Vk: enforce binding and location ordering in MeshLayout.

In order to make them easier to compare.

src/Magnum/Vk/MeshLayout.cpp

@@ -125,6 +125,10 @@ MeshLayout& MeshLayout::operator=(MeshLayout&& other) noexcept {
 MeshLayout& MeshLayout::addBinding(const UnsignedInt binding, const UnsignedInt stride) {
     if(!_state) _state.emplace();
 
+    /* Ensure order for efficient comparisons */
+    CORRADE_ASSERT(_state->bindings.empty() || _state->bindings.back().binding < binding,
+        "Vk::MeshLayout::addBinding(): binding" << binding << "can't be ordered after" << _state->bindings.back().binding, *this);
+
     VkVertexInputBindingDescription description{};
     description.binding = binding;
     description.stride = stride;
@@ -139,6 +143,10 @@ MeshLayout& MeshLayout::addBinding(const UnsignedInt binding, const UnsignedInt
 MeshLayout& MeshLayout::addInstancedBinding(const UnsignedInt binding, const UnsignedInt stride, const UnsignedInt divisor) {
     if(!_state) _state.emplace();
 
+    /* Ensure order for efficient comparisons */
+    CORRADE_ASSERT(_state->bindings.empty() || _state->bindings.back().binding < binding,
+        "Vk::MeshLayout::addInstancedBinding(): binding" << binding << "can't be ordered after" << _state->bindings.back().binding, *this);
+
     VkVertexInputBindingDescription description{};
     description.binding = binding;
     description.stride = stride;
@@ -166,6 +174,10 @@ MeshLayout& MeshLayout::addInstancedBinding(const UnsignedInt binding, const Uns
 MeshLayout& MeshLayout::addAttribute(const UnsignedInt location, const UnsignedInt binding, const VertexFormat format, const UnsignedInt offset) {
     if(!_state) _state.emplace();
 
+    /* Ensure order for efficient comparisons */
+    CORRADE_ASSERT(_state->attributes.empty() || _state->attributes.back().location < location,
+        "Vk::MeshLayout::addAttribute(): location" << location << "can't be ordered after" << _state->attributes.back().location, *this);
+
     VkVertexInputAttributeDescription description{};
     description.location = location;
     description.binding = binding;

src/Magnum/Vk/MeshLayout.h

@@ -253,7 +253,9 @@ class MAGNUM_VK_EXPORT MeshLayout {
          * @brief Add a buffer binding
          * @param binding   Binding index, to which a buffer subrange will be
          *      bound when drawing the mesh. Has to be unique among all
-         *      @ref addBinding() and @ref addInstancedBinding() calls.
+         *      @ref addBinding() and @ref addInstancedBinding() calls, and
+         *      monotonically increasing in order to make the layouts
+         *      efficiently comparable.
          * @param stride    Binding stride, in bytes
          * @return Reference to self (for method chaining)
          *
@@ -273,7 +275,9 @@ class MAGNUM_VK_EXPORT MeshLayout {
          * @brief Add an instanced buffer binding
          * @param binding   Binding index, to which a buffer subrange will be
          *      bound when drawing the mesh. Has to be unique among all
-         *      @ref addBinding() and @ref addInstancedBinding() calls.
+         *      @ref addBinding() and @ref addInstancedBinding() calls, and
+         *      monotonically increasing in order to make the layouts
+         *      efficiently comparable.
          * @param stride    Binding stride, in bytes
          * @param divisor   Attribute divisor. @cpp 1 @ce means the attribute
          *      will be advanced for each instance, larger values will mean
@@ -306,7 +310,9 @@ class MAGNUM_VK_EXPORT MeshLayout {
 
         /**
          * @brief Add an attribute
-         * @param location      Attribute location, matching a shader input
+         * @param location      Attribute location, matching a shader input.
+         *      Has to be monotonically increasing in order to make the layouts
+         *      efficiently comparable.
          * @param binding       Binding index, corresponding to the @p binding
          *      parameter of one of the @ref addBinding() /
          *      @ref addInstancedBinding() calls.

src/Magnum/Vk/Test/MeshLayoutTest.cpp

@@ -53,7 +53,9 @@ struct MeshLayoutTest: TestSuite::Tester {
     void addBinding();
     void addInstancedBinding();
     void addInstancedBindingDivisor();
+    void addBindingWrongOrder();
     template<class T> void addAttribute();
+    void addAttributeWrongOrder();
 
     void debugMeshPrimitive();
 };
@@ -74,8 +76,10 @@ MeshLayoutTest::MeshLayoutTest() {
               &MeshLayoutTest::addBinding,
               &MeshLayoutTest::addInstancedBinding,
               &MeshLayoutTest::addInstancedBindingDivisor,
+              &MeshLayoutTest::addBindingWrongOrder,
               &MeshLayoutTest::addAttribute<VertexFormat>,
               &MeshLayoutTest::addAttribute<Magnum::VertexFormat>,
+              &MeshLayoutTest::addAttributeWrongOrder,
 
               &MeshLayoutTest::debugMeshPrimitive});
 }
@@ -322,6 +326,23 @@ void MeshLayoutTest::addInstancedBindingDivisor() {
     CORRADE_COMPARE(vertexDivisorInfo.pVertexBindingDivisors[1].divisor, 0);
 }
 
+void MeshLayoutTest::addBindingWrongOrder() {
+    #ifdef CORRADE_NO_ASSERT
+    CORRADE_SKIP("CORRADE_NO_ASSERT defined, can't test assertions");
+    #endif
+
+    MeshLayout layout{MeshPrimitive::Triangles};
+    layout.addBinding(15, 23);
+
+    std::ostringstream out;
+    Error redirectError{&out};
+    layout.addBinding(15, 27)
+        .addInstancedBinding(15, 27);
+    CORRADE_COMPARE(out.str(),
+        "Vk::MeshLayout::addBinding(): binding 15 can't be ordered after 15\n"
+        "Vk::MeshLayout::addInstancedBinding(): binding 15 can't be ordered after 15\n");
+}
+
 template<class T> void MeshLayoutTest::addAttribute() {
     setTestCaseTemplateName(VertexFormatTraits<T>::name());
 
@@ -341,6 +362,21 @@ template<class T> void MeshLayoutTest::addAttribute() {
     CORRADE_COMPARE(layout.vkPipelineVertexInputStateCreateInfo().pVertexAttributeDescriptions[1].offset, 22);
 }
 
+void MeshLayoutTest::addAttributeWrongOrder() {
+    #ifdef CORRADE_NO_ASSERT
+    CORRADE_SKIP("CORRADE_NO_ASSERT defined, can't test assertions");
+    #endif
+
+    MeshLayout layout{MeshPrimitive::Triangles};
+    layout.addAttribute(5, 17, VertexFormat{}, 0);
+
+    std::ostringstream out;
+    Error redirectError{&out};
+    layout.addAttribute(5, 25, VertexFormat{}, 1);
+    CORRADE_COMPARE(out.str(),
+        "Vk::MeshLayout::addAttribute(): location 5 can't be ordered after 5\n");
+}
+
 void MeshLayoutTest::debugMeshPrimitive() {
     std::ostringstream out;
     Debug{&out} << MeshPrimitive::TriangleFan << MeshPrimitive(-10007655);