Meegoexperts

Using Qt scene graph + hardware acceleration

Posted: 22 Mar 2011 11:12 AM PDT

All things Qt are progressing quite well at the moment and here is the one of the directions that Qt Scene graph is going in:

The ShaderEffectItem is simply a rectangle with a custom vertex and fragment shader. The vertices passed to the vertex shader are the corners of the rectangle defined by the "width" and "height" properties of the item. (There is a property you can set to divide the rectangle into multiple rows and columns, but by default, you get four vertices.) The nifty thing about the ShaderEffectItem, though, is that you can define your own properties on the QML item, and they will be available to you as uniform variables in the shaders. For instance, you can define a property called "tint" of type "color" and animate it in QML, and you can read it in the shaders as "uniform vec4 tint". Several types are supported: real, point, size, color, vector3d, and a new type, ShaderEffectSource, which maps to a "sampler2D" in the shader code. The ShaderEffectSource allows you to render a QML item into a texture and pass it to the ShaderEffectItem. The ShaderEffectSource has properties like wrap mode and mipmapping, and a reference to the QML item to render into the texture. ShaderEffectItems can be strung together by letting one ShaderEffectItem be the source of another. The ShaderEffectItem is powerful, and as with anything powerful, you need to use it with caution. A poorly written shader or too many effects active at once can easily ruin the performance, well, on devices at least.

The code below shows how the wobble effect can be implemented.

import QtQuick 2.0

Image {

width: 180

height: 180

source: "winter.jpg"

Text {

id: theItem

anchors.fill: parent

horizontalAlignment: Text.AlignHCenter

verticalAlignment: Text.AlignVCenter

font.pixelSize: 120

font.family: "Times"

color: "blue"

text: "Qt"

}

ShaderEffectItem {

anchors.fill: parent

property variant source: ShaderEffectSource {

sourceItem: theItem

smooth: true

hideSource: true

}

property real amplitude: 0.02

property real frequency: 20

property real time: 0

NumberAnimation on time { loops: Animation.Infinite; from: 0; to: Math.PI * 2; duration: 600 }

fragmentShader: "

uniform highp float amplitude;

uniform highp float frequency;

uniform highp float time;

uniform sampler2D source;

uniform lowp float qt_Opacity;

varying highp vec2 qt_TexCoord0;

void main() {

highp vec2 p = sin(time + frequency * qt_TexCoord0);

gl_FragColor = qt_Opacity * texture2D(source, qt_TexCoord0 + amplitude * vec2(p.y, -p.x));

}"

}

The source code can be found in the qml-team/qtquick2 branch of http://qt.gitorious.org/+qt-developers/qt/staging/.

source

Mozilla release FireFox 4 Release Candidate – Tasty – Maemo

Posted: 21 Mar 2011 07:35 PM PDT

Mozilla has this evening released FireFox 4 for Android and more importantly Maemo. Download directly onto the Nokia N900 from this link.

Heres what Mozilla have to say about FireFox4 Release Candidate:

This release offers faster scrolling, better responsiveness with Firefox Sync and improves the overall user experience of Firefox. Firefox 4 for Android and Maemo brings the performance and customization of Firefox to mobile devices with features like Firefox Sync, Awesome Screen, tabbed browsing and Firefox Add-ons, to create a personalized and effortless mobile browsing experience.

Installation is 14.9Mb which is the usual for Firefox. After you go through the installation process (shown as pictures further down) you are left with a “dare I say it”, snappy feeling FireFox on Maemo. Now this came as quite a surprise to me as usually I have found FireFox to be quite slow and cumbersome on the Nokia N900. I couldn’t get additional plugins listed (other than google / Amazon / Twitter and Wikipedia) so this might be just down to early teething problems.

The multitab screen panel is accessed when swiping from outer left hand side of the screen towards the middle is really a refreshing change and also the same can be said from the right hand side that lets you access the page forward / back and favourite icon + settings).

Quick Video: