examples,build: add Qt client example

* CMake: Adds C++ as project language

* CMake: Adds WITH_QT option to build Qt client example

* Examples: Adds qt5client.cpp

* CMake: adds specific way of building Qt client example

* CMake: try to find Qt if needed

* CMake: makes Qt not required, quiet if not found

* CMake: removes CXX as language

* CMake: checks if we have C++ compiler before setting standard

* CMake: checks C++ compiler before setting project languages

I could not find a better solution. It seems like the languages must be set before almost everything.

* CMake: check if C++ compiler defined instead of string comparison

* CMake: appends CXX to languages, in a better syntax

As suggested by dantti

* Examples: changes to static_cast in Qt5 client example

As suggested by @dantti

* Examples: adds description to Qt example

* Examples: Qt example can't handle new fb size

* Examples: adds additional condition to build Qt example

This is need to remove the following message: 'CMake Error: Cannot determine link language for target'

* CMake: adds comment about C++ example (Qt client)

* Examples: adds CMake remarks to Qt client example

* CMake: changes Qt5::Widgets to Qt5Widgets_LIBRARIES

Just for standardization

Author: nicmorais

CMakeLists.txt

@@ -1,6 +1,13 @@
 cmake_minimum_required(VERSION 3.4)
 
-project(LibVNCServer VERSION 0.9.14 LANGUAGES C)
+set(PROJECT_LANGUAGES C)
+
+if(DEFINED CMAKE_CXX_COMPILER)
+  set(CMAKE_CXX_STANDARD 17)
+  list(APPEND PROJECT_LANGUAGES CXX)
+endif(DEFINED CMAKE_CXX_COMPILER)
+
+project(LibVNCServer VERSION 0.9.14 LANGUAGES ${PROJECT_LANGUAGES})
 include(CheckFunctionExists)
 include(CheckSymbolExists)
 include(CheckIncludeFile)
@@ -25,6 +32,7 @@ set(TESTS_DIR ${CMAKE_CURRENT_SOURCE_DIR}/test)
 set(CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS ON)
 set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${CMAKE_CURRENT_SOURCE_DIR}/cmake/Modules/")
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
+
 if(CMAKE_GENERATOR MATCHES "Unix Makefiles|Ninja")
 # some LSP servers expect compile_commands.json in the project root
 add_custom_target(
@@ -67,7 +75,7 @@ option(WITH_SASL "Build with SASL support" ON)
 option(WITH_XCB "Build with XCB support" ON)
 option(WITH_EXAMPLES "Build examples" ON)
 option(WITH_TESTS "Build tests" ON)
-
+option(WITH_QT "Build the Qt client example" ON)
 
 
 if(WITH_ZLIB)
@@ -147,6 +155,10 @@ if(WITH_GTK)
   find_package(GTK2)
 endif(WITH_GTK)
 
+if(WITH_QT)
+  find_package(Qt5 COMPONENTS Core Widgets QUIET)
+endif(WITH_QT)
+
 if(WITH_LIBSSHTUNNEL)
   find_path(LIBSSHTUNNEL_INCLUDE_DIR libsshtunnel.h)
   find_library(LIBSSHTUNNEL_LIBRARY sshtunnel)
@@ -656,6 +668,17 @@ if(WITH_EXAMPLES)
     set_target_properties(client_examples_${e} PROPERTIES RUNTIME_OUTPUT_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/examples/client)
     target_link_libraries(client_examples_${e} vncclient ${CMAKE_THREAD_LIBS_INIT} ${SDL2_LIBRARY} ${GTK2_LIBRARIES} ${FFMPEG_LIBRARIES} ${LIBSSHTUNNEL_LIBRARY})
   endforeach(e ${LIBVNCCLIENT_EXAMPLES})
+
+  #This example must have its own building instructions,
+  #apart from the other examples because it is written in
+  #C++, so it has a distinct file extension and depends on
+  #a C++ compiler
+  if(Qt5Widgets_FOUND AND WITH_QT AND DEFINED CMAKE_CXX_COMPILER)
+    add_executable(client_examples_qt5client ${LIBVNCCLIEXAMPLE_DIR}/qt5client.cpp ${LIBVNCCLIEXAMPLE_DIR}/${qt5client_EXTRA_SOURCES})
+    set_target_properties(client_examples_qt5client PROPERTIES OUTPUT_NAME qt5client)
+    set_target_properties(client_examples_qt5client PROPERTIES RUNTIME_OUTPUT_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/examples/client)
+    target_link_libraries(client_examples_qt5client vncclient ${CMAKE_THREAD_LIBS_INIT} ${Qt5Widgets_LIBRARIES})
+  endif(Qt5Widgets_FOUND AND WITH_QT AND DEFINED CMAKE_CXX_COMPILER)
 endif(WITH_EXAMPLES)
 
 #

examples/client/qt5client.cpp

@@ -0,0 +1,149 @@
+/*
+ *
+ * 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.
+ *
+ * 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, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+ /*
+ * This is an example on how to make a simple VNC client with
+ * Qt5 Widgets. It suitable for desktop apps, but may not be
+ * good for mobile.
+ * It does not implement any form of cryptography,
+ * authentication support, client-side cursors or framebuffer
+ * resizing. If you want to make this a part of your
+ * application, please notice that you may need to change
+ * the while(true) loop to disconnect the client.
+ *
+ * To build this example with all the other components of
+ * libvncserver, you may need to explicitly define a C++
+ * compiler and the path to Qt libs when calling CMake.
+ * e.g. cmake -DCMAKE_PREFIX_PATH=~/Qt/5.15.2/gcc_64
+ * -DCMAKE_CXX_COMPILER=g++
+ */
+
+#include <QApplication>
+#include <iostream>
+#include <thread>
+#include <QPaintEvent>
+#include <QPainter>
+#include "rfb/rfbclient.h"
+#include <QWidget>
+
+class VncViewer : public QWidget
+{
+    //if you want to make use of signals/slots, uncomment the line bellow:
+    //Q_OBJECT
+public:
+    VncViewer(QWidget *parent = nullptr) {};
+    virtual ~VncViewer() {};
+    void start();
+    std::string serverIp;
+    int serverPort;
+    std::thread *vncThread() const;
+    void paintEvent(QPaintEvent *event) override;
+
+private:
+    QImage m_image;
+    rfbClient *cl;
+    std::thread *m_vncThread;
+    static void finishedFramebufferUpdateStatic(rfbClient *cl);
+    void finishedFramebufferUpdate(rfbClient *cl);
+};
+
+void VncViewer::finishedFramebufferUpdateStatic(rfbClient *cl)
+{
+    VncViewer *ptr = static_cast<VncViewer*>(rfbClientGetClientData(cl, nullptr));
+    ptr->finishedFramebufferUpdate(cl);
+}
+
+void VncViewer::finishedFramebufferUpdate(rfbClient *cl)
+{
+    m_image = QImage(cl->frameBuffer, cl->width, cl->height, QImage::Format_RGB16);
+
+    update();
+}
+void VncViewer::paintEvent(QPaintEvent *event)
+{
+    event->accept();
+
+    QPainter painter(this);
+    painter.drawImage(this->rect(), m_image);
+}
+
+void VncViewer::start()
+{
+    cl = rfbGetClient(8, 3, 4);
+    cl->format.depth = 24;
+    cl->format.depth = 16;
+    cl->format.bitsPerPixel = 16;
+    cl->format.redShift = 11;
+    cl->format.greenShift = 5;
+    cl->format.blueShift = 0;
+    cl->format.redMax = 0x1f;
+    cl->format.greenMax = 0x3f;
+    cl->format.blueMax = 0x1f;
+    cl->appData.compressLevel = 9;
+    cl->appData.qualityLevel = 1;
+    cl->appData.encodingsString = "tight ultra";
+    cl->FinishedFrameBufferUpdate = finishedFramebufferUpdateStatic;
+    cl->serverHost = strdup(serverIp.c_str());
+    cl->serverPort = serverPort;
+    cl->appData.useRemoteCursor = TRUE;
+
+    rfbClientSetClientData(cl, nullptr, this);
+
+    if (rfbInitClient(cl, 0, nullptr)) {
+    } else {
+        std::cout << "[INFO] disconnected" << std::endl;
+        return;
+    }
+
+    m_vncThread = new std::thread([this]() {
+        while (true) {
+            int i = WaitForMessage(cl, 500);
+            if (i < 0) {
+                std::cout << "[INFO] disconnected" << std::endl;
+                rfbClientCleanup(cl);
+                break;
+            }
+
+            if (i && !HandleRFBServerMessage(cl)) {
+                std::cout << "[INFO] disconnected" << std::endl;
+                rfbClientCleanup(cl);
+                break;
+            }
+        };
+    });
+}
+
+int main(int argc, char *argv[])
+{
+    if(argc < 3) {
+        std::cout << "Usage: "
+                  << argv[0]
+                  << " <server ip>"
+                  << " <port>"
+                  << "\n";
+        return 1;
+    }
+
+    QApplication a(argc, argv);
+    VncViewer vncViewer;
+    vncViewer.serverIp = std::string{argv[1]};
+    vncViewer.serverPort = std::atoi(argv[2]);
+    vncViewer.show();
+    vncViewer.start();
+    return a.exec();
+}