fix: render RDP sessions at native pixel density (#1059)

src/ui/features/guacamole/GuacamoleApp.tsx

@@ -96,7 +96,7 @@ const GuacamoleApp = React.forwardRef<GuacamoleAppHandle, GuacamoleAppProps>(
 
 interface GuacamoleAppInnerProps {
   hostId: number;
-  hostConfig: Pick<SSHHost, "connectionType">;
+  hostConfig: Pick<SSHHost, "connectionType" | "guacamoleConfig">;
   hostName: string;
   tabId?: string;
   protocol?: "rdp" | "vnc" | "telnet";
@@ -213,6 +213,7 @@ const GuacamoleAppInner = React.forwardRef<
     | "rdp"
     | "vnc"
     | "telnet";
+  const configuredDpi = Number(hostConfig.guacamoleConfig?.dpi);
 
   return (
     <div className="relative w-full h-full">
@@ -250,6 +251,10 @@ const GuacamoleAppInner = React.forwardRef<
           token,
           protocol: resolvedProtocol,
           type: resolvedProtocol,
+          dpi:
+            Number.isFinite(configuredDpi) && configuredDpi > 0
+              ? configuredDpi
+              : undefined,
         }}
         isVisible={true}
         onError={(err) => setConnectionError(err)}

src/ui/features/guacamole/GuacamoleDisplay.tsx

@@ -17,6 +17,7 @@ import {
   isPasteShortcut,
   pasteTextToRemote,
 } from "./guacamole-clipboard.ts";
+import { getGuacamoleDisplaySize } from "./guacamole-display-size.ts";
 
 export type GuacamoleConnectionType = "rdp" | "vnc" | "telnet";
 
@@ -129,13 +130,14 @@ export const GuacamoleDisplay = forwardRef<
     ): Promise<string | null> => {
       try {
         let token: string;
-        const protocol = connectionConfig.protocol ?? connectionConfig.type;
+        const connectionProtocol =
+          connectionConfig.protocol ?? connectionConfig.type;
 
         if (connectionConfig.token) {
           token = connectionConfig.token;
         } else {
           const data = await getGuacamoleToken({
-            protocol: protocol ?? "rdp",
+            protocol: connectionProtocol ?? "rdp",
             hostname: String(connectionConfig.hostname ?? ""),
             port: connectionConfig.port,
             username: connectionConfig.username,
@@ -156,8 +158,13 @@ export const GuacamoleDisplay = forwardRef<
           token = data.token;
         }
 
-        const width = connectionConfig.width ?? containerWidth ?? 1280;
-        const height = connectionConfig.height ?? containerHeight ?? 720;
+        const displaySize = getGuacamoleDisplaySize(
+          connectionConfig.width ?? containerWidth ?? 1280,
+          connectionConfig.height ?? containerHeight ?? 720,
+          connectionProtocol,
+          window.devicePixelRatio,
+          connectionConfig.dpi,
+        );
 
         const wsBase = buildGuacamoleWebSocketBaseUrl({
           isDev,
@@ -171,9 +178,10 @@ export const GuacamoleDisplay = forwardRef<
 
         const params = new URLSearchParams({
           token,
-          width: String(width),
-          height: String(height),
+          width: String(displaySize.width),
+          height: String(displaySize.height),
         });
+        if (displaySize.dpi) params.set("dpi", String(displaySize.dpi));
         return `${wsBase}?${params.toString()}`;
       } catch (error) {
         const errorMessage =
@@ -434,9 +442,14 @@ export const GuacamoleDisplay = forwardRef<
           onConnect?.();
           if (containerRef.current) {
             const rect = containerRef.current.getBoundingClientRect();
-            const w = Math.round(rect.width);
-            const h = Math.round(rect.height);
-            if (w > 0 && h > 0) client.sendSize(w, h);
+            const size = getGuacamoleDisplaySize(
+              rect.width,
+              rect.height,
+              protocol,
+              window.devicePixelRatio,
+              connectionConfig.dpi,
+            );
+            client.sendSize(size.width, size.height);
           }
           rescaleDisplay(false);
           break;
@@ -515,6 +528,7 @@ export const GuacamoleDisplay = forwardRef<
     rescaleDisplay,
     connectionConfig.protocol,
     connectionConfig.type,
+    connectionConfig.dpi,
     t,
   ]);
 
@@ -588,10 +602,15 @@ export const GuacamoleDisplay = forwardRef<
       resizeTimeoutRef.current = setTimeout(() => {
         if (clientRef.current && containerRef.current) {
           const rect = containerRef.current.getBoundingClientRect();
-          const w = Math.round(rect.width);
-          const h = Math.round(rect.height);
-          if (w > 0 && h > 0) {
-            clientRef.current.sendSize(w, h);
+          const size = getGuacamoleDisplaySize(
+            rect.width,
+            rect.height,
+            connectionConfig.protocol ?? connectionConfig.type,
+            window.devicePixelRatio,
+            connectionConfig.dpi,
+          );
+          if (rect.width > 0 && rect.height > 0) {
+            clientRef.current.sendSize(size.width, size.height);
             rescaleDisplay(true);
           }
         }
@@ -603,7 +622,12 @@ export const GuacamoleDisplay = forwardRef<
     return () => {
       resizeObserver.disconnect();
     };
-  }, [rescaleDisplay]);
+  }, [
+    connectionConfig.dpi,
+    connectionConfig.protocol,
+    connectionConfig.type,
+    rescaleDisplay,
+  ]);
 
   const syncClipboard = useCallback(() => {
     const client = clientRef.current;

src/ui/features/guacamole/guacamole-display-size.test.ts

@@ -0,0 +1,39 @@
+import { describe, expect, it } from "vitest";
+import { getGuacamoleDisplaySize } from "./guacamole-display-size";
+
+describe("getGuacamoleDisplaySize", () => {
+  it("requests native pixels and matching DPI for HiDPI RDP", () => {
+    expect(getGuacamoleDisplaySize(1280, 720, "rdp", 2)).toEqual({
+      width: 2560,
+      height: 1440,
+      dpi: 192,
+      pixelRatio: 2,
+    });
+  });
+
+  it("scales a configured RDP DPI with the device pixel ratio", () => {
+    expect(getGuacamoleDisplaySize(1000, 600, "rdp", 1.5, 120)).toEqual({
+      width: 1500,
+      height: 900,
+      dpi: 180,
+      pixelRatio: 1.5,
+    });
+  });
+
+  it("leaves non-RDP protocols at CSS-pixel dimensions", () => {
+    expect(getGuacamoleDisplaySize(1280, 720, "vnc", 2)).toEqual({
+      width: 1280,
+      height: 720,
+      pixelRatio: 1,
+    });
+  });
+
+  it("caps pathological pixel ratios to protect remote session size", () => {
+    expect(getGuacamoleDisplaySize(400, 800, "rdp", 4)).toEqual({
+      width: 1200,
+      height: 2400,
+      dpi: 288,
+      pixelRatio: 3,
+    });
+  });
+});

src/ui/features/guacamole/guacamole-display-size.ts

@@ -0,0 +1,39 @@
+const DEFAULT_RDP_DPI = 96;
+const MAX_DEVICE_PIXEL_RATIO = 3;
+
+export interface GuacamoleDisplaySize {
+  width: number;
+  height: number;
+  dpi?: number;
+  pixelRatio: number;
+}
+
+export function getGuacamoleDisplaySize(
+  cssWidth: number,
+  cssHeight: number,
+  protocol: string | undefined,
+  devicePixelRatio: number,
+  configuredDpi?: number,
+): GuacamoleDisplaySize {
+  const isRdp = protocol === "rdp";
+  const pixelRatio = isRdp
+    ? Math.min(
+        MAX_DEVICE_PIXEL_RATIO,
+        Math.max(1, Number.isFinite(devicePixelRatio) ? devicePixelRatio : 1),
+      )
+    : 1;
+
+  const size = {
+    width: Math.max(1, Math.round(cssWidth * pixelRatio)),
+    height: Math.max(1, Math.round(cssHeight * pixelRatio)),
+    pixelRatio,
+  };
+
+  if (!isRdp) return size;
+
+  const baseDpi =
+    configuredDpi && Number.isFinite(configuredDpi) && configuredDpi > 0
+      ? configuredDpi
+      : DEFAULT_RDP_DPI;
+  return { ...size, dpi: Math.round(baseDpi * pixelRatio) };
+}