Add backbutton

meson.build

@@ -169,7 +169,8 @@ libtranslationlayer_so = shared_library('translation_layer_main', [
 
 executable('android-translation-layer', [
                                         	'src/main-executable/main.c',
-                                        	'src/main-executable/r_debug.c'
+                                        	'src/main-executable/r_debug.c',
+                                        	'src/main-executable/back_button.c'
                                         ],
                                         install: true,
                                         dependencies: [

src/api-impl-jni/app/android_app_Activity.c

@@ -6,6 +6,7 @@
 
 #include "../defines.h"
 #include "../util.h"
+#include "../main-executable/back_button.h"
 #include "android_app_Activity.h"
 #include "../generated_headers/android_app_Activity.h"
 
@@ -75,6 +76,19 @@ static void activity_update_current(JNIEnv *env)
 
 		activity_current = activity_new;
 	}
+
+	if(activity_current != NULL){
+		jclass current_activity_class = (*env)->GetObjectClass(env, activity_current);
+		jmethodID current_activity_on_back_pressed_method_id = (*env) ->GetMethodID(env, current_activity_class, "onBackPressed", "()V");
+		if((*env)->ExceptionCheck(env))
+			(*env)->ExceptionDescribe(env);
+
+		if(g_list_length(activity_backlog) > 1 || handle_cache.activity.onBackPressed != current_activity_on_back_pressed_method_id){
+			back_button_set_sensitive(true);
+		} else {
+			back_button_set_sensitive(false);
+		}
+	}
 }
 
 void activity_window_ready(void)
@@ -88,6 +102,24 @@ void activity_window_ready(void)
 	}
 }
 
+void current_activity_back_pressed(void){
+	JNIEnv *env = get_jni_env();
+
+	jclass current_activity_class = (*env)->GetObjectClass(env, activity_current);
+	jmethodID current_activity_on_back_pressed_method_id = (*env) ->GetMethodID(env, current_activity_class, "onBackPressed", "()V");
+	if((*env)->ExceptionCheck(env))
+		(*env)->ExceptionDescribe(env);
+	
+	// Either a new activity was added to the backlog or the current activity's onBackPressed method was changed
+	if(g_list_length(activity_backlog) > 1 || handle_cache.activity.onBackPressed != current_activity_on_back_pressed_method_id){
+		(*env)->CallVoidMethod(env, activity_current, handle_cache.activity.onBackPressed);
+		if((*env)->ExceptionCheck(env))
+			(*env)->ExceptionDescribe(env);
+	} else {
+		back_button_set_sensitive(false);
+	}
+}
+
 void activity_close_all(void)
 {
 	GList *activities, *l;

src/api-impl-jni/app/android_app_Activity.h

@@ -3,3 +3,4 @@
 void activity_start(JNIEnv *env, jobject activity_object);
 void activity_window_ready(void);
 void activity_close_all(void);
+void current_activity_back_pressed(void);

src/api-impl-jni/util.c

@@ -75,6 +75,7 @@ void set_up_handle_cache(JNIEnv *env)
 	handle_cache.activity.onDestroy = _METHOD(handle_cache.activity.class, "onDestroy", "()V");
 	handle_cache.activity.onStop = _METHOD(handle_cache.activity.class, "onStop", "()V");
 	handle_cache.activity.onPause = _METHOD(handle_cache.activity.class, "onPause", "()V");
+	handle_cache.activity.onBackPressed = _METHOD(handle_cache.activity.class, "onBackPressed", "()V");
 
 	handle_cache.attribute_set.class = _REF((*env)->FindClass(env, "android/util/AttributeSet"));
 	if((*env)->ExceptionCheck(env))

src/api-impl-jni/util.h

@@ -17,6 +17,7 @@ struct handle_cache {
 		jmethodID onDestroy;
 		jmethodID onStop;
 		jmethodID onPause;
+		jmethodID onBackPressed;
 	} activity;
 	struct {
 		jclass class;

src/api-impl/android/app/Activity.java

@@ -482,6 +482,7 @@ public class Activity extends ContextThemeWrapper implements Window.Callback {
 	}
 
 	public void onBackPressed() {
+		System.out.println("onBackPressed() called");
 		finish();
 	}
 

src/main-executable/back_button.c

@@ -0,0 +1,18 @@
+#include "back_button.h"
+
+#include "../api-impl-jni/app/android_app_Activity.h"
+
+GtkWidget *back_button;
+
+GtkWidget* back_button_new() {
+	back_button = gtk_button_new_from_icon_name("go-previous");
+
+	g_signal_connect(back_button, "clicked", G_CALLBACK(current_activity_back_pressed), NULL);
+
+	back_button_set_sensitive(false);
+	return back_button;
+}
+
+void back_button_set_sensitive(bool sensitive) {
+	gtk_widget_set_sensitive(GTK_WIDGET(back_button), sensitive);
+}

src/main-executable/back_button.h

@@ -0,0 +1,4 @@
+#include <gtk/gtk.h>
+
+GtkWidget* back_button_new(); 
+void back_button_set_sensitive(bool sensitive);

src/main-executable/main.c

@@ -10,6 +10,8 @@
 #include "../api-impl-jni/util.h"
 #include "../api-impl-jni/app/android_app_Activity.h"
 
+#include "back_button.h"
+
 #include <dlfcn.h>
 #include <errno.h>
 #include <libgen.h>
@@ -547,6 +549,11 @@ static void open(GtkApplication *app, GFile **files, gint nfiles, const gchar *h
 	gtk_window_set_default_size(GTK_WINDOW(window), d->window_width, d->window_height);
 	g_signal_connect(window, "close-request", G_CALLBACK(app_exit), env);
 
+	GtkWidget *header_bar = gtk_header_bar_new();
+	GtkWidget *back_button = back_button_new();
+
+	gtk_header_bar_pack_start(GTK_HEADER_BAR(header_bar), back_button);
+	gtk_window_set_titlebar(GTK_WINDOW(window), header_bar);
 	gtk_window_present(GTK_WINDOW(window));
 
 	// set package name as application id for window icon on Wayland. Needs a {package_name}.desktop file defining the icon