qt-build-utils: add QmlPluginCppBuilder for the extension plugin

Author: ahayzen-kdab

crates/qt-build-utils/src/builder/mod.rs

@@ -6,6 +6,9 @@
 mod qmldir;
 pub use qmldir::QmlDirBuilder;
 
+mod qmlplugincpp;
+pub use qmlplugincpp::QmlPluginCppBuilder;
+
 mod qmluri;
 pub use qmluri::QmlUriBuilder;
 

crates/qt-build-utils/src/builder/qmlplugincpp.rs

@@ -0,0 +1,84 @@
+// SPDX-FileCopyrightText: 2025 Klarälvdalens Datakonsult AB, a KDAB Group company <[email protected]>
+// SPDX-FileContributor: Andrew Hayzen <[email protected]>
+//
+// SPDX-License-Identifier: MIT OR Apache-2.0
+
+use crate::QmlUriBuilder;
+
+/// A builder for representing a QML Extension Plugin C++ code
+pub struct QmlPluginCppBuilder {
+    plugin_class_name: String,
+    qml_cache: bool,
+    uri: QmlUriBuilder,
+}
+
+impl QmlPluginCppBuilder {
+    /// Construct a [QmlPluginCppBuilder] from a uri and plugin class name
+    pub fn new(uri: QmlUriBuilder, plugin_class_name: String) -> Self {
+        Self {
+            plugin_class_name,
+            qml_cache: false,
+            uri,
+        }
+    }
+
+    /// Whether to enable qmlcache methods
+    pub fn with_qml_cache(mut self, enabled: bool) -> Self {
+        self.qml_cache = enabled;
+        self
+    }
+
+    /// Build the resultant QML extension plugin C++ contents
+    pub fn build(self) -> String {
+        let plugin_class_name = self.plugin_class_name;
+        let qml_uri_underscores = self.uri.as_underscores();
+
+        let mut declarations = Vec::default();
+        let mut usages = Vec::default();
+
+        let mut generate_usage = |return_type: &str, function_name: &str| {
+            declarations.push(format!("extern {return_type} {function_name}();"));
+            usages.push(format!("volatile auto {function_name}_usage = &{function_name};\nQ_UNUSED({function_name}_usage);"));
+        };
+
+        // This function is generated by qmltyperegistrar
+        generate_usage("void", &format!("qml_register_types_{qml_uri_underscores}"));
+        generate_usage(
+            "int",
+            &format!("qInitResources_qml_module_resources_{qml_uri_underscores}_qrc"),
+        );
+
+        if self.qml_cache {
+            generate_usage(
+                "int",
+                &format!("qInitResources_qmlcache_{qml_uri_underscores}"),
+            );
+        }
+        let declarations = declarations.join("\n");
+        let usages = usages.join("\n");
+        format!(
+            r#"
+#include <QtQml/qqmlextensionplugin.h>
+
+// TODO: Add missing handling for GHS (Green Hills Software compiler) that is in
+// https://code.qt.io/cgit/qt/qtbase.git/plain/src/corelib/global/qtsymbolmacros.h
+{declarations}
+
+class {plugin_class_name} : public QQmlEngineExtensionPlugin
+{{
+    Q_OBJECT
+    Q_PLUGIN_METADATA(IID "org.qt-project.Qt.QQmlEngineExtensionInterface")
+
+public:
+    {plugin_class_name}(QObject *parent = nullptr) : QQmlEngineExtensionPlugin(parent)
+    {{
+        {usages}
+    }}
+}};
+
+// The moc-generated cpp file doesn't compile on its own; it needs to be #included here.
+#include "moc_{plugin_class_name}.cpp.cpp"
+"#
+        )
+    }
+}

crates/qt-build-utils/src/builder/qmluri.rs

@@ -4,6 +4,7 @@
 // SPDX-License-Identifier: MIT OR Apache-2.0
 
 /// A builder for representing a QML uri
+#[derive(Clone)]
 pub struct QmlUriBuilder {
     uri: Vec<String>,
 }

crates/qt-build-utils/src/lib.rs

@@ -16,7 +16,9 @@
 #![allow(clippy::too_many_arguments)]
 
 mod builder;
-pub use builder::{QResource, QResourceBuilder, QResourceFile, QmlDirBuilder, QmlUriBuilder};
+pub use builder::{
+    QResource, QResourceBuilder, QResourceFile, QmlDirBuilder, QmlPluginCppBuilder, QmlUriBuilder,
+};
 
 mod error;
 pub use error::QtBuildError;
@@ -172,7 +174,7 @@ impl QtBuild {
         // Generate qmldir file
         let qmldir_file_path = qml_module_dir.join("qmldir");
         {
-            let qmldir = QmlDirBuilder::new(qml_uri)
+            let qmldir = QmlDirBuilder::new(qml_uri.clone())
                 .with_plugin(plugin_name.to_string(), true)
                 .with_class_name(plugin_class_name.clone())
                 .with_type_info(plugin_type_info.to_string())
@@ -272,58 +274,11 @@ impl QtBuild {
         let qml_plugin_cpp_path = qml_plugin_dir.join(format!("{plugin_class_name}.cpp"));
         let include_path;
         {
-            let mut declarations = Vec::default();
-            let mut usages = Vec::default();
-
-            let mut generate_usage = |return_type: &str, function_name: &str| {
-                declarations.push(format!("extern {return_type} {function_name}();"));
-                usages.push(format!("volatile auto {function_name}_usage = &{function_name};\nQ_UNUSED({function_name}_usage);"));
-            };
-
-            // This function is generated by qmltyperegistrar
-            generate_usage("void", &format!("qml_register_types_{qml_uri_underscores}"));
-            generate_usage(
-                "int",
-                &format!("qInitResources_qml_module_resources_{qml_uri_underscores}_qrc"),
-            );
-
-            if !qml_files.is_empty() && !qmlcachegen_file_paths.is_empty() {
-                generate_usage(
-                    "int",
-                    &format!("qInitResources_qmlcache_{qml_uri_underscores}"),
-                );
-            }
-            let declarations = declarations.join("\n");
-            let usages = usages.join("\n");
-
-            std::fs::write(
-                &qml_plugin_cpp_path,
-                format!(
-                    r#"
-#include <QtQml/qqmlextensionplugin.h>
-
-// TODO: Add missing handling for GHS (Green Hills Software compiler) that is in
-// https://code.qt.io/cgit/qt/qtbase.git/plain/src/corelib/global/qtsymbolmacros.h
-{declarations}
-
-class {plugin_class_name} : public QQmlEngineExtensionPlugin
-{{
-    Q_OBJECT
-    Q_PLUGIN_METADATA(IID "org.qt-project.Qt.QQmlEngineExtensionInterface")
-
-public:
-    {plugin_class_name}(QObject *parent = nullptr) : QQmlEngineExtensionPlugin(parent)
-    {{
-        {usages}
-    }}
-}};
-
-// The moc-generated cpp file doesn't compile on its own; it needs to be #included here.
-#include "moc_{plugin_class_name}.cpp.cpp"
-"#,
-                ),
-            )
-            .expect("Failed to write plugin definition");
+            let qml_plugin_cpp = QmlPluginCppBuilder::new(qml_uri, plugin_class_name.clone())
+                .with_qml_cache(!qml_files.is_empty() && !qmlcachegen_file_paths.is_empty())
+                .build();
+            std::fs::write(&qml_plugin_cpp_path, qml_plugin_cpp)
+                .expect("Failed to write plugin definition");
 
             let moc_product = self.moc().compile(
                 &qml_plugin_cpp_path,