ES2: Enable Renderbuffer usage with either Depth or Stencil

Current we require a combined DepthStencil RenderBuffer, however this is
an extension in ES2 so it's not a given that it will be available.  It
is still possible to setup separate Depth and Stencil buffers for those
devices that only support that (similar to what Scenegraph does).

Change-Id: Ia112b30e229bfc553cd0cdc0f8dd8b57290c7081
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>

3 files changed, 24 insertions, 6 deletions

diff --git a/src/render/renderers/opengl/graphicshelpers/graphicshelperes2.cpp b/src/render/renderers/opengl/graphicshelpers/graphicshelperes2.cpp
index 966528ad8..798457edb 100644
--- a/src/render/renderers/opengl/graphicshelpers/graphicshelperes2.cpp
+++ b/src/render/renderers/opengl/graphicshelpers/graphicshelperes2.cpp
@@ -399,9 +399,13 @@ bool GraphicsHelperES2::checkFrameBufferComplete()
 
 bool GraphicsHelperES2::frameBufferNeedsRenderBuffer(const Attachment &attachment)
 {
-    // Use a renderbuffer for combined depth+stencil attachments since this is
+    // Use a renderbuffer for depth or stencil attachments since this is
     // problematic before GLES 3.2. Keep using textures for everything else.
-    return attachment.m_point == QRenderTargetOutput::DepthStencil;
+    // For ES2 individual Depth and Stencil buffers need to be an option because
+    // DepthStencil is an extension.
+    return attachment.m_point == QRenderTargetOutput::DepthStencil ||
+           attachment.m_point == QRenderTargetOutput::Depth ||
+           attachment.m_point == QRenderTargetOutput::Stencil;
 }
 
 void GraphicsHelperES2::bindFrameBufferAttachment(QOpenGLTexture *texture, const Attachment &attachment)
@@ -436,15 +440,21 @@ void GraphicsHelperES2::bindFrameBufferAttachment(QOpenGLTexture *texture, const
 
 void GraphicsHelperES2::bindFrameBufferAttachment(RenderBuffer *renderBuffer, const Attachment &attachment)
 {
-    if (attachment.m_point != QRenderTargetOutput::DepthStencil) {
-        qCritical() << "Renderbuffers only supported for combined depth-stencil, but got attachment point"
+    if (attachment.m_point != QRenderTargetOutput::DepthStencil &&
+        attachment.m_point != QRenderTargetOutput::Depth &&
+        attachment.m_point != QRenderTargetOutput::Stencil) {
+        qCritical() << "Renderbuffers only supported for combined depth-stencil, depth, or stencil, but got attachment point"
                     << attachment.m_point;
         return;
     }
 
     renderBuffer->bind();
-    m_funcs->glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, renderBuffer->renderBufferId());
-    m_funcs->glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_STENCIL_ATTACHMENT, GL_RENDERBUFFER, renderBuffer->renderBufferId());
+    if (attachment.m_point == QRenderTargetOutput::DepthStencil ||
+        attachment.m_point == QRenderTargetOutput::Depth)
+        m_funcs->glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, renderBuffer->renderBufferId());
+    if (attachment.m_point == QRenderTargetOutput::DepthStencil ||
+        attachment.m_point == QRenderTargetOutput::Stencil)
+        m_funcs->glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_STENCIL_ATTACHMENT, GL_RENDERBUFFER, renderBuffer->renderBufferId());
     renderBuffer->release();
 }
 
diff --git a/src/render/renderers/opengl/graphicshelpers/graphicshelperes3.cpp b/src/render/renderers/opengl/graphicshelpers/graphicshelperes3.cpp
index 813c627b8..d324baf1f 100644
--- a/src/render/renderers/opengl/graphicshelpers/graphicshelperes3.cpp
+++ b/src/render/renderers/opengl/graphicshelpers/graphicshelperes3.cpp
@@ -314,6 +314,13 @@ void GraphicsHelperES3::bindBufferBase(GLenum target, GLuint index, GLuint buffe
     m_extraFuncs->glBindBufferBase(target, index, buffer);
 }
 
+bool GraphicsHelperES3::frameBufferNeedsRenderBuffer(const Attachment &attachment)
+{
+    // Use a renderbuffer for combined depth+stencil attachments since this is
+    // problematic before GLES 3.2. Keep using textures for everything else.
+    return attachment.m_point == QRenderTargetOutput::DepthStencil;
+}
+
 void GraphicsHelperES3::bindUniformBlock(GLuint programId, GLuint uniformBlockIndex, GLuint uniformBlockBinding)
 {
     m_extraFuncs->glUniformBlockBinding(programId, uniformBlockIndex, uniformBlockBinding);
diff --git a/src/render/renderers/opengl/graphicshelpers/graphicshelperes3_p.h b/src/render/renderers/opengl/graphicshelpers/graphicshelperes3_p.h
index 9bca2d48d..518226116 100644
--- a/src/render/renderers/opengl/graphicshelpers/graphicshelperes3_p.h
+++ b/src/render/renderers/opengl/graphicshelpers/graphicshelperes3_p.h
@@ -67,6 +67,7 @@ public:
 
     // QGraphicHelperInterface interface
     void bindBufferBase(GLenum target, GLuint index, GLuint buffer) override;
+    bool frameBufferNeedsRenderBuffer(const Attachment &attachment) override;
     void bindFrameBufferAttachment(QOpenGLTexture *texture, const Attachment &attachment) override;
     void bindUniformBlock(GLuint programId, GLuint uniformBlockIndex, GLuint uniformBlockBinding) override;
     void blitFramebuffer(GLint srcX0, GLint srcY0, GLint srcX1, GLint srcY1, GLint dstX0, GLint dstY0, GLint dstX1, GLint dstY1, GLbitfield mask, GLenum filter) override;