Add shader registry (#924)

test/renderer/shader_registry.test.cpp

@@ -0,0 +1,113 @@
+#include <mbgl/test/util.hpp>
+
+#include <mbgl/gfx/shader_registry.hpp>
+#include <mbgl/gfx/shader.hpp>
+
+#include <string_view>
+#include <iostream>
+
+using namespace mbgl;
+
+namespace {
+
+template<uint32_t token_value>
+class StubProgramBase : public gfx::Shader {
+    public:
+        static constexpr auto Token = token_value;
+        virtual uint32_t draw() { return token; }
+
+    protected:
+        uint32_t token{token_value};
+};
+
+class StubProgram_1 final : public StubProgramBase<10> {
+    public:
+        static constexpr std::string_view Name{"StubProgram_1"};
+        const std::string_view name() const noexcept override {
+            return Name;
+        }
+
+        void setToken(uint32_t tok) { token = tok; }
+};
+
+class StubProgram_2 final : public StubProgramBase<20> {
+    public:
+        static constexpr std::string_view Name{"StubProgram_2"};
+        const std::string_view name() const noexcept override {
+            return Name;
+        }
+};
+
+class StubShaderConsumer {
+    public:
+        template<typename T>
+        uint32_t useShader(gfx::ShaderRegistry& registry) {
+            auto program = registry.get<T>();
+            return program ? program->draw() : 0;
+        }
+};
+
+} // namespace
+
+// Ensure we can register a gfx::Shader-based type with a registry object 
+TEST(ShaderRegistry, RegisterShader) {
+    gfx::ShaderRegistry registry;
+
+    // The registry should start empty
+    ASSERT_FALSE(registry.isShader(std::string{StubProgram_1::Name}));
+
+    // Register the program
+    auto program = std::make_shared<StubProgram_1>();
+    ASSERT_TRUE(registry.registerShader(program));
+    // We can't re-register the same program name
+    ASSERT_FALSE(registry.registerShader(program));
+    // Ensure the shader is present in the registry now
+    ASSERT_TRUE(registry.isShader(std::string{StubProgram_1::Name}));
+    // And we can fetch it
+    ASSERT_EQ(registry.get<StubProgram_1>(), program);
+
+    // Make sure downcasting to program1 works as expected
+    StubShaderConsumer consumer;
+    ASSERT_EQ(consumer.useShader<StubProgram_1>(registry), 10);
+}
+
+// Validate replacing a shader by name with a different instance
+TEST(ShaderRegistry, ReplaceShaderType) {
+    gfx::ShaderRegistry registry;
+
+    ASSERT_FALSE(registry.isShader(std::string{StubProgram_1::Name}));
+
+    auto program = std::make_shared<StubProgram_1>();
+    ASSERT_TRUE(registry.registerShader(program));
+    // Ensure the shader is present in the registry now
+    ASSERT_TRUE(registry.isShader(std::string{StubProgram_1::Name}));
+    ASSERT_TRUE(registry.isShader(std::string{program->name()}));
+
+    // Make sure downcasting to program1 works as expected
+    StubShaderConsumer consumer;
+    ASSERT_EQ(consumer.useShader<StubProgram_1>(registry), 10);
+
+    // StubProgram_1 and StubProgram_2 are disconnected types,
+    // and as such this replacement should fail as StubProgram_2
+    // has never been registered.
+    auto program2 = std::make_shared<StubProgram_2>();
+    ASSERT_FALSE(registry.replaceShader(program2));
+
+    // Make a second instance of program1 and change the token
+    auto program3 = std::make_shared<StubProgram_1>();
+    program3->setToken(30);
+    // Replace it in the registry
+    ASSERT_TRUE(registry.replaceShader(program3));
+    // Assert the new program downcasts from the registry as expected
+    ASSERT_EQ(consumer.useShader<StubProgram_1>(registry), 30);
+}
+
+// Validate shader type info and downcasting are functioning
+TEST(ShaderRegistry, ShaderRTTI) {
+    auto program1 = StubProgram_1();
+    auto asBase = static_cast<gfx::Shader*>(&program1);
+
+    // Should convert to program 1 but not program 2
+    ASSERT_EQ(asBase->to<StubProgram_1>(), &program1);
+    ASSERT_EQ(asBase->to<StubProgram_2>(), nullptr);
+}