Fractional scaling fixes + bar border settings

Common/Theme.qml

@@ -685,7 +685,17 @@ Singleton {
     function withAlpha(c, a) { return Qt.rgba(c.r, c.g, c.b, a); }
 
     function snap(value, dpr) {
-        return Math.round(value * dpr) / dpr
+        const s = dpr || 1
+        return Math.round(value * s) / s
+    }
+
+    function px(value, dpr) {
+        const s = dpr || 1
+        return Math.round(value * s) / s
+    }
+
+    function hairline(dpr) {
+        return 1 / (dpr || 1)
     }
 
     function invertHex(hex) {