[Audit][Medium] text_input.zig letter key mapping ignores shift for uppercase ASCII

[MichaelFisher1997]

🔍 Module Scanned

modules/game-core/src/ (automated audit scan)

📝 Summary

The handleTextTyping function in text_input.zig has a bug where it converts key enum values to uppercase ASCII characters via direct casting, ignoring the actual character values of the key enums. Since Key.a = 'a' (lowercase), the shift conversion produces lowercase letters instead of uppercase.

📍 Location

• File: modules/game-core/src/text_input.zig:11-14
• Function/Scope: handleTextTyping

🔴 Severity: Medium

• Medium: Performance degradation, missing error handling, suboptimal patterns

💥 Impact

When a user holds Shift and types letters (a-z), the text input receives lowercase letters instead of uppercase. This affects:

• World naming (when creating new worlds)
• Seed text input fields
• Any text input requiring uppercase letters

The bug only affects letters; numbers, space, and backspace work correctly.

🔎 Evidence

const letters = [_]Key{ .a, .b, .c, .d, .e, .f, .g, .h, .i, .j, .k, .l, .m, .n, .o, .p, .q, .r, .s, .t, .u, .v, .w, .x, .y, .z };
inline for (letters) |key| if (input.isKeyPressed(key) and text_input.items.len < max_len) {
    var ch: u8 = @intCast(@intFromEnum(key));  // BUG: This is 'a' (97), not 'A' (65)
    if (shift) ch = std.ascii.toUpper(ch);      // toUpper('a') = 'a' (no change!)
    try text_input.append(allocator, ch);
};

Root cause: Key.a = 'a' (lowercase, value 97). std.ascii.toUpper('a') returns 'a' (no change) since 'a' is already lowercase. The intent was to produce 'A' (65) when shift is held.

Expected behavior: When shift is held, typing 'a' should produce 'A'.

Compare to correct code in input_mapper.zig line 42-50:

bindings[@intFromEnum(GameAction.slot_1)] = ActionBinding.init(.{ .key = .@"1" });
bindings[@intFromEnum(GameAction.slot_2)] = ActionBinding.init(.{ .key = .@"2" });
// ... numbers work correctly because .@"1" = '1' (49) and '1'-'9' have no case

🛠️ Proposed Fix

Replace the key-to-char conversion with character constants:

const shift = input.isKeyDown(.left_shift) or input.isKeyDown(.right_shift);
const letters = [_]u8{ 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z' };
inline for (letters, 0..) |letter, idx| {
    const key = @as(Key, @enumFromInt(letter));
    if (input.isKeyPressed(key) and text_input.items.len < max_len) {
        var ch = letter;
        if (shift) ch = std.ascii.toUpper(ch);
        try text_input.append(allocator, ch);
    }
}

Or simplify further by removing the array:

const letters = "abcdefghijklmnopqrstuvwxyz";
for (letters) |letter| {
    const key = @as(Key, @enumFromInt(letter));
    if (input.isKeyPressed(key) and text_input.items.len < max_len) {
        var ch = letter;
        if (shift) ch = std.ascii.toUpper(ch);
        try text_input.append(allocator, ch);
    }
}

✅ Acceptance Criteria

• nix develop --command zig build test passes
• Typing 'a' with Shift produces 'A' in text input
• Typing 'z' with Shift produces 'Z' in text input
• Lowercase letters still work when Shift is not held
• Numbers and space continue to work correctly

📚 References

• Key enum definition in modules/engine-core/src/interfaces.zig:186-271
• std.ascii.toUpper behavior: toUpper('a') = 'a' (unchanged since already lowercase)
• Shift modifier handling is correct (line 9)

[github-actions]

The bug is confirmed. On line 12, Key.a = 'a' (value 97), so @intCast(@intFromEnum(key)) produces 97 ('a'). Then std.ascii.toUpper('a') returns 'a' unchanged since it's already lowercase — the shift modifier has no effect.

The proposed fix (using u8 letter constants like 'a' instead of Key enum values) is correct. When shift is true, std.ascii.toUpper('a') will properly produce 'A' (65).

Suggested fix: Replace the letter array with character constants:

const letters = "abcdefghijklmnopqrstuvwxyz";
for (letters) |letter| {
    const key = @as(Key, @enumFromInt(letter));
    if (input.isKeyPressed(key) and text_input.items.len < max_len) {
        var ch = letter;
        if (shift) ch = std.ascii.toUpper(ch);
        try text_input.append(allocator, ch);
    }
}

The digits on line 17 are unaffected since .@"0" = '0' (49) and digits have no uppercase/lowercase distinction.

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