Improve terminal renderer recovery

packages/app/src/terminal/runtime/terminal-emulator-runtime.ts

@@ -158,6 +158,7 @@ export class TerminalEmulatorRuntime {
       convertEol: false,
       cursorBlink: true,
       cursorStyle: "bar",
+      customGlyphs: true,
       fontFamily: DEFAULT_TERMINAL_FONT_FAMILY,
       fontSize: 13,
       lineHeight: 1.0,
@@ -173,6 +174,7 @@ export class TerminalEmulatorRuntime {
     const fitAddon = new FitAddon();
     const unicode11Addon = new Unicode11Addon();
     let webglAddon: WebglAddon | null = null;
+    let imageAddon: ImageAddon | null = null;
     terminal.loadAddon(fitAddon);
     terminal.loadAddon(unicode11Addon);
     terminal.loadAddon(
@@ -195,34 +197,46 @@ export class TerminalEmulatorRuntime {
       // Ignore if unicode API isn't available in this build/runtime.
     }
 
-    // Prefer GPU rendering when available. This tends to reduce visible seams in block characters
-    // and improves scroll performance, but must gracefully fall back on platforms without WebGL.
+    const disposeImageAddon = (): void => {
+      try {
+        imageAddon?.dispose();
+      } catch {
+        // ignore
+      }
+      imageAddon = null;
+    };
+    const disposeWebglRenderer = (): void => {
+      if (!webglAddon) {
+        return;
+      }
+      try {
+        webglAddon.dispose();
+      } catch {
+        // ignore
+      }
+      webglAddon = null;
+      disposeImageAddon();
+      // WebGL and DOM renderers can have different cell dimensions.
+      this.fitAndEmitResize?.(true);
+    };
+
     let webglAddonRaf: number | null = requestAnimationFrame(() => {
       webglAddonRaf = null;
       try {
+        disposeWebglRenderer();
         webglAddon = new WebglAddon();
         webglAddon.onContextLoss(() => {
-          try {
-            webglAddon?.dispose();
-          } catch {
-            // ignore
-          }
-          webglAddon = null;
-          // Force a refresh after context loss to avoid visual corruption.
-          try {
-            terminal.refresh(0, terminal.rows - 1);
-          } catch {
-            // ignore
-          }
+          disposeWebglRenderer();
         });
         terminal.loadAddon(webglAddon);
+        imageAddon = new ImageAddon();
+        terminal.loadAddon(imageAddon);
+        this.fitAndEmitResize?.(true);
       } catch {
-        webglAddon = null;
+        disposeWebglRenderer();
       }
     });
 
-    terminal.loadAddon(new ImageAddon());
-
     // Suppress terminal query responses — the server-side headless xterm handles these.
     // Without this, xterm.js generates DA/CPR responses via onData that feed back
     // to the PTY as visible text.
@@ -451,12 +465,8 @@ export class TerminalEmulatorRuntime {
           cancelAnimationFrame(webglAddonRaf);
           webglAddonRaf = null;
         }
-        try {
-          webglAddon?.dispose();
-        } catch {
-          // ignore
-        }
-        webglAddon = null;
+        disposeWebglRenderer();
+        disposeImageAddon();
       },
       disposeTerminal: () => {
         terminal.dispose();

packages/desktop/src/main.ts

@@ -21,6 +21,7 @@ import {
   getMainWindowChromeOptions,
   getWindowBackgroundColor,
   resolveSystemWindowTheme,
+  setupDarwinPaintRefresh,
   setupWindowResizeEvents,
   setupDefaultContextMenu,
   setupDragDropPrevention,
@@ -189,6 +190,7 @@ async function createMainWindow(): Promise<void> {
     app.dock?.setBadge(devWorktreeName);
   }
 
+  setupDarwinPaintRefresh(mainWindow);
   setupWindowResizeEvents(mainWindow);
   setupDefaultContextMenu(mainWindow);
   setupDragDropPrevention(mainWindow);

packages/desktop/src/window/window-manager.ts

@@ -219,6 +219,59 @@ export function setupWindowResizeEvents(win: BrowserWindow): void {
   });
 }
 
+function refreshChromiumSurface(win: BrowserWindow): void {
+  if (win.isDestroyed()) {
+    return;
+  }
+
+  win.webContents.invalidate();
+  if (win.isMaximized() || win.isFullScreen()) {
+    return;
+  }
+
+  const [width, height] = win.getSize();
+  win.setSize(width + 1, height);
+  setTimeout(() => {
+    if (!win.isDestroyed()) {
+      win.setSize(width, height);
+    }
+  }, 32);
+}
+
+export function setupDarwinPaintRefresh(win: BrowserWindow): void {
+  if (process.platform !== "darwin") {
+    return;
+  }
+
+  win.webContents.setBackgroundThrottling(false);
+
+  const requestSurfaceRefresh = () => {
+    if (!win.isDestroyed()) {
+      win.webContents.invalidate();
+    }
+  };
+  const handleChildProcessGone = (
+    _event: Electron.Event,
+    details: { type?: string; reason?: string },
+  ) => {
+    if (details.type !== "GPU") {
+      return;
+    }
+
+    console.warn("[window] GPU process gone:", details.reason);
+    refreshChromiumSurface(win);
+  };
+
+  win.on("restore", requestSurfaceRefresh);
+  win.on("show", requestSurfaceRefresh);
+  app.on("child-process-gone", handleChildProcessGone);
+  win.once("closed", () => {
+    win.off("restore", requestSurfaceRefresh);
+    win.off("show", requestSurfaceRefresh);
+    app.off("child-process-gone", handleChildProcessGone);
+  });
+}
+
 export function setupDefaultContextMenu(win: BrowserWindow): void {
   win.webContents.on("context-menu", (_event, params) => {
     const menu = Menu.buildFromTemplate([