add new example 'qsqlite': use SQL from Lisp, load QML images from DB

examples/qsqlite/cpp/qt.cpp

@@ -0,0 +1,94 @@
+#include "qt.h"
+#include <QSqlQuery>
+#include <QSqlError>
+#include <QQuickView>
+#include <QtDebug>
+
+QObject* ini() {
+  static QObject* qt = nullptr;
+  if (qt == nullptr) {
+    qt = new QT;
+  }
+  return qt;
+}
+
+QT::QT() : QObject() {
+}
+
+QVariant QT::dataPath(const QVariant& prefix) {
+  // for desktop
+  QString path = QStandardPaths::writableLocation(QStandardPaths::AppLocalDataLocation);
+  path.truncate(path.lastIndexOf(QChar('/')));
+  path.append(QStringLiteral("/lqml-qsqlite/") + prefix.toString());
+  return path;
+}
+
+// SQL
+
+QVariant QT::iniDb(const QVariant& vName, const QVariant& vQuickView) {
+  // add database image provider, in order to load images in QML directly from a SQL database
+  auto quickView = vQuickView.value<QQuickView*>();
+  quickView->engine()->addImageProvider(QLatin1String("db"), new DatabaseImageProvider(this));
+  // ini
+  db = QSqlDatabase::addDatabase("QSQLITE");
+  db.setDatabaseName(vName.toString());
+  return vName;
+}
+
+QVariant QT::sqlQuery(const QVariant& vQuery, const QVariant& vValues, const QVariant& vCols) {
+  QVariantList results;
+  QSqlQuery sqlQuery(db);
+  if (db.open()) {
+    QString query = vQuery.toString();
+    sqlQuery.prepare(vQuery.toString());
+    const QVariantList values = vValues.value<QVariantList>();
+    for (auto value : values) {
+      sqlQuery.addBindValue(value);
+    }
+    if (sqlQuery.exec()) {
+      auto cols = vCols.toInt();
+      while (sqlQuery.next()) {
+        if (cols > 1) {
+          QVariantList list;
+          for (auto r = 0; r < cols; r++) {
+            list << sqlQuery.value(r);
+          }
+          results << QVariant(list);
+        } else {
+          results << sqlQuery.value(0);
+        }
+      }
+      if (!cols && query.startsWith("insert", Qt::CaseInsensitive)) {
+        results << sqlQuery.lastInsertId();
+      }
+      db.close();
+      return results;
+    }
+    db.close();
+  }
+  QString text;
+  if (sqlQuery.lastError().isValid()) {
+    text = sqlQuery.lastError().text();
+  } else {
+    text = db.lastError().text();
+  }
+  qDebug() << "SQL error:" << text;
+  return QVariant();
+}
+
+// database image provider
+
+QPixmap DatabaseImageProvider::requestPixmap(const QString& name, QSize* size, const QSize& requestedSize) {
+  auto result = qt->sqlQuery(
+    "select data from images where name = ?",
+    QVariantList() << name,
+    1); // number of returned columns
+  QPixmap pixmap;
+  pixmap.loadFromData(result.value<QVariantList>().first().toByteArray());
+  *size = pixmap.size();
+  if (requestedSize.isValid() && (pixmap.size() != requestedSize)) {
+    pixmap = pixmap.scaled(requestedSize);
+  }
+  return pixmap;
+}
+

examples/qsqlite/cpp/qt.h

@@ -0,0 +1,36 @@
+#pragma once
+
+#include <QtCore>
+#include <QSqlDatabase>
+#include <QQuickImageProvider>
+
+#ifdef Q_CC_MSVC
+#define LIB_EXPORT __declspec(dllexport)
+#else
+#define LIB_EXPORT
+#endif
+
+extern "C" { LIB_EXPORT QObject* ini(); }
+
+class QT : public QObject {
+  Q_OBJECT
+
+public:
+  Q_INVOKABLE QVariant dataPath(const QVariant&);
+  Q_INVOKABLE QVariant iniDb(const QVariant&, const QVariant&);
+  Q_INVOKABLE QVariant sqlQuery(const QVariant&, const QVariant&, const QVariant&);
+
+  QT();
+
+  QSqlDatabase db;
+};
+
+class DatabaseImageProvider : public QQuickImageProvider {
+
+public:
+  DatabaseImageProvider(QT* _qt) : QQuickImageProvider(QQuickImageProvider::Pixmap), qt(_qt) {}
+
+  QPixmap requestPixmap(const QString&, QSize*, const QSize&);
+
+  QT* qt;
+};

examples/qsqlite/cpp/qt.pro

@@ -0,0 +1,27 @@
+QT          += sql quick
+TEMPLATE    = lib
+CONFIG      += c++17 plugin release no_keywords
+DEFINES     += PLUGIN
+INCLUDEPATH = /usr/local/include ../../../src/cpp
+LIBS        = -L/usr/local/lib -lecl
+DESTDIR     = ./
+TARGET      = qt
+OBJECTS_DIR = ./tmp/
+MOC_DIR     = ./tmp/
+
+HEADERS += qt.h
+SOURCES += qt.cpp
+
+linux {
+  LIBS += -L../../../platforms/linux/lib
+}
+
+macx {
+  LIBS += -L../../../platforms/macos/lib
+}
+
+win32 {
+  include(../../../src/windows.pri)
+
+  LIBS += -L../../../platforms/windows/lib
+}