From 7000b66f7e85e58d267b71322fbb3d5a0fc356b8 Mon Sep 17 00:00:00 2001
From: Laszlo Agocs <laszlo.agocs@qt.io>
Date: Sat, 28 Sep 2019 15:19:09 +0200
Subject: Remove QVector in the API of QRhiResource subclasses
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Forcing users to go through a QVector, when in practice they almost
always want to source the data from an initializer list, a QVarLengthArray,
or a plain C array, is not ideal. Especially since we can reason about
the maximum number of elements in the vast majority of use cases for all
the affected lists. QRhiResource is also not copyable so we do not need
the usual machinery offered by containers. So switch to a
QVarLengthArray.

Note that a resource is not a container. The only operations we are
interested in is to be able to source data either via an initializer
list or by iterating on something, and to be able to extract the data,
in case a user wishes to set up another resource based on the existing
one.

In some cases a QVector overload is kept for source compatibility with
other modules (Qt Quick). These may be removed in the future.

Also do a similar QVector->QVarLengthArray change in the srb-related
data in the backends.

Change-Id: I6f5b2ebd8e75416ce0cca0817bb529446a4cb664
Reviewed-by: Christian Strømme <christian.stromme@qt.io>
---
 src/gui/rhi/qrhi_p.h | 51 ++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 42 insertions(+), 9 deletions(-)

(limited to 'src/gui/rhi/qrhi_p.h')

diff --git a/src/gui/rhi/qrhi_p.h b/src/gui/rhi/qrhi_p.h
index fec69c607f..f8f922cfdb 100644
--- a/src/gui/rhi/qrhi_p.h
+++ b/src/gui/rhi/qrhi_p.h
@@ -52,6 +52,7 @@
 #include <QSize>
 #include <QMatrix4x4>
 #include <QVector>
+#include <QVarLengthArray>
 #include <QThread>
 #include <QColor>
 #include <QImage>
@@ -926,8 +927,22 @@ class Q_GUI_EXPORT QRhiShaderResourceBindings : public QRhiResource
 public:
     QRhiResource::Type resourceType() const override;
 
-    QVector<QRhiShaderResourceBinding> bindings() const { return m_bindings; }
-    void setBindings(const QVector<QRhiShaderResourceBinding> &b) { m_bindings = b; }
+    void setBindings(std::initializer_list<QRhiShaderResourceBinding> list) { m_bindings = list; }
+
+    template<typename InputIterator>
+    void setBindings(InputIterator first, InputIterator last)
+    {
+        m_bindings.clear();
+        std::copy(first, last, std::back_inserter(m_bindings));
+    }
+
+    void setBindings(const QVector<QRhiShaderResourceBinding> &bindings) // compat., to be removed
+    {
+        setBindings(bindings.cbegin(), bindings.cend());
+    }
+
+    const QRhiShaderResourceBinding *cbeginBindings() const { return m_bindings.cbegin(); }
+    const QRhiShaderResourceBinding *cendBindings() const { return m_bindings.cend(); }
 
     bool isLayoutCompatible(const QRhiShaderResourceBindings *other) const;
 
@@ -935,7 +950,7 @@ public:
 
 protected:
     QRhiShaderResourceBindings(QRhiImplementation *rhi);
-    QVector<QRhiShaderResourceBinding> m_bindings;
+    QVarLengthArray<QRhiShaderResourceBinding, 8> m_bindings;
 #ifndef QT_NO_DEBUG_STREAM
     friend Q_GUI_EXPORT QDebug operator<<(QDebug, const QRhiShaderResourceBindings &);
 #endif
@@ -1066,8 +1081,15 @@ public:
     FrontFace frontFace() const { return m_frontFace; }
     void setFrontFace(FrontFace f) { m_frontFace = f; }
 
-    QVector<TargetBlend> targetBlends() const { return m_targetBlends; }
-    void setTargetBlends(const QVector<TargetBlend> &blends) { m_targetBlends = blends; }
+    void setTargetBlends(std::initializer_list<TargetBlend> list) { m_targetBlends = list; }
+    template<typename InputIterator>
+    void setTargetBlends(InputIterator first, InputIterator last)
+    {
+        m_targetBlends.clear();
+        std::copy(first, last, std::back_inserter(m_targetBlends));
+    }
+    const TargetBlend *cbeginTargetBlends() const { return m_targetBlends.cbegin(); }
+    const TargetBlend *cendTargetBlends() const { return m_targetBlends.cend(); }
 
     bool hasDepthTest() const { return m_depthTest; }
     void setDepthTest(bool enable) { m_depthTest = enable; }
@@ -1099,8 +1121,19 @@ public:
     float lineWidth() const { return m_lineWidth; }
     void setLineWidth(float width) { m_lineWidth = width; }
 
-    QVector<QRhiShaderStage> shaderStages() const { return m_shaderStages; }
-    void setShaderStages(const QVector<QRhiShaderStage> &stages) { m_shaderStages = stages; }
+    void setShaderStages(std::initializer_list<QRhiShaderStage> list) { m_shaderStages = list; }
+    template<typename InputIterator>
+    void setShaderStages(InputIterator first, InputIterator last)
+    {
+        m_shaderStages.clear();
+        std::copy(first, last, std::back_inserter(m_shaderStages));
+    }
+    void setShaderStages(const QVector<QRhiShaderStage> &stages) // compat., to be removed
+    {
+        setShaderStages(stages.cbegin(), stages.cend());
+    }
+    const QRhiShaderStage *cbeginShaderStages() const { return m_shaderStages.cbegin(); }
+    const QRhiShaderStage *cendShaderStages() const { return m_shaderStages.cend(); }
 
     QRhiVertexInputLayout vertexInputLayout() const { return m_vertexInputLayout; }
     void setVertexInputLayout(const QRhiVertexInputLayout &layout) { m_vertexInputLayout = layout; }
@@ -1119,7 +1152,7 @@ protected:
     Topology m_topology = Triangles;
     CullMode m_cullMode = None;
     FrontFace m_frontFace = CCW;
-    QVector<TargetBlend> m_targetBlends;
+    QVarLengthArray<TargetBlend, 8> m_targetBlends;
     bool m_depthTest = false;
     bool m_depthWrite = false;
     CompareOp m_depthOp = Less;
@@ -1130,7 +1163,7 @@ protected:
     quint32 m_stencilWriteMask = 0xFF;
     int m_sampleCount = 1;
     float m_lineWidth = 1.0f;
-    QVector<QRhiShaderStage> m_shaderStages;
+    QVarLengthArray<QRhiShaderStage, 4> m_shaderStages;
     QRhiVertexInputLayout m_vertexInputLayout;
     QRhiShaderResourceBindings *m_shaderResourceBindings = nullptr;
     QRhiRenderPassDescriptor *m_renderPassDesc = nullptr;
-- 
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