refactor: move msg_box out of engine qtutils into the dialog layer

The engine-side QtUtils no longer references QMessageBox; the two
dialog call sites use the identical olive::msg_box() inline helper.

app/common/qtutils.cpp

@@ -50,28 +50,6 @@ QFrame *QtUtils::create_vertical_line()
 	return l;
 }
 
-int QtUtils::msg_box(QWidget *parent, QMessageBox::Icon icon,
-					const QString &title, const QString &message,
-					QMessageBox::StandardButtons buttons)
-{
-	QMessageBox b(parent);
-	b.setIcon(icon);
-	b.setWindowModality(Qt::WindowModal);
-	b.setWindowTitle(title);
-	b.setText(message);
-
-	uint mask = QMessageBox::FirstButton;
-	while (mask <= QMessageBox::LastButton) {
-		uint sb = buttons & mask;
-		if (sb) {
-			b.addButton(static_cast<QMessageBox::StandardButton>(sb));
-		}
-		mask <<= 1;
-	}
-
-	return b.exec();
-}
-
 QDateTime QtUtils::get_creation_date(const QFileInfo &info)
 {
 #if QT_VERSION < QT_VERSION_CHECK(5, 10, 0)

app/common/qtutils.h

@@ -28,7 +28,6 @@
 #include <QFileInfo>
 #include <QFontMetrics>
 #include <QFrame>
-#include <QMessageBox>
 
 namespace olive
 {
@@ -48,10 +47,6 @@ public:
 
 	static QFrame *create_vertical_line();
 
-	static int msg_box(QWidget *parent, QMessageBox::Icon icon,
-					  const QString &title, const QString &message,
-					  QMessageBox::StandardButtons buttons = QMessageBox::Ok);
-
 	static QDateTime get_creation_date(const QFileInfo &info);
 
 	static QString get_formatted_date_time(const QDateTime &dt);

app/dialog/export/export.cpp

@@ -33,6 +33,7 @@
 
 #include "common/digit.h"
 #include "common/qtutils.h"
+#include "dialog/msgbox.h"
 #include "dialog/task/task.h"
 #include "exportsavepresetdialog.h"
 #include "node/project.h"
@@ -308,7 +309,7 @@ void ExportDialog::start_export()
 {
 	if (!video_enabled_->isChecked() && !audio_enabled_->isChecked() &&
 		!subtitles_enabled_->isChecked()) {
-		QtUtils::msg_box(
+		msg_box(
 			this, QMessageBox::Critical, tr("Invalid parameters"),
 			tr("Video, audio, and subtitles are disabled. There's nothing to export."));
 		return;
@@ -322,7 +323,7 @@ void ExportDialog::start_export()
 
 	// If it doesn't, see if the user wants to append it automatically. If not, we don't abort the export.
 	if (!proposed_filename.endsWith(necessary_ext, Qt::CaseInsensitive)) {
-		if (QtUtils::msg_box(
+		if (msg_box(
 				this, QMessageBox::Warning, tr("Invalid filename"),
 				tr("The filename must contain the extension \"%1\". Would you like to append it "
 				   "automatically?")
@@ -341,7 +342,7 @@ void ExportDialog::start_export()
 	// If the directory does not exist, try to create it
 	QDir dest_dir(file_info.path());
 	if (!FileFunctions::directory_is_valid(dest_dir)) {
-		QtUtils::msg_box(
+		msg_box(
 			this, QMessageBox::Critical,
 			tr("Failed to create output directory"),
 			tr("The intended output directory doesn't exist and Oak Video Editor couldn't create it. "
@@ -353,7 +354,7 @@ void ExportDialog::start_export()
 	if (video_tab_->is_image_sequence_set()) {
 		// Ensure filename contains digits
 		if (!Encoder::filename_contains_digit_placeholder(proposed_filename)) {
-			QtUtils::msg_box(
+			msg_box(
 				this, QMessageBox::Critical, tr("Invalid filename"),
 				tr("Export is set to an image sequence, but the filename does not have a section for digits "
 				   "(formatted as [#####] where the amount of # is the amount of digits)."));
@@ -365,7 +366,7 @@ void ExportDialog::start_export()
 		int current_digit_count =
 			Encoder::get_image_sequence_placeholder_digit_count(proposed_filename);
 		if (current_digit_count < needed_digit_count) {
-			QtUtils::msg_box(
+			msg_box(
 				this, QMessageBox::Critical, tr("Invalid filename"),
 				tr("Filename doesn't contain enough digits for the amount of frames "
 				   "this export will need (need %1 for %n frame(s)).",
@@ -377,7 +378,7 @@ void ExportDialog::start_export()
 
 	// Validate if the file exists and whether the user wishes to overwrite it
 	if (file_info.exists()) {
-		if (QtUtils::msg_box(
+		if (msg_box(
 				this, QMessageBox::Warning, tr("Confirm Overwrite"),
 				tr("The file \"%1\" already exists. Do you want to overwrite it?")
 					.arg(proposed_filename),
@@ -392,7 +393,7 @@ void ExportDialog::start_export()
 		 video_tab_->get_selected_codec() == ExportCodec::k_codec_h265) &&
 		(video_tab_->width_slider()->get_value() % 2 != 0 ||
 		 video_tab_->height_slider()->get_value() % 2 != 0)) {
-		QtUtils::msg_box(this, QMessageBox::Critical, tr("Invalid Parameters"),
+		msg_box(this, QMessageBox::Critical, tr("Invalid Parameters"),
 						tr("Width and height must be multiples of 2."));
 		return;
 	}

app/dialog/msgbox.h

@@ -0,0 +1,60 @@
+/***
+
+  Oak - Non-Linear Video Editor
+  Copyright (C) 2026 Oak Team
+
+  This program is free software: you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation, either version 3 of the License, or
+  (at your option) any later version.
+
+  This program is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+***/
+
+#ifndef OAK_MSGBOX_H
+#define OAK_MSGBOX_H
+
+#include <QMessageBox>
+#include <QWidget>
+
+namespace olive
+{
+
+/**
+ * @brief Shows a simple window-modal message box
+ *
+ * Lives in the UI layer: the engine (common/qtutils) must not reference
+ * QMessageBox. Previously QtUtils::msg_box.
+ */
+inline int msg_box(QWidget *parent, QMessageBox::Icon icon,
+				   const QString &title, const QString &message,
+				   QMessageBox::StandardButtons buttons = QMessageBox::Ok)
+{
+	QMessageBox b(parent);
+	b.setIcon(icon);
+	b.setWindowModality(Qt::WindowModal);
+	b.setWindowTitle(title);
+	b.setText(message);
+
+	uint mask = QMessageBox::FirstButton;
+	while (mask <= QMessageBox::LastButton) {
+		uint sb = buttons & mask;
+		if (sb) {
+			b.addButton(static_cast<QMessageBox::StandardButton>(sb));
+		}
+		mask <<= 1;
+	}
+
+	return b.exec();
+}
+
+}
+
+#endif // OAK_MSGBOX_H

app/dialog/sequence/sequence.cpp

@@ -33,6 +33,7 @@
 #include "config/config.h"
 #include "core.h"
 #include "common/qtutils.h"
+#include "dialog/msgbox.h"
 #include "undo/undostack.h"
 
 namespace olive
@@ -107,7 +108,7 @@ void SequenceDialog::set_name_is_editable(bool e)
 void SequenceDialog::accept()
 {
 	if (name_field_->isEnabled() && name_field_->text().isEmpty()) {
-		QtUtils::msg_box(this, QMessageBox::Critical,
+		msg_box(this, QMessageBox::Critical,
 						tr("Error editing Sequence"),
 						tr("Please enter a name for this Sequence."));
 		return;
@@ -178,7 +179,7 @@ void SequenceDialog::accept()
 
 void SequenceDialog::set_as_default_clicked()
 {
-	if (QtUtils::msg_box(
+	if (msg_box(
 			this, QMessageBox::Question, tr("Confirm Set As Default"),
 			tr("Are you sure you want to set the current parameters as defaults?"),
 			QMessageBox::Yes | QMessageBox::No) == QMessageBox::Yes) {