Rewrite MarkEditWritingTools in pure Swift by Copilot · Pull Request #1265 · MarkEdit-app/MarkEdit

Copilot · 2026-03-07T11:29:02Z

Original prompt

This section details on the original issue you should resolve

<issue_title>MarkEditWritingTools Swift Rewrite</issue_title>
<issue_description>## Motivation

Eliminate Objective-C usage entirely.

Proposal

Rewrite MarkEditWritingTools.m in pure Swift while preserving exactly the same behavior.

Do not question the private API usage in this file. All calls have already been verified and are correct. The application will not be submitted to the Mac App Store.

Some Objective-C runtime APIs have direct Swift equivalents, such as NSSelectorFromString → sel_getUid.

However, Swift does not provide an equivalent to NSInvocation. One possible approach is to obtain a function pointer using method(for:) and then cast it with unsafeBitCast. See the following example for reference:

https://developer.apple.com/documentation/objectivec/nsobject-swift.class/method(for:)

https://github.com/TextGrabber2-app/TextGrabber2/blob/main/TextGrabber2/Sources/LookUp.swift

Investigate the necessary runtime techniques and implement the port accordingly. The result must match the existing behavior without regressions.</issue_description>

<agent_instructions>Follow the PR description closely.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

Fixes MarkEditWritingTools Swift Rewrite #1264

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cyanzhong · 2026-03-07T12:50:02Z

MarkEditMac/Sources/Main/MarkEditWritingTools.swift

+
+  static func shouldReselect(with tool: WritingTool) -> Bool {
+    // Compose mode can start without text selections
+    return tool != .compose


@copilot Why not use implicit return when you have Swift?

Try making the entire write more "Swifty", you should always seek for best practices.

Applied implicit return in shouldReselect(with:) to match the codebase convention (e.g., AppTheme.current, AppDesign.modernTitleBar). The other functions in the file require explicit return due to guard statements and multi-expression bodies. Fixed in 46139b9.

MarkEditMac/Sources/Main/MarkEditWritingTools.swift

- Replace NSInvocation with method(for:) + unsafeBitCast pattern - Replace NSSelectorFromString with sel_getUid - Use class_getClassMethod + method_getImplementation for class methods - Define WritingTool as a Swift enum with Int raw value - Remove ObjC files (.h, .m), bridging header, and ObjC directory - Update project.pbxproj: remove ObjC group, add Swift file to Main group, remove SWIFT_OBJC_BRIDGING_HEADER build setting Co-authored-by: cyanzhong <6745066+cyanzhong@users.noreply.github.com>

Co-authored-by: cyanzhong <6745066+cyanzhong@users.noreply.github.com>

cyanzhong · 2026-03-07T13:22:20Z

@copilot I reviewed and trust you that the current rewrite is correct.

Now, let's focus on improving the implementation, the goals are:

More Swifty
Better code reuse
Clean

Interfaces exposed shouldn't be changed, functionality should be 100% preserved.

…Map+first(where:), simplify writingToolsInstance Co-authored-by: cyanzhong <6745066+cyanzhong@users.noreply.github.com>

Copilot · 2026-03-07T13:29:41Z

@copilot I reviewed and trust you that the current rewrite is correct.

Now, let's focus on improving the implementation, the goals are:
...

Implemented in 1cedb1d:

Code reuse: Extracted two invoke overloads (returning NSObject? and Int) that encapsulate the repeated responds(to:) + unsafeBitCast + method(for:) pattern — the Swift equivalent of the original ObjC invocationWithTarget:selectorString: helper.
More Swifty: Replaced the for-loop + guard-continue with compactMap(\.contentViewController).first(where:). The requestedTool body went from ~25 lines to 5.
Cleaner: Eliminated intermediate variables — unsafeBitCast results are invoked directly inline.

cyanzhong · 2026-03-07T13:41:18Z

MarkEditMac/Sources/Main/AppWritingTools.swift

+@available(macOS 15.1, *)
+private extension AppWritingTools {
+  /// Invokes a selector on a target and returns the result as `NSObject?`.
+  static func invoke(_ target: NSObject, selector name: String) -> NSObject? {


@copilot Can you further combine two invoke methods by leveraging generic types?

Combined into a single generic invoke<Result> with a fallback parameter — the compiler infers Result from the fallback value (nil → NSObject?, 0 → Int). Fixed in bbaa48e.

…h fallback parameter Co-authored-by: cyanzhong <6745066+cyanzhong@users.noreply.github.com>

cyanzhong · 2026-03-07T13:54:25Z

MarkEditMac/Sources/Main/AppWritingTools.swift

+
+    return unsafeBitCast(
+      target.method(for: selector),
+      to: (@convention(c) (NSObject, Selector) -> Result).self


@copilot It looks like

Generic parameter 'U' could not be inferred

'(NSObject, Selector) -> Result' is not representable in Objective-C, so it cannot be used with '@convention(c)'

Reverted to two concrete overloads in 976c800. @convention(c) requires concrete types — generic type parameters are not representable in the C calling convention, so the two overloads are the minimum needed here.

…c) requires concrete types Co-authored-by: cyanzhong <6745066+cyanzhong@users.noreply.github.com>

cyanzhong · 2026-03-07T14:19:45Z

@copilot I noticed writingToolsInstance isn't used and have removed it. Can you double check if there's still unused code?

Copilot · 2026-03-07T14:21:33Z

@copilot I noticed writingToolsInstance isn't used and have removed it. Can you double check if there's still unused code?

Confirmed — no unused code remains. All public interfaces are referenced externally: requestedTool and shouldReselect(with:) in EditorViewController+UI.swift:212, affordanceIcon in EditorToolbarItems.swift:19, and shouldReselect(withItem:) in Application.swift:49. Both private invoke overloads are called on lines 35 and 39. The MarkEditKit import is needed for Logger.assertFail.

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Pull request overview

Copilot reviewed 11 out of 11 changed files in this pull request and generated 2 comments.

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MarkEditMac/Sources/Main/AppWritingTools.swift

Copilot AI assigned Copilot and cyanzhong Mar 7, 2026

Copilot started work on behalf of cyanzhong March 7, 2026 11:29 View session

Copilot AI changed the title ~~[WIP] Rewrite MarkEditWritingTools in pure Swift~~ Rewrite MarkEditWritingTools in pure Swift Mar 7, 2026

Copilot finished work on behalf of cyanzhong March 7, 2026 11:44

cyanzhong reviewed Mar 7, 2026

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Copilot started work on behalf of cyanzhong March 7, 2026 12:50 View session

cyanzhong reviewed Mar 7, 2026

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Copilot finished work on behalf of cyanzhong March 7, 2026 12:52

Copilot started work on behalf of cyanzhong March 7, 2026 12:52 View session

Copilot finished work on behalf of cyanzhong March 7, 2026 12:53

Copilot AI and others added 4 commits March 7, 2026 21:03

Initial plan

182424c

Use implicit return in shouldReselect(with:) for Swifty style

7771ffa

Co-authored-by: cyanzhong <6745066+cyanzhong@users.noreply.github.com>

Add line break before return on line 59 for consistent code style

8453f6c

Co-authored-by: cyanzhong <6745066+cyanzhong@users.noreply.github.com>

cyanzhong force-pushed the copilot/rewrite-markeditwritingtools-swift branch from cad3342 to 8453f6c Compare March 7, 2026 13:04

cyanzhong added 2 commits March 7, 2026 21:07

Fix build

60e5a85

nit-picking

2e8680e

Copilot started work on behalf of cyanzhong March 7, 2026 13:22 View session

Improve AppWritingTools: extract reusable invoke helpers, use compact…

1cedb1d

…Map+first(where:), simplify writingToolsInstance Co-authored-by: cyanzhong <6745066+cyanzhong@users.noreply.github.com>

Copilot finished work on behalf of cyanzhong March 7, 2026 13:30

cyanzhong reviewed Mar 7, 2026

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Copilot started work on behalf of cyanzhong March 7, 2026 13:41 View session

Combine two invoke overloads into a single generic invoke<Result> wit…

bbaa48e

…h fallback parameter Co-authored-by: cyanzhong <6745066+cyanzhong@users.noreply.github.com>

Copilot finished work on behalf of cyanzhong March 7, 2026 13:44

cyanzhong reviewed Mar 7, 2026

View reviewed changes

Copilot started work on behalf of cyanzhong March 7, 2026 13:54 View session

Revert generic invoke<Result> to two concrete overloads — @convention(…

976c800

…c) requires concrete types Co-authored-by: cyanzhong <6745066+cyanzhong@users.noreply.github.com>

Copilot finished work on behalf of cyanzhong March 7, 2026 13:57

cyanzhong force-pushed the copilot/rewrite-markeditwritingtools-swift branch from 24d7e3a to 223ddb2 Compare March 7, 2026 14:19

Copilot started work on behalf of cyanzhong March 7, 2026 14:19 View session

Copilot finished work on behalf of cyanzhong March 7, 2026 14:22

cyanzhong force-pushed the copilot/rewrite-markeditwritingtools-swift branch from 223ddb2 to ea74b35 Compare March 7, 2026 14:44

cyanzhong marked this pull request as ready for review March 7, 2026 14:45

nit-picking

133e035

cyanzhong force-pushed the copilot/rewrite-markeditwritingtools-swift branch from ea74b35 to 133e035 Compare March 7, 2026 14:52

cyanzhong requested a review from Copilot March 7, 2026 14:56

Copilot AI reviewed Mar 7, 2026

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cyanzhong requested a review from Copilot March 8, 2026 00:15

Copilot started reviewing on behalf of cyanzhong March 8, 2026 00:15 View session

Copilot AI reviewed Mar 8, 2026

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MarkEditMac/Sources/Main/AppWritingTools.swift Show resolved Hide resolved

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cyanzhong merged commit 7a87648 into main Mar 8, 2026
5 checks passed

cyanzhong deleted the copilot/rewrite-markeditwritingtools-swift branch March 8, 2026 01:07

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Copilot AI commented Mar 7, 2026 •

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