rhi: gl: Add support for importing an existing renderbuffer object

Normally we only allow creating wrappers for texture objects. These
can then be used with a QRhiTextureRenderTarget to allow rendering into
an externally created texture.

With OpenGL (ES), there are additional, special cases, especially on
embedded. Consider EGLImages for example. An EGLImageKHR can be bound to
a renderbuffer object (glEGLImageTargetRenderbufferStorageOES), which
can then be associated with a framebuffer object to allow rendering into
the external buffer represented by the EGLImage. To implement the same
via QRhi one needs a way to create a wrapping QRhiRenderBuffer for the
native OpenGL renderbuffer object.

Here we add a createFrom() to QRhiRenderBuffer, while providing a dummy,
default implementation. The only real implementation is in the OpenGL
backend, which simply takes a renderbuffer id, without taking ownership.

Task-number: QTBUG-92116
Change-Id: I4e68e665fb35a7d7803b7780db901c8bed5740e2
Reviewed-by: Andy Nichols <andy.nichols@qt.io>

1 files changed, 32 insertions, 1 deletions

diff --git a/src/gui/rhi/qrhigles2.cpp b/src/gui/rhi/qrhigles2.cpp
index 43569d3752..8a5361b29a 100644
--- a/src/gui/rhi/qrhigles2.cpp
+++ b/src/gui/rhi/qrhigles2.cpp
@@ -1011,6 +1011,8 @@ bool QRhiGles2::isFeatureSupported(QRhi::Feature feature) const
         return caps.programBinary;
     case QRhi::ImageDataStride:
         return !caps.gles || caps.ctxMajor >= 3;
+    case QRhi::RenderBufferImport:
+        return true;
     default:
         Q_UNREACHABLE();
         return false;
@@ -4287,7 +4289,8 @@ void QGles2RenderBuffer::destroy()
     stencilRenderbuffer = 0;
 
     QRHI_RES_RHI(QRhiGles2);
-    rhiD->releaseQueue.append(e);
+    if (owns)
+        rhiD->releaseQueue.append(e);
     QRHI_PROF;
     QRHI_PROF_F(releaseRenderBuffer(this));
     rhiD->unregisterResource(this);
@@ -4375,6 +4378,34 @@ bool QGles2RenderBuffer::create()
         break;
     }
 
+    owns = true;
+    rhiD->registerResource(this);
+    return true;
+}
+
+bool QGles2RenderBuffer::createFrom(NativeRenderBuffer src)
+{
+    if (!src.object)
+        return false;
+
+    if (renderbuffer)
+        destroy();
+
+    QRHI_RES_RHI(QRhiGles2);
+    samples = rhiD->effectiveSampleCount(m_sampleCount);
+
+    if (m_flags.testFlag(UsedWithSwapChainOnly))
+        qWarning("RenderBuffer: UsedWithSwapChainOnly is meaningless when importing an existing native object");
+
+    if (!rhiD->ensureContext())
+        return false;
+
+    renderbuffer = src.object;
+
+    QRHI_PROF;
+    QRHI_PROF_F(newRenderBuffer(this, false, false, samples));
+
+    owns = false;
     rhiD->registerResource(this);
     return true;
 }