The Zoom 1:1 icon is not shown in the main toolbar (but it is shown in the "View" menu). Is that intentional? If no, the fix is rather simple:

diff --git a/pv/mainwindow.cpp b/pv/mainwindow.cpp
index 0089b11..1447efd 100644
--- a/pv/mainwindow.cpp
+++ b/pv/mainwindow.cpp
@@ -257,6 +257,7 @@ void MainWindow::setup_ui()
        toolbar->addAction(action_view_zoom_in);
        toolbar->addAction(action_view_zoom_out);
        toolbar->addAction(action_view_zoom_fit);
+       toolbar->addAction(action_view_zoom_one_to_one);
        addToolBar(toolbar);

        // Setup the sampling bar