From 40732985f87942d10d470e840d8f01339cca8677 Mon Sep 17 00:00:00 2001
From: "Michael Z. Kadaner" <MKadaner@users.noreply.github.com>
Date: Tue, 23 Jan 2024 20:26:34 -0800
Subject: [PATCH] WIP

---
 far/vmenu.cpp | 43 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)

diff --git a/far/vmenu.cpp b/far/vmenu.cpp
index 36be448925..3368fdfcb9 100644
--- a/far/vmenu.cpp
+++ b/far/vmenu.cpp
@@ -401,6 +401,19 @@ namespace
 		return true;
 	}
 
+	int adjust_hpos_shift(const int Shift, const int Left, const int Right, const int TextAreaWidth)
+	{
+		if (Right <= 0)
+			return Shift <= 0 ? 0 : Shift - Right;
+		if (Left >= TextAreaWidth)
+			return Shift >= 0 ? 0 : Shift - (Left - TextAreaWidth);
+		if (Shift <= 0)
+			return std::max(Shift, 1 - Right);
+		if (Shift >= 0)
+			return std::min(Shift, TextAreaWidth - Left - 1);
+		return Shift;
+	}
+
 	int adjust_en_bloc_shift(const int Shift, const int EnBlocHScrollDiscriminator, const int TextAreaWidth)
 	{
 		assert(TextAreaWidth > 0);
@@ -3664,6 +3677,36 @@ TEST_CASE("list.hpos.classifier")
 	}
 }
 
+TEST_CASE("adjust.hpos.shift")
+{
+	static constexpr int TextAreaWidth{ 10 };
+	static constexpr std::array Shifts{ -10 };
+	static const struct test_data
+	{
+		int Left;
+		int Right;
+		std::array<int, Shifts.size()> Expected;
+	} TestDataPoints[] =
+	{
+		{ -5, { { 0, 0 }, { -7, 0 }, { -5, 0 }, { -1, 0 }, { 1, 6 }, { 3, 8 }, { 10, 15 }, { 15, 20 }, } },
+		{ 0, { { 0, 0 }, { -7, 0 }, { -5, 0 }, { -1, 0 }, { 1, 1 }, { 3, 3 }, { 10, 10 }, { 15, 15 }, } },
+		{ 1, { { 0, 0 }, { -7, -7 }, { -5, -5 }, { -1, -1 }, { 1, 1 }, { 3, 3 }, { 10, 10 }, { 15, 15 }, } },
+		{ 5, { { 0, 0 }, { -7, -7 }, { -5, -5 }, { -1, -1 }, { 1, 1 }, { 3, 3 }, { 10, 10 }, { 15, 15 }, } },
+		{ 10, { { 0, 0 }, { -7, -7 }, { -5, -5 }, { -1, -1 }, { 1, 0 }, { 3, 0 }, { 10, 0 }, { 15, 0 }, } },
+		{ 15, { { 0, 0 }, { -7, -12 }, { -5, -10 }, { -1, -6 }, { 1, 0 }, { 3, 0 }, { 10, 0 }, { 15, 0 }, } },
+	};
+
+	for (const auto& TestDataPoint : TestDataPoints)
+	{
+		for (const auto& ShiftAndExpected : TestDataPoint.ShiftAndExpectedList)
+		{
+			REQUIRE(ShiftAndExpected.second == adjust_en_bloc_shift(ShiftAndExpected.first, TestDataPoint.EnBlocHScrollDiscriminator, TextAreaWidth));
+		}
+	}
+
+	// adjust_hpos_shift
+}
+
 TEST_CASE("adjust.en.bloc.shift")
 {
 	static constexpr int TextAreaWidth{ 10 };