Limit bottom fullscreen controls panel width

Fullscreen bottom controls panel does not look good when progress bar is too long (especially on "ultrawide" displays), so limit its max width to 1720 application-pixels. This should make it still long enough for convenient chapter seeking.

src/revealers.js

@@ -228,6 +228,19 @@ class ClapperRevealerBottom extends CustomRevealer
         this.revealerBox.remove(widget);
     }
 
+    setLayoutMargins(layoutWidth)
+    {
+        const maxWidth = 1720;
+
+        if(layoutWidth <= maxWidth)
+            return;
+
+        const margin = (layoutWidth - maxWidth) / 2;
+
+        this.margin_start = margin;
+        this.margin_end = margin;
+    }
+
     _onMotion(controller, x, y)
     {
         const clapperWidget = this.root.child;

src/widget.js

@@ -563,6 +563,10 @@ class ClapperWidget extends Gtk.Grid
             return;
 
         this.layoutWidth = width;
+
+        if(this.isFullscreenMode)
+            this.revealerBottom.setLayoutMargins(width);
+
         this.controls._onPlayerResize(width, height);
     }