LibWeb+CodeGenerators: Generate EnvironmentVariable enum and functions

Author: https://github.com/AtkinsSJ
Commit: 7b30c94fcf
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/5736
Reviewed-by: https://github.com/kalenikaliaksandr

Documentation/CSSGeneratedFiles.md

@@ -312,3 +312,24 @@ The generated code provides:
 - `Optional<TransformFunction> transform_function_from_string(StringView)` to parse a string as a `TransformFunction`
 - `StringView to_string(TransformFunction)` to convert a `TransformFunction` back to a string
 - `TransformFunctionMetadata transform_function_metadata(TransformFunction)` to obtain metadata about the transform function, such as its parameter list
+
+## EnvironmentVariables.json
+
+This is a single JSON object, describing each [CSS environment variable](https://drafts.csswg.org/css-env/#css-environment-variable),
+with the keys being the environment variable names, and the values being objects describing the variable's properties.
+This generates `EnvironmentVariable.h` and `EnvironmentVariable.cpp`.
+
+Each entry has 3 properties, all taken from the 
+
+| Field        | Description                                                         |
+|--------------|---------------------------------------------------------------------|
+| `spec`       | String. URL to the spec definition for this environment variable.   |
+| `type`       | String. CSS value type of the variable, eg `<length>`.              |
+| `dimensions` | Integer. Number of dimensions for the variable, or `0` for scalars. |
+
+The generated code provides:
+- An `EnvironmentVariable` enum listing the environment variables
+- `Optional<EnvironmentVariable> environment_variable_from_string(StringView)` to parse a string as an `EnvironmentVariable`
+- `StringView to_string(EnvironmentVariable)` to convert the `EnvironmentVariable` back to a string
+- `ValueType environment_variable_type(EnvironmentVariable)` to get the variable's value type
+- `u32 environment_variable_dimension_count(EnvironmentVariable)` to get its dimension count

Libraries/LibWeb/CMakeLists.txt

@@ -1021,6 +1021,7 @@ set(GENERATED_SOURCES
     CSS/DefaultStyleSheetSource.cpp
     CSS/DescriptorID.cpp
     CSS/Enums.cpp
+    CSS/EnvironmentVariable.cpp
     CSS/GeneratedCSSStyleProperties.cpp
     CSS/GeneratedCSSStyleProperties.idl
     CSS/Keyword.cpp

Libraries/LibWeb/CSS/EnvironmentVariables.json

@@ -0,0 +1,77 @@
+{
+  "preferred-text-scale": {
+    "spec": "https://drafts.csswg.org/css-env/#valdef-env-preferred-text-scale",
+    "type": "<number>",
+    "dimensions": 0
+  },
+  "safe-area-inset-bottom": {
+    "spec": "https://drafts.csswg.org/css-env/#valdef-env-safe-area-inset-bottom",
+    "type": "<length>",
+    "dimensions": 0
+  },
+  "safe-area-inset-left": {
+    "spec": "https://drafts.csswg.org/css-env/#valdef-env-safe-area-inset-left",
+    "type": "<length>",
+    "dimensions": 0
+  },
+  "safe-area-inset-right": {
+    "spec": "https://drafts.csswg.org/css-env/#valdef-env-safe-area-inset-right",
+    "type": "<length>",
+    "dimensions": 0
+  },
+  "safe-area-inset-top": {
+    "spec": "https://drafts.csswg.org/css-env/#valdef-env-safe-area-inset-top",
+    "type": "<length>",
+    "dimensions": 0
+  },
+  "safe-area-max-inset-bottom": {
+    "spec": "https://drafts.csswg.org/css-env/#valdef-env-safe-area-max-inset-bottom",
+    "type": "<length>",
+    "dimensions": 0
+  },
+  "safe-area-max-inset-left": {
+    "spec": "https://drafts.csswg.org/css-env/#valdef-env-safe-area-max-inset-left",
+    "type": "<length>",
+    "dimensions": 0
+  },
+  "safe-area-max-inset-right": {
+    "spec": "https://drafts.csswg.org/css-env/#valdef-env-safe-area-max-inset-right",
+    "type": "<length>",
+    "dimensions": 0
+  },
+  "safe-area-max-inset-top": {
+    "spec": "https://drafts.csswg.org/css-env/#valdef-env-safe-area-max-inset-top",
+    "type": "<length>",
+    "dimensions": 0
+  },
+  "viewport-segment-bottom": {
+    "spec": "https://drafts.csswg.org/css-env/#valdef-env-viewport-segment-bottom",
+    "type": "<length>",
+    "dimensions": 2
+  },
+  "viewport-segment-height": {
+    "spec": "https://drafts.csswg.org/css-env/#valdef-env-viewport-segment-height",
+    "type": "<length>",
+    "dimensions": 2
+  },
+  "viewport-segment-left": {
+    "spec": "https://drafts.csswg.org/css-env/#valdef-env-viewport-segment-left",
+    "type": "<length>",
+    "dimensions": 2
+  },
+  "viewport-segment-right": {
+    "spec": "https://drafts.csswg.org/css-env/#valdef-env-viewport-segment-right",
+    "type": "<length>",
+    "dimensions": 2
+  },
+  "viewport-segment-top": {
+    "spec": "https://drafts.csswg.org/css-env/#valdef-env-viewport-segment-top",
+    "type": "<length>",
+    "dimensions": 2
+  },
+  "viewport-segment-width": {
+    "spec": "https://drafts.csswg.org/css-env/#valdef-env-viewport-segment-width",
+    "type": "<length>",
+    "dimensions": 2
+  }
+}

Meta/CMake/libweb_generators.cmake

@@ -20,6 +20,15 @@ function (generate_css_implementation)
         arguments -j "${LIBWEB_INPUT_FOLDER}/CSS/Enums.json"
     )
 
+    invoke_cpp_generator(
+        "EnvironmentVariable.cpp"
+        Lagom::GenerateCSSEnvironmentVariable
+        "${LIBWEB_INPUT_FOLDER}/CSS/EnvironmentVariables.json"
+        "CSS/EnvironmentVariable.h"
+        "CSS/EnvironmentVariable.cpp"
+        arguments -j "${LIBWEB_INPUT_FOLDER}/CSS/EnvironmentVariables.json"
+    )
+
     invoke_cpp_generator(
         "MathFunctions.cpp"
         Lagom::GenerateCSSMathFunctions
@@ -131,6 +140,7 @@ function (generate_css_implementation)
 
     set(CSS_GENERATED_HEADERS
        "CSS/Enums.h"
+       "CSS/EnvironmentVariable.h"
        "CSS/GeneratedCSSStyleProperties.h"
        "CSS/Keyword.h"
        "CSS/MathFunctions.h"

Meta/Lagom/Tools/CodeGenerators/LibWeb/CMakeLists.txt

@@ -2,6 +2,7 @@ set(SOURCES "") # avoid pulling SOURCES from parent scope
 
 lagom_tool(GenerateCSSDescriptors           SOURCES GenerateCSSDescriptors.cpp LIBS LibMain)
 lagom_tool(GenerateCSSEnums                 SOURCES GenerateCSSEnums.cpp LIBS LibMain)
+lagom_tool(GenerateCSSEnvironmentVariable   SOURCES GenerateCSSEnvironmentVariable.cpp LIBS LibMain)
 lagom_tool(GenerateCSSKeyword               SOURCES GenerateCSSKeyword.cpp LIBS LibMain)
 lagom_tool(GenerateCSSMathFunctions         SOURCES GenerateCSSMathFunctions.cpp LIBS LibMain)
 lagom_tool(GenerateCSSMediaFeatureID        SOURCES GenerateCSSMediaFeatureID.cpp LIBS LibMain)

Meta/Lagom/Tools/CodeGenerators/LibWeb/GenerateCSSEnvironmentVariable.cpp

@@ -0,0 +1,197 @@
+/*
+ * Copyright (c) 2025, Sam Atkins <sam@ladybird.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include "GeneratorUtil.h"
+#include <AK/SourceGenerator.h>
+#include <LibCore/ArgsParser.h>
+#include <LibMain/Main.h>
+
+ErrorOr<void> generate_header_file(JsonObject const& environment_variables, Core::File& file);
+ErrorOr<void> generate_implementation_file(JsonObject const& environment_variables, Core::File& file);
+
+ErrorOr<int> ladybird_main(Main::Arguments arguments)
+{
+    StringView generated_header_path;
+    StringView generated_implementation_path;
+    StringView json_path;
+
+    Core::ArgsParser args_parser;
+    args_parser.add_option(generated_header_path, "Path to the EnvironmentVariable header file to generate", "generated-header-path", 'h', "generated-header-path");
+    args_parser.add_option(generated_implementation_path, "Path to the EnvironmentVariable implementation file to generate", "generated-implementation-path", 'c', "generated-implementation-path");
+    args_parser.add_option(json_path, "Path to the JSON file to read from", "json-path", 'j', "json-path");
+    args_parser.parse(arguments);
+
+    auto read_json_object = [](auto& path) -> ErrorOr<JsonObject> {
+        auto json = TRY(read_entire_file_as_json(path));
+        VERIFY(json.is_object());
+
+        // Check we're in alphabetical order
+        String most_recent_name;
+        json.as_object().for_each_member([&](auto& name, auto&) {
+            if (name < most_recent_name) {
+                warnln("`{}` is in the wrong position in `{}`. Please keep this list alphabetical!", name, path);
+                VERIFY_NOT_REACHED();
+            }
+            most_recent_name = name;
+        });
+
+        return json.as_object();
+    };
+
+    auto environment_variables = TRY(read_json_object(json_path));
+
+    auto generated_header_file = TRY(Core::File::open(generated_header_path, Core::File::OpenMode::Write));
+    auto generated_implementation_file = TRY(Core::File::open(generated_implementation_path, Core::File::OpenMode::Write));
+
+    TRY(generate_header_file(environment_variables, *generated_header_file));
+    TRY(generate_implementation_file(environment_variables, *generated_implementation_file));
+
+    return 0;
+}
+
+ErrorOr<void> generate_header_file(JsonObject const& environment_variables, Core::File& file)
+{
+    StringBuilder builder;
+    SourceGenerator generator { builder };
+
+    generator.set("environment_variable_underlying_type", underlying_type_for_enum(environment_variables.size()));
+
+    generator.append(R"~~~(
+#pragma once
+
+#include <AK/Optional.h>
+#include <AK/StringView.h>
+#include <LibWeb/CSS/ValueType.h>
+
+namespace Web::CSS {
+
+enum class EnvironmentVariable : @environment_variable_underlying_type@ {
+)~~~");
+
+    environment_variables.for_each_member([&](auto& name, JsonValue const&) {
+        auto member_generator = generator.fork();
+        member_generator.set("name:titlecase", title_casify(name));
+        member_generator.appendln("    @name:titlecase@,");
+    });
+    generator.append(R"~~~(
+};
+
+Optional<EnvironmentVariable> environment_variable_from_string(StringView);
+StringView to_string(EnvironmentVariable);
+
+ValueType environment_variable_type(EnvironmentVariable);
+u32 environment_variable_dimension_count(EnvironmentVariable);
+}
+)~~~");
+
+    TRY(file.write_until_depleted(generator.as_string_view().bytes()));
+    return {};
+}
+
+ErrorOr<void> generate_implementation_file(JsonObject const& environment_variables, Core::File& file)
+{
+    StringBuilder builder;
+    SourceGenerator generator { builder };
+
+    generator.append(R"~~~(
+#include <LibWeb/CSS/EnvironmentVariable.h>
+
+namespace Web::CSS {
+
+Optional<EnvironmentVariable> environment_variable_from_string(StringView string)
+{
+)~~~");
+    environment_variables.for_each_member([&](auto& name, JsonValue const&) {
+        auto member_generator = generator.fork();
+        member_generator.set("name", name);
+        member_generator.set("name:titlecase", title_casify(name));
+
+        member_generator.append(R"~~~(
+    if (string.equals_ignoring_ascii_case("@name@"sv))
+        return EnvironmentVariable::@name:titlecase@;
+)~~~");
+    });
+
+    generator.append(R"~~~(
+
+    return {};
+}
+
+StringView to_string(EnvironmentVariable environment_variable)
+{
+    switch (environment_variable) {
+)~~~");
+
+    environment_variables.for_each_member([&](auto& name, JsonValue const&) {
+        auto member_generator = generator.fork();
+        member_generator.set("name", name);
+        member_generator.set("name:titlecase", title_casify(name));
+
+        member_generator.append(R"~~~(
+    case EnvironmentVariable::@name:titlecase@:
+        return "@name@"sv;
+)~~~");
+    });
+
+    generator.append(R"~~~(
+    }
+    VERIFY_NOT_REACHED();
+}
+
+ValueType environment_variable_type(EnvironmentVariable environment_variable)
+{
+    switch (environment_variable) {
+)~~~");
+
+    environment_variables.for_each_member([&](auto& name, JsonValue const& value) {
+        auto& variable = value.as_object();
+        auto member_generator = generator.fork();
+        member_generator.set("name", name);
+        member_generator.set("name:titlecase", title_casify(name));
+
+        auto value_type = MUST(variable.get_string("type"sv)->trim("<>"sv));
+        member_generator.set("value_type:titlecase", title_casify(value_type));
+
+        member_generator.append(R"~~~(
+    case EnvironmentVariable::@name:titlecase@:
+        return ValueType::@value_type:titlecase@;
+)~~~");
+    });
+
+    generator.append(R"~~~(
+    }
+    VERIFY_NOT_REACHED();
+}
+
+u32 environment_variable_dimension_count(EnvironmentVariable environment_variable)
+{
+    switch (environment_variable) {
+)~~~");
+
+    environment_variables.for_each_member([&](auto& name, JsonValue const& value) {
+        auto& variable = value.as_object();
+        auto member_generator = generator.fork();
+        member_generator.set("name", name);
+        member_generator.set("name:titlecase", title_casify(name));
+        member_generator.set("dimension_count", String::number(variable.get_u32("dimensions"sv).value()));
+
+        member_generator.append(R"~~~(
+    case EnvironmentVariable::@name:titlecase@:
+        return @dimension_count@;
+)~~~");
+    });
+
+    generator.append(R"~~~(
+    }
+    VERIFY_NOT_REACHED();
+}
+
+}
+)~~~");
+
+    TRY(file.write_until_depleted(generator.as_string_view().bytes()));
+    return {};
+}