avoid double backspace #133

forketyfork · 2026-01-16T16:08:21Z

Solution:

Add a macOS accessibility text input layer (Objective-C NSTextView + Zig wrapper) that exposes accessibility attributes and forwards insertText/accessibility value text and Cmd+V paste into the focused session.
Keep SDL text input active across focus changes, update the text input area on resize, and handle committed TEXT_EDITING input so external sources like emoji picker/speech-to-text deliver text reliably.
Filter backspace control bytes (0x08/0x7f) from text payloads and route SDL/accessibility text through a shared handler to prevent duplicate deletes.
Document the new macOS accessibility input path and backspace filtering behavior in the README and architecture notes.

Enable external text input sources like Superwhisper (speech-to-text) and the emoji picker to work with SDL windows. SDL doesn't natively support NSTextInputClient for accessibility-based input. The solution adds a transparent NSTextView overlay that: - Acts as first responder to receive accessibility queries - Forwards keyboard events to SDL for normal input - Intercepts Cmd+V to handle paste (used by Superwhisper) - Captures insertText: for emoji picker and keyboard input - Exposes accessibility attributes so apps can discover the text field

Both emoji picker and Superwhisper simulate Cmd+V after putting text on the pasteboard. The Cmd+V interception handles both cases, so the pasteboard check on window focus was causing double-paste and also incorrectly pasting clipboard contents when switching back to the app.

Issue: Backspace deletes two characters after adding accessibility paste/input support. Solution: Route SDL and accessibility text input through a shared handler. Filter backspace control bytes (0x08/0x7f) out of text payloads to avoid duplicate deletes. Document macOS accessibility input and backspace filtering behavior.

Copilot

Pull request overview

This PR implements macOS accessibility support to prevent duplicate backspace events when using external text input sources like emoji pickers and speech-to-text apps. The solution adds a hidden NSTextView that exposes proper accessibility attributes, keeps SDL text input active across focus changes, and filters backspace control bytes from text payloads to ensure deletion only occurs via keyboard events.

Changes:

Added macOS-specific accessibility text input layer using Objective-C NSTextView with Zig wrapper
Modified text input handling to keep SDL text input active across window focus changes
Implemented backspace control byte filtering (0x08/0x7f) in text input processing

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/platform/sdl.zig	Added SDL text input area configuration function
src/platform/macos_text_input.zig	New Zig wrapper for macOS accessibility text input
src/platform/macos_text_input.m	New Objective-C implementation of accessible NSTextView
src/main.zig	Integrated accessibility input, removed focus-based text input toggling, added backspace filtering
src/c.zig	Added SDL3 property and text input area API bindings
docs/architecture.md	Documented backspace filtering behavior
build.zig	Added Objective-C source file compilation with ARC

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Copilot · 2026-01-16T16:10:43Z

src/platform/macos_text_input.zig

+
+        // Store the new text
+        instance.pending_text = instance.allocator.dupe(u8, text) catch {
+            log.err("Failed to allocate text buffer", .{});


The error log message is missing format placeholders. While the current code compiles, the logging framework expects format arguments. Consider using log.err(\"Failed to allocate text buffer\", .{}); consistently with other logging calls, or add relevant error context if available.

Won't fix. In Zig's scoped logging API, .{} is the standard way to pass an empty format argument struct. The format specifier is always the second parameter, and passing .{} is idiomatic for messages without dynamic content.

Copilot · 2026-01-16T16:10:43Z

src/platform/macos_text_input.m

+// after putting text on the pasteboard. SDL receives other keys through its own mechanism.
+- (void)keyDown:(NSEvent*)event {
+    NSEventModifierFlags cmdOnly = event.modifierFlags & NSEventModifierFlagDeviceIndependentFlagsMask;
+    if (cmdOnly == NSEventModifierFlagCommand && event.keyCode == 9) { // Cmd+V


The magic number 9 for the Cmd+V keyCode should be defined as a named constant (e.g., kVirtualKeyCode_V or KEY_CODE_V) to improve code readability and maintainability.

Fixed. Added kKeyCodeV constant for the macOS virtual key code.

Copilot · 2026-01-16T16:10:44Z

src/platform/macos_text_input.m

+
+        // Make it nearly transparent but still functional
+        // Note: alpha=0 causes issues with text input
+        [g_textView setAlphaValue:0.01];


The magic number 0.01 for alpha value should be defined as a named constant (e.g., MINIMUM_VISIBLE_ALPHA) with a comment explaining why this specific value is required instead of 0.

Fixed. Added kTextViewAlpha constant with a comment explaining its purpose.

Copilot · 2026-01-16T16:10:44Z

src/main.zig

+    var sent_any = false;
+    while (idx < text.len) : (idx += 1) {
+        const ch = text[idx];
+        if (ch == 8 or ch == 0x7f) {


The magic numbers 8 and 0x7f for backspace control bytes should be defined as named constants (e.g., BACKSPACE_CTRL and DELETE_CTRL) to improve code clarity and maintainability.

Fixed. Added CTRL_BACKSPACE and CTRL_DELETE named constants.

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chatgpt-codex-connector · 2026-01-16T16:14:35Z

src/platform/macos_text_input.zig

+            instance.allocator.free(old);
+        }
+
+        // Store the new text
+        instance.pending_text = instance.allocator.dupe(u8, text) catch {


Queue multiple accessibility text events

The accessibility callback replaces pending_text each time it fires, and pollText() only returns a single slice per frame. If macOS delivers multiple insertText:/accessibility updates before the main loop polls (common with speech-to-text or IME updates), earlier chunks are freed and lost, so users see missing characters. Consider appending to a buffer or storing a small queue so successive callbacks are preserved.

Useful? React with 👍 / 👎.

Fixed. Changed pending_text from ?[]u8 to std.ArrayList(u8) to queue multiple text events instead of replacing.

- Queue multiple text events using ArrayList instead of replacing - Add named constants for control characters (CTRL_BACKSPACE, CTRL_DELETE) - Add named constants for macOS text input (kTextViewAlpha, kKeyCodeV)

forketyfork added 5 commits January 16, 2026 15:07

Improvements

9f424e2

Merge branch 'main' into hello

95af2a3

forketyfork requested a review from Copilot January 16, 2026 16:09

Copilot AI reviewed Jan 16, 2026

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chatgpt-codex-connector bot reviewed Jan 16, 2026

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refactor: address PR review feedback

823de37

- Queue multiple text events using ArrayList instead of replacing - Add named constants for control characters (CTRL_BACKSPACE, CTRL_DELETE) - Add named constants for macOS text input (kTextViewAlpha, kKeyCodeV)

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