From d388ef762d91766b09564ce1b52a18da3e2df3f3 Mon Sep 17 00:00:00 2001
From: Axel Kohlmeyer <akohlmey@gmail.com>
Date: Fri, 6 Oct 2023 06:42:40 -0400
Subject: [PATCH] Implement more conventional behavior when opening
 non-existing file.

Instead of only printing a warning we now create a *named* and
empty buffer and change to the directory of the filename, so that
the file will be created in the desired location as soon as it is saved.
---
 tools/lammps-gui/lammpsgui.cpp | 15 ++++++++-------
 tools/lammps-gui/main.cpp      |  5 -----
 2 files changed, 8 insertions(+), 12 deletions(-)

diff --git a/tools/lammps-gui/lammpsgui.cpp b/tools/lammps-gui/lammpsgui.cpp
index 01933c46eb..c9d8b9bef0 100644
--- a/tools/lammps-gui/lammpsgui.cpp
+++ b/tools/lammps-gui/lammpsgui.cpp
@@ -588,22 +588,23 @@ void LammpsGui::open_file(const QString &fileName)
     if (!file.open(QIODevice::ReadOnly | QFile::Text)) {
         QMessageBox::warning(this, "Warning",
                              "Cannot open file " + path.absoluteFilePath() + ": " +
-                                 file.errorString());
-        return;
+                                 file.errorString() + ".\nWill create new file on saving editor buffer.");
+        ui->textEdit->document()->setPlainText(QString());
+    } else {
+        QTextStream in(&file);
+        QString text = in.readAll();
+        ui->textEdit->document()->setPlainText(text);
+        ui->textEdit->moveCursor(QTextCursor::Start, QTextCursor::MoveAnchor);
+        file.close();
     }
     setWindowTitle(QString("LAMMPS-GUI - " + current_file));
     run_counter = 0;
-    QTextStream in(&file);
-    QString text = in.readAll();
-    ui->textEdit->document()->setPlainText(text);
-    ui->textEdit->moveCursor(QTextCursor::Start, QTextCursor::MoveAnchor);
     ui->textEdit->document()->setModified(false);
     ui->textEdit->setGroupList();
     ui->textEdit->setVarNameList();
     ui->textEdit->setComputeIDList();
     ui->textEdit->setFixIDList();
     ui->textEdit->setFileList();
-    file.close();
     dirstatus->setText(QString(" Directory: ") + current_dir);
     status->setText("Ready.");
 
diff --git a/tools/lammps-gui/main.cpp b/tools/lammps-gui/main.cpp
index 310ccb291f..cf09fbb892 100644
--- a/tools/lammps-gui/main.cpp
+++ b/tools/lammps-gui/main.cpp
@@ -32,11 +32,6 @@ int main(int argc, char *argv[])
             printf("Usage: %s [-h|-help|<inputfile>]\n", argv[0]);
             return 1;
         }
-        if (!QFileInfo::exists(infile)) {
-            printf("Input file %s does not exist\n", infile);
-            printf("Usage: %s [-h|-help|<inputfile>]\n", argv[0]);
-            return 2;
-        }
     }
 
     LammpsGui w(nullptr, infile);