[SailfishDevel] Different behaviour of ShaderEffectSource in emulator vs. device

[Luca Donaggio]

Anybody is willing to try my test code and confirm or deny my finding?

On Fri, Feb 6, 2015 at 2:12 PM, Luca Donaggio <donaggio at gmail.com> wrote:

> The following code works fine in Emulator, changing the gradient of the
> Rectangle correctly updates the nested ShaderEffectSource and it is
> reflected on the ShaderEffect which uses it as its texture:
>
> Page {
>     id: page
>
>     SilicaFlickable {
>         anchors.fill: parent
>
>         contentHeight: column.height
>
>         Column {
>             id: column
>
>             anchors { top: parent.top; left: parent.left; right:
> parent.right; leftMargin: Theme.paddingLarge; rightMargin:
> Theme.paddingLarge; }
>             spacing: Theme.paddingLarge
>
>             PageHeader {
>                 title: qsTr("ShaderEffect Test")
>             }
>
>             Row {
>                 anchors.horizontalCenter: parent.horizontalCenter
>                 spacing: Theme.paddingLarge
>
>                 Column {
>                     spacing: Theme.paddingSmall
>
>                     Rectangle {
>                         id: gradientSource
>
>                         property list<Gradient> gradients: [
>                             Gradient {
>                                 GradientStop { position: 0.0; color:
> "black"; }
>                                 GradientStop { position: 1.0; color:
> "blue"; }
>                             },
>
>                             Gradient {
>                                 GradientStop { position: 0.0; color:
> "black"; }
>                                 GradientStop { position: 1.0; color:
> "red"; }
>                             }
>                         ]
>
>                         width: 100
>                         height: 100
>
>                         gradient: gradients[0]
>
>                         ShaderEffectSource {
>                             id: gradientTexture
>
>                             anchors.fill: parent
>                             sourceItem: gradientSource
>                             hideSource: false
>                             live: true
>                         }
>                     }
>
>                     Label {
>                         font.pixelSize: Theme.fontSizeExtraSmall
>                         wrapMode: Text.WordWrap
>                         text: "Rectangle\nShaderEffectSource"
>                     }
>                 }
>
>                 Column {
>                     spacing: Theme.paddingSmall
>
>                     ShaderEffect {
>                         property variant source: gradientTexture
>
>                         width: 100
>                         height: 100
>
>                         blending: false
>                         cullMode: ShaderEffect.BackFaceCulling
>                         fragmentShader: "
>                             varying highp vec2 qt_TexCoord0;
>                             uniform lowp float qt_Opacity;
>                             uniform sampler2D source;
>
>                             void main() {
>                                 gl_FragColor = texture2D(source,
> qt_TexCoord0) * qt_Opacity;
>                             }"
>                     }
>
>                     Label {
>                         font.pixelSize: Theme.fontSizeExtraSmall
>                         text: "ShaderEffect"
>                     }
>                 }
>             }
>
>             Button {
>                 anchors.horizontalCenter: parent.horizontalCenter
>                 text: "Blue gradient"
>
>                 onClicked: gradientSource.gradient =
> gradientSource.gradients[0]
>             }
>
>             Button {
>                 anchors.horizontalCenter: parent.horizontalCenter
>                 text: "Red gradient"
>
>                 onClicked: gradientSource.gradient =
> gradientSource.gradients[1]
>             }
>         }
>     }
> }
>
> It doesn't work on device though (changing Reactangle's gradient doesn't
> update the ShaderEffectSource).
>
> Un-nesting the ShaderEffectSource from its source item (the Rectangle)
> works fine both on emulator and on device:
>
> Page {
>     id: page
>
>     SilicaFlickable {
>         anchors.fill: parent
>
>         contentHeight: column.height
>
>         Column {
>             id: column
>
>             anchors { top: parent.top; left: parent.left; right:
> parent.right; leftMargin: Theme.paddingLarge; rightMargin:
> Theme.paddingLarge; }
>             spacing: Theme.paddingLarge
>
>             PageHeader {
>                 title: qsTr("ShaderEffect Test")
>             }
>
>             Row {
>                 anchors.horizontalCenter: parent.horizontalCenter
>                 spacing: Theme.paddingLarge
>
>                 Column {
>                     spacing: Theme.paddingSmall
>
>                     Rectangle {
>                         id: gradientSource
>
>                         property list<Gradient> gradients: [
>                             Gradient {
>                                 GradientStop { position: 0.0; color:
> "black"; }
>                                 GradientStop { position: 1.0; color:
> "blue"; }
>                             },
>
>                             Gradient {
>                                 GradientStop { position: 0.0; color:
> "black"; }
>                                 GradientStop { position: 1.0; color:
> "red"; }
>                             }
>                         ]
>
>                         width: 100
>                         height: 100
>
>                         gradient: gradients[0]
>                     }
>
>                     Label {
>                         font.pixelSize: Theme.fontSizeExtraSmall
>                         text: "Rectangle"
>                     }
>                 }
>
>                 Column {
>                     spacing: Theme.paddingSmall
>
>                     ShaderEffectSource {
>                         id: gradientTexture
>
>                         width: 100
>                         height: 100
>                         sourceItem: gradientSource
>                         hideSource: false
>                         live: true
>                     }
>
>                     Label {
>                         font.pixelSize: Theme.fontSizeExtraSmall
>                         text: "ShaderEffectSource"
>                     }
>                 }
>
>                 Column {
>                     spacing: Theme.paddingSmall
>
>                     ShaderEffect {
>                         property variant source: gradientTexture
>
>                         width: 100
>                         height: 100
>
>                         blending: false
>                         cullMode: ShaderEffect.BackFaceCulling
>                         fragmentShader: "
>                             varying highp vec2 qt_TexCoord0;
>                             uniform lowp float qt_Opacity;
>                             uniform sampler2D source;
>
>                             void main() {
>                                 gl_FragColor = texture2D(source,
> qt_TexCoord0) * qt_Opacity;
>                             }"
>                     }
>
>                     Label {
>                         font.pixelSize: Theme.fontSizeExtraSmall
>                         text: "ShaderEffect"
>                     }
>                 }
>             }
>
>             Button {
>                 anchors.horizontalCenter: parent.horizontalCenter
>                 text: "Blue gradient"
>
>                 onClicked: gradientSource.gradient =
> gradientSource.gradients[0]
>             }
>
>             Button {
>                 anchors.horizontalCenter: parent.horizontalCenter
>                 text: "Red gradient"
>
>                 onClicked: gradientSource.gradient =
> gradientSource.gradients[1]
>             }
>         }
>     }
> }
>
> Is it a bug?
>
> --
> Luca Donaggio
>



-- 
Luca Donaggio
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