From c1d690d190b4ad94ab9876025e2a01d254911a74 Mon Sep 17 00:00:00 2001
From: Axel Kohlmeyer <akohlmey@gmail.com>
Date: Fri, 28 Jul 2023 05:04:19 -0400
Subject: [PATCH] implement drag-n-drop for files

---
 tools/lammps-gui/TODO.md        |  1 -
 tools/lammps-gui/codeeditor.cpp | 27 +++++++++++++++++++++++++++
 tools/lammps-gui/codeeditor.h   |  3 +++
 tools/lammps-gui/lammpsgui.cpp  |  7 +++----
 tools/lammps-gui/lammpsgui.h    |  3 ++-
 tools/lammps-gui/lammpsgui.ui   |  8 ++++++--
 6 files changed, 41 insertions(+), 8 deletions(-)

diff --git a/tools/lammps-gui/TODO.md b/tools/lammps-gui/TODO.md
index 2c1e70a647..f6c97c12b6 100644
--- a/tools/lammps-gui/TODO.md
+++ b/tools/lammps-gui/TODO.md
@@ -3,7 +3,6 @@ LAMMPS-GUI TODO list:
 # Short term goals
 
 - add indicator for when the file in editor is modified (-> status bar?)
-- add support for drag-n-drop of files into the editor
 - add "Help" entry to menu bar. Should open a popup window with a one page description of how to use it. Use HTML or Markdown text.
 - add dialog when exiting asking if file should be saved when it is modified, similar dialog when opening a new file
 - add CTRL-q hotkey to log windows so you can exit the entire application (add do you really want to? dialog to this)
diff --git a/tools/lammps-gui/codeeditor.cpp b/tools/lammps-gui/codeeditor.cpp
index ff3fa2f300..13519b0652 100644
--- a/tools/lammps-gui/codeeditor.cpp
+++ b/tools/lammps-gui/codeeditor.cpp
@@ -13,7 +13,11 @@
 
 #include "codeeditor.h"
 #include "linenumberarea.h"
+#include "lammpsgui.h"
 
+#include <QDragEnterEvent>
+#include <QDropEvent>
+#include <QMimeData>
 #include <QPainter>
 #include <QTextBlock>
 
@@ -58,6 +62,29 @@ void CodeEditor::updateLineNumberArea(const QRect &rect, int dy)
     if (rect.contains(viewport()->rect())) updateLineNumberAreaWidth(0);
 }
 
+void CodeEditor::dragEnterEvent(QDragEnterEvent *event)
+{
+    event->acceptProposedAction();
+}
+
+bool CodeEditor::canInsertFromMimeData(const QMimeData *source) const
+{
+    return  source->hasUrls(); // || source->hasText();
+}
+
+void CodeEditor::dropEvent(QDropEvent *event)
+{
+    event->acceptProposedAction();
+    if (event->mimeData()->hasUrls()) {
+        auto file = event->mimeData()->urls()[0].url().remove("file://");
+        auto gui = dynamic_cast<LammpsGui *>(parent());
+        if (gui) gui->open_file(file);
+    } else if (event->mimeData()->hasText()) {
+        fprintf(stderr, "Drag - Drop for text block not yet implemented: text=%s\n",
+                event->mimeData()->text().toStdString().c_str());
+    }
+}
+
 void CodeEditor::resizeEvent(QResizeEvent *e)
 {
     QPlainTextEdit::resizeEvent(e);
diff --git a/tools/lammps-gui/codeeditor.h b/tools/lammps-gui/codeeditor.h
index c501e8771c..49abf81553 100644
--- a/tools/lammps-gui/codeeditor.h
+++ b/tools/lammps-gui/codeeditor.h
@@ -27,6 +27,9 @@ public:
 
 protected:
     void resizeEvent(QResizeEvent *event) override;
+    void dragEnterEvent(QDragEnterEvent *event) override;
+    bool canInsertFromMimeData(const QMimeData *source) const override;
+    void dropEvent(QDropEvent *event) override;
 
 private slots:
     void updateLineNumberAreaWidth(int newBlockCount);
diff --git a/tools/lammps-gui/lammpsgui.cpp b/tools/lammps-gui/lammpsgui.cpp
index bb6a1a4549..4f6d7d74fa 100644
--- a/tools/lammps-gui/lammpsgui.cpp
+++ b/tools/lammps-gui/lammpsgui.cpp
@@ -79,7 +79,8 @@ LammpsGui::LammpsGui(QWidget *parent, const char *filename) :
 
 #if defined(LAMMPS_GUI_USE_PLUGIN)
     liblammpsplugin_t *lammps = nullptr;
-    for (const auto libfile : {"liblammps.so", "./liblammps.so", "liblammps.dylib", "./liblammps.dylib", "liblammps.dll"}) {
+    for (const auto libfile : {"liblammps.so", "./liblammps.so", "liblammps.dylib",
+                               "./liblammps.dylib", "liblammps.dll"}) {
         if (!lammps) lammps = liblammpsplugin_load(libfile);
         if (lammps) {
             plugin_path = libfile;
@@ -106,7 +107,6 @@ LammpsGui::LammpsGui(QWidget *parent, const char *filename) :
     progress->setRange(0, 1000);
     progress->setFixedWidth(500);
     ui->statusbar->addWidget(progress);
-
 }
 
 LammpsGui::~LammpsGui()
@@ -141,7 +141,6 @@ void LammpsGui::open()
 // open file and switch CWD to path of file
 void LammpsGui::open_file(const QString &fileName)
 {
-
     QFileInfo path(fileName);
     current_file = path.fileName();
     current_dir  = path.absolutePath();
@@ -393,7 +392,7 @@ void LammpsGui::about()
 #else
     version += " - LAMMPS linked statically";
 #endif
-    std::string info    = "LAMMPS is currently running. LAMMPS config info not available.";
+    std::string info = "LAMMPS is currently running. LAMMPS config info not available.";
 
     // LAMMPS is not re-entrant, so we can only query LAMMPS when it is not running
     if (!is_running) {
diff --git a/tools/lammps-gui/lammpsgui.h b/tools/lammps-gui/lammpsgui.h
index 5a7b4fb0e6..1ce4946bec 100644
--- a/tools/lammps-gui/lammpsgui.h
+++ b/tools/lammps-gui/lammpsgui.h
@@ -36,9 +36,10 @@ class StdCapture;
 class LammpsGui : public QMainWindow {
     Q_OBJECT
 
+    friend class CodeEditor;
 public:
     LammpsGui(QWidget *parent = nullptr, const char *filename = nullptr);
-    ~LammpsGui();
+    ~LammpsGui() override;
 
 protected:
     void open_file(const QString &filename);
diff --git a/tools/lammps-gui/lammpsgui.ui b/tools/lammps-gui/lammpsgui.ui
index d2d1cc9bad..d9f9ca077a 100644
--- a/tools/lammps-gui/lammpsgui.ui
+++ b/tools/lammps-gui/lammpsgui.ui
@@ -25,7 +25,11 @@
     </property>
     <layout class="QVBoxLayout" name="verticalLayout">
      <item>
-      <widget class="CodeEditor" name="textEdit" native="true"/>
+      <widget class="CodeEditor" name="textEdit" native="true">
+       <property name="acceptDrops">
+        <bool>true</bool>
+       </property>
+      </widget>
      </item>
     </layout>
    </widget>
@@ -303,7 +307,7 @@
  <customwidgets>
   <customwidget>
    <class>CodeEditor</class>
-   <extends>QWidget</extends>
+   <extends>QPlainTextEdit</extends>
    <header>codeeditor.h</header>
   </customwidget>
  </customwidgets>