[FEATURE] New form widget for binary (blob) fields

This widget is available for binary fields only (and is the default
widget used for binary fields). It offers a label showing
whether the blob field is empty or not, and if non-empty shows
the content size (in bytes/kb/etc).

A drop down menu button allows users to save the current binary
contents of the field out to a disk based file, clear the contents
of a blob field, or embed binary contents by picking a file
from their system.

src/gui/CMakeLists.txt

@@ -95,6 +95,8 @@ SET(QGIS_GUI_SRCS
   editorwidgets/core/qgssearchwidgetwrapper.cpp
   editorwidgets/core/qgswidgetwrapper.cpp
 
+  editorwidgets/qgsbinarywidgetfactory.cpp
+  editorwidgets/qgsbinarywidgetwrapper.cpp
   editorwidgets/qgscheckboxconfigdlg.cpp
   editorwidgets/qgscheckboxsearchwidgetwrapper.cpp
   editorwidgets/qgscheckboxwidgetwrapper.cpp
@@ -657,6 +659,7 @@ SET(QGIS_GUI_MOC_HDRS
   editorwidgets/core/qgssearchwidgetwrapper.h
   editorwidgets/core/qgswidgetwrapper.h
 
+  editorwidgets/qgsbinarywidgetwrapper.h
   editorwidgets/qgscheckboxconfigdlg.h
   editorwidgets/qgscheckboxsearchwidgetwrapper.h
   editorwidgets/qgscheckboxwidgetwrapper.h
@@ -831,6 +834,7 @@ SET(QGIS_GUI_HDRS
   editorwidgets/core/qgseditorwidgetfactory.h
   editorwidgets/core/qgseditorwidgetautoconf.h
 
+  editorwidgets/qgsbinarywidgetfactory.h
   editorwidgets/qgscheckboxwidgetfactory.h
   editorwidgets/qgsclassificationwidgetwrapperfactory.h
   editorwidgets/qgscolorwidgetfactory.h

src/gui/editorwidgets/core/qgseditorwidgetregistry.cpp

@@ -23,6 +23,7 @@
 #include "qgssearchwidgetwrapper.h"
 
 // Editors
+#include "qgsbinarywidgetfactory.h"
 #include "qgsclassificationwidgetwrapperfactory.h"
 #include "qgscheckboxwidgetfactory.h"
 #include "qgscolorwidgetfactory.h"
@@ -63,6 +64,7 @@ void QgsEditorWidgetRegistry::initEditors( QgsMapCanvas *mapCanvas, QgsMessageBa
   registerWidget( QStringLiteral( "ExternalResource" ), new QgsExternalResourceWidgetFactory( tr( "Attachment" ) ) );
   registerWidget( QStringLiteral( "KeyValue" ), new QgsKeyValueWidgetFactory( tr( "Key/Value" ) ) );
   registerWidget( QStringLiteral( "List" ), new QgsListWidgetFactory( tr( "List" ) ) );
+  registerWidget( QStringLiteral( "Binary" ), new QgsBinaryWidgetFactory( tr( "Binary (BLOB)" ) ) );
 }
 
 QgsEditorWidgetRegistry::~QgsEditorWidgetRegistry()

src/gui/editorwidgets/qgsbinarywidgetfactory.cpp

@@ -0,0 +1,44 @@
+/***************************************************************************
+    qgsbinarywidgetfactory.cpp
+     -------------------------
+    Date                 : November 2018
+    Copyright            : (C) 2018 Nyall Dawson
+    Email                : nyall dot dawson at gmail dot com
+ ***************************************************************************
+ *                                                                         *
+ *   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 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#include "qgsbinarywidgetfactory.h"
+
+#include "qgsbinarywidgetwrapper.h"
+#include "qgsdummyconfigdlg.h"
+#include "qgsvectorlayer.h"
+#include "qgsvectordataprovider.h"
+
+QgsBinaryWidgetFactory::QgsBinaryWidgetFactory( const QString &name )
+  :  QgsEditorWidgetFactory( name )
+{
+}
+
+QgsEditorWidgetWrapper *QgsBinaryWidgetFactory::create( QgsVectorLayer *vl, int fieldIdx, QWidget *editor, QWidget *parent ) const
+{
+  return new QgsBinaryWidgetWrapper( vl, fieldIdx, editor, parent );
+}
+
+QgsEditorConfigWidget *QgsBinaryWidgetFactory::configWidget( QgsVectorLayer *vl, int fieldIdx, QWidget *parent ) const
+{
+  return new QgsDummyConfigDlg( vl, fieldIdx, parent, QObject::tr( "A widget for interacting with binary (BLOB) fields." ) );
+}
+
+unsigned int QgsBinaryWidgetFactory::fieldScore( const QgsVectorLayer *vl, int fieldIdx ) const
+{
+  const QgsField field = vl->fields().field( fieldIdx );
+  const QVariant::Type type = field.type();
+  // ByteArray fields only
+  return type == QVariant::ByteArray ? 20 : 0;
+}

src/gui/editorwidgets/qgsbinarywidgetfactory.h

@@ -0,0 +1,45 @@
+/***************************************************************************
+    qgsbinarywidgetfactory.h
+     -----------------------
+    Date                 : November 2018
+    Copyright            : (C) 2018 Nyall Dawson
+    Email                : nyall dot dawson at gmail dot com
+ ***************************************************************************
+ *                                                                         *
+ *   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 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#ifndef QGSBINARYWIDGETFACTORY_H
+#define QGSBINARYWIDGETFACTORY_H
+
+#include "qgseditorwidgetfactory.h"
+#include "qgis_gui.h"
+
+SIP_NO_FILE
+
+/**
+ * \ingroup gui
+ * \class QgsBinaryWidgetFactory
+ * Editor widget factory for binary (BLOB) widgets.
+ * \note not available in Python bindings
+ * \since QGIS 3.6
+ */
+
+class GUI_EXPORT QgsBinaryWidgetFactory : public QgsEditorWidgetFactory
+{
+  public:
+    explicit QgsBinaryWidgetFactory( const QString &name );
+
+    // QgsEditorWidgetFactory interface
+  public:
+    QgsEditorWidgetWrapper *create( QgsVectorLayer *vl, int fieldIdx, QWidget *editor, QWidget *parent ) const override;
+    QgsEditorConfigWidget *configWidget( QgsVectorLayer *vl, int fieldIdx, QWidget *parent ) const override;
+
+    unsigned int fieldScore( const QgsVectorLayer *vl, int fieldIdx ) const override;
+};
+
+#endif // QGSBINARYWIDGETFACTORY_H

src/gui/editorwidgets/qgsbinarywidgetwrapper.cpp

@@ -0,0 +1,188 @@
+/***************************************************************************
+    qgsbinarywidgetwrapper.cpp
+     -------------------------
+    Date                 : November 2018
+    Copyright            : (C) 2018 Nyall Dawson
+    Email                : nyall dot dawson at gmail dot com
+ ***************************************************************************
+ *                                                                         *
+ *   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 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#include "qgsbinarywidgetwrapper.h"
+#include "qgsvectorlayer.h"
+#include "qgsvectordataprovider.h"
+#include "qgsfileutils.h"
+#include "qgssettings.h"
+#include <QHBoxLayout>
+#include <QFileDialog>
+#include <QLabel>
+#include <QToolButton>
+#include <QAction>
+#include <QMenu>
+#include <QMessageBox>
+
+QgsBinaryWidgetWrapper::QgsBinaryWidgetWrapper( QgsVectorLayer *vl, int fieldIdx, QWidget *editor, QWidget *parent )
+  : QgsEditorWidgetWrapper( vl, fieldIdx, editor, parent )
+
+{
+}
+
+
+QVariant QgsBinaryWidgetWrapper::value() const
+{
+  return mValue;
+}
+
+void QgsBinaryWidgetWrapper::showIndeterminateState()
+{
+  if ( mLabel )
+    mLabel->clear();
+}
+
+void QgsBinaryWidgetWrapper::setEnabled( bool enabled )
+{
+  if ( mSetAction )
+    mSetAction->setEnabled( enabled );
+  if ( mClearAction )
+    mClearAction->setEnabled( enabled && !mValue.isEmpty() );
+}
+
+QWidget *QgsBinaryWidgetWrapper::createWidget( QWidget *parent )
+{
+  QWidget *container = new QWidget( parent );
+  QHBoxLayout *layout = new QHBoxLayout();
+  container->setLayout( layout );
+  layout->setMargin( 0 );
+  layout->setContentsMargins( 0, 0, 0, 0 );
+
+  QLabel *label = new QLabel();
+  layout->addWidget( label, 1 );
+
+  QToolButton *button = new QToolButton();
+  button->setText( QChar( 0x2026 ) );
+  layout->addWidget( button, 0 );
+
+  container->setSizePolicy( QSizePolicy::Preferred, QSizePolicy::Minimum );
+  return container;
+}
+
+void QgsBinaryWidgetWrapper::initWidget( QWidget *editor )
+{
+  mLabel = editor->findChild<QLabel *>();
+  mButton = editor->findChild<QToolButton *>();
+
+  if ( mLabel )
+  {
+    QFont f = mLabel->font();
+    f.setItalic( true );
+    mLabel->setFont( f );
+  }
+
+  if ( mButton )
+  {
+    mButton->setPopupMode( QToolButton::InstantPopup );
+
+    mSetAction = new QAction( tr( "Embed File…" ), mButton );
+    connect( mSetAction, &QAction::triggered, this, &QgsBinaryWidgetWrapper::setContent );
+    mClearAction = new QAction( tr( "Clear Contents…" ), mButton );
+    connect( mClearAction, &QAction::triggered, this, &QgsBinaryWidgetWrapper::clear );
+    mSaveAction = new QAction( tr( "Save Contents to File…" ), mButton );
+    connect( mSaveAction, &QAction::triggered, this, &QgsBinaryWidgetWrapper::saveContent );
+    QMenu *menu = new QMenu( mButton );
+    menu->addAction( mSetAction );
+    menu->addAction( mClearAction );
+    menu->addSeparator();
+    menu->addAction( mSaveAction );
+    mButton->setMenu( menu );
+  }
+}
+
+bool QgsBinaryWidgetWrapper::valid() const
+{
+  return mLabel && mButton;
+}
+
+void QgsBinaryWidgetWrapper::setValue( const QVariant &value )
+{
+  mValue = value.toByteArray();
+  if ( mLabel )
+  {
+    if ( !mValue.isEmpty() )
+    {
+      mLabel->setText( tr( "Binary (%1)" ).arg( QgsFileUtils::representFileSize( mValue.size() ) ) );
+    }
+    else
+    {
+      mLabel->setText( QgsApplication::nullRepresentation() );
+    }
+  }
+  if ( mSaveAction )
+    mSaveAction->setEnabled( !mValue.isEmpty() );
+  if ( mClearAction )
+    mClearAction->setEnabled( !mValue.isEmpty() );
+}
+
+void QgsBinaryWidgetWrapper::saveContent()
+{
+  QgsSettings s;
+  QString file = QFileDialog::getSaveFileName( nullptr,
+                 tr( "Save Contents to File" ),
+                 defaultPath(),
+                 tr( "All files" ) + " (*.*)" );
+  if ( file.isEmpty() )
+  {
+    return;
+  }
+
+  QFileInfo fi( file );
+  s.setValue( QStringLiteral( "/UI/lastBinaryDir" ), fi.absolutePath() );
+
+  QFile fileOut( file );
+  fileOut.open( QIODevice::WriteOnly );
+  fileOut.write( mValue );
+  fileOut.close();
+}
+
+void QgsBinaryWidgetWrapper::setContent()
+{
+  QgsSettings s;
+  QString file = QFileDialog::getOpenFileName( nullptr,
+                 tr( "Embed File" ),
+                 defaultPath(),
+                 tr( "All files" ) + " (*.*)" );
+  QFileInfo fi( file );
+  if ( file.isEmpty() || !fi.exists() )
+  {
+    return;
+  }
+
+  s.setValue( QStringLiteral( "/UI/lastBinaryDir" ), fi.absolutePath() );
+
+  QFile fileSource( file );
+  if ( !fileSource.open( QIODevice::ReadOnly ) )
+  {
+    return;
+  }
+
+  setValue( fileSource.readAll() );
+  emitValueChanged();
+}
+
+void QgsBinaryWidgetWrapper::clear()
+{
+  if ( QMessageBox::question( nullptr, tr( "Clear Contents" ), tr( "Are you sure you want the clear this field's content?" ), QMessageBox::Yes | QMessageBox::No, QMessageBox::No ) != QMessageBox::Yes )
+    return;
+
+  setValue( QByteArray() );
+}
+
+QString QgsBinaryWidgetWrapper::defaultPath()
+{
+  return QgsSettings().value( QStringLiteral( "/UI/lastBinaryDir" ), QDir::homePath() ).toString();
+}
+

src/gui/editorwidgets/qgsbinarywidgetwrapper.h

@@ -0,0 +1,73 @@
+/***************************************************************************
+    qgsbinarywidgetwrapper.h
+     -----------------------
+    Date                 : November 2018
+    Copyright            : (C) 2018 Nyall Dawson
+    Email                : nyall dot dawson at gmail dot com
+ ***************************************************************************
+ *                                                                         *
+ *   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 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#ifndef QGSBINARYWIDGETWRAPPER_H
+#define QGSBINARYWIDGETWRAPPER_H
+
+#include "qgseditorwidgetwrapper.h"
+#include "qgis_gui.h"
+
+class QLabel;
+class QToolButton;
+
+SIP_NO_FILE
+
+/**
+ * \ingroup gui
+ * \class QgsBinaryWidgetWrapper
+ * Widget wrapper for binary (BLOB) fields.
+ * \note not available in Python bindings
+ * \since QGIS 3.6
+ */
+
+class GUI_EXPORT QgsBinaryWidgetWrapper : public QgsEditorWidgetWrapper
+{
+    Q_OBJECT
+  public:
+    explicit QgsBinaryWidgetWrapper( QgsVectorLayer *vl, int fieldIdx, QWidget *editor = nullptr, QWidget *parent = nullptr );
+
+    // QgsEditorWidgetWrapper interface
+  public:
+    QVariant value() const override;
+    void showIndeterminateState() override;
+    void setEnabled( bool enabled ) override;
+
+  protected:
+    QWidget *createWidget( QWidget *parent ) override;
+    void initWidget( QWidget *editor ) override;
+    bool valid() const override;
+
+  public slots:
+    void setValue( const QVariant &value ) override;
+
+  private slots:
+
+    void saveContent();
+    void setContent();
+    void clear();
+
+  private:
+    QString defaultPath();
+
+    QByteArray mValue;
+
+    QLabel *mLabel = nullptr;
+    QToolButton *mButton = nullptr;
+    QAction *mSetAction = nullptr;
+    QAction *mClearAction = nullptr;
+    QAction *mSaveAction = nullptr;
+};
+
+#endif // QGSBINARYWIDGETWRAPPER_H