Insert: Do not move end of line on open line (o/O)

Change the logic of open line commands so that if a selection lies
on the end of line character of the line from which we open a new
line, that selection does not move.

If we have two clients, A and B, with B's cursor on the eol character
of line L, and A hits `o` while on line L, B's cursor should stay
on the same (logical) line. Previous behaviour would make B's cursor
jump on the newly inserted line.

11 files changed, 48 insertions, 25 deletions

diff --git a/src/input_handler.cc b/src/input_handler.cc
index 6fa41d6f..ffa923b1 100644
--- a/src/input_handler.cc
+++ b/src/input_handler.cc
@@ -1314,19 +1314,6 @@ private:
         SelectionList& selections = context().selections();
         Buffer& buffer = context().buffer();
 
-        auto duplicate_selections = [](SelectionList& sels, int count) {
-            count = count > 0 ? count : 1;
-            Vector<Selection> new_sels;
-            new_sels.reserve(count * sels.size());
-            for (auto& sel : sels)
-                for (int i = 0; i < count; ++i)
-                    new_sels.push_back(sel);
-
-            size_t new_main = sels.main_index() * count + count - 1;
-            sels = SelectionList{sels.buffer(), std::move(new_sels)};
-            sels.set_main_index(new_main);
-        };
-
         switch (mode)
         {
         case InsertMode::Insert:
@@ -1351,22 +1338,41 @@ private:
                 sel.set({sel.max().line, buffer[sel.max().line].length() - 1});
             break;
         case InsertMode::OpenLineBelow:
-            for (auto& sel : selections)
-                sel.set({sel.max().line, buffer[sel.max().line].length() - 1});
-            duplicate_selections(selections, count);
-            insert('\n');
+        {
+            Vector<Selection> new_sels;
+            count = count > 0 ? count : 1;
+            LineCount inserted_count = 0;
+            for (auto sel : selections)
+            {
+                buffer.insert(sel.max().line + inserted_count + 1,
+                              String{'\n', CharCount{count}});
+                for (int i = 0; i < count; ++i)
+                    new_sels.push_back({sel.max().line + inserted_count + i + 1});
+                inserted_count += count;
+            }
+            selections.set(std::move(new_sels),
+                           selections.main_index() * count + count - 1);
+            context().hooks().run_hook("InsertChar", "\n", context());
             break;
+        }
         case InsertMode::OpenLineAbove:
-            for (auto& sel : selections)
-                sel.set({sel.min().line});
-            duplicate_selections(selections, count);
-            // Do not use insert method here as we need to fixup selection
-            // before running the InsertChar hook.
-            selections.insert("\n"_str, InsertMode::InsertCursor);
-            for (auto& sel : selections) // fixup selection positions
-                sel.set({sel.cursor().line - 1});
+        {
+            Vector<Selection> new_sels;
+            count = count > 0 ? count : 1;
+            LineCount inserted_count = 0;
+            for (auto sel : selections)
+            {
+                buffer.insert(sel.min().line + inserted_count,
+                              String{'\n', CharCount{count}});
+                for (int i = 0; i < count; ++i)
+                    new_sels.push_back({sel.max().line + inserted_count + i});
+                inserted_count += count;
+            }
+            selections.set(std::move(new_sels),
+                           selections.main_index() * count + count - 1);
             context().hooks().run_hook("InsertChar", "\n", context());
             break;
+        }
         case InsertMode::InsertAtLineBegin:
             for (auto& sel : selections)
             {
diff --git a/test/normal/open-multiple-above/cmd b/test/normal/open-multiple-above/cmd
new file mode 100644
index 00000000..b07421f6
--- /dev/null
+++ b/test/normal/open-multiple-above/cmd
@@ -0,0 +1 @@
+3Obar<esc>
diff --git a/test/normal/open-multiple-above/in b/test/normal/open-multiple-above/in
new file mode 100644
index 00000000..257cc564
--- /dev/null
+++ b/test/normal/open-multiple-above/in
@@ -0,0 +1 @@
+foo
diff --git a/test/normal/open-multiple-above/out b/test/normal/open-multiple-above/out
new file mode 100644
index 00000000..de926059
--- /dev/null
+++ b/test/normal/open-multiple-above/out
@@ -0,0 +1,4 @@
+bar
+bar
+bar
+foo
diff --git a/test/normal/open-multiple-below/cmd b/test/normal/open-multiple-below/cmd
new file mode 100644
index 00000000..e4be15d6
--- /dev/null
+++ b/test/normal/open-multiple-below/cmd
@@ -0,0 +1 @@
+3obar<esc>
diff --git a/test/normal/open-multiple-below/in b/test/normal/open-multiple-below/in
new file mode 100644
index 00000000..257cc564
--- /dev/null
+++ b/test/normal/open-multiple-below/in
@@ -0,0 +1 @@
+foo
diff --git a/test/normal/open-multiple-below/out b/test/normal/open-multiple-below/out
new file mode 100644
index 00000000..1458786c
--- /dev/null
+++ b/test/normal/open-multiple-below/out
@@ -0,0 +1,4 @@
+foo
+bar
+bar
+bar
diff --git a/test/regression/0-open-below-should-not-move-cursor-on-eol/cmd b/test/regression/0-open-below-should-not-move-cursor-on-eol/cmd
new file mode 100644
index 00000000..f180a6b2
--- /dev/null
+++ b/test/regression/0-open-below-should-not-move-cursor-on-eol/cmd
@@ -0,0 +1 @@
+x;:exec -draft o<ret>
diff --git a/test/regression/0-open-below-should-not-move-cursor-on-eol/in b/test/regression/0-open-below-should-not-move-cursor-on-eol/in
new file mode 100644
index 00000000..257cc564
--- /dev/null
+++ b/test/regression/0-open-below-should-not-move-cursor-on-eol/in
@@ -0,0 +1 @@
+foo
diff --git a/test/regression/0-open-below-should-not-move-cursor-on-eol/out b/test/regression/0-open-below-should-not-move-cursor-on-eol/out
new file mode 100644
index 00000000..75d7bfb8
--- /dev/null
+++ b/test/regression/0-open-below-should-not-move-cursor-on-eol/out
@@ -0,0 +1,2 @@
+foo
+
diff --git a/test/regression/0-open-below-should-not-move-cursor-on-eol/state b/test/regression/0-open-below-should-not-move-cursor-on-eol/state
new file mode 100644
index 00000000..d022d3dd
--- /dev/null
+++ b/test/regression/0-open-below-should-not-move-cursor-on-eol/state
@@ -0,0 +1 @@
+1.4,1.4