qt5: GLSL renderers draw signal at wrong scale and position

[mixxxbot]

Reported by: rryan
Date: 2016-01-03T19:30:32Z
Status: Fix Released
Importance: Medium
Launchpad Issue: lp1530697
Tags: qt5
Attachments: [Screen Shot 2016-01-03 at 2.29.51 PM.png](https://bugs.launchpad.net/bugs/1530697/+attachment/4543553/+files/Screen Shot 2016-01-03 at 2.29.51 PM.png)

---

[Impact]

With qt5 the GLSL renderer draw signal at wrong scale and position. See attachment in comment #⁠1.

[Test Case]

• Start Mixxx on and verify if the GLSL waveforms are are drawn correctly.

[Regression Potential]

There might be regressions with other waveforms.

[Other Info]

The Cosmic 2.1.3 build is also effected, see: https://bugs.launchpad.net/ubuntu/+source/mixxx/+bug/1804513

[mixxxbot]

Commented by: rryan
Date: 2016-01-03T19:30:32Z
Attachments: [Screen Shot 2016-01-03 at 2.29.51 PM.png](https://bugs.launchpad.net/mixxx/+bug/1530697/+attachment/4543553/+files/Screen Shot 2016-01-03 at 2.29.51 PM.png)

[mixxxbot]

Commented by: rryan
Date: 2016-01-03T19:33:56Z

---

OpenGL version 4.1
Qt 5.5.1

[mixxxbot]

Commented by: rryan
Date: 2016-01-03T19:34:11Z

---

OSX 10.11.2

[mixxxbot]

Commented by: rryan
Date: 2016-01-04T01:00:53Z

---

I haven't debugged yet, but I think this may be because of my hidpi display:

http://blog.qt.io/blog/2013/04/25/retina-display-support-for-mac-os-ios-and-x11/

"""
QGlWidget

OpenGL operates in device pixel space. For example, the width and height passed to glViewport should be in device pixels. QGLWidget::resizeGL() gives the width and height in device pixels.

However, QGLWidget::width() is really QWidget::width() which returns a value in device-independent pixels. Resolve it by multiplying with widget->windowHandle()->devicePixelRatio() if needed.
"""

Now that devicePIxelRatio is exposed by Qt we need to scale the widget width/height we pass to the shaders by it.

[mixxxbot]

Commented by: Be-ing
Date: 2018-10-21T17:44:39Z

---

#1739

[mixxxbot]

Issue closed with status Fix Released.