Add WebGPU Backend w/ Dawn Support (#3838)

src/mbgl/webgpu/vertex_attribute.cpp

@@ -0,0 +1,43 @@
+#include <mbgl/webgpu/vertex_attribute.hpp>
+#include <mbgl/gfx/vertex_vector.hpp>
+#include <mbgl/webgpu/buffer_resource.hpp>
+#include <mbgl/webgpu/upload_pass.hpp>
+#include <mbgl/util/logging.hpp>
+#include <mbgl/util/convert.hpp>
+
+#include <cstring>
+#include <sstream>
+
+namespace mbgl {
+namespace webgpu {
+
+const gfx::UniqueVertexBufferResource& VertexAttribute::getBuffer(gfx::VertexAttribute& attrib_,
+                                                                  UploadPass& uploadPass,
+                                                                  const gfx::BufferUsageType usage,
+                                                                  bool forceUpdate) {
+    if (!attrib_.getBuffer()) {
+        auto& attrib = static_cast<VertexAttribute&>(attrib_);
+        if (attrib.sharedRawData) {
+            return uploadPass.getBuffer(attrib.sharedRawData, usage, forceUpdate);
+        } else {
+            if (!attrib.rawData.empty()) {
+                auto buffer = uploadPass.createVertexBufferResource(
+                    attrib.rawData.data(), attrib.rawData.size(), usage, false);
+                attrib.setBuffer(std::move(buffer));
+                attrib.setRawData({});
+                attrib_.setDirty(false);
+            } else {
+                assert(false);
+            }
+        }
+    }
+    return attrib_.getBuffer();
+}
+
+bool VertexAttributeArray::isModifiedAfter(std::chrono::duration<double> time) const {
+    // Use the base class implementation
+    return gfx::VertexAttributeArray::isModifiedAfter(time);
+}
+
+} // namespace webgpu
+} // namespace mbgl