[librsvg: 3/8] c_api.rs: Check the incoming cairo context here to emit a g_warning()

[Federico Mena Quintero <federico src gnome org>]

commit c2811e084be3adcd606e8ebcf161d1f6bae7f1eb
Author: Federico Mena Quintero <federico gnome org>
Date:   Mon Aug 26 12:15:42 2019 +0300

    c_api.rs: Check the incoming cairo context here to emit a g_warning()
    
    We want to emit a g_warning only from the C API code, not from the
    internals Rust code.
    
    The internals Rust code needs to check the Cairo context as well, in
    case it is called form the librsvg_crate, but not emit a g_warning in
    that case.

 rsvg_internals/src/c_api.rs  | 23 +++++++++++++++++++++++
 rsvg_internals/src/handle.rs |  6 ------
 2 files changed, 23 insertions(+), 6 deletions(-)
---
diff --git a/rsvg_internals/src/c_api.rs b/rsvg_internals/src/c_api.rs
index f8d2477c..5d1c3f7a 100644
--- a/rsvg_internals/src/c_api.rs
+++ b/rsvg_internals/src/c_api.rs
@@ -685,6 +685,8 @@ impl CHandle {
         cr: &cairo::Context,
         id: Option<&str>,
     ) -> Result<(), RenderingError> {
+        check_cairo_context(cr)?;
+
         let handle = self.get_handle_ref()?;
         let size_callback = self.size_callback.borrow();
         handle.render_cairo_sub(
@@ -707,6 +709,8 @@ impl CHandle {
         cr: &cairo::Context,
         viewport: &cairo::Rectangle,
     ) -> Result<(), RenderingError> {
+        check_cairo_context(cr)?;
+
         let handle = self.get_handle_ref()?;
         handle.render_document(cr, viewport, self.dpi.get(), self.is_testing.get())
     }
@@ -726,6 +730,8 @@ impl CHandle {
         id: Option<&str>,
         viewport: &cairo::Rectangle,
     ) -> Result<(), RenderingError> {
+        check_cairo_context(cr)?;
+
         let handle = self.get_handle_ref()?;
         handle.render_layer(cr, id, viewport, self.dpi.get(), self.is_testing.get())
     }
@@ -744,6 +750,8 @@ impl CHandle {
         id: Option<&str>,
         element_viewport: &cairo::Rectangle,
     ) -> Result<(), RenderingError> {
+        check_cairo_context(cr)?;
+
         let handle = self.get_handle_ref()?;
         handle.render_element(cr, id, element_viewport, self.dpi.get(), self.is_testing.get())
     }
@@ -1450,6 +1458,21 @@ impl PathOrUrl {
     }
 }
 
+fn check_cairo_context(cr: &cairo::Context) -> Result<(), RenderingError> {
+    let status = cr.status();
+    if status == Status::Success {
+        Ok(())
+    } else {
+        let msg = format!(
+            "cannot render on a cairo_t with a failure status (status={:?})",
+            status,
+        );
+
+        rsvg_g_warning(&msg);
+        Err(RenderingError::Cairo(status))
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/rsvg_internals/src/handle.rs b/rsvg_internals/src/handle.rs
index 270b266e..73b227db 100644
--- a/rsvg_internals/src/handle.rs
+++ b/rsvg_internals/src/handle.rs
@@ -511,12 +511,6 @@ fn check_cairo_context(cr: &cairo::Context) -> Result<(), RenderingError> {
     if status == Status::Success {
         Ok(())
     } else {
-        let msg = format!(
-            "cannot render on a cairo_t with a failure status (status={:?})",
-            status,
-        );
-
-        rsvg_g_warning(&msg);
         Err(RenderingError::Cairo(status))
     }
 }