remove broken accelerator from preview button; add tooltip

aqt/browser.py

@@ -383,6 +383,8 @@ class Browser(QMainWindow):
         # edit
         c(f.actionUndo, s, self.mw.onUndo)
         c(f.previewButton, SIGNAL("clicked()"), self.onTogglePreview)
+        f.previewButton.setToolTip(_("Preview Selected Card (%s)") %
+            shortcut(_("Ctrl+Shift+P")))
         c(f.actionInvertSelection, s, self.invertSelection)
         c(f.actionSelectNotes, s, self.selectNotes)
         c(f.actionFindReplace, s, self.onFindReplace)

designer/browser.ui

@@ -122,7 +122,7 @@
            <item row="0" column="2">
             <widget class="QPushButton" name="previewButton">
              <property name="text">
-              <string>&amp;Preview</string>
+              <string>Preview</string>
              </property>
              <property name="shortcut">
               <string>Ctrl+Shift+P</string>