[Linux] How to enable sub-pixel rendering for Qt Quick/QML 6.5.3?

hawky

Hi!

(I'd to remove relevant information due to be marked as Spam by Aksmet .com)

We've problems enablling sub-pixel rendering for Qt Quick/QML.

First of all we're using Qt 6.5.3 and sub-pixel rendering is system wide enabled via font-config.

To verify that sub-pxel rendering works at all with a native Qt application we've used fontsampler example:

Nevertheless we're unable to enable sub-pixel rendering for Qt Quick/QML. To verify that we've used the textexample from qtdeclarative:

From what we've read Qt Quick/QML can render text in various ways:

QtTextRendering
NativeTextRendering
~~CurveTextRendering~~ (since 6.7.0)

Qt Quick/QML is using QtTextRendering per default. So to change the default behavior and to enable native rendering (which will enable sub-pixel rendering hopefully as well) one can either

Call setTextRenderType()
Build qtdeclarative with different build options as mentioned here and here. But with a different keyword: "NativeTextRendering" insteadof "NativeRendering" as mentioned here.

However, none of both of options enabled sub-pixel rendering in our case, even if sub-pixel rendering works with native Qt.

To verify that our changes really applied we added a short code snippet to our Qt Quick/QML application:

qInfo("QQuickWindow::QtTextRendering = 0x%x", QQuickWindow::QtTextRendering);
qInfo("QQuickWindow::NativeTextRendering = 0x%x", QQuickWindow::NativeTextRendering);
qInfo("old render type = 0x%x", window->textRenderType());
window->setTextRenderType(QQuickWindow::NativeTextRendering);
qInfo("new render type = 0x%x", window->textRenderType());

The output is on the first option:

QQuickWindow::QtTextRendering = 0x0
QQuickWindow::NativeTextRendering = 0x1
old render type = 0x0
new render type = 0x1

and on the second option:

QQuickWindow::QtTextRendering = 0x0
QQuickWindow::NativeTextRendering = 0x1
old render type = 0x1
new render type = 0x1

So our changes apply but sub-pixel rendering is not enabled/visible.

How can we enable sub-pixel rendering with an Qt Quick/QML application?

Thank you!