Remove timer-based polling, always use CADisplayLink for frame updates

CADisplayLink provides better vsync alignment and consistent 60fps updates.
The timer-based 400Hz polling path added unnecessary complexity and CPU
overhead without meaningful benefits.

- Remove useCADisplayLink parameter and displaysync preference
- Simplify FrameUpdater to always use CADisplayLink
- Remove preference UI toggle for display sync option
- Add CLAUDE.md project documentation

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

screendump/CLAUDE.md

@@ -0,0 +1,86 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+ScreenDump is a VNC server for jailbroken iOS 15+ devices (rootless/Ellekit). It captures the device screen and streams it via VNC protocol while supporting remote keyboard and touch input.
+
+## Build Commands
+
+```bash
+# Build the package (requires Theos installed)
+make package
+
+# Clean build artifacts
+make clean
+
+# Build and install to device (requires SSH access)
+make package install THEOS_DEVICE_IP=<device-ip>
+```
+
+The build produces `screendumpd` daemon installed to `/usr/libexec`.
+
+## Architecture
+
+### Core Components
+
+- **ScreenDumpVNC** ([ScreenDumpVNC.m](ScreenDumpVNC.m)) - Main singleton controller that:
+  - Initializes libvncserver with screen dimensions
+  - Manages IOSurface framebuffer acquisition via IOMobileFramebuffer
+  - Creates IOSurfaceAccelerator for frame scaling/transfer
+  - Handles dual capture mode switching
+
+- **FrameUpdater** ([FrameUpdater.m](FrameUpdater.m)) - Frame capture loop:
+  - Runs on NSOperationQueue with max 1 concurrent operation (serialized)
+  - Uses CADisplayLink for vsync-based updates at 60fps
+  - Transfers frames via IOSurfaceAcceleratorTransferSurface or CARenderServerRenderDisplay
+
+- **VNC Event Handlers** ([vnc.m](vnc.m)) - Input injection:
+  - Keyboard events via IOHIDEventSystemClient (XK keysym to HID usage mapping)
+  - Touch/pointer via IOHIDDigitizer events (normalized coordinates)
+  - Backslash key (`\`) toggles capture mode
+
+### Capture Modes
+
+Two capture modes available, toggled via backslash key during VNC session:
+
+1. **CARenderServer** (default) - Uses `CARenderServerRenderDisplay()`, faster but hides secure text fields
+2. **IOMobileFramebuffer** (legacy) - Direct framebuffer access, shows password fields but auto-reverts after 10 seconds
+
+### Frame Pipeline
+
+```
+IOMobileFramebuffer → screenSurface (native res)
+                           ↓
+              [CARenderServer or direct transfer]
+                           ↓
+         renderServerSurface (if scaling needed)
+                           ↓
+            IOSurfaceAccelerator transfer
+                           ↓
+              staticBuffer (VNC output res)
+                           ↓
+            rfbMarkRectAsModified → VNC clients
+```
+
+### Dependencies
+
+Pre-built libraries in `vncbuild/`:
+- libvncserver (VNC protocol)
+- libpng, libjpeg (image encoding)
+- libssl, libcrypto (VNC authentication)
+
+## Configuration
+
+User preferences read from `com.mousen.screendump` preference domain:
+- `enabled` - Enable/disable daemon
+- `width`, `height` - Custom output resolution (maintains aspect ratio, aligns to 4px)
+- `password` - VNC authentication password
+
+## Entitlements
+
+[en.plist](en.plist) contains required entitlements for:
+- IOSurface/IOMobileFramebuffer access
+- HID event dispatch (input injection)
+- QuartzCore global capture

screendump/FrameUpdater.h

@@ -13,7 +13,6 @@
                             height:(size_t)height
                        nativeWidth:(size_t)nativeWidth
                       nativeHeight:(size_t)nativeHeight
-                  useCADisplayLink:(BOOL)useCADisplayLink
                renderServerSurface:(IOSurfaceRef)renderServerSurface
                   captureModeBlock:(CaptureMode(^)(void))captureModeBlock;
 - (void)startFrameLoop;

screendump/FrameUpdater.m

@@ -5,8 +5,7 @@
 	// Process
 	NSOperationQueue *_q;
 	BOOL _updatingFrames;
-	uint32_t _lastUpdatedSeed;
+	CADisplayLink *_displayLink;
-	NSTimer* _updateFrameTimer;
 
 	// Shared from ScreenDumpVNC
 	IOSurfaceRef _screenSurface;
@@ -17,7 +16,6 @@
 	size_t _height;
 	size_t _nativeWidth;
 	size_t _nativeHeight;
-	BOOL _useCADisplayLink;
 
 	// Dual capture mode support
 	IOSurfaceRef _renderServerSurface; // Separate surface for CARenderServer (avoids framebuffer locking)
@@ -32,15 +30,13 @@
                             height:(size_t)height
                        nativeWidth:(size_t)nativeWidth
                       nativeHeight:(size_t)nativeHeight
-                  useCADisplayLink:(BOOL)useCADisplayLink
                renderServerSurface:(IOSurfaceRef)renderServerSurface
                   captureModeBlock:(CaptureMode(^)(void))captureModeBlock {
 	if ((self = [super init])) {
 		_q = [[NSOperationQueue alloc] init];
 		_q.maxConcurrentOperationCount = 1; // Serialize to prevent frame queue buildup
 		_updatingFrames = NO;
-		_lastUpdatedSeed = 0;
+		_displayLink = nil;
-		_updateFrameTimer = nil;
 
 		_screenSurface = screenSurface;
 		_rfbScreenInfo = rfbScreenInfo;
@@ -50,7 +46,6 @@
 		_height = height;
 		_nativeWidth = nativeWidth;
 		_nativeHeight = nativeHeight;
-		_useCADisplayLink = useCADisplayLink;
 
 		_renderServerSurface = renderServerSurface;
 		_captureModeBlock = [captureModeBlock copy];
@@ -70,18 +65,6 @@
 		return;
 	}
 
-	bool updateFrame = true;
-	if (!_useCADisplayLink) {
-		bool updateFrame = false;
-		int32_t currentFrameSeed = IOSurfaceGetSeed(_screenSurface);
-		if (_lastUpdatedSeed != currentFrameSeed && rfbIsActive(_rfbScreenInfo)) {
-			_lastUpdatedSeed = currentFrameSeed;
-			updateFrame = true;
-		}
-	};
-
-	if (updateFrame) {
-		// dispatch_async(dispatch_get_main_queue(), ^{
 	[_q addOperationWithBlock: ^{
 		// Get current capture mode
 		CaptureMode mode = _captureModeBlock ? _captureModeBlock() : CaptureModeCARenderServer;
@@ -105,16 +88,14 @@
 
 		rfbMarkRectAsModified(_rfbScreenInfo, 0, 0, _width, _height);
 	}];
-		// });
-	}
 }
 
 -(void)stopFrameLoop {
-	if (_updateFrameTimer == nil || ![_updateFrameTimer isValid]) return;
+	if (_displayLink == nil) return;
 
 	dispatch_async(dispatch_get_main_queue(), ^(void){
-		[_updateFrameTimer invalidate];
+		[_displayLink invalidate];
-		_updateFrameTimer = nil;
+		_displayLink = nil;
 		_updatingFrames = NO;
 	});
 }
@@ -123,17 +104,10 @@
 	[self stopFrameLoop];
 	_updatingFrames = YES;
 
-	if (_useCADisplayLink) {
 	CADisplayLink *displayLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(_updateFrame)];
 	displayLink.preferredFramesPerSecond = 60; // Limit to 60 FPS
 	[displayLink addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode];
-		_updateFrameTimer = (NSTimer *)displayLink;
+	_displayLink = displayLink;
-	} else {
-		dispatch_async(dispatch_get_main_queue(), ^(void){
-			// Reduced from 1/400 (400 Hz) to 1/60 (60 Hz) to reduce overhead
-			_updateFrameTimer = [NSTimer scheduledTimerWithTimeInterval:1.0/400.0 target:self selector:@selector(_updateFrame) userInfo:nil repeats:YES];
-		});
-	}
 }
 
 -(void)dealloc {

screendump/ScreenDumpVNC.m

@@ -286,9 +286,6 @@
 
     free(arg0);
 
-    NSDictionary* defaults = getPrefsForAppId(@"com.mousen.screendump");
-	bool useCADisplayLink = [[defaults objectForKey:@"displaysync"]?:@NO boolValue];
-
 	__weak ScreenDumpVNC *weakSelf = self;
 	_frameUpdater = [[FrameUpdater alloc] initWithSurfaceInfo:_screenSurface
                                                  rfbScreenInfo:_rfbScreenInfo
@@ -298,7 +295,6 @@
                                                         height:_height
                                                    nativeWidth:_nativeWidth
                                                   nativeHeight:_nativeHeight
-                                              useCADisplayLink:useCADisplayLink
                                            renderServerSurface:_renderServerSurface
                                               captureModeBlock:^CaptureMode(void) {
         ScreenDumpVNC *strongSelf = weakSelf;

screendump/layout/Library/PreferenceLoader/Preferences/screendump/Preferences.plist

@@ -81,26 +81,6 @@
 			<key>isNumeric</key>
 			<true/>
 		</dict>
-		<dict>
-			<key>cell</key>
-			<string>PSGroupCell</string>
-			<key>label</key>
-			<string>Tuning</string>
-		</dict>
-		<dict>
-			<key>PostNotification</key>
-			<string>com.mousen.screendump/restart</string>
-			<key>cell</key>
-			<string>PSSwitchCell</string>
-			<key>default</key>
-			<false/>
-			<key>defaults</key>
-			<string>com.mousen.screendump</string>
-			<key>key</key>
-			<string>displaysync</string>
-			<key>label</key>
-			<string>Update screen using CADisplayLink</string>
-		</dict>
 	</array>
 </dict>
 </plist>