From 5d34f171a046fb181f5d44a4c9a6659a75967364 Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <mitchell.hashimoto@gmail.com>
Date: Sun, 15 May 2022 21:17:27 -0700
Subject: [PATCH] insertLines with scroll region support

---
 src/terminal/Terminal.zig | 65 +++++++++++++++++++++++++++------------
 1 file changed, 45 insertions(+), 20 deletions(-)

diff --git a/src/terminal/Terminal.zig b/src/terminal/Terminal.zig
index 2f6395da8..5b1bcc0e6 100644
--- a/src/terminal/Terminal.zig
+++ b/src/terminal/Terminal.zig
@@ -438,40 +438,32 @@ pub fn linefeed(self: *Terminal, alloc: Allocator) void {
 ///
 /// Moves the cursor to the left margin.
 pub fn insertLines(self: *Terminal, alloc: Allocator, count: usize) !void {
-    // TODO: scroll region bounds
-    if (self.scrolling_region.bottom != self.rows - 1 or
-        self.scrolling_region.top != 0) @panic("unimplemented");
-
     // Move the cursor to the left margin
     self.cursor.x = 0;
 
     // Remaining rows from our cursor
-    const rem = self.rows - (self.cursor.y + 1);
+    const rem = self.scrolling_region.bottom - self.cursor.y + 1;
 
-    // If we're trying to insert more than the remaining number of rows, we just
-    // erase below and we're done.
-    if (count >= rem) {
-        try self.eraseDisplay(alloc, .below);
-        return;
-    }
+    // If count is greater than the amount of rows, adjust down.
+    const adjusted_count = @minimum(count, rem);
 
     // The the top `scroll_amount` lines need to move to the bottom
-    // scroll area.
-    const scroll_amount = rem - count;
-    var y: usize = self.rows - 1;
-    const top = y - scroll_amount - 1;
+    // scroll area. We may have nothing to scroll if we're clearing.
+    const scroll_amount = rem - adjusted_count;
+    var y: usize = self.scrolling_region.bottom;
+    const top = y - scroll_amount;
 
     // Ensure we have the lines populated to the end
     _ = try self.getOrPutCell(alloc, 0, y);
     while (y > top) : (y -= 1) {
         self.screen.items[y].deinit(alloc);
-        self.screen.items[y] = self.screen.items[y - count];
-        self.screen.items[y - count] = .{};
+        self.screen.items[y] = self.screen.items[y - adjusted_count];
+        self.screen.items[y - adjusted_count] = .{};
     }
 
     // Insert count blank lines
     y = self.cursor.y;
-    while (y < self.cursor.y + count) : (y += 1) {
+    while (y < self.cursor.y + adjusted_count) : (y += 1) {
         var x: usize = 0;
         while (x < self.cols) : (x += 1) {
             const cell = try self.getOrPutCell(alloc, x, y);
@@ -825,6 +817,39 @@ test "Terminal: insertLines" {
     }
 }
 
+test "Terminal: insertLines with scroll region" {
+    const alloc = testing.allocator;
+    var t = try init(alloc, 2, 6);
+    defer t.deinit(alloc);
+
+    // Initial value
+    try t.print(alloc, 'A');
+    t.carriageReturn();
+    t.linefeed(alloc);
+    try t.print(alloc, 'B');
+    t.carriageReturn();
+    t.linefeed(alloc);
+    try t.print(alloc, 'C');
+    t.carriageReturn();
+    t.linefeed(alloc);
+    try t.print(alloc, 'D');
+    t.carriageReturn();
+    t.linefeed(alloc);
+    try t.print(alloc, 'E');
+
+    t.setScrollingRegion(1, 2);
+    t.setCursorPos(1, 1);
+    try t.insertLines(alloc, 1);
+
+    try t.print(alloc, 'X');
+
+    {
+        var str = try t.plainString(testing.allocator);
+        defer testing.allocator.free(str);
+        try testing.expectEqualStrings("X\nA\nC\nD\nE", str);
+    }
+}
+
 test "Terminal: insertLines more than remaining" {
     const alloc = testing.allocator;
     var t = try init(alloc, 2, 5);
@@ -848,8 +873,8 @@ test "Terminal: insertLines more than remaining" {
     // Move to row 2
     t.setCursorPos(2, 1);
 
-    // Insert two lines
-    try t.insertLines(alloc, 10);
+    // Insert a bunch of  lines
+    try t.insertLines(alloc, 20);
 
     {
         var str = try t.plainString(testing.allocator);