gtk4-macros: Stop appending using Gtk for blueprint

As that breaks language servers

Author: bilelmoussaoui

CHANGELOG.md

@@ -93,6 +93,7 @@ yuraiz:
 ```rust
 #[derive(Debug, Default, gtk::CompositeTemplate)]
 #[template(string = "
+using Gtk 4.0;
 template $MyWidget : Widget {
     Label label {
         label: 'foobar';

gtk4-macros/src/blueprint.rs

@@ -1,7 +1,7 @@
 // Take a look at the license at the top of the repository in the LICENSE file.
 
 use std::{
-    io::{Error, ErrorKind, Read, Result, Write},
+    io::{Error, ErrorKind, Result, Write},
     process::{Command, Stdio},
 };
 
@@ -12,14 +12,15 @@ pub(crate) fn compile_blueprint(blueprint: &[u8]) -> Result<String> {
         .stdout(Stdio::piped())
         .spawn()
         .unwrap_or_else(|_| panic!("blueprint-compiler not found"));
-
     let mut stdin = compiler.stdin.take().unwrap();
-    stdin.write_all(b"using Gtk 4.0;\n")?;
     stdin.write_all(blueprint)?;
     drop(stdin);
 
-    let mut buf = String::new();
-    compiler.stdout.unwrap().read_to_string(&mut buf)?;
+    let output = compiler
+        .wait_with_output()
+        .unwrap_or_else(|e| panic!("blueprint-compiler process failed {e}"));
+
+    let buf = String::from_utf8(output.stdout).unwrap();
 
     if !buf.starts_with('<') {
         return Err(Error::new(ErrorKind::Other, buf));

gtk4-macros/src/lib.rs

@@ -158,6 +158,7 @@ pub fn include_blueprint(input: TokenStream) -> TokenStream {
 ///
 ///     #[derive(Debug, Default, gtk::CompositeTemplate)]
 ///     #[template(string = "
+///     using Gtk 4.0;
 ///     template $MyWidget : Widget {
 ///         Label label {
 ///             label: 'foobar';

gtk4-macros/tests/my_widget.blp

@@ -1,3 +1,4 @@
+using Gtk 4.0;
 template $MyWidget5 {
     Label label {
         label: 'foobar';

gtk4-macros/tests/templates.rs

@@ -212,6 +212,7 @@ mod imp4 {
 
     #[derive(Debug, Default, gtk::CompositeTemplate)]
     #[template(string = "
+    using Gtk 4.0;
     template $MyWidget4 : Widget {
         Label label {
             label: 'foobar';