Add SwiftUI minimal display-list LLDB hook

Example/Example_Legacy.xcodeproj/xcshareddata/xcschemes/SUI_Example.xcscheme

@@ -50,6 +50,7 @@
    </TestAction>
    <LaunchAction
       buildConfiguration = "SwiftUIDebug"
+      customLLDBInitFile = "$(SRCROOT)/../Scripts/LLDB/.lldbinit-swiftui"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
       launchStyle = "0"

Example/Example_Legacy.xcodeproj/xcshareddata/xcschemes/SUI_HostingExample.xcscheme

@@ -37,6 +37,7 @@
    </TestAction>
    <LaunchAction
       buildConfiguration = "SwiftUIDebug"
+      customLLDBInitFile = "$(SRCROOT)/../Scripts/LLDB/.lldbinit-swiftui"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
       launchStyle = "0"

Example/Example_Legacy.xcodeproj/xcshareddata/xcschemes/SUI_TestingHost.xcscheme

@@ -32,6 +32,7 @@
    </TestAction>
    <LaunchAction
       buildConfiguration = "SwiftUIDebug"
+      customLLDBInitFile = "$(SRCROOT)/../Scripts/LLDB/.lldbinit-swiftui"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
       launchStyle = "0"

Example/Project.swift

@@ -333,6 +333,9 @@ let targets: [Target] = [
 
 // MARK: - Schemes
 
+let swiftUIDisplayListLLDBInitFile: Path =
+    "../Scripts/LLDB/.lldbinit-swiftui"
+
 func scheme(
     name: String,
     target: TargetReference,
@@ -342,7 +345,8 @@ func scheme(
         .testableTarget(target: "OpenSwiftUIUITests", parallelization: .enabled),
     ],
     includeTestAction: Bool = true,
-    runArguments: Arguments = launchArguments
+    runArguments: Arguments = launchArguments,
+    customLLDBInitFile: Path? = nil
 ) -> Scheme {
     .scheme(
         name: name,
@@ -358,6 +362,7 @@ func scheme(
             : nil,
         runAction: .runAction(
             configuration: debugConfiguration,
+            customLLDBInitFile: customLLDBInitFile,
             executable: .executable(target),
             arguments: runArguments
         ),
@@ -382,7 +387,8 @@ let schemes: [Scheme] = [
         name: "SUI_Example",
         target: "Example",
         debugConfiguration: swiftUIDebug,
-        releaseConfiguration: swiftUIRelease
+        releaseConfiguration: swiftUIRelease,
+        customLLDBInitFile: swiftUIDisplayListLLDBInitFile
     ),
     scheme(
         name: "OSUI_HostingExample",
@@ -398,7 +404,8 @@ let schemes: [Scheme] = [
         debugConfiguration: swiftUIDebug,
         releaseConfiguration: swiftUIRelease,
         testableTargets: [],
-        runArguments: swiftUIHostingLaunchArguments
+        runArguments: swiftUIHostingLaunchArguments,
+        customLLDBInitFile: swiftUIDisplayListLLDBInitFile
     ),
     scheme(
         name: "OSUI_TestingHost",
@@ -412,7 +419,8 @@ let schemes: [Scheme] = [
         target: "TestingHost",
         debugConfiguration: swiftUIDebug,
         releaseConfiguration: swiftUIRelease,
-        includeTestAction: false
+        includeTestAction: false,
+        customLLDBInitFile: swiftUIDisplayListLLDBInitFile
     ),
     .scheme(
         name: "OSUI_UITests",

Scripts/LLDB/.lldbinit-swiftui

@@ -0,0 +1 @@
+command script import --relative-to-command-file swiftui_displaylist_minimal_description.py

Scripts/LLDB/README.md

@@ -0,0 +1,77 @@
+# SwiftUI Display-List LLDB Commands
+
+`swiftui_displaylist_minimal_description.py` redirects SwiftUI's full
+display-list description to its minimal description while debugging.
+
+SwiftUI normally checks `SWIFTUI_PRINT_TREE` and then calls `description`.
+The two getters use the same Swift calling convention and return the same type:
+
+```text
+$s7SwiftUI11DisplayListV11descriptionSSvg
+$s7SwiftUI11DisplayListV18minimalDescriptionSSvg
+```
+
+While the process is paused, the script replaces the first arm64 instruction
+of `description` with a direct branch to `minimalDescription`. SwiftUI retains
+its existing environment-variable check, output prefix, and printing schedule;
+only the display-list payload changes from the full form to the minimal form.
+No breakpoint is required, so Xcode does not stop for each printed tree.
+
+## Usage
+
+Enable `SWIFTUI_PRINT_TREE=1` in the Xcode Scheme before launching the app.
+SwiftUI caches this setting, so changing it after launch requires a relaunch.
+
+Run the app until SwiftUICore is loaded, pause it, then import and enable the
+hook:
+
+```text
+(lldb) command script import <path-to-checkout>/Scripts/LLDB/swiftui_displaylist_minimal_description.py
+(lldb) swiftui-display-list-minimal enable
+```
+
+The `SUI_Example`, `SUI_HostingExample`, and `SUI_TestingHost` schemes import
+the script automatically through the adjacent `.lldbinit-swiftui` file; for
+those schemes, only the `enable` command is needed after pausing.
+
+Continue execution. Tree output now uses `minimalDescription`, for example:
+
+```text
+View 0x... at Time(...):
+(DL(I:...))
+```
+
+Inspect or remove the hook while the process is paused:
+
+```text
+(lldb) swiftui-display-list-minimal status
+(lldb) swiftui-display-list-minimal disable
+```
+
+`disable` restores the exact instruction bytes that were present before
+`enable`. A process restart also restores the original SwiftUICore mapping.
+
+## Existing description breakpoints
+
+Xcode can persist script-created breakpoints while dropping their Python
+actions. Such a breakpoint stops in `DisplayList.description` and then executes
+the full getter when continued.
+
+When enabling the hook, the script temporarily disables any breakpoint location
+already resolved at the `description` entry. It restores those locations when
+the hook is disabled. A stale symbolic breakpoint can also be removed once from
+Xcode's Breakpoint navigator.
+
+## Scope
+
+- The script has been validated against SwiftUI 6.5.4 on an arm64 iOS 18.5
+  Simulator.
+- The hook currently supports arm64 and arm64e targets. It validates instruction
+  alignment and the direct-branch range before changing memory.
+- The getters are private implementation details and may change between OS
+  releases. Missing or ambiguous symbols leave the process unchanged.
+- While enabled, every direct call to `DisplayList.description` is redirected,
+  not only calls originating from `SWIFTUI_PRINT_TREE`.
+- The change exists only in the debugged process. It does not modify the
+  SwiftUICore binary on disk.
+- Disable the hook before detaching LLDB if the process will remain alive.