Use children bounding box for FramebufferWidget

src/app/RackWidget.cpp

@@ -345,18 +345,13 @@ void RackWidget::step() {
 	Widget *rail = rails->children.front();
 	Rect bound = getViewport(Rect(Vec(), box.size));
 	if (!rails->box.contains(bound)) {
-		// Add a margin around the otherwise tight bound, so that scrolling slightly will not require a re-render of rails.
-		Vec margin = Vec(100, 100);
-		bound.pos = bound.pos.minus(margin);
-		bound.size = bound.size.plus(margin.mult(2));
-		rails->box = bound;
-		// Compute offset of rail within rails framebuffer
-		Vec grid = Vec(RACK_GRID_WIDTH, RACK_GRID_HEIGHT);
-		Vec gridPos = bound.pos.div(grid).floor().mult(grid);
-		bound.pos = gridPos.minus(bound.pos);
-		bound.size = bound.size.minus(bound.pos);
-		rail->box = bound;
+		Vec cellMargin = Vec(20, 1);
+		rails->box.pos = bound.pos.div(RACK_GRID_SIZE).floor().minus(cellMargin).mult(RACK_GRID_SIZE);
+		rails->box.size = bound.size.plus(cellMargin.mult(RACK_GRID_SIZE).mult(2));
+		printf("%f %f %f %f\n", rails->box.pos.x, rails->box.pos.y, rails->box.size.x, rails->box.size.y);
 		rails->dirty = true;
+
+		rail->box.size = rails->box.size;
 	}
 
 	// Autosave every 15 seconds

src/widgets/FramebufferWidget.cpp

@@ -53,13 +53,15 @@ void FramebufferWidget::draw(NVGcontext *vg) {
 	if (dirty) {
 		dirty = false;
 
-		internal->box.pos = Vec(0, 0);
-		internal->box.size = box.size.mult(s).ceil().plus(Vec(1, 1));
+		internal->box = getChildrenBoundingBox();
+		internal->box.pos = internal->box.pos.mult(s).floor();
+		internal->box.size = internal->box.size.mult(s).ceil().plus(Vec(1, 1));
+
 		Vec fbSize = internal->box.size.mult(gPixelRatio * oversample);
 
-		// assert(fbSize.isFinite());
-		// Reject zero area size
-		if (fbSize.x <= 0.0 || fbSize.y <= 0.0)
+		if (!fbSize.isFinite())
+			return;
+		if (fbSize.isZero())
 			return;
 
 		// printf("rendering framebuffer %f %f\n", fbSize.x, fbSize.y);
@@ -81,6 +83,7 @@ void FramebufferWidget::draw(NVGcontext *vg) {
 		nvgScale(gFramebufferVg, gPixelRatio * oversample, gPixelRatio * oversample);
 		// Use local scaling
 		nvgTranslate(gFramebufferVg, bf.x, bf.y);
+		nvgTranslate(gFramebufferVg, internal->box.pos.x, internal->box.pos.y);
 		nvgScale(gFramebufferVg, s.x, s.y);
 		Widget::draw(gFramebufferVg);