From af387e1a6c85f8c50f955b0c88f3a14772e961c4 Mon Sep 17 00:00:00 2001
From: "KOSMOS, Tzushih.K" <48860861+kisaraki@users.noreply.github.com>
Date: Mon, 24 Aug 2026 13:50:20 +0800
Subject: [PATCH] feat: add boundary alignment command

---
 crates/edit/src/bin/edit/draw_boundary.rs | 181 ++++++++++++++++++++++
 crates/edit/src/bin/edit/draw_menubar.rs  |   9 ++
 crates/edit/src/bin/edit/main.rs          |   5 +
 crates/edit/src/bin/edit/state.rs         |   6 +
 i18n/edit.toml                            |  22 +++
 5 files changed, 223 insertions(+)
 create mode 100644 crates/edit/src/bin/edit/draw_boundary.rs

diff --git a/crates/edit/src/bin/edit/draw_boundary.rs b/crates/edit/src/bin/edit/draw_boundary.rs
new file mode 100644
index 00000000000..78c26589237
--- /dev/null
+++ b/crates/edit/src/bin/edit/draw_boundary.rs
@@ -0,0 +1,181 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+use edit::buffer::TextBuffer;
+use edit::framebuffer::IndexedColor;
+use edit::helpers::*;
+use edit::input::vk;
+use edit::tui::*;
+
+use crate::localization::*;
+use crate::state::*;
+
+pub fn draw_dialog_boundary_align(ctx: &mut Context, state: &mut State) {
+    // EN: Ask for a positive boundary column, defaulting to 80, before changing the document.
+    // 中文：修改文件前要求輸入正整數邊界欄位，預設值為 80。
+    let mut apply;
+    let mut cancel;
+
+    ctx.modal_begin("boundary-align", loc(LocId::BoundaryAlignDialogTitle));
+    {
+        ctx.block_begin("boundary-align-content");
+        ctx.inherit_focus();
+        ctx.attr_padding(Rect::three(1, 2, 1));
+        {
+            let contains_focus = ctx.contains_focus();
+            ctx.label("boundary-align-description", loc(LocId::BoundaryAlignDescription));
+
+            if ctx.editline("boundary-align-column", &mut state.boundary_align_column) {
+                state.boundary_align_invalid = false;
+            }
+            ctx.attr_intrinsic_size(Size { width: 24, height: 1 });
+            if state.boundary_align_invalid {
+                ctx.attr_background_rgba(ctx.indexed(IndexedColor::Red));
+                ctx.attr_foreground_rgba(ctx.indexed(IndexedColor::BrightWhite));
+                ctx.label("boundary-align-invalid", loc(LocId::BoundaryAlignInvalid));
+                ctx.attr_foreground_rgba(ctx.indexed(IndexedColor::Red));
+            }
+
+            ctx.table_begin("boundary-align-choices");
+            ctx.inherit_focus();
+            ctx.attr_padding(Rect::three(1, 0, 0));
+            ctx.attr_position(Position::Center);
+            ctx.table_set_cell_gap(Size { width: 2, height: 0 });
+            {
+                ctx.table_next_row();
+                ctx.inherit_focus();
+                apply = ctx.button("ok", loc(LocId::Ok), ButtonStyle::default());
+                ctx.inherit_focus();
+                cancel = ctx.button("cancel", loc(LocId::Cancel), ButtonStyle::default());
+            }
+            ctx.table_end();
+
+            if contains_focus && ctx.consume_shortcut(vk::RETURN) {
+                apply = true;
+            }
+        }
+        ctx.block_end();
+    }
+    cancel |= ctx.modal_end();
+
+    if apply {
+        let column =
+            state.boundary_align_column.trim().parse::<usize>().ok().filter(|column| *column > 0);
+        if let Some(column) = column {
+            if let Some(doc) = state.documents.active_mut() {
+                let mut tb = doc.buffer.borrow_mut();
+                align_buffer_to_boundary(&mut tb, column);
+                tb.make_cursor_visible();
+            }
+            state.wants_boundary_align = false;
+            reset_boundary_input(state);
+            ctx.needs_rerender();
+        } else {
+            state.boundary_align_invalid = true;
+            ctx.needs_rerender();
+        }
+    } else if cancel {
+        state.wants_boundary_align = false;
+        reset_boundary_input(state);
+        ctx.needs_rerender();
+    }
+}
+
+/// EN: Restores the input state shared by apply and cancel paths.
+/// 中文：還原套用與取消流程共用的輸入狀態。
+fn reset_boundary_input(state: &mut State) {
+    state.boundary_align_column.clear();
+    state.boundary_align_column.push_str("80");
+    state.boundary_align_invalid = false;
+}
+
+fn align_buffer_to_boundary(tb: &mut TextBuffer, column: usize) {
+    let text = read_buffer_text(tb);
+    let aligned = align_text_to_boundary(&String::from_utf8_lossy(&text), column);
+    if aligned.as_bytes() == text {
+        return;
+    }
+
+    tb.select_all();
+    tb.write_raw(aligned.as_bytes());
+}
+
+fn read_buffer_text(tb: &TextBuffer) -> Vec<u8> {
+    let mut text = Vec::with_capacity(tb.text_length());
+    while text.len() < tb.text_length() {
+        let chunk = tb.read_forward(text.len());
+        if chunk.is_empty() {
+            break;
+        }
+        text.extend_from_slice(chunk);
+    }
+    text
+}
+
+fn align_text_to_boundary(text: &str, column: usize) -> String {
+    // EN: Overflow becomes carry text joined to the next original line until end-of-file.
+    // 中文：超出邊界的文字會成為延續內容，與下一原始行合併並持續處理至檔尾。
+    if column == 0 || text.is_empty() {
+        return text.to_string();
+    }
+
+    let newline = if text.contains("\r\n") { "\r\n" } else { "\n" };
+    let has_final_newline = text.ends_with('\n');
+    let mut output = Vec::new();
+    let mut carry = None::<String>;
+
+    for line in text.lines() {
+        let mut combined = carry.take().unwrap_or_default();
+        combined.push_str(line);
+        let mut split = false;
+
+        while let Some(byte_offset) = combined.char_indices().nth(column).map(|(offset, _)| offset)
+        {
+            output.push(combined[..byte_offset].to_string());
+            combined = combined[byte_offset..].to_string();
+            split = true;
+        }
+
+        if split {
+            carry = Some(combined);
+        } else {
+            output.push(combined);
+        }
+    }
+
+    if let Some(carry) = carry {
+        output.push(carry);
+    }
+
+    let mut aligned = output.join(newline);
+    if has_final_newline {
+        aligned.push_str(newline);
+    }
+    aligned
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn wraps_overflow_and_merges_it_with_the_next_line() {
+        assert_eq!(
+            align_text_to_boundary("1234567\nABC\nshort\n12345678901\nXY", 5),
+            "12345\n67ABC\nshort\n12345\n67890\n1XY"
+        );
+    }
+
+    #[test]
+    fn counts_unicode_characters_and_preserves_crlf_and_final_newline() {
+        assert_eq!(
+            align_text_to_boundary("一二三四五六\r\n甲乙\r\n短\r\n", 5),
+            "一二三四五\r\n六甲乙\r\n短\r\n"
+        );
+    }
+
+    #[test]
+    fn keeps_short_lines_unchanged() {
+        assert_eq!(align_text_to_boundary("one\ntwo\nthree", 80), "one\ntwo\nthree");
+    }
+}
diff --git a/crates/edit/src/bin/edit/draw_menubar.rs b/crates/edit/src/bin/edit/draw_menubar.rs
index 401614786a1..9f42ffa4d07 100644
--- a/crates/edit/src/bin/edit/draw_menubar.rs
+++ b/crates/edit/src/bin/edit/draw_menubar.rs
@@ -118,6 +118,15 @@ fn draw_menu_edit(ctx: &mut Context, state: &mut State) {
         tb.select_all();
         ctx.needs_rerender();
     }
+    drop(tb);
+    // EN: Boundary Alignment is the final Edit-menu command and starts at column 80.
+    // 中文：「邊界對齊」位於編輯選單末項，輸入欄預設為第 80 字元。
+    if ctx.menubar_menu_button(loc(LocId::EditBoundaryAlign), 'B', vk::NULL) {
+        state.wants_boundary_align = true;
+        state.boundary_align_column.clear();
+        state.boundary_align_column.push_str("80");
+        state.boundary_align_invalid = false;
+    }
     ctx.menubar_menu_end();
 }
 
diff --git a/crates/edit/src/bin/edit/main.rs b/crates/edit/src/bin/edit/main.rs
index 27ae7fab6c0..0fe770a433e 100644
--- a/crates/edit/src/bin/edit/main.rs
+++ b/crates/edit/src/bin/edit/main.rs
@@ -3,6 +3,7 @@
 
 mod apperr;
 mod documents;
+mod draw_boundary;
 mod draw_editor;
 mod draw_filepicker;
 mod draw_menubar;
@@ -15,6 +16,7 @@ use std::path::Path;
 use std::time::Duration;
 use std::{env, process};
 
+use draw_boundary::*;
 use draw_editor::*;
 use draw_filepicker::*;
 use draw_menubar::*;
@@ -365,6 +367,9 @@ fn draw(ctx: &mut Context, state: &mut State) {
     if state.wants_go_to_file {
         draw_go_to_file(ctx, state);
     }
+    if state.wants_boundary_align {
+        draw_dialog_boundary_align(ctx, state);
+    }
     if state.wants_about {
         draw_dialog_about(ctx, state);
     }
diff --git a/crates/edit/src/bin/edit/state.rs b/crates/edit/src/bin/edit/state.rs
index 13a1cefbbea..ea8091d7344 100644
--- a/crates/edit/src/bin/edit/state.rs
+++ b/crates/edit/src/bin/edit/state.rs
@@ -166,6 +166,9 @@ pub struct State {
     pub wants_statusbar_focus: bool,
     pub wants_indentation_picker: bool,
     pub wants_go_to_file: bool,
+    pub wants_boundary_align: bool,
+    pub boundary_align_column: String,
+    pub boundary_align_invalid: bool,
     pub wants_about: bool,
     pub wants_close: bool,
     pub wants_exit: bool,
@@ -216,6 +219,9 @@ impl State {
             wants_encoding_change: StateEncodingChange::None,
             wants_indentation_picker: false,
             wants_go_to_file: false,
+            wants_boundary_align: false,
+            boundary_align_column: "80".into(),
+            boundary_align_invalid: false,
             wants_about: false,
             wants_close: false,
             wants_exit: false,
diff --git a/i18n/edit.toml b/i18n/edit.toml
index 11039636308..107cce6d413 100644
--- a/i18n/edit.toml
+++ b/i18n/edit.toml
@@ -888,6 +888,28 @@ zh-hans = "全选"
 zh-hant = "全選"
 
 # A menu bar item
+# EN: Hard boundary alignment commands.
+# 中文：固定邊界對齊命令。
+[EditBoundaryAlign]
+en = "Boundary Alignment…"
+zh-hans = "边界对齐…"
+zh-hant = "邊界對齊…"
+
+[BoundaryAlignDialogTitle]
+en = "Boundary Alignment"
+zh-hans = "边界对齐"
+zh-hant = "邊界對齊"
+
+[BoundaryAlignDescription]
+en = "Right boundary column (positive integer):"
+zh-hans = "右边界字元位置（正整数）："
+zh-hant = "右邊界字元位置（正整數）："
+
+[BoundaryAlignInvalid]
+en = "Enter a positive integer."
+zh-hans = "请输入正整数。"
+zh-hant = "請輸入正整數。"
+
 [View]
 en = "View"
 ar = "عرض"