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<td >Qt 5.12</td><td ><a href="qtdatavisualization-index.html">Qt Data Visualization</a></td><td >Qt Quick 2 Axis Dragging Example</td></tr></table><table class="buildversion"><tr>
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<h3><a name="toc">Contents</a></h3>
<ul>
<li class="level1"><a href="#running-the-example">Running the Example</a></li>
<li class="level1"><a href="#overriding-default-input-handling">Overriding Default Input Handling</a></li>
<li class="level1"><a href="#translating-mouse-movement-to-axis-range-change">Translating Mouse Movement to Axis Range Change</a></li>
<li class="level1"><a href="#other-features">Other Features</a></li>
<li class="level1"><a href="#example-contents">Example Contents</a></li>
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<h1 class="title">Qt Quick 2 Axis Dragging Example</h1>
<span class="subtitle"></span>
<!-- $$$qmlaxisdrag-brief -->
<p>Implementing axis dragging in QML.</p>
<!-- @@@qmlaxisdrag -->
<!-- $$$qmlaxisdrag-description -->
<div class="descr"> <a name="details"></a>
<p>The Qt Quick 2 axis dragging example concentrates on showing how to implement axis range changing by dragging axis labels in QML. It also gives a quick peek to two other new features in Qt Data Visualization 1.1: orthographic projection and dynamic custom item handling.</p>
<p class="centerAlign"><img src="images/qmlaxisdrag-example.png" alt="" /></p><a name="running-the-example"></a>
<h2 id="running-the-example">Running the Example</h2>
<p>To run the example from Qt Creator, open the <b>Welcome</b> mode and select the example from <b>Examples</b>. For more information, visit Building and Running an Example.</p>
<a name="overriding-default-input-handling"></a>
<h2 id="overriding-default-input-handling">Overriding Default Input Handling</h2>
<p>First we deactivate the default input handling mechanism by setting the active input handler of <a href="qml-qtdatavisualization-scatter3d.html">Scatter3D</a> graph to <code>null</code>:</p>
<pre class="qml">
Scatter3D {
id: scatterGraph
inputHandler: null
...
</pre>
<p>Then we add a MouseArea and set it to fill the parent, which is the same <code>Item</code> our <code>scatterGraph</code> is contained in. We also set it to accept only left mouse button presses, as in this example we are not interested in other buttons:</p>
<pre class="qml">
MouseArea {
anchors.fill: parent
hoverEnabled: true
acceptedButtons: Qt.LeftButton
...
</pre>
<p>Then we need to listen to mouse presses, and when caught, send a selection query to the graph:</p>
<pre class="qml">
onPressed: {
scatterGraph.scene.selectionQueryPosition = Qt.point(mouse.x, mouse.y);
}
</pre>
<p>Current mouse position, that will be needed for move distance calculation, is caught in <code>onPositionChanged</code>:</p>
<pre class="qml">
onPositionChanged: {
currentMouseX = mouse.x;
currentMouseY = mouse.y;
...
</pre>
<p>At the end of <code>onPositionChanged</code>, we'll save the previous mouse position for move distance calculation that will be introduced later:</p>
<pre class="cpp">
...
previousMouseX = currentMouseX;
previousMouseY = currentMouseY;
}
</pre>
<a name="translating-mouse-movement-to-axis-range-change"></a>
<h2 id="translating-mouse-movement-to-axis-range-change">Translating Mouse Movement to Axis Range Change</h2>
<p>in <code>scatterGraph</code> we will need to listen to <code>onSelectedElementChanged</code> signal. The signal is emitted after the selection query has been made in the <code>onPressed</code> of <code>inputArea</code>. We set the element type into a property we defined (<code>property int selectedAxisLabel: -1</code>) in our main component, since it is of a type we are interested in:</p>
<pre class="qml">
onSelectedElementChanged: {
if (selectedElement >= AbstractGraph3D.ElementAxisXLabel
&& selectedElement <= AbstractGraph3D.ElementAxisZLabel)
selectedAxisLabel = selectedElement
else
selectedAxisLabel = -1
}
</pre>
<p>Then, back in the <code>onPositionChanged</code> of <code>inputArea</code>, we check if a mouse button is pressed and if we have a current axis label selection. If the conditions are met, we'll call the function that does the conversion from mouse movement to axis range update:</p>
<pre class="cpp">
...
if (pressed && selectedAxisLabel != -1)
dragAxis();
...
</pre>
<p>The conversion is easy in this case, as we have a fixed camera rotation. We can use some precalculated values, calculate mouse move distance, and apply the values to the selected axis range:</p>
<pre class="qml">
function dragAxis() {
// Do nothing if previous mouse position is uninitialized
if (previousMouseX === -1)
return
// Directional drag multipliers based on rotation. Camera is locked to 45 degrees, so we
// can use one precalculated value instead of calculating xx, xy, zx and zy individually
var cameraMultiplier = 0.70710678
// Calculate the mouse move amount
var moveX = currentMouseX - previousMouseX
var moveY = currentMouseY - previousMouseY
// Adjust axes
switch (selectedAxisLabel) {
case AbstractGraph3D.ElementAxisXLabel:
var distance = ((moveX - moveY) * cameraMultiplier) / dragSpeedModifier
// Check if we need to change min or max first to avoid invalid ranges
if (distance > 0) {
scatterGraph.axisX.min -= distance
scatterGraph.axisX.max -= distance
} else {
scatterGraph.axisX.max -= distance
scatterGraph.axisX.min -= distance
}
break
case AbstractGraph3D.ElementAxisYLabel:
distance = moveY / dragSpeedModifier
// Check if we need to change min or max first to avoid invalid ranges
if (distance > 0) {
scatterGraph.axisY.max += distance
scatterGraph.axisY.min += distance
} else {
scatterGraph.axisY.min += distance
scatterGraph.axisY.max += distance
}
break
case AbstractGraph3D.ElementAxisZLabel:
distance = ((moveX + moveY) * cameraMultiplier) / dragSpeedModifier
// Check if we need to change min or max first to avoid invalid ranges
if (distance > 0) {
scatterGraph.axisZ.max += distance
scatterGraph.axisZ.min += distance
} else {
scatterGraph.axisZ.min += distance
scatterGraph.axisZ.max += distance
}
break
}
}
</pre>
<p>For a more sophisticated conversion from mouse movement to axis range update, see <a href="qtdatavisualization-draggableaxes-example.html">this example</a>.</p>
<a name="other-features"></a>
<h2 id="other-features">Other Features</h2>
<p>The example also demonstrates how to use orthographic projection and how to update properties of a custom item on the fly.</p>
<p>Orthographic projection is very simple. You'll just need to change <code>orthoProjection</code> property of <code>scatterGraph</code>. In this example we have a button for toggling it on and off:</p>
<pre class="qml">
NewButton {
id: orthoToggle
width: parent.width / 3
text: "Display Orthographic"
anchors.left: rangeToggle.right
onClicked: {
if (scatterGraph.orthoProjection) {
text = "Display Orthographic";
scatterGraph.orthoProjection = false
// Orthographic projection disables shadows, so we need to switch them back on
scatterGraph.shadowQuality = AbstractGraph3D.ShadowQualityLow
} else {
text = "Display Perspective";
scatterGraph.orthoProjection = true
}
}
}
</pre>
<p>For custom items, first we'll add one in the <code>customItemList</code> of <code>scatterGraph</code>:</p>
<pre class="qml">
customItemList: [
Custom3DItem {
id: qtCube
meshFile: ":/mesh/cube"
textureFile: ":/texture/texture"
position: Qt.vector3d(0.65,0.35,0.65)
scaling: Qt.vector3d(0.3,0.3,0.3)
}
]
</pre>
<p>We have implemented a timer to add, remove, and rotate all the items in the graph, and we'll use the same timer for rotating the custom item:</p>
<pre class="qml">
onTriggered: {
rotationAngle = rotationAngle + 1
qtCube.setRotationAxisAndAngle(Qt.vector3d(1,0,1), rotationAngle)
...
</pre>
<a name="example-contents"></a>
<h2 id="example-contents">Example Contents</h2>
<p>Files:</p>
<ul>
<li><a href="qtdatavisualization-qmlaxisdrag-main-cpp.html">qmlaxisdrag/main.cpp</a></li>
<li><a href="qtdatavisualization-qmlaxisdrag-qml-qmlaxisdrag-newbutton-qml.html">qmlaxisdrag/qml/qmlaxisdrag/NewButton.qml</a></li>
<li><a href="qtdatavisualization-qmlaxisdrag-qml-qmlaxisdrag-main-qml.html">qmlaxisdrag/qml/qmlaxisdrag/main.qml</a></li>
<li><a href="qtdatavisualization-qmlaxisdrag-qmlaxisdrag-pro.html">qmlaxisdrag/qmlaxisdrag.pro</a></li>
<li><a href="qtdatavisualization-qmlaxisdrag-qmlaxisdrag-qrc.html">qmlaxisdrag/qmlaxisdrag.qrc</a></li>
</ul>
<p>Images:</p>
<ul>
<li><a href="images/used-in-examples/qmlaxisdrag/qml/qmlaxisdrag/cubetexture.png">qmlaxisdrag/qml/qmlaxisdrag/cubetexture.png</a></li>
</ul>
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