

gui/fpgaviewwidget.cc

diff --git a/gui/fpgaviewwidget.cc b/gui/fpgaviewwidget.cc
index 0bbf80e..2b0a3ef 100644
--- a/gui/fpgaviewwidget.cc
+++ b/gui/fpgaviewwidget.cc
@@ -781,4 +781,12 @@
     }
 }
 
+void FPGAViewWidget::leaveEvent(QEvent *event)
+{
+    QMutexLocker locked(&rendererArgsLock_);
+    rendererArgs_->hoveredDecal = DecalXY();
+    rendererArgs_->changed = true;
+    pokeRenderer();
+}
+
 NEXTPNR_NAMESPACE_END

gui/fpgaviewwidget.h

diff --git a/gui/fpgaviewwidget.h b/gui/fpgaviewwidget.h
index a40a015..ee05aae 100644
--- a/gui/fpgaviewwidget.h
+++ b/gui/fpgaviewwidget.h
@@ -107,6 +107,7 @@
     void wheelEvent(QWheelEvent *event) Q_DECL_OVERRIDE;
     QSize minimumSizeHint() const override;
     QSize sizeHint() const override;
+    void leaveEvent(QEvent *event) override;
 
   public Q_SLOTS:
     void newContext(Context *ctx);