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  1. Qt
  2. QTBUG-93670

Canvas.FramebufferObject broken rendering for small Canvas size (<50)

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    • Icon: Bug Bug
    • Resolution: Cannot Reproduce
    • Icon: P2: Important P2: Important
    • None
    • 5.15.2
    • Quick: Core Declarative QML
    • None
    • All

      Run this in qmlscene. If bug is true, it will render a window that is 50% white, and 50% green. If bug is false, the window is 100% green. If you do not set the render target, the bug is gone. Setting a canvasSize has no effect on the bug.

      This seems to be quite a nasty rounding error.

      The only workaround we have found is to not render so small things.

      Unable to find source-code formatter for language: qml. Available languages are: actionscript, ada, applescript, bash, c, c#, c++, cpp, css, erlang, go, groovy, haskell, html, java, javascript, js, json, lua, none, nyan, objc, perl, php, python, r, rainbow, ruby, scala, sh, sql, swift, visualbasic, xml, yaml
      import QtQuick 2.14

Item {
    id: root
    width: 100
    
    property bool bug: true
    
    height: bug ? 30 : 75

    Canvas {
        renderTarget: Canvas.FramebufferObject // comment out to remove bug
        anchors.fill: parent

        onPaint: {
            var ctx = getContext('2d')
            ctx.lineCap = "square"
            ctx.clearRect(0, 0, width, height)

            ctx.fillStyle = Qt.rgba(0, 1, 0, 1.0);
            ctx.fillRect(0, 0, width, height);
        }
    }
}

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            tokorpip Tomi Korpipää
            andrhans Andreas Aardal Hanssen
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              Created:
              Updated:
              Resolved:

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