Route debug() calls in Slint consistently through Platform's debug_log() (#5718)

api/cpp/include/slint.h

@@ -124,6 +124,11 @@ upgrade_item_weak(const cbindgen_private::ItemWeak &item_weak)
     }
 }
 
+inline void debug(const SharedString &str)
+{
+    cbindgen_private::slint_debug(&str);
+}
+
 } // namespace private_api
 
 template<typename T>

api/cpp/lib.rs

@@ -152,6 +152,11 @@ pub extern "C" fn slint_string_to_float(string: &SharedString, value: &mut f32)
     }
 }
 
+#[no_mangle]
+pub extern "C" fn slint_debug(string: &SharedString) {
+    i_slint_core::debug_log!("{string}");
+}
+
 #[cfg(not(feature = "std"))]
 mod allocator {
     use core::alloc::Layout;

api/rs/slint/private_unstable_api.rs

@@ -127,12 +127,7 @@ pub fn debug(s: SharedString) {
     #[cfg(feature = "log")]
     log::debug!("{s}");
     #[cfg(not(feature = "log"))]
-    {
+    i_slint_core::debug_log!("{s}");
-        #[cfg(all(feature = "std", not(target_arch = "wasm32")))]
-        println!("{s}");
-        #[cfg(any(not(feature = "std"), target_arch = "wasm32"))]
-        i_slint_core::debug_log!("{s}");
-    }
 }
 
 pub fn ensure_backend() -> Result<(), crate::PlatformError> {

internal/compiler/generator/cpp.rs

@@ -3128,7 +3128,7 @@ fn compile_builtin_function_call(
         BuiltinFunction::AnimationTick => "slint::cbindgen_private::slint_animation_tick()".into(),
         BuiltinFunction::Debug => {
             ctx.generator_state.conditional_includes.iostream.set(true);
-            format!("std::cout << {} << std::endl;", a.join("<<"))
+            format!("slint::private_api::debug({});", a.join(","))
         }
         BuiltinFunction::Mod => {
             ctx.generator_state.conditional_includes.cmath.set(true);