size of horizontal layout

This is my code

myplot * p = new myplot(gao.structpayloadgraph,gao1.structpayloadgraph, gao.structcol-2, "payload");
myplot * p1 = new myplot(gao.structsessiongraph,gao.structsessiongraph, gao.structcol-2, "session");

ui->horizontalLayout_3->addWidget(p);
ui->horizontalLayout_3->addWidget(p1);

It's working fine, my graphs are shown side by size but the problem is that it is good for small graphs having 5 ,6 points but when I try to show some bigger graph the window(in which graph is shown) become extremely large, so it didn't fit on screen. Is there a way by which I can take the size of horizontal layout and then resize my p开发者_如何学Go, p1 to fit in to that area, something like that?

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i am quite sure there is not a method to know the size of a layout..