[gnome-shell/wip/carlosg/issue-91: 47/47] st: Round CSS units to the nearest multiple of the scale factor

[Florian Müllner <fmuellner src gnome org>]

commit a540fe41309ccf6f6a1d3e3d0f1ce46c7cb3ab19
Author: Carlos Garnacho <carlosg gnome org>
Date:   Sat Mar 23 16:33:58 2019 +0100

    st: Round CSS units to the nearest multiple of the scale factor
    
    Actors themed through CSS should ideally get sizes and positions that
    conform to the "pixel grid". A notorious example is the panel that has a
    height of 1.86em. On unchanged font settings and hidpi that translates to
    55px, which leaves the workarea with "half pixels" that hidpi wayland
    applications don't know how to fully cover.
    
    If the requested height is a multiple of the scale factor, the workarea
    and maximized applications can then work on full pixels.
    
    Closes: https://gitlab.gnome.org/GNOME/gnome-shell/issues/91

 src/st/st-theme-node.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)
---
diff --git a/src/st/st-theme-node.c b/src/st/st-theme-node.c
index c05ca78fc..8a6ebf03f 100644
--- a/src/st/st-theme-node.c
+++ b/src/st/st-theme-node.c
@@ -1136,10 +1136,14 @@ get_length_from_term_int (StThemeNode *node,
 {
   double value;
   GetFromTermResult result;
+  int scale_factor;
 
   result = get_length_from_term (node, term, use_parent_font, &value);
   if (result == VALUE_FOUND)
-    *length = (int) (0.5 + value);
+    {
+      g_object_get (node->context, "scale-factor", &scale_factor, NULL);
+      *length = (int) ((value / scale_factor) + 0.5) * scale_factor;
+    }
   return result;
 }