OpenGL scene under Qt qml application
This should be the best way how to add custom opengl into qml app.
http://qt-project.org/doc/qt-5/qtquick-scenegraph-openglunderqml-example.html
The problem is, i dont want to paint over the whole window, but just in rectangle that is occupied by my opengl custom qt quick item. I thought i can just call glViewport with appropriate parameters, so opengl will paint just rectangle of my item.
Actually, this doesn't work for me.
qml:
import QtQuick 2.2
import QtQuick.Controls 1.1
import ge.components 1.0
ApplicationWindow {
visible: true
width: 640
height: 480
title: qsTr("Hello World")
color: "red"
menuBar: MenuBar {
Menu {
title: qsTr("Filxe")
MenuItem {
text: qsTr("Exit")
onTriggered: Qt.quit();
}
}
}
GLViewer {
width: 200
height: 200
x: 100
y: 100
}
}
qt quick item: In paint method, i first fill whole window with color of ApplicationWindow and then i want to fill just rectangle occupied by my item with black color. Actually it fill the whole window with black, why???
#include "glviewer.h"
#include <QQuickWindow>
#include <iostream>
#include <QColor>
using namespace std;
GLViewer::GLViewer(QQuickItem *parent) :
QQuickItem(parent)
{
connect(this, SIGNAL(windowChanged(QQuickWindow*)), this, SLOT(handleWindowChanged(QQuickWindow*)));
}
void GLViewer::handleWindowChanged(QQuickWindow *win)
{
if (win) {
connect(win, SIGNAL(beforeRendering()), this, SLOT(paint()), Qt::DirectConnection);
win->setClearBeforeRendering(false);
}
}
void GLViewer::paint() {
QColor color = window()->color();
glClearColor(color.red(), color.green(), color.blue(), color.alpha());
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
cout << "X: " << x() << ", Y: " << y() << ", W: " << width() << ", H: " << height() << endl;
glViewport(x(), y(), width(), height());
glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
}
There are two issues with your code. First one, ApplicationWindow has no color attribute then when you set
color: "red"
in this component you don't set any color (that is color is black). You can set a background color for your ApplicationWindow adding a Rectangle component before your GLViewer as follow
Rectangle {
width: parent.width
height: parent.height
anchors.centerIn: parent
color: "red"
}
Second one, you are drawing in main windows GL context then, even if viewport is correctly setted, the following lines of code
glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
will clear the entire window. If you want to clear only a part of the window you have to use glScissor
glViewport(x, y, w, h);
glEnable(GL_SCISSOR_TEST);
glScissor(x,y,w,h);
glClearColor(0, 0, 0, 1);
glClear(GL_COLOR_BUFFER_BIT);
glDisable(GL_SCISSOR_TEST);
You can find a complete example (based on your link) on github.
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