On X11, fix IME crashing without available styles

Fixes rust-windowing#2510.

CHANGELOG.md

@@ -23,6 +23,7 @@ And please only add new entries to the top of this list, right below the `# Unre
 - On Wayland, `wayland-csd-adwaita` now uses `ab_glyph` instead of `crossfont` to render the title for decorations.
 - On Wayland, a new `wayland-csd-adwaita-crossfont` feature was added to use `crossfont` instead of `ab_glyph` for decorations.
 - On Wayland, if not otherwise specified use upstream automatic CSD theme selection.
+- On X11, fix XIM not picking IME when no styles advertised.
 
 # 0.27.3
 

src/platform_impl/linux/x11/ime/input_method.rs

@@ -40,26 +40,36 @@ unsafe fn open_im(xconn: &Arc<XConnection>, locale_modifiers: &CStr) -> Option<f
 #[derive(Debug)]
 pub struct InputMethod {
     pub im: ffi::XIM,
-    pub preedit_style: Style,
-    pub none_style: Style,
     _name: String,
 }
 
+#[derive(Debug, Default)]
+pub struct InputMethodStyles {
+    pub preedit_style: Option<Style>,
+    pub none_style: Option<Style>,
+}
+
 impl InputMethod {
-    fn new(xconn: &Arc<XConnection>, im: ffi::XIM, name: String) -> Option<Self> {
+    fn new(im: ffi::XIM, name: String) -> Self {
+        Self { im, _name: name }
+    }
+
+    // XXX checking this during creation is not desired, since we don't want to filter
+    // ime based on styles since IME could be reloading, etc, so we ask for that when needed.
+    pub(crate) fn query_styles(&self, xconn: &Arc<XConnection>) -> InputMethodStyles {
         let mut styles: *mut XIMStyles = std::ptr::null_mut();
 
         // Query the styles supported by the XIM.
         unsafe {
             if !(xconn.xlib.XGetIMValues)(
-                im,
+                self.im,
                 ffi::XNQueryInputStyle_0.as_ptr() as *const _,
                 (&mut styles) as *mut _,
                 std::ptr::null_mut::<()>(),
             )
             .is_null()
             {
-                return None;
+                return InputMethodStyles::default();
             }
         }
 
@@ -83,19 +93,10 @@ impl InputMethod {
             (xconn.xlib.XFree)(styles.cast());
         };
 
-        if preedit_style.is_none() && none_style.is_none() {
-            return None;
-        }
-
-        let preedit_style = preedit_style.unwrap_or_else(|| none_style.unwrap());
-        let none_style = none_style.unwrap_or(preedit_style);
-
-        Some(InputMethod {
-            im,
-            _name: name,
+        InputMethodStyles {
             preedit_style,
             none_style,
-        })
+        }
     }
 }
 
@@ -256,7 +257,7 @@ impl PotentialInputMethod {
     pub fn open_im(&mut self, xconn: &Arc<XConnection>) -> Option<InputMethod> {
         let im = unsafe { open_im(xconn, &self.name.c_string) };
         self.successful = Some(im.is_some());
-        im.and_then(|im| InputMethod::new(xconn, im, self.name.string.clone()))
+        im.map(|im| InputMethod::new(im, self.name.string.clone()))
     }
 }
 

src/platform_impl/linux/x11/ime/mod.rs

@@ -122,11 +122,13 @@ impl Ime {
             None
         } else {
             let im = self.inner.im.as_ref().unwrap();
+            let styles = im.query_styles(&self.inner.xconn);
             let style = if with_preedit {
-                im.preedit_style
+                styles.preedit_style.or(styles.none_style)
             } else {
-                im.none_style
-            };
+                styles.none_style.or(styles.preedit_style)
+            }
+            .unwrap_or_default();
 
             let context = unsafe {
                 ImeContext::new(