rhi: Autotest rendering a triangle

Also improve (docs and runtime checks) and test the minimum set
of required data to create a graphics pipeline.

Task-number: QTBUG-78971
Change-Id: If5c14f1ab1ff3cf70f168fde585f05fc9d28ec91
Reviewed-by: Paul Olav Tvete <paul.tvete@qt.io>

8 files changed, 61 insertions, 4 deletions

diff --git a/src/gui/rhi/qrhi.cpp b/src/gui/rhi/qrhi.cpp
index 57c466678e..dabad35688 100644
--- a/src/gui/rhi/qrhi.cpp
+++ b/src/gui/rhi/qrhi.cpp
@@ -3084,9 +3084,13 @@ QDebug operator<<(QDebug dbg, const QRhiShaderResourceBindings &srb)
     \inmodule QtGui
     \brief Graphics pipeline state resource.
 
+    \note Setting the shader stages is mandatory. There must be at least one
+    stage, and there must be a vertex stage.
+
     \note Setting the shader resource bindings is mandatory. The referenced
     QRhiShaderResourceBindings must already be built by the time build() is
-    called.
+    called. Associating with a QRhiShaderResourceBindings that has no bindings
+    is also valid, as long as no shader in any stage expects any resources.
 
     \note Setting the render pass descriptor is mandatory. To obtain a
     QRhiRenderPassDescriptor that can be passed to setRenderPassDescriptor(),
@@ -3095,8 +3099,6 @@ QDebug operator<<(QDebug dbg, const QRhiShaderResourceBindings &srb)
 
     \note Setting the vertex input layout is mandatory.
 
-    \note Setting the shader stages is mandatory.
-
     \note sampleCount() defaults to 1 and must match the sample count of the
     render target's color and depth stencil attachments.
 
@@ -3912,6 +3914,46 @@ quint32 QRhiImplementation::approxByteSizeForTexture(QRhiTexture::Format format,
     return approxSize;
 }
 
+bool QRhiImplementation::sanityCheckGraphicsPipeline(QRhiGraphicsPipeline *ps)
+{
+    if (ps->cbeginShaderStages() == ps->cendShaderStages()) {
+        qWarning("Cannot build a graphics pipeline without any stages");
+        return false;
+    }
+
+    bool hasVertexStage = false;
+    for (auto it = ps->cbeginShaderStages(), itEnd = ps->cendShaderStages(); it != itEnd; ++it) {
+        if (!it->shader().isValid()) {
+            qWarning("Empty shader passed to graphics pipeline");
+            return false;
+        }
+        if (it->type() == QRhiShaderStage::Vertex) {
+            hasVertexStage = true;
+            const QRhiVertexInputLayout inputLayout = ps->vertexInputLayout();
+            if (inputLayout.cbeginAttributes() == inputLayout.cendAttributes()) {
+                qWarning("Vertex stage present without any vertex inputs");
+                return false;
+            }
+        }
+    }
+    if (!hasVertexStage) {
+        qWarning("Cannot build a graphics pipeline without a vertex stage");
+        return false;
+    }
+
+    if (!ps->renderPassDescriptor()) {
+        qWarning("Cannot build a graphics pipeline without a QRhiRenderPassDescriptor");
+        return false;
+    }
+
+    if (!ps->shaderResourceBindings()) {
+        qWarning("Cannot build a graphics pipeline without QRhiShaderResourceBindings");
+        return false;
+    }
+
+    return true;
+}
+
 /*!
     \internal
  */
diff --git a/src/gui/rhi/qrhi_p.h b/src/gui/rhi/qrhi_p.h
index bfcc1d39f5..907924c788 100644
--- a/src/gui/rhi/qrhi_p.h
+++ b/src/gui/rhi/qrhi_p.h
@@ -72,7 +72,6 @@ class QRhiCommandBuffer;
 class QRhiResourceUpdateBatch;
 class QRhiResourceUpdateBatchPrivate;
 class QRhiProfiler;
-class QRhiShaderResourceBindingPrivate;
 
 class Q_GUI_EXPORT QRhiDepthStencilClearValue
 {
diff --git a/src/gui/rhi/qrhi_p_p.h b/src/gui/rhi/qrhi_p_p.h
index cc14293580..baffe28202 100644
--- a/src/gui/rhi/qrhi_p_p.h
+++ b/src/gui/rhi/qrhi_p_p.h
@@ -205,6 +205,8 @@ public:
         cleanupCallbacks.append(callback);
     }
 
+    bool sanityCheckGraphicsPipeline(QRhiGraphicsPipeline *ps);
+
     QRhi *q;
 
     static const int MAX_SHADER_CACHE_ENTRIES = 128;
diff --git a/src/gui/rhi/qrhid3d11.cpp b/src/gui/rhi/qrhid3d11.cpp
index 096a8c2756..57ebb2909f 100644
--- a/src/gui/rhi/qrhid3d11.cpp
+++ b/src/gui/rhi/qrhid3d11.cpp
@@ -3491,6 +3491,8 @@ bool QD3D11GraphicsPipeline::build()
         release();
 
     QRHI_RES_RHI(QRhiD3D11);
+    if (!rhiD->sanityCheckGraphicsPipeline(this))
+        return false;
 
     D3D11_RASTERIZER_DESC rastDesc;
     memset(&rastDesc, 0, sizeof(rastDesc));
diff --git a/src/gui/rhi/qrhigles2.cpp b/src/gui/rhi/qrhigles2.cpp
index ca1c91499d..4163ab1e79 100644
--- a/src/gui/rhi/qrhigles2.cpp
+++ b/src/gui/rhi/qrhigles2.cpp
@@ -3690,6 +3690,9 @@ bool QGles2GraphicsPipeline::build()
     if (!rhiD->ensureContext())
         return false;
 
+    if (!rhiD->sanityCheckGraphicsPipeline(this))
+        return false;
+
     drawMode = toGlTopology(m_topology);
 
     program = rhiD->f->glCreateProgram();
diff --git a/src/gui/rhi/qrhimetal.mm b/src/gui/rhi/qrhimetal.mm
index 694882ab93..ef5ab696d7 100644
--- a/src/gui/rhi/qrhimetal.mm
+++ b/src/gui/rhi/qrhimetal.mm
@@ -3139,6 +3139,8 @@ bool QMetalGraphicsPipeline::build()
         release();
 
     QRHI_RES_RHI(QRhiMetal);
+    if (!rhiD->sanityCheckGraphicsPipeline(this))
+        return false;
 
     // same binding space for vertex and constant buffers - work it around
     const int firstVertexBinding = QRHI_RES(QMetalShaderResourceBindings, m_shaderResourceBindings)->maxBinding + 1;
diff --git a/src/gui/rhi/qrhinull.cpp b/src/gui/rhi/qrhinull.cpp
index d78b5e20c5..2eb55e705b 100644
--- a/src/gui/rhi/qrhinull.cpp
+++ b/src/gui/rhi/qrhinull.cpp
@@ -805,6 +805,10 @@ void QNullGraphicsPipeline::release()
 
 bool QNullGraphicsPipeline::build()
 {
+    QRHI_RES_RHI(QRhiNull);
+    if (!rhiD->sanityCheckGraphicsPipeline(this))
+        return false;
+
     return true;
 }
 
diff --git a/src/gui/rhi/qrhivulkan.cpp b/src/gui/rhi/qrhivulkan.cpp
index 0d364dd9fc..fca2125f10 100644
--- a/src/gui/rhi/qrhivulkan.cpp
+++ b/src/gui/rhi/qrhivulkan.cpp
@@ -5886,6 +5886,9 @@ bool QVkGraphicsPipeline::build()
         release();
 
     QRHI_RES_RHI(QRhiVulkan);
+    if (!rhiD->sanityCheckGraphicsPipeline(this))
+        return false;
+
     if (!rhiD->ensurePipelineCache())
         return false;