diff --git a/src/linecomps.tsx b/src/linecomps.tsx
index 53248b19..7621dd50 100644
--- a/src/linecomps.tsx
+++ b/src/linecomps.tsx
@@ -531,7 +531,7 @@ class LineCmd extends React.Component<{screen : LineContainerModel, line : LineT
                     <TerminalRenderer screen={screen} line={line} width={width} staticRender={staticRender} visible={visible} onHeightChange={this.handleHeightChange} collapsed={isCollapsed}/>
                 </If>
                 <If condition={rendererPlugin != null}>
-                    <SimpleBlobRenderer lcm={screen} line={line} cmd={cmd} plugin={rendererPlugin}/>
+                    <SimpleBlobRenderer lcm={screen} line={line} cmd={cmd} plugin={rendererPlugin} onHeightChange={this.handleHeightChange}/>
                 </If>
                 <If condition={!isCollapsed && cmd.getRtnState()}>
                     <div key="rtnstate" className="cmd-rtnstate" style={{visibility: ((cmd.getStatus() == "done") ? "visible" : "hidden")}}>
diff --git a/src/simplerenderer.tsx b/src/simplerenderer.tsx
index ca120d70..fd65936f 100644
--- a/src/simplerenderer.tsx
+++ b/src/simplerenderer.tsx
@@ -52,6 +52,7 @@ class SimpleBlobRendererModel {
         if (this.savedHeight != newHeight) {
             this.savedHeight = newHeight;
             this.api.saveHeight(newHeight);
+            console.log("saveheight", sprintf("[%d]", this.context.lineNum), newHeight);
         }
     }
     
@@ -118,9 +119,10 @@ function apiAdapter(lcm : LineContainerModel, line : LineType, cmd : Cmd) : Rend
 }
 
 @mobxReact.observer
-class SimpleBlobRenderer extends React.Component<{lcm : LineContainerModel, line : LineType, cmd : Cmd, plugin : RendererPluginType}, {}> {
+class SimpleBlobRenderer extends React.Component<{lcm : LineContainerModel, line : LineType, cmd : Cmd, plugin : RendererPluginType, onHeightChange : () => void}, {}> {
     model : SimpleBlobRendererModel;
     wrapperDivRef : React.RefObject<any> = React.createRef();
+    rszObs : ResizeObserver;
 
     constructor(props : any) {
         super(props);
@@ -151,27 +153,44 @@ class SimpleBlobRenderer extends React.Component<{lcm : LineContainerModel, line
         this.model.initialize(initOpts);
         lcm.registerRenderer(line.cmdid, this.model);
     }
+
+    handleResize(entries : ResizeObserverEntry[]) : void {
+        console.log("simplerender resize", sprintf("[%d]", this.model.context.lineNum), entries);
+        if (this.props.onHeightChange) {
+            this.props.onHeightChange();
+        }
+        if (!this.model.loading.get() && this.wrapperDivRef.current != null) {
+            let height = this.wrapperDivRef.current.offsetHeight;
+            this.model.updateHeight(height);
+        }
+    }
+
+    checkRszObs() {
+        if (this.rszObs != null) {
+            return;
+        }
+        if (this.wrapperDivRef.current == null) {
+            return;
+        }
+        this.rszObs = new ResizeObserver(this.handleResize.bind(this));
+        this.rszObs.observe(this.wrapperDivRef.current);
+    }
     
     componentDidMount() {
-        this.checkHeight();
+        this.checkRszObs();
     }
 
     componentWillUnmount() {
         let {lcm, line} = this.props;
         lcm.unloadRenderer(line.cmdid);
+        if (this.rszObs != null) {
+            this.rszObs.disconnect();
+            this.rszObs = null;
+        }
     }
 
     componentDidUpdate() {
-        this.checkHeight();
-    }
-
-    checkHeight() : void {
-        // TODO: use resizeobserver instead of ref.
-        if (this.wrapperDivRef.current == null) {
-            return;
-        }
-        let height = this.wrapperDivRef.current.offsetHeight;
-        this.model.updateHeight(height);
+        this.checkRszObs();
     }
 
     render() {
@@ -179,7 +198,7 @@ class SimpleBlobRenderer extends React.Component<{lcm : LineContainerModel, line
         let model = this.model;
         if (model.loading.get()) {
             let height = this.model.savedHeight;
-            return (<div style={{minHeight: height}}>...</div>);
+            return (<div ref={this.wrapperDivRef} style={{minHeight: height}}>...</div>);
         }
         let Comp = plugin.component;
         let dataBlob = new Blob([model.ptyData.data]);
diff --git a/src/types.ts b/src/types.ts
index e679c019..99c3cf2d 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -405,17 +405,6 @@ type SimpleBlobRendererComponent = React.ComponentType<{data : Blob, context : R
 type SimpleJsonRendererComponent = React.ComponentType<{data : any, context : RendererContext, opts : RendererOpts}>;
 type FullRendererComponent = React.ComponentType<{model : any}>;
 
-type OldRendererModel = {
-    dispose : () => void,
-    reload : (delayMs : number) => void,
-    receiveData : (pos : number, data : Uint8Array, reason? : string) => void,
-    cmdDone : () => void,
-    resizeWindow : (size : WindowSize) => void,
-    resizeCols : (cols : number) => void,
-    giveFocus : () => void,
-    getUsedRows : () => number,
-};
-
 type WindowSize = {
     height : number,
     width: number,