Pass non-trivial/large function args by reference

Fixes a bunch of `-Wclazy-function-args-by-ref` warnings. See
https://github.com/KDE/clazy/blob/master/docs/checks/README-function-args-by-ref.md
for details.

Most of these changes are automated, using the clazy fixit by setting
the `CLAZY_EXPORT_FIXES` before compilation and then running:

    $ mkdir /tmp/patch
    $ find ../src -iname "*.yaml" -exec mv {} /tmp/patch \;
    $ clang-apply-replacements /tmp/patch

1 files changed, 6 insertions, 3 deletions

diff --git a/src/widget/wpushbutton.h b/src/widget/wpushbutton.h
index ac5f6ef525..6393ea5710 100644
--- a/src/widget/wpushbutton.h
+++ b/src/widget/wpushbutton.h
@@ -95,13 +95,16 @@ class WPushButton : public WWidget {
     virtual void restyleAndRepaint();
 
     // Associates a pixmap of a given state of the button with the widget
-    void setPixmap(int iState, bool bPressed, PixmapSource source,
-                   Paintable::DrawMode mode, double scaleFactor);
+    void setPixmap(int iState,
+            bool bPressed,
+            const PixmapSource& source,
+            Paintable::DrawMode mode,
+            double scaleFactor);
 
     // Associates a background pixmap with the widget. This is only needed if
     // the button pixmaps contains alpha channel values.
     void setPixmapBackground(
-            PixmapSource source,
+            const PixmapSource& source,
             Paintable::DrawMode mode,
             double scaleFactor);