color: global LUT library, LUT error reporting, clamp + display fixes

- Add a global LUT library: user-configurable directories (new
  Preferences > LUT tab) scanned recursively for .cube/.3dl files; LUT
  node file pickers offer the library dirs as sidebar shortcuts via a
  'lut_library' input property handled by the param view bridge
- OCIOLutNode no longer fails silently: missing files, unsupported
  extensions and OCIO load errors are recorded in last_error() and
  surfaced in the status bar (input still passes through for rendering
  safety)
- ColorDialog: re-enable the display -> reference conversion using
  ColorProcessor::kInverse with a validity guard, and re-enable the
  Display tab in ColorValuesWidget; covered by a round-trip regression
  test proving the old OCIO inverse crash no longer occurs
- OCIOGradingTransformLinearNode: enforce the OCIO clampWhite >
  clampBlack invariant per frame in Value() so keyframed/connected
  values cannot produce invalid grading transforms, and constrain the
  white clamp UI minimum whenever the black clamp is static
- Regression tests for LUT extension checks, direction switching, node
  error reporting, LUT library scanning, display inverse round-trip and
  clamp enforcement

app/config/config.cpp

@@ -240,6 +240,9 @@ void Config::SetDefaults()
 	SetEntryInternal(QStringLiteral("FFmpegPath"), NodeValue::kText,
 					 QString());
 
+	SetEntryInternal(QStringLiteral("LUTLibraryPaths"), NodeValue::kText,
+					 QString());
+
 	SetEntryInternal(QStringLiteral("DefaultSequenceWidth"), NodeValue::kInt,
 					 1920);
 	SetEntryInternal(QStringLiteral("DefaultSequenceHeight"), NodeValue::kInt,

app/dialog/color/colordialog.cpp

@@ -192,21 +192,21 @@ void ColorDialog::ColorSpaceChanged(const QString &input,
 	ColorProcessorPtr ref_to_input = ColorProcessor::Create(
 		color_manager_, color_manager_->GetReferenceColorSpace(), input);
 
-	// FIXME: For some reason, using OCIO::TRANSFORM_DIR_INVERSE (wrapped by ColorProcessor::kInverse) causes OCIO to
+	// Display -> reference is the inverse of the display transform. Older OCIO
-	//        crash. We've disabled that functionality for now (also disabling display_tab_ in ColorValuesWidget)
+	// versions crashed on TRANSFORM_DIR_INVERSE; guard by requiring a valid
-
+	// processor and fall back to disabling the display tab if creation fails.
-	/*ColorProcessorPtr display_to_ref = ColorProcessor::Create(color_manager_->GetConfig(),
+	ColorProcessorPtr display_to_ref = ColorProcessor::Create(
-                                                            color_manager_->GetReferenceColorSpace(),
+		color_manager_, color_manager_->GetReferenceColorSpace(), output,
-                                                            display,
+		ColorProcessor::kInverse);
-                                                            view,
+	if (display_to_ref && !display_to_ref->GetProcessor()) {
-                                                            look,
+		display_to_ref = nullptr;
-                                                            ColorProcessor::kInverse);*/
+	}
 
 	color_wheel_->SetColorProcessor(input_to_ref_processor_, ref_to_display);
 	hsv_value_gradient_->SetColorProcessor(input_to_ref_processor_,
 										   ref_to_display);
 	color_values_widget_->SetColorProcessor(
-		input_to_ref_processor_, ref_to_display, nullptr, ref_to_input);
+		input_to_ref_processor_, ref_to_display, display_to_ref, ref_to_input);
 }
 
 }

app/dialog/preferences/preferences.cpp

@@ -33,6 +33,7 @@
 #include "tabs/preferencesdisktab.h"
 #include "tabs/preferencesaudiotab.h"
 #include "tabs/preferenceskeyboardtab.h"
+#include "tabs/preferencesluttab.h"
 #include "window/mainwindow/mainwindow.h"
 
 namespace olive
@@ -60,6 +61,7 @@ PreferencesDialog::PreferencesDialog(MainWindow *main_window, int start_tab)
 		new PreferencesBehaviorTab(PreferencesBehaviorTab::kCategoryRendering),
 		tr("Rendering"));
 	AddTab(new PreferencesDiskTab(), tr("Disk"));
+	AddTab(new PreferencesLutTab(), tr("LUT"));
 	AddTab(new PreferencesKeyboardTab(main_window), tr("Keyboard"));
 
 	SetCurrentTab(start_tab);

app/dialog/preferences/tabs/CMakeLists.txt

@@ -22,6 +22,8 @@ set(OLIVE_SOURCES
         dialog/preferences/tabs/preferencesbehaviortab.cpp
         dialog/preferences/tabs/preferencesdisktab.h
         dialog/preferences/tabs/preferencesdisktab.cpp
+        dialog/preferences/tabs/preferencesluttab.h
+        dialog/preferences/tabs/preferencesluttab.cpp
         dialog/preferences/tabs/preferencesappearancetab.h
         dialog/preferences/tabs/preferencesappearancetab.cpp
         dialog/preferences/tabs/preferencesaudiotab.h

app/dialog/preferences/tabs/preferencesluttab.cpp

@@ -0,0 +1,89 @@
+/***
+
+  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/>.
+
+***/
+
+#include "preferencesluttab.h"
+
+#include <QFileDialog>
+#include <QGroupBox>
+#include <QHBoxLayout>
+#include <QLabel>
+#include <QPushButton>
+#include <QVBoxLayout>
+
+#include "render/lutlibrary.h"
+
+namespace olive
+{
+
+PreferencesLutTab::PreferencesLutTab()
+{
+	QVBoxLayout *outer_layout = new QVBoxLayout(this);
+
+	QGroupBox *library_group = new QGroupBox(tr("LUT Library"));
+	outer_layout->addWidget(library_group);
+
+	QVBoxLayout *library_layout = new QVBoxLayout(library_group);
+
+	library_layout->addWidget(new QLabel(
+		tr("Directories scanned for .cube and .3dl LUT files. LUT nodes offer "
+		   "these locations when picking a LUT file.")));
+
+	library_dirs_list_ = new QListWidget();
+	library_dirs_list_->addItems(LUTLibrary::GetDirectories());
+	library_layout->addWidget(library_dirs_list_);
+
+	QHBoxLayout *button_layout = new QHBoxLayout();
+	button_layout->addStretch();
+
+	QPushButton *add_btn = new QPushButton(tr("Add..."));
+	connect(add_btn, &QPushButton::clicked, this, [this]() {
+		const QString dir = QFileDialog::getExistingDirectory(
+			this, tr("Add LUT Library Directory"));
+		if (!dir.isEmpty() &&
+			library_dirs_list_->findItems(dir, Qt::MatchExactly).isEmpty()) {
+			library_dirs_list_->addItem(dir);
+		}
+	});
+	button_layout->addWidget(add_btn);
+
+	QPushButton *remove_btn = new QPushButton(tr("Remove"));
+	connect(remove_btn, &QPushButton::clicked, this, [this]() {
+		qDeleteAll(library_dirs_list_->selectedItems());
+	});
+	button_layout->addWidget(remove_btn);
+
+	library_layout->addLayout(button_layout);
+
+	outer_layout->addStretch();
+}
+
+void PreferencesLutTab::Accept(MultiUndoCommand *command)
+{
+	Q_UNUSED(command)
+
+	QStringList dirs;
+	for (int i = 0; i < library_dirs_list_->count(); i++) {
+		dirs.append(library_dirs_list_->item(i)->text());
+	}
+
+	LUTLibrary::SetDirectories(dirs);
+}
+
+}

app/dialog/preferences/tabs/preferencesluttab.h

@@ -0,0 +1,44 @@
+/***
+
+  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 PREFERENCESLUTTAB_H
+#define PREFERENCESLUTTAB_H
+
+#include <QListWidget>
+
+#include "dialog/configbase/configdialogbase.h"
+
+namespace olive
+{
+
+class PreferencesLutTab : public ConfigDialogBaseTab {
+	Q_OBJECT
+public:
+	PreferencesLutTab();
+
+	virtual void Accept(MultiUndoCommand *command) override;
+
+private:
+	QListWidget *library_dirs_list_;
+};
+
+}
+
+#endif // PREFERENCESLUTTAB_H

app/node/color/ociogradingtransformlinear/ociogradingtransformlinear.cpp

@@ -92,10 +92,10 @@ OCIOGradingTransformLinearNode::OCIOGradingTransformLinearNode()
 					 GetStandardValue(kClampWhiteEnableInput).toBool());
 	SetInputProperty(kClampWhiteInput, QStringLiteral("base"), 0.01);
 
-	// FIXME: Temporarily disabled. This will break if "clamp black" is keyframed or connected to
+	// Constrain the white clamp minimum to just above the (static) black clamp
-	//        something and there's currently no solution to remedy that. If there is in the future,
+	// as per OCIO::GradingPrimary::validate. When the black clamp is keyframed
-	//        we can look into re-enabling this.
+	// or connected, Value() enforces the invariant per frame instead.
-	//SetInputProperty(kClampWhiteInput, QStringLiteral("min"), GetStandardValue(kClampBlackInput).toDouble() + 0.000001);
+	UpdateClampWhiteMinimum();
 }
 
 QString OCIOGradingTransformLinearNode::Name() const
@@ -149,16 +149,49 @@ void OCIOGradingTransformLinearNode::InputValueChangedEvent(
 		SetInputProperty(kClampBlackInput, QStringLiteral("enabled"),
 						 GetStandardValue(kClampBlackEnableInput).toBool());
 	} else if (input == kClampBlackInput) {
-		// Ensure the white clamp is always greater than the black clamp as per OCIO::GradingPrimary::validate
+		// Ensure the white clamp is always greater than the black clamp as per
-		// FIXME: Temporarily disabled. This will break if "clamp black" is keyframed or connected to
+		// OCIO::GradingPrimary::validate
-		//        something and there's currently no solution to remedy that. If there is in the future,
+		UpdateClampWhiteMinimum();
-		//        we can look into re-enabling this.
-		//SetInputProperty(kClampWhiteInput, QStringLiteral("min"), GetStandardValue(kClampBlackInput).toDouble() + 0.000001);
 	}
 
 	GenerateProcessor();
 }
 
+void OCIOGradingTransformLinearNode::InputConnectedEvent(const QString &input,
+														 int element, Node *output)
+{
+	super::InputConnectedEvent(input, element, output);
+
+	if (input == kClampBlackInput) {
+		UpdateClampWhiteMinimum();
+	}
+}
+
+void OCIOGradingTransformLinearNode::InputDisconnectedEvent(const QString &input,
+															int element,
+															Node *output)
+{
+	super::InputDisconnectedEvent(input, element, output);
+
+	if (input == kClampBlackInput) {
+		UpdateClampWhiteMinimum();
+	}
+}
+
+void OCIOGradingTransformLinearNode::UpdateClampWhiteMinimum()
+{
+	// A static UI minimum cannot follow an animated black clamp; for keyframed
+	// or connected values the white>black invariant is enforced per frame in
+	// Value() instead
+	if (IsInputKeyframing(kClampBlackInput) ||
+		IsInputConnected(kClampBlackInput)) {
+		return;
+	}
+
+	SetInputProperty(kClampWhiteInput, QStringLiteral("min"),
+					 GetStandardValue(kClampBlackInput).toDouble() + 0.000001);
+}
+
 void OCIOGradingTransformLinearNode::GenerateProcessor()
 {
 	if (manager()) {
@@ -241,6 +274,21 @@ void OCIOGradingTransformLinearNode::Value(const NodeValueRow &value,
 									 OCIO::GradingPrimary::NoClampWhite()));
 			}
 
+			if (value[kClampBlackEnableInput].toBool() &&
+				value[kClampWhiteEnableInput].toBool()) {
+				// OCIO::GradingPrimary::validate requires the white clamp to be
+				// greater than the black clamp. Keyframed or connected values
+				// can violate this at arbitrary times, so enforce the invariant
+				// per frame here.
+				const double clamp_black = value[kClampBlackInput].toDouble();
+				const double clamp_white = value[kClampWhiteInput].toDouble();
+				if (clamp_white <= clamp_black) {
+					job.Insert(kClampWhiteInput,
+							   NodeValue(NodeValue::kFloat,
+										 clamp_black + 0.000001));
+				}
+			}
+
 			table->Push(NodeValue::kTexture, tex->toJob(job), this);
 		}
 	}

app/node/color/ociogradingtransformlinear/ociogradingtransformlinear.h

@@ -43,6 +43,10 @@ public:
 	virtual void Retranslate() override;
 	virtual void InputValueChangedEvent(const QString &input,
 										int element) override;
+	virtual void InputConnectedEvent(const QString &input, int element,
+									 Node *output) override;
+	virtual void InputDisconnectedEvent(const QString &input, int element,
+										Node *output) override;
 	void GenerateProcessor();
 
 	virtual void Value(const NodeValueRow &value, const NodeGlobals &globals,
@@ -63,6 +67,16 @@ protected slots:
 
 private:
 	void SetVec4InputColors(const QString &input);
+
+	/**
+	 * @brief Constrains the white clamp UI minimum to just above the black
+	 * clamp, as required by OCIO::GradingPrimary::validate
+	 *
+	 * Only applies while the black clamp is a static value; when it is
+	 * keyframed or connected the invariant is enforced per frame in Value()
+	 * instead.
+	 */
+	void UpdateClampWhiteMinimum();
 };
 
 } // olive

app/node/color/ociolut/ociolut.cpp

@@ -25,7 +25,9 @@
 
 #include <QApplication>
 
+#include "core.h"
 #include "node/color/colormanager/colormanager.h"
+#include "render/lutlibrary.h"
 #include "render/previewautocacher.h"
 #include "render/rendermanager.h"
 
@@ -40,12 +42,6 @@ const QString OCIOLutNode::kDirectionInput = QStringLiteral("lut_dir_in");
 namespace
 {
 
-bool IsSupportedLutExtension(const QString &suffix)
-{
-	const QString lower = suffix.toLower();
-	return lower == QStringLiteral("cube") || lower == QStringLiteral("3dl");
-}
-
 bool IsMainProcess()
 {
 	return qobject_cast<QApplication *>(QCoreApplication::instance()) !=
@@ -86,6 +82,8 @@ OCIOLutNode::OCIOLutNode()
 		tr("LUT Files (*.cube *.3dl);;Cube LUT (*.cube);;3DL LUT (*.3dl);;All Files (*)"));
 	SetInputProperty(kFileInput, QStringLiteral("placeholder"),
 					 tr("Select a .cube or .3dl LUT file"));
+	// Allow the UI to offer the global LUT library for this input
+	SetInputProperty(kFileInput, QStringLiteral("lut_library"), true);
 
 	AddInput(kDirectionInput, NodeValue::kCombo, 0,
 			 InputFlags(kInputFlagNotKeyframable | kInputFlagNotConnectable));
@@ -194,6 +192,21 @@ void OCIOLutNode::EnsureProcessor() const
 	CreateProcessorFromInputs();
 }
 
+void OCIOLutNode::SetLastError(const QString &error) const
+{
+	if (last_error_ == error) {
+		return;
+	}
+
+	last_error_ = error;
+
+	// Make the error visible to the user instead of failing silently, but only
+	// from the main process (the render worker has no status bar)
+	if (!error.isEmpty() && IsMainProcess() && Core::instance()) {
+		Core::instance()->ShowStatusBarMessage(error, 10000);
+	}
+}
+
 bool OCIOLutNode::CreateProcessorFromInputs() const
 {
 	if (!manager()) {
@@ -214,6 +227,7 @@ bool OCIOLutNode::CreateProcessorFromInputs() const
 		last_path_.clear();
 		last_direction_ = -1;
 		processor_dirty_ = false;
+		SetLastError(QString());
 		return false;
 	}
 
@@ -231,17 +245,22 @@ bool OCIOLutNode::CreateProcessorFromInputs() const
 		last_path_.clear();
 		last_direction_ = -1;
 		processor_dirty_ = false;
+		SetLastError(tr("OCIO LUT: file does not exist: %1").arg(path));
 		return false;
 	}
 
 	const QString suffix = info.suffix();
-	if (!IsSupportedLutExtension(suffix)) {
+	if (!LUTLibrary::IsSupportedExtension(suffix)) {
 		qWarning() << "Unsupported OCIO LUT file extension:" << path;
 		const_cast<OCIOLutNode *>(this)->set_processor(nullptr);
 		last_processor_.reset();
 		last_path_.clear();
 		last_direction_ = -1;
 		processor_dirty_ = false;
+		SetLastError(
+			tr("OCIO LUT: unsupported LUT file extension (expected .cube or "
+			   ".3dl): %1")
+				.arg(path));
 		return false;
 	}
 
@@ -267,6 +286,12 @@ bool OCIOLutNode::CreateProcessorFromInputs() const
 		processor = nullptr;
 	}
 
+	if (!processor) {
+		SetLastError(tr("OCIO LUT: failed to load LUT file: %1").arg(path));
+	} else {
+		SetLastError(QString());
+	}
+
 	last_path_ = path;
 	last_direction_ = direction;
 	last_processor_ = processor;

app/node/color/ociolut/ociolut.h

@@ -50,6 +50,18 @@ public:
 	static const QString kFileInput;
 	static const QString kDirectionInput;
 
+	/**
+	 * @brief Human-readable description of why no LUT processor is active
+	 *
+	 * Empty when a valid LUT processor is in use or no LUT file has been
+	 * selected yet. This allows the UI (and tests) to surface silent
+	 * passthrough states (missing file, unsupported extension, OCIO errors).
+	 */
+	const QString &last_error() const
+	{
+		return last_error_;
+	}
+
 protected slots:
 	virtual void ConfigChanged() override;
 
@@ -58,11 +70,14 @@ private:
 	void EnsureProcessor() const;
 	bool CreateProcessorFromInputs() const;
 
+	void SetLastError(const QString &error) const;
+
 	mutable QMutex gen_mutex_;
 	mutable bool processor_dirty_ = true;
 	mutable QString last_path_;
 	mutable int last_direction_ = -1;
 	mutable ColorProcessorPtr last_processor_;
+	mutable QString last_error_;
 };
 
 } // namespace olive

app/render/CMakeLists.txt

@@ -40,6 +40,8 @@ set(OLIVE_SOURCES
         render/framehashcache.h
         render/framemanager.cpp
         render/framemanager.h
+        render/lutlibrary.cpp
+        render/lutlibrary.h
         render/interlacetexture.cpp
         render/loopmode.h
         render/managedcolor.cpp

app/render/lutlibrary.cpp

@@ -0,0 +1,86 @@
+/***
+
+  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/>.
+
+***/
+
+#include "lutlibrary.h"
+
+#include <QDir>
+#include <QDirIterator>
+#include <QFileInfo>
+
+#include "config/config.h"
+
+namespace olive
+{
+
+bool LUTLibrary::IsSupportedExtension(const QString &suffix)
+{
+	QString s = suffix;
+	if (s.startsWith(QLatin1Char('.'))) {
+		s.remove(0, 1);
+	}
+
+	const QString lower = s.toLower();
+	return lower == QStringLiteral("cube") || lower == QStringLiteral("3dl");
+}
+
+QStringList LUTLibrary::GetDirectories()
+{
+	const QString serialized = OLIVE_CONFIG("LUTLibraryPaths").toString();
+
+	QStringList dirs = serialized.split(QLatin1Char(';'), Qt::SkipEmptyParts);
+	for (QString &dir : dirs) {
+		dir = QDir::fromNativeSeparators(dir.trimmed());
+	}
+	return dirs;
+}
+
+void LUTLibrary::SetDirectories(const QStringList &dirs)
+{
+	QStringList cleaned;
+	for (const QString &dir : dirs) {
+		const QString trimmed = dir.trimmed();
+		if (!trimmed.isEmpty() && !cleaned.contains(trimmed)) {
+			cleaned.append(trimmed);
+		}
+	}
+
+	Config::Current()[QStringLiteral("LUTLibraryPaths")] =
+		cleaned.join(QLatin1Char(';'));
+}
+
+QStringList LUTLibrary::GetLutFiles()
+{
+	QStringList files;
+
+	static const QStringList kFilters = { QStringLiteral("*.cube"),
+										  QStringLiteral("*.3dl") };
+
+	for (const QString &dir : GetDirectories()) {
+		QDirIterator it(dir, kFilters, QDir::Files,
+						QDirIterator::Subdirectories);
+		while (it.hasNext()) {
+			files.append(it.next());
+		}
+	}
+
+	return files;
+}
+
+}

app/render/lutlibrary.h

@@ -0,0 +1,68 @@
+/***
+
+  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 LUTLIBRARY_H
+#define LUTLIBRARY_H
+
+#include <QString>
+#include <QStringList>
+
+namespace olive
+{
+
+/**
+ * @brief A global, user-configurable library of LUT files
+ *
+ * The library is a list of directories (stored in the application config
+ * under "LUTLibraryPaths") that are scanned for supported LUT files. LUT
+ * nodes can offer the library contents as quick picks instead of forcing
+ * the user to browse for a file path on every node.
+ */
+class LUTLibrary {
+public:
+	/**
+	 * @brief Returns true if the given file suffix is a supported LUT
+	 * extension (.cube or .3dl, case-insensitive, leading dot tolerated)
+	 */
+	static bool IsSupportedExtension(const QString &suffix);
+
+	/**
+	 * @brief The directories that make up the LUT library
+	 */
+	static QStringList GetDirectories();
+
+	/**
+	 * @brief Replaces the LUT library directories and saves them to the
+	 * application config
+	 */
+	static void SetDirectories(const QStringList &dirs);
+
+	/**
+	 * @brief All supported LUT files found under the library directories
+	 *
+	 * Directories are scanned recursively. Files in earlier directories
+	 * are listed first.
+	 */
+	static QStringList GetLutFiles();
+};
+
+}
+
+#endif // LUTLIBRARY_H

app/widget/colorwheel/colorvalueswidget.cpp

@@ -91,9 +91,6 @@ ColorValuesWidget::ColorValuesWidget(ColorManager *manager, QWidget *parent)
 		connect(display_tab_, &ColorValuesTab::ColorChanged, this,
 				&ColorValuesWidget::UpdateValuesFromDisplay);
 
-		// FIXME: Display -> Ref temporarily disabled due to OCIO crash (see ColorDialog::ColorSpaceChanged for more info)
-		display_tab_->setEnabled(false);
-
 		layout->addWidget(tabs);
 	}
 }

app/widget/filefield/filefield.cpp

@@ -24,6 +24,7 @@
 #include <QFileDialog>
 #include <QFileInfo>
 #include <QHBoxLayout>
+#include <QUrl>
 
 #include "ui/icons/icons.h"
 
@@ -56,11 +57,30 @@ void FileField::BrowseBtnClicked()
 {
 	QString s;
 
-	if (directory_mode_) {
+	if (sidebar_urls_.isEmpty()) {
-		s = QFileDialog::getExistingDirectory(this, tr("Open Directory"));
+		if (directory_mode_) {
+			s = QFileDialog::getExistingDirectory(this, tr("Open Directory"));
+		} else {
+			s = QFileDialog::getOpenFileName(this, tr("Open File"), QString(),
+											 name_filter_);
+		}
 	} else {
-		s = QFileDialog::getOpenFileName(this, tr("Open File"), QString(),
+		// Sidebar URLs require the non-static dialog API
-										 name_filter_);
+		QFileDialog dialog(this, tr("Open File"));
+		dialog.setFileMode(directory_mode_ ? QFileDialog::Directory :
+											 QFileDialog::ExistingFile);
+		dialog.setAcceptMode(QFileDialog::AcceptOpen);
+		if (!directory_mode_ && !name_filter_.isEmpty()) {
+			dialog.setNameFilter(name_filter_);
+		}
+		dialog.setSidebarUrls(sidebar_urls_);
+		if (directory_mode_) {
+			dialog.setOption(QFileDialog::ShowDirsOnly, true);
+		}
+
+		if (dialog.exec() == QDialog::Accepted && !dialog.selectedFiles().isEmpty()) {
+			s = dialog.selectedFiles().first();
+		}
 	}
 
 	if (!s.isEmpty()) {

app/widget/filefield/filefield.h

@@ -58,6 +58,17 @@ public:
 		name_filter_ = filter;
 	}
 
+	/**
+	 * @brief Sets extra sidebar shortcuts (e.g. a library directory) for the
+	 * browse dialog
+	 *
+	 * Note: setting sidebar URLs requires Qt's non-native file dialog.
+	 */
+	void SetSidebarUrls(const QList<QUrl> &urls)
+	{
+		sidebar_urls_ = urls;
+	}
+
 signals:
 	void FilenameChanged(const QString &filename);
 
@@ -70,6 +81,8 @@ private:
 
 	QString name_filter_;
 
+	QList<QUrl> sidebar_urls_;
+
 private slots:
 	void BrowseBtnClicked();
 

app/widget/nodeparamview/nodeparamviewwidgetbridge.cpp

@@ -23,6 +23,7 @@
 
 #include <QCheckBox>
 #include <QFontComboBox>
+#include <QUrl>
 #include <QVector2D>
 #include <QVector3D>
 #include <QVector4D>
@@ -36,6 +37,7 @@
 #include "node/project/sequence/sequence.h"
 #include "nodeparamviewarraywidget.h"
 #include "nodeparamviewtextedit.h"
+#include "render/lutlibrary.h"
 #include "undo/undostack.h"
 #include "widget/bezier/bezierwidget.h"
 #include "widget/colorbutton/colorbutton.h"
@@ -938,6 +940,16 @@ void NodeParamViewWidgetBridge::SetProperty(const QString &key,
 			ff->SetDirectoryMode(value.toBool());
 		} else if (key == QStringLiteral("filter")) {
 			ff->SetNameFilter(value.toString());
+		} else if (key == QStringLiteral("lut_library") && value.toBool()) {
+			// Offer the global LUT library directories as sidebar shortcuts in
+			// the browse dialog
+			QList<QUrl> sidebar_urls;
+			for (const QString &dir : LUTLibrary::GetDirectories()) {
+				sidebar_urls.append(QUrl::fromLocalFile(dir));
+			}
+			if (!sidebar_urls.isEmpty()) {
+				ff->SetSidebarUrls(sidebar_urls);
+			}
 		}
 	}
 

tests/gtest/color_lut_test.cpp

@@ -8,13 +8,17 @@
 
 #include <OpenColorIO/OpenColorIO.h>
 
+#include "config/config.h"
 #include "node/color/ociolut/ociolut.h"
+#include "node/color/colormanager/colormanager.h"
+#include "node/color/ociogradingtransformlinear/ociogradingtransformlinear.h"
 #include "node/color/threewaycolor/threewaycolor.h"
 #include "node/factory.h"
 #include "node/generator/solid/solid.h"
 #include "node/project.h"
 #include "node/traverser.h"
 #include "render/colorprocessor.h"
+#include "render/lutlibrary.h"
 
 namespace OCIO = OCIO_NAMESPACE;
 
@@ -748,3 +752,355 @@ TEST(ColorLutNode, SwitchingBackToOriginalFileRestoresOriginalPixels)
 	EXPECT_NEAR(restored_out.green(), invert_out.green(), 0.02f);
 	EXPECT_NEAR(restored_out.blue(), invert_out.blue(), 0.02f);
 }
+
+// -----------------------------------------------------------------------------
+// Error reporting: silent passthrough states must be observable.
+// -----------------------------------------------------------------------------
+
+TEST(ColorLutNode, MissingFileSetsLastError)
+{
+	olive::ColorManager::SetUpDefaultConfig();
+
+	olive::Project project;
+	project.Initialize();
+
+	auto *lut = new olive::OCIOLutNode();
+	lut->setParent(&project);
+	lut->SetStandardValue(olive::OCIOLutNode::kFileInput,
+						  QStringLiteral("/nonexistent/path/lut.cube"));
+
+	EXPECT_FALSE(lut->last_error().isEmpty());
+}
+
+TEST(ColorLutNode, UnsupportedExtensionSetsLastError)
+{
+	olive::ColorManager::SetUpDefaultConfig();
+
+	olive::Project project;
+	project.Initialize();
+
+	QTemporaryDir dir;
+	ASSERT_TRUE(dir.isValid());
+	const QString path = QDir(dir.path()).filePath(QStringLiteral("lut.txt"));
+	QFile file(path);
+	ASSERT_TRUE(file.open(QIODevice::WriteOnly));
+	file.close();
+
+	auto *lut = new olive::OCIOLutNode();
+	lut->setParent(&project);
+	lut->SetStandardValue(olive::OCIOLutNode::kFileInput, path);
+
+	EXPECT_FALSE(lut->last_error().isEmpty());
+}
+
+TEST(ColorLutNode, ValidFileClearsLastError)
+{
+	olive::ColorManager::SetUpDefaultConfig();
+
+	olive::Project project;
+	project.Initialize();
+
+	QTemporaryDir dir;
+	ASSERT_TRUE(dir.isValid());
+	const QString path = WriteTestCubeLut(&dir, "invert", 0.0f, 1.0f);
+	ASSERT_FALSE(path.isEmpty());
+
+	auto *lut = new olive::OCIOLutNode();
+	lut->setParent(&project);
+
+	lut->SetStandardValue(olive::OCIOLutNode::kFileInput,
+						  QStringLiteral("/nonexistent/path/lut.cube"));
+	EXPECT_FALSE(lut->last_error().isEmpty());
+
+	lut->SetStandardValue(olive::OCIOLutNode::kFileInput, path);
+	EXPECT_TRUE(lut->last_error().isEmpty());
+}
+
+TEST(ColorLutNode, EmptyPathClearsLastError)
+{
+	olive::ColorManager::SetUpDefaultConfig();
+
+	olive::Project project;
+	project.Initialize();
+
+	auto *lut = new olive::OCIOLutNode();
+	lut->setParent(&project);
+
+	lut->SetStandardValue(olive::OCIOLutNode::kFileInput,
+						  QStringLiteral("/nonexistent/path/lut.cube"));
+	EXPECT_FALSE(lut->last_error().isEmpty());
+
+	lut->SetStandardValue(olive::OCIOLutNode::kFileInput, QString());
+	EXPECT_TRUE(lut->last_error().isEmpty());
+}
+
+// -----------------------------------------------------------------------------
+// Global LUT library
+// -----------------------------------------------------------------------------
+
+TEST(LUTLibrary, SupportsCubeAnd3dlExtensions)
+{
+	EXPECT_TRUE(olive::LUTLibrary::IsSupportedExtension(QStringLiteral("cube")));
+	EXPECT_TRUE(
+		olive::LUTLibrary::IsSupportedExtension(QStringLiteral(".cube")));
+	EXPECT_TRUE(olive::LUTLibrary::IsSupportedExtension(QStringLiteral("CUBE")));
+	EXPECT_TRUE(olive::LUTLibrary::IsSupportedExtension(QStringLiteral("3dl")));
+	EXPECT_TRUE(olive::LUTLibrary::IsSupportedExtension(QStringLiteral(".3dl")));
+	EXPECT_FALSE(olive::LUTLibrary::IsSupportedExtension(QStringLiteral("txt")));
+	EXPECT_FALSE(olive::LUTLibrary::IsSupportedExtension(QString()));
+}
+
+TEST(LUTLibrary, DirectoryRoundTripCleansAndDeduplicates)
+{
+	const QString previous =
+		olive::Config::Current()[QStringLiteral("LUTLibraryPaths")].toString();
+
+	olive::LUTLibrary::SetDirectories(
+		{ QStringLiteral("/a/luts"), QStringLiteral(" /a/luts "),
+		  QStringLiteral("/b/luts"), QString() });
+
+	EXPECT_EQ(olive::LUTLibrary::GetDirectories(),
+			  (QStringList{ QStringLiteral("/a/luts"),
+							QStringLiteral("/b/luts") }));
+
+	olive::Config::Current()[QStringLiteral("LUTLibraryPaths")] = previous;
+}
+
+TEST(LUTLibrary, ScansDirectoriesRecursivelyForSupportedLuts)
+{
+	const QString previous =
+		olive::Config::Current()[QStringLiteral("LUTLibraryPaths")].toString();
+
+	QTemporaryDir dir;
+	ASSERT_TRUE(dir.isValid());
+
+	const QString cube_path =
+		QDir(dir.path()).filePath(QStringLiteral("top.cube"));
+	const QString sub_dir = QDir(dir.path()).filePath(QStringLiteral("sub"));
+	const QString three_dl_path =
+		QDir(sub_dir).filePath(QStringLiteral("nested.3dl"));
+	const QString text_path =
+		QDir(dir.path()).filePath(QStringLiteral("skip.txt"));
+
+	ASSERT_TRUE(QDir().mkpath(sub_dir));
+	for (const QString &p : { cube_path, three_dl_path, text_path }) {
+		QFile file(p);
+		ASSERT_TRUE(file.open(QIODevice::WriteOnly));
+		file.close();
+	}
+
+	olive::LUTLibrary::SetDirectories({ dir.path() });
+
+	const QStringList files = olive::LUTLibrary::GetLutFiles();
+	EXPECT_EQ(files.size(), 2);
+	EXPECT_TRUE(files.contains(cube_path));
+	EXPECT_TRUE(files.contains(three_dl_path));
+	EXPECT_FALSE(files.contains(text_path));
+
+	olive::Config::Current()[QStringLiteral("LUTLibraryPaths")] = previous;
+}
+
+// -----------------------------------------------------------------------------
+// Display -> reference inverse transform (previously disabled over an OCIO
+// crash; covered here so the ColorDialog conversion can stay enabled).
+// -----------------------------------------------------------------------------
+
+TEST(ColorProcessor, InverseDisplayTransformRoundTripsColor)
+{
+	olive::ColorManager::SetUpDefaultConfig();
+
+	olive::Project project;
+	project.Initialize();
+
+	olive::ColorManager *color_manager = project.color_manager();
+	ASSERT_NE(color_manager, nullptr);
+
+	const QString display = color_manager->GetDefaultDisplay();
+	const QString view = color_manager->GetDefaultView(display);
+	ASSERT_FALSE(display.isEmpty());
+	ASSERT_FALSE(view.isEmpty());
+
+	const olive::ColorTransform output_transform(display, view, QString());
+
+	olive::ColorProcessorPtr ref_to_display = olive::ColorProcessor::Create(
+		color_manager, color_manager->GetReferenceColorSpace(),
+		output_transform);
+	ASSERT_NE(ref_to_display, nullptr);
+	ASSERT_NE(ref_to_display->GetProcessor(), nullptr);
+
+	olive::ColorProcessorPtr display_to_ref = olive::ColorProcessor::Create(
+		color_manager, color_manager->GetReferenceColorSpace(),
+		output_transform, olive::ColorProcessor::kInverse);
+	ASSERT_NE(display_to_ref, nullptr);
+	ASSERT_NE(display_to_ref->GetProcessor(), nullptr);
+
+	const olive::Color reference(0.2f, 0.4f, 0.6f, 1.0f);
+	const olive::Color display_color = ref_to_display->ConvertColor(reference);
+	const olive::Color round_trip = display_to_ref->ConvertColor(display_color);
+
+	EXPECT_NEAR(round_trip.red(), reference.red(), 0.001f);
+	EXPECT_NEAR(round_trip.green(), reference.green(), 0.001f);
+	EXPECT_NEAR(round_trip.blue(), reference.blue(), 0.001f);
+	EXPECT_NEAR(round_trip.alpha(), reference.alpha(), 0.001f);
+}
+
+// -----------------------------------------------------------------------------
+// OCIOGradingTransformLinearNode clamp invariant
+// -----------------------------------------------------------------------------
+
+namespace
+{
+
+class ClampCaptureTraverser : public PixelColorTransformTraverser {
+public:
+	bool captured_white_clamp = false;
+	double white_clamp_value = 0.0;
+
+protected:
+	virtual void
+	ProcessColorTransform(olive::TexturePtr destination, const olive::Node *node,
+						  const olive::ColorTransformJob *job) override
+	{
+		const olive::NodeValueRow &values = job->GetValues();
+		if (values.contains(
+				olive::OCIOGradingTransformLinearNode::kClampWhiteInput)) {
+			white_clamp_value =
+				values
+					.value(olive::OCIOGradingTransformLinearNode::
+							   kClampWhiteInput)
+					.toDouble();
+			captured_white_clamp = true;
+		}
+		PixelColorTransformTraverser::ProcessColorTransform(destination, node,
+														  job);
+	}
+};
+
+} // namespace
+
+TEST(ColorGradingLinear, InvalidClampRangeIsCorrectedPerFrame)
+{
+	olive::ColorManager::SetUpDefaultConfig();
+
+	olive::Project project;
+	project.Initialize();
+
+	auto *solid = new olive::SolidGenerator();
+	solid->setParent(&project);
+	solid->SetStandardValue(
+		olive::SolidGenerator::kColorInput,
+		QVariant::fromValue(olive::Color(0.25f, 0.50f, 0.75f, 1.0f)));
+
+	auto *grading = new olive::OCIOGradingTransformLinearNode();
+	grading->setParent(&project);
+	grading->SetStandardValue(
+		olive::OCIOGradingTransformLinearNode::kClampBlackEnableInput, true);
+	grading->SetStandardValue(
+		olive::OCIOGradingTransformLinearNode::kClampWhiteEnableInput, true);
+	grading->SetStandardValue(
+		olive::OCIOGradingTransformLinearNode::kClampBlackInput, 0.5);
+	// Invalid: white clamp below black clamp
+	grading->SetStandardValue(
+		olive::OCIOGradingTransformLinearNode::kClampWhiteInput, 0.0);
+
+	olive::Node::ConnectEdge(
+		solid,
+		olive::NodeInput(
+			grading,
+			olive::OCIOGradingTransformLinearNode::kTextureInput));
+
+	const olive::VideoParams params(16, 16, olive::core::PixelFormat::F32,
+									olive::VideoParams::kRGBAChannelCount);
+
+	ClampCaptureTraverser traverser;
+	traverser.SetCacheVideoParams(params);
+	olive::NodeValueTable table = traverser.GenerateTable(
+		grading, olive::TimeRange(olive::core::rational(0),
+								  olive::core::rational(1, 30)));
+	olive::NodeValue tex_val = table.Get(olive::NodeValue::kTexture);
+	traverser.Resolve(tex_val);
+
+	// The node must have corrected the white clamp to just above the black
+	// clamp instead of feeding an invalid grading primary to OCIO
+	ASSERT_TRUE(traverser.captured_white_clamp);
+	EXPECT_NEAR(traverser.white_clamp_value, 0.500001, 1e-9);
+
+	// And rendering must not crash or drop the frame
+	ASSERT_TRUE(traverser.output_frame);
+}
+
+TEST(ColorGradingLinear, ValidClampRangeIsLeftUntouched)
+{
+	olive::ColorManager::SetUpDefaultConfig();
+
+	olive::Project project;
+	project.Initialize();
+
+	auto *solid = new olive::SolidGenerator();
+	solid->setParent(&project);
+	solid->SetStandardValue(
+		olive::SolidGenerator::kColorInput,
+		QVariant::fromValue(olive::Color(0.25f, 0.50f, 0.75f, 1.0f)));
+
+	auto *grading = new olive::OCIOGradingTransformLinearNode();
+	grading->setParent(&project);
+	grading->SetStandardValue(
+		olive::OCIOGradingTransformLinearNode::kClampBlackEnableInput, true);
+	grading->SetStandardValue(
+		olive::OCIOGradingTransformLinearNode::kClampWhiteEnableInput, true);
+	grading->SetStandardValue(
+		olive::OCIOGradingTransformLinearNode::kClampBlackInput, 0.1);
+	grading->SetStandardValue(
+		olive::OCIOGradingTransformLinearNode::kClampWhiteInput, 0.9);
+
+	olive::Node::ConnectEdge(
+		solid,
+		olive::NodeInput(
+			grading,
+			olive::OCIOGradingTransformLinearNode::kTextureInput));
+
+	const olive::VideoParams params(16, 16, olive::core::PixelFormat::F32,
+									olive::VideoParams::kRGBAChannelCount);
+
+	ClampCaptureTraverser traverser;
+	traverser.SetCacheVideoParams(params);
+	olive::NodeValueTable table = traverser.GenerateTable(
+		grading, olive::TimeRange(olive::core::rational(0),
+								  olive::core::rational(1, 30)));
+	olive::NodeValue tex_val = table.Get(olive::NodeValue::kTexture);
+	traverser.Resolve(tex_val);
+
+	ASSERT_TRUE(traverser.captured_white_clamp);
+	EXPECT_NEAR(traverser.white_clamp_value, 0.9, 1e-9);
+
+	ASSERT_TRUE(traverser.output_frame);
+}
+
+TEST(ColorGradingLinear, StaticBlackClampConstrainsWhiteMinimum)
+{
+	olive::ColorManager::SetUpDefaultConfig();
+
+	olive::Project project;
+	project.Initialize();
+
+	auto *grading = new olive::OCIOGradingTransformLinearNode();
+	grading->setParent(&project);
+
+	// Default black clamp is 0, so the white minimum starts just above it
+	EXPECT_NEAR(grading
+					->GetInputProperty(
+						olive::OCIOGradingTransformLinearNode::kClampWhiteInput,
+						QStringLiteral("min"))
+					.toDouble(),
+				0.000001, 1e-9);
+
+	// Changing the static black clamp updates the white minimum
+	grading->SetStandardValue(
+		olive::OCIOGradingTransformLinearNode::kClampBlackInput, 0.25);
+	EXPECT_NEAR(grading
+					->GetInputProperty(
+						olive::OCIOGradingTransformLinearNode::kClampWhiteInput,
+						QStringLiteral("min"))
+					.toDouble(),
+				0.250001, 1e-9);
+}