wasm: fix QSGContext warning message

When runing the scenegraph example sgengine, gets rid if this error:
 QSGContext::initialize: stencil buffer support missing, expect
 rendering errors

Change-Id: I7f3a82409bc2cf81cf8217876e527f9c45be3bf4
Fixes: QTBUG-74694
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>
 
 

1 files changed, 14 insertions, 2 deletions

diff --git a/src/plugins/platforms/wasm/qwasmopenglcontext.cpp b/src/plugins/platforms/wasm/qwasmopenglcontext.cpp
index ae43e2ebf0..1658f32f9e 100644
--- a/src/plugins/platforms/wasm/qwasmopenglcontext.cpp
+++ b/src/plugins/platforms/wasm/qwasmopenglcontext.cpp
@@ -37,6 +37,14 @@ QWasmOpenGLContext::QWasmOpenGLContext(const QSurfaceFormat &format)
     : m_requestedFormat(format)
 {
     m_requestedFormat.setRenderableType(QSurfaceFormat::OpenGLES);
+
+    // if we set one, we need to set the other as well since in webgl, these are tied together
+    if (format.depthBufferSize() < 0 && format.stencilBufferSize() > 0)
+       m_requestedFormat.setDepthBufferSize(16);
+
+   if (format.stencilBufferSize() < 0 && format.depthBufferSize() > 0)
+       m_requestedFormat.setStencilBufferSize(8);
+
 }
 
 QWasmOpenGLContext::~QWasmOpenGLContext()
@@ -91,10 +99,14 @@ EMSCRIPTEN_WEBGL_CONTEXT_HANDLE QWasmOpenGLContext::createEmscriptenContext(cons
         attributes.majorVersion = 2;
     }
 
+    // WebGL doesn't allow separate attach buffers to STENCIL_ATTACHMENT and DEPTH_ATTACHMENT
+    // we need both or none
+    bool useDepthStencil = (format.depthBufferSize() > 0 || format.stencilBufferSize() > 0);
+
     // WebGL offers enable/disable control but not size control for these
     attributes.alpha = format.alphaBufferSize() > 0;
-    attributes.depth = format.depthBufferSize() > 0;
-    attributes.stencil = format.stencilBufferSize() > 0;
+    attributes.depth = useDepthStencil;
+    attributes.stencil = useDepthStencil;
 
     EMSCRIPTEN_WEBGL_CONTEXT_HANDLE context = emscripten_webgl_create_context(canvasId.toLocal8Bit().constData(), &attributes);