Fix: NativeRendering text for non-integer screen scaling

Commit 6e883c53 introduced snapping to pixel grid for non-integer
device pixel ratios. But the snapping also modified the w element of
the coord vector, which resulted in mangled and offset rendering.

As a driveby, add the dpr snapping also to the outlinetext shader, as
it improves rendering quality.

Fixes: QTBUG-70481
Fixes: QTBUG-78160
Change-Id: I4c4b1788005514adc0255878ba24cdf1acc6755f
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>

1 files changed, 2 insertions, 1 deletions

diff --git a/src/quick/scenegraph/shaders/styledtext_core.vert b/src/quick/scenegraph/shaders/styledtext_core.vert
index c522877bb3..7e313eb797 100644
--- a/src/quick/scenegraph/shaders/styledtext_core.vert
+++ b/src/quick/scenegraph/shaders/styledtext_core.vert
@@ -15,5 +15,6 @@ void main()
 {
      sampleCoord = tCoord * textureScale;
      shiftedSampleCoord = (tCoord - shift) * textureScale;
-     gl_Position = matrix * round(vCoord * dpr) / dpr;
+     vec3 dprSnapPos = round(vCoord.xyz * dpr + 0.5) / dpr;
+     gl_Position = matrix * vec4(dprSnapPos, vCoord.w);
 }