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  1. Qt
  2. QTBUG-41451

Scenegraph redraws when nothing changes

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    • Icon: Bug Bug
    • Resolution: Cannot Reproduce
    • Icon: P2: Important P2: Important
    • None
    • 5.4.0 Alpha
    • Quick: SceneGraph
    • None

      Using the 'basic' or 'windows' render loop makes the scenegraph continuously redraw this simple qml test:

      import QtQuick 2.2
      
      Item {
          width: 100
          height: 100
      
          ShaderEffect {
              property variant gradientImage: ShaderEffectSource {
                  sourceItem: Rectangle { width: 10; height: 10 }
              }
              anchors.fill: parent
      
              fragmentShader: "
                  uniform lowp sampler2D gradientImage;
                  uniform lowp float qt_Opacity;
      
                  void main() {
                      gl_FragColor = vec4(1,1,1,1) * qt_Opacity;
                  }
              "
          }
      }
      

      Commenting out the "uniform lowp sampler2D gradientImage;" in the shader hides the problem.

      Tested on X11 and Wayland. It does't happen when using the threaded render loop.

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            sletta Gunnar Sletta
            giucam Giulio Camuffo
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              Created:
              Updated:
              Resolved:

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