gl: Fix wrong extension check for R8

src/rhi/qrhigles2.cpp

@@ -326,8 +326,8 @@ bool QRhiGles2::create(QRhi::Flags flags)
     caps.bgraExternalFormat = f->hasOpenGLExtension(QOpenGLExtensions::BGRATextureFormat);
     caps.bgraInternalFormat = caps.bgraExternalFormat && actualFormat.renderableType() == QSurfaceFormat::OpenGLES;
 
-    caps.sized8Formats = f->hasOpenGLExtension(QOpenGLExtensions::Sized8Formats);
-    caps.sized16Formats = f->hasOpenGLExtension(QOpenGLExtensions::Sized16Formats);
+    caps.r8Format = f->hasOpenGLFeature(QOpenGLFunctions::TextureRGFormats);
+    caps.r16Format = f->hasOpenGLExtension(QOpenGLExtensions::Sized16Formats);
 
     nativeHandlesStruct.context = ctx;
 
@@ -537,10 +537,10 @@ bool QRhiGles2::isTextureFormatSupported(QRhiTexture::Format format, QRhiTexture
         return caps.bgraExternalFormat;
 
     case QRhiTexture::R8:
-        return caps.sized8Formats;
+        return caps.r8Format;
 
     case QRhiTexture::R16:
-        return caps.sized16Formats;
+        return caps.r16Format;
 
     default:
         break;

src/rhi/qrhigles2_p.h

@@ -567,8 +567,8 @@ public:
               fixedIndexPrimitiveRestart(false),
               bgraExternalFormat(false),
               bgraInternalFormat(false),
-              sized8Formats(false),
-              sized16Formats(false)
+              r8Format(false),
+              r16Format(false)
         { }
         int maxTextureSize;
         // Multisample fb and blit are supported (GLES 3.0 or OpenGL 3.x). Not
@@ -579,8 +579,8 @@ public:
         uint fixedIndexPrimitiveRestart : 1;
         uint bgraExternalFormat : 1;
         uint bgraInternalFormat : 1;
-        uint sized8Formats : 1;
-        uint sized16Formats : 1;
+        uint r8Format : 1;
+        uint r16Format : 1;
     } caps;
     bool inFrame = false;
     bool inPass = false;