diff --git a/remglk/src/glkapi/mod.rs b/remglk/src/glkapi/mod.rs
index 3fe1597..4cd3f25 100644
--- a/remglk/src/glkapi/mod.rs
+++ b/remglk/src/glkapi/mod.rs
@@ -1503,19 +1503,23 @@ where S: Default + GlkSystem {
                     let keywin = Into::<GlkWindow>::into(&win.key);
                     let keywin = lock!(keywin);
                     match keywin.wintype {
-                        WindowType::Buffer => if win.vertical {
+                        WindowType::Buffer => if win.size > 0 {
+                            if win.vertical {
                                 win.size as f64 * self.metrics.buffercharwidth + self.metrics.buffermarginx
                             }
                             else {
                                 win.size as f64 * self.metrics.buffercharheight + self.metrics.buffermarginy
                             }
-                        WindowType::Graphics => win.size as f64 + (if win.vertical {self.metrics.graphicsmarginx} else {self.metrics.graphicsmarginy}),
-                        WindowType::Grid => if win.vertical {
+                        } else {0.0},
+                        WindowType::Graphics => if win.size > 0 {win.size as f64 + (if win.vertical {self.metrics.graphicsmarginx} else {self.metrics.graphicsmarginy})} else {0.0},
+                        WindowType::Grid => if win.size > 0 {
+                            if win.vertical {
                                 win.size as f64 * self.metrics.gridcharwidth + self.metrics.gridmarginx
                             }
                             else {
                                 win.size as f64 * self.metrics.gridcharheight + self.metrics.gridmarginy
                             }
+                        } else {0.0},
                         _ => unreachable!(),
                     }
                 }
diff --git a/remglk/src/glkapi/protocol.rs b/remglk/src/glkapi/protocol.rs
index c3177e9..37ddc3f 100644
--- a/remglk/src/glkapi/protocol.rs
+++ b/remglk/src/glkapi/protocol.rs
@@ -733,6 +733,9 @@ pub struct WindowUpdate {
     #[serde(skip_serializing_if = "Option::is_none")]
     pub gridwidth: Option<u32>,
     pub height: f64,
+    /** Whether the window should be completely hidden, though could potentially still respond to character events */
+    #[serde(skip_serializing_if = "Not::not")]
+    pub hidden: bool,
     /** Window ID */
     pub id: u32,
     /** Left position */
diff --git a/remglk/src/glkapi/windows.rs b/remglk/src/glkapi/windows.rs
index 6ffcbc9..6e1811b 100644
--- a/remglk/src/glkapi/windows.rs
+++ b/remglk/src/glkapi/windows.rs
@@ -86,17 +86,20 @@ impl Window {
         }
 
         // Now give it to the specific window types for them to fill in
+        let height = self.wbox.bottom - self.wbox.top;
+        let width = self.wbox.right - self.wbox.left;
         self.data.update(WindowUpdate {
             id: self.id,
             input: input_update,
             size: protocol::WindowUpdate {
-                height: self.wbox.bottom - self.wbox.top,
+                height,
+                hidden: height == 0.0 || width == 0.0,
                 id: self.id,
                 left: self.wbox.left,
                 rock: self.rock,
                 top: self.wbox.top,
                 wintype: self.wintype,
-                width: self.wbox.right - self.wbox.left,
+                width,
                 ..Default::default()
             },
             ..Default::default()