Fix rendering of Flipable content.

When a batch is merged in the renderer, we use the z component to
stack the item front to back. This works because each item is
guaranteed to have a z-range of 0->1. However, when a projective
matrix is used, we need to compensate for the implicit [x,y,z]/w,
which GL applies to gl_Position after the vertex stage completes,
so that this guarantee still holds.

Task-number: QTBUG-35020
Change-Id: I254a3d4dc9ad22f53717160ec6ad8f3a27b43d1c
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/src/quick/scenegraph/coreapi/qsgshaderrewriter.cpp b/src/quick/scenegraph/coreapi/qsgshaderrewriter.cpp
index 909def2c19..2849eff304 100644
--- a/src/quick/scenegraph/coreapi/qsgshaderrewriter.cpp
+++ b/src/quick/scenegraph/coreapi/qsgshaderrewriter.cpp
@@ -222,7 +222,7 @@ QByteArray qsgShaderRewriter_insertZAttributes(const char *input, QSurfaceFormat
             braceDepth--;
             if (braceDepth == 0) {
                 result += QByteArray::fromRawData(voidPos, tok.pos - 1 - voidPos);
-                result += QByteArrayLiteral("    gl_Position.z = gl_Position.z * _qt_zRange + _qt_order;\n");
+                result += QByteArrayLiteral("    gl_Position.z = (gl_Position.z * _qt_zRange + _qt_order) * gl_Position.w;\n");
                 result += QByteArray(tok.pos - 1);
                 return result;
             }