[Linux] Test text input (flutter#34186)

This PR finishes what flutter#33661 and flutter#33111 started - most of `FlTextInputPlugin` is now covered by tests.

shell/platform/linux/BUILD.gn

@@ -226,6 +226,7 @@ executable("flutter_linux_unittests") {
     "testing/mock_binary_messenger_response_handle.cc",
     "testing/mock_engine.cc",
     "testing/mock_epoxy.cc",
+    "testing/mock_im_context.cc",
     "testing/mock_plugin_registrar.cc",
     "testing/mock_renderer.cc",
     "testing/mock_settings.cc",

shell/platform/linux/fl_text_input_plugin.cc

@@ -80,14 +80,8 @@ struct FlTextInputPluginPrivate {
   // Input method.
   GtkIMContext* im_context;
 
-  // IM filter.
-  FlTextInputPluginImFilter im_filter;
-
   flutter::TextInputModel* text_model;
 
-  // The owning native window.
-  GdkWindow* window;
-
   // A 4x4 matrix that maps from `EditableText` local coordinates to the
   // coordinate system of `PipelineOwner.rootNode`.
   double editabletext_transform[4][4];
@@ -216,8 +210,8 @@ static void update_editing_state_with_delta(FlTextInputPlugin* self,
 
   g_autoptr(FlValue) deltas = fl_value_new_list();
   fl_value_append(deltas, deltaValue);
-  FlValue* value = fl_value_new_map();
-  fl_value_set_string_take(value, "deltas", deltas);
+  g_autoptr(FlValue) value = fl_value_new_map();
+  fl_value_set_string(value, "deltas", deltas);
 
   fl_value_append(args, value);
 
@@ -258,9 +252,6 @@ static void im_preedit_start_cb(FlTextInputPlugin* self) {
   FlTextInputPluginPrivate* priv = static_cast<FlTextInputPluginPrivate*>(
       fl_text_input_plugin_get_instance_private(self));
   priv->text_model->BeginComposing();
-
-  // Set the native window used for system input method windows.
-  gtk_im_context_set_client_window(priv->im_context, priv->window);
 }
 
 // Signal handler for GtkIMContext::preedit-changed
@@ -418,9 +409,6 @@ static FlMethodResponse* show(FlTextInputPlugin* self) {
     return hide(self);
   }
 
-  // Set the native window used for system input method windows.
-  gtk_im_context_set_client_window(priv->im_context, priv->window);
-
   gtk_im_context_focus_in(priv->im_context);
 
   return FL_METHOD_RESPONSE(fl_method_success_response_new(nullptr));
@@ -599,7 +587,6 @@ static void fl_text_input_plugin_dispose(GObject* object) {
     delete priv->text_model;
     priv->text_model = nullptr;
   }
-  priv->window = nullptr;
 
   G_OBJECT_CLASS(fl_text_input_plugin_parent_class)->dispose(object);
 }
@@ -617,7 +604,8 @@ static gboolean fl_text_input_plugin_filter_keypress_default(
     return FALSE;
   }
 
-  if (priv->im_filter(priv->im_context, event->origin)) {
+  GdkEventKey* key_event = reinterpret_cast<GdkEventKey*>(event->origin);
+  if (gtk_im_context_filter_keypress(priv->im_context, key_event)) {
     return TRUE;
   }
 
@@ -698,12 +686,20 @@ static void fl_text_input_plugin_init(FlTextInputPlugin* self) {
       fl_text_input_plugin_get_instance_private(self));
 
   priv->client_id = kClientIdUnset;
-  priv->im_context = gtk_im_multicontext_new();
+  priv->input_type = FL_TEXT_INPUT_TYPE_TEXT;
+  priv->text_model = new flutter::TextInputModel();
+}
+
+static void init_im_context(FlTextInputPlugin* self, GtkIMContext* im_context) {
+  FlTextInputPluginPrivate* priv = static_cast<FlTextInputPluginPrivate*>(
+      fl_text_input_plugin_get_instance_private(self));
+  priv->im_context = GTK_IM_CONTEXT(g_object_ref(im_context));
+
   // On Wayland, this call sets up the input method so it can be enabled
   // immediately when required. Without it, on-screen keyboard's don't come up
   // the first time a text field is focused.
   gtk_im_context_focus_out(priv->im_context);
-  priv->input_type = FL_TEXT_INPUT_TYPE_TEXT;
+
   g_signal_connect_object(priv->im_context, "preedit-start",
                           G_CALLBACK(im_preedit_start_cb), self,
                           G_CONNECT_SWAPPED);
@@ -721,15 +717,12 @@ static void fl_text_input_plugin_init(FlTextInputPlugin* self) {
   g_signal_connect_object(priv->im_context, "delete-surrounding",
                           G_CALLBACK(im_delete_surrounding_cb), self,
                           G_CONNECT_SWAPPED);
-  priv->text_model = new flutter::TextInputModel();
 }
 
-FlTextInputPlugin* fl_text_input_plugin_new(
-    FlBinaryMessenger* messenger,
-    GdkWindow* window,
-    FlTextInputPluginImFilter im_filter) {
+FlTextInputPlugin* fl_text_input_plugin_new(FlBinaryMessenger* messenger,
+                                            GtkIMContext* im_context) {
   g_return_val_if_fail(FL_IS_BINARY_MESSENGER(messenger), nullptr);
-  g_return_val_if_fail(im_filter != nullptr, nullptr);
+  g_return_val_if_fail(GTK_IS_IM_CONTEXT(im_context), nullptr);
 
   FlTextInputPlugin* self = FL_TEXT_INPUT_PLUGIN(
       g_object_new(fl_text_input_plugin_get_type(), nullptr));
@@ -741,8 +734,8 @@ FlTextInputPlugin* fl_text_input_plugin_new(
       fl_method_channel_new(messenger, kChannelName, FL_METHOD_CODEC(codec));
   fl_method_channel_set_method_call_handler(priv->channel, method_call_cb, self,
                                             nullptr);
-  priv->window = window;
-  priv->im_filter = im_filter;
+
+  init_im_context(self, im_context);
 
   return self;
 }

shell/platform/linux/fl_text_input_plugin.h

@@ -10,19 +10,6 @@
 #include "flutter/shell/platform/linux/fl_key_event.h"
 #include "flutter/shell/platform/linux/public/flutter_linux/fl_binary_messenger.h"
 
-/**
- * FlTextInputPluginImFilter:
- * @event: the pointer to the GdkEventKey.
- *
- * The signature for a callback with which a #FlTextInputPlugin allow an input
- * method to internally handle key press and release events.
- *
- * The #gdk_event is an opaque pointer. It will be GdkEvent* in actual
- * applications, or a dummy pointer in unit tests.
- **/
-typedef gboolean (*FlTextInputPluginImFilter)(GtkIMContext* im_context,
-                                              gpointer gdk_event);
-
 G_BEGIN_DECLS
 
 G_DECLARE_DERIVABLE_TYPE(FlTextInputPlugin,
@@ -50,20 +37,15 @@ struct _FlTextInputPluginClass {
 /**
  * fl_text_input_plugin_new:
  * @messenger: an #FlBinaryMessenger.
- * @window: the #GdkWindow with which the text input plugin is associated.
- * @im_filter: a function used to allow an input method to internally handle
- * key press and release events. Typically a wrap of
- * #gtk_im_context_filter_keypress. Must not be nullptr.
+ * @im_context: (allow-none): a #GtkIMContext.
  *
  * Creates a new plugin that implements SystemChannels.textInput from the
  * Flutter services library.
  *
  * Returns: a new #FlTextInputPlugin.
  */
-FlTextInputPlugin* fl_text_input_plugin_new(
-    FlBinaryMessenger* messenger,
-    GdkWindow* window,
-    FlTextInputPluginImFilter im_filter);
+FlTextInputPlugin* fl_text_input_plugin_new(FlBinaryMessenger* messenger,
+                                            GtkIMContext* im_context);
 
 /**
  * fl_text_input_plugin_filter_keypress