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, 2 insertions, 2 deletions

diff --git a/src/quick/scenegraph/util/qsgopenglatlastexture.cpp b/src/quick/scenegraph/util/qsgopenglatlastexture.cpp
index 94f77c8a08..f9bc0a552c 100644
--- a/src/quick/scenegraph/util/qsgopenglatlastexture.cpp
+++ b/src/quick/scenegraph/util/qsgopenglatlastexture.cpp
@@ -522,7 +522,7 @@ TextureBase::~TextureBase()
     m_atlas->remove(this);
 }
 
-int TextureBase::comparisonKey() const
+qint64 TextureBase::comparisonKey() const
 {
     // We need special care here: a typical comparisonKey() implementation
     // returns a unique result when there is no underlying texture yet. This is
@@ -532,7 +532,7 @@ int TextureBase::comparisonKey() const
 
     // base the comparison on the atlas ptr; this way textures for the same
     // atlas are considered equal
-    return int(qintptr(m_atlas));
+    return qint64(m_atlas);
 }
 
 void TextureBase::bind()