From f08db308e4d4989678a315e7b306ef247050e7fd Mon Sep 17 00:00:00 2001
From: prewettg <prewettg@gmail.com>
Date: Wed, 23 Dec 2020 23:32:40 -0800
Subject: [PATCH] Automatically add extension to non-native file dialog if none
 is specified (#2818)

---
 cpp/open3d/visualization/gui/FileDialog.cpp   | 27 ++++++++++++++++---
 cpp/open3d/visualization/gui/FileDialog.h     |  2 ++
 .../visualization/gui/FileDialogNative.cpp    |  8 +++---
 3 files changed, 30 insertions(+), 7 deletions(-)

diff --git a/cpp/open3d/visualization/gui/FileDialog.cpp b/cpp/open3d/visualization/gui/FileDialog.cpp
index 5fb7194d1e0..073712f8cf9 100644
--- a/cpp/open3d/visualization/gui/FileDialog.cpp
+++ b/cpp/open3d/visualization/gui/FileDialog.cpp
@@ -24,12 +24,13 @@
 // IN THE SOFTWARE.
 // ----------------------------------------------------------------------------
 
-#if defined(__APPLE__)
+// Include FileDialog here to get value of GUI_USE_NATIVE_FILE_DIALOG
+#include "open3d/visualization/gui/FileDialog.h"
+
+#if defined(__APPLE__) && GUI_USE_NATIVE_FILE_DIALOG
 // see FileDialogNative.cpp
 #else
 
-#include "open3d/visualization/gui/FileDialog.h"
-
 #include <string>
 #include <unordered_map>
 #include <unordered_set>
@@ -387,7 +388,25 @@ void FileDialog::OnDone() {
     if (this->impl_->on_done_) {
         auto dir = this->impl_->CalcCurrentDirectory();
         utility::filesystem::ChangeWorkingDirectory(dir);
-        auto name = this->impl_->filename_->GetText();
+        std::string name = this->impl_->filename_->GetText();
+        // If the user didn't specify an extension, automatically add one
+        // (unless we don't have the any-files (*.*) filter selected).
+        if (name.find(".") == std::string::npos && !name.empty()) {
+            int idx = this->impl_->filter_->GetSelectedIndex();
+            if (idx >= 0) {
+                auto &exts = impl_->filter_idx_2_filter[idx];
+                // Prefer PNG if available (otherwise in a list of common
+                // image files, e.g., ".jpg .png", we might pick the lossy one.
+                if (exts.find(".png") != exts.end()) {
+                    name += ".png";
+                } else {
+                    if (!exts.empty()) {
+                        name += *exts.begin();
+                    }
+                }
+            }
+        }
+        std::cout << "[o3d] name: '" << name << "'" << std::endl;
         this->impl_->on_done_((dir + "/" + name).c_str());
     } else {
         utility::LogError("FileDialog: need to call SetOnDone()");
diff --git a/cpp/open3d/visualization/gui/FileDialog.h b/cpp/open3d/visualization/gui/FileDialog.h
index d16ebd67b9c..7d40950c1c2 100644
--- a/cpp/open3d/visualization/gui/FileDialog.h
+++ b/cpp/open3d/visualization/gui/FileDialog.h
@@ -30,6 +30,8 @@
 
 #include "open3d/visualization/gui/Dialog.h"
 
+#define GUI_USE_NATIVE_FILE_DIALOG 1
+
 namespace open3d {
 namespace visualization {
 namespace gui {
diff --git a/cpp/open3d/visualization/gui/FileDialogNative.cpp b/cpp/open3d/visualization/gui/FileDialogNative.cpp
index 275495a08f4..0a20ca45406 100644
--- a/cpp/open3d/visualization/gui/FileDialogNative.cpp
+++ b/cpp/open3d/visualization/gui/FileDialogNative.cpp
@@ -24,12 +24,14 @@
 // IN THE SOFTWARE.
 // ----------------------------------------------------------------------------
 
-#if defined(__APPLE__)
+// Include FileDialog here to get value of GUI_USE_NATIVE_FILE_DIALOG
+#include "open3d/visualization/gui/FileDialog.h"
+
+#if defined(__APPLE__) && GUI_USE_NATIVE_FILE_DIALOG
 
 #include <string>
 #include <vector>
 
-#include "open3d/visualization/gui/FileDialog.h"
 #include "open3d/visualization/gui/Native.h"
 
 namespace open3d {
@@ -83,4 +85,4 @@ void FileDialog::OnDone() {}
 }  // namespace visualization
 }  // namespace open3d
 
-#endif  // __APPLE__
+#endif  // __APPLE__ && GUI_USE_NATIVE_FILE_DIALOG