diff --git a/include/widget/Widget.hpp b/include/widget/Widget.hpp
index 0e5a37ef..bd631f00 100644
--- a/include/widget/Widget.hpp
+++ b/include/widget/Widget.hpp
@@ -50,14 +50,27 @@ struct Widget {
 
 	void requestDelete();
 
+	/** Returns the smallest rectangle containing this widget's children (visible and invisible) in its local coordinates.
+	Returns `Rect(Vec(inf, inf), Vec(-inf, -inf))` if there are no children.
+	*/
 	virtual math::Rect getChildrenBoundingBox();
-	/**  Returns `v` transformed into the coordinate system of `relative` */
+	/**  Returns `v` (given in local coordinates) transformed into the coordinate system of `relative`.
+	*/
 	virtual math::Vec getRelativeOffset(math::Vec v, Widget* relative);
-	/** Returns `v` transformed into world coordinates */
+	/** Returns `v` transformed into world/root/global/absolute coordinates.
+	*/
 	math::Vec getAbsoluteOffset(math::Vec v) {
 		return getRelativeOffset(v, NULL);
 	}
-	/** Returns a subset of the given math::Rect bounded by the box of this widget and all ancestors */
+	/** Returns the zoom level in the coordinate system of `relative`.
+	Only `ZoomWidget` should override this to return value other than 1.
+	*/
+	virtual float getRelativeZoom(Widget* relative);
+	float getAbsoluteZoom() {
+		return getRelativeZoom(NULL);
+	}
+	/** Returns a subset of the given Rect bounded by the box of this widget and all ancestors.
+	*/
 	virtual math::Rect getViewport(math::Rect r);
 
 	template <class T>
diff --git a/include/widget/ZoomWidget.hpp b/include/widget/ZoomWidget.hpp
index ee3f5cfc..167b54cd 100644
--- a/include/widget/ZoomWidget.hpp
+++ b/include/widget/ZoomWidget.hpp
@@ -11,6 +11,7 @@ struct ZoomWidget : Widget {
 	float zoom = 1.f;
 
 	math::Vec getRelativeOffset(math::Vec v, Widget* relative) override;
+	float getRelativeZoom(Widget* relative) override;
 	math::Rect getViewport(math::Rect r) override;
 	void setZoom(float zoom);
 	float getZoom() {
diff --git a/src/widget/Widget.cpp b/src/widget/Widget.cpp
index 35d4f089..2c053379 100644
--- a/src/widget/Widget.cpp
+++ b/src/widget/Widget.cpp
@@ -87,8 +87,6 @@ math::Rect Widget::getChildrenBoundingBox() {
 	math::Vec min = math::Vec(INFINITY, INFINITY);
 	math::Vec max = math::Vec(-INFINITY, -INFINITY);
 	for (Widget* child : children) {
-		if (!child->visible)
-			continue;
 		min = min.min(child->box.getTopLeft());
 		max = max.max(child->box.getBottomRight());
 	}
@@ -97,14 +95,22 @@ math::Rect Widget::getChildrenBoundingBox() {
 
 
 math::Vec Widget::getRelativeOffset(math::Vec v, Widget* relative) {
-	if (this == relative) {
+	if (this == relative)
 		return v;
-	}
+	// Translate offset
 	v = v.plus(box.pos);
-	if (parent) {
-		v = parent->getRelativeOffset(v, relative);
-	}
-	return v;
+	if (!parent)
+		return v;
+	return parent->getRelativeOffset(v, relative);
+}
+
+
+float Widget::getRelativeZoom(Widget* relative) {
+	if (this == relative)
+		return 1.f;
+	if (!parent)
+		return 1.f;
+	return parent->getRelativeZoom(relative);
 }
 
 
diff --git a/src/widget/ZoomWidget.cpp b/src/widget/ZoomWidget.cpp
index c4ffca85..d608d278 100644
--- a/src/widget/ZoomWidget.cpp
+++ b/src/widget/ZoomWidget.cpp
@@ -6,9 +6,17 @@ namespace widget {
 
 
 math::Vec ZoomWidget::getRelativeOffset(math::Vec v, Widget* relative) {
-	return Widget::getRelativeOffset(v.mult(zoom), relative);
+	// Transform `v` (which is in child coordinates) to local coordinates.
+	v = v.mult(zoom);
+	return Widget::getRelativeOffset(v, relative);
 }
 
+
+float ZoomWidget::getRelativeZoom(Widget* relative) {
+	return zoom * Widget::getRelativeZoom(relative);
+}
+
+
 math::Rect ZoomWidget::getViewport(math::Rect r) {
 	r.pos = r.pos.mult(zoom);
 	r.size = r.size.mult(zoom);
@@ -18,6 +26,7 @@ math::Rect ZoomWidget::getViewport(math::Rect r) {
 	return r;
 }
 
+
 void ZoomWidget::setZoom(float zoom) {
 	if (zoom == this->zoom)
 		return;
@@ -30,6 +39,7 @@ void ZoomWidget::setZoom(float zoom) {
 	Widget::onDirty(eDirty);
 }
 
+
 void ZoomWidget::draw(const DrawArgs& args) {
 	DrawArgs zoomCtx = args;
 	zoomCtx.clipBox.pos = zoomCtx.clipBox.pos.div(zoom);