how to maximaize the label by using mouse click?

[jefftee]

Look at your if statement and figure out why the following statement works for the left button but not the right:

if(event->button()==Qt::LeftButton || Qt::RightButton)

if(event->button()==Qt::LeftButton || Qt::RightButton)

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Your if statement reads as:

• If the button for this event == Qt::LeftButton or
• Qt::RightButton is true or non-zero (note how I didn't mention the button?)

Figure out why and you have solved your problem.