Adjust QSGTexture comparisonKey type

The original choice was int, simply following textureId(). This was later
deemed insufficient: instead of a GLuint, the value is now often a 64-bit
value (on 64 bit systems), based on a pointer, since the identity of a texture
in the RHI world is the QRhiTexture* itself. In a custom texture implementation
it is likely that the value here is the value of a native object handle, either
a pointer or some 32 or 64 bit integer.

Inspired by the recent QSGTexture::NativeTexture struct change (void* -> quint64),
switch to a qint64 which is big enough to hold all these without truncation.

We choose a signed value here, in order to allow for the following pattern that
is widespread in material compare() implementations:
if (qint64 diff = m_texture->comparisonKey() - other->texture()->comparisonKey())
  return diff;

Fixes: QTBUG-83769
Change-Id: I8bdae8cd835282358ded53b3703142b8f26e4400
Reviewed-by: Christian Strømme <christian.stromme@qt.io>

1 files changed, 1 insertions, 1 deletions

diff --git a/src/quick/scenegraph/qsgopengllayer.cpp b/src/quick/scenegraph/qsgopengllayer.cpp
index c585cd05f8..6f06c27459 100644
--- a/src/quick/scenegraph/qsgopengllayer.cpp
+++ b/src/quick/scenegraph/qsgopengllayer.cpp
@@ -141,7 +141,7 @@ int QSGOpenGLLayer::textureId() const
     return m_fbo ? m_fbo->texture() : 0;
 }
 
-int QSGOpenGLLayer::comparisonKey() const
+qint64 QSGOpenGLLayer::comparisonKey() const
 {
     return m_fbo ? m_fbo->texture() : 0;
 }