Grab keyboard focus when clickable area hovered

Finally figured out how to do this. This change makes it possible for the first time for the overlay window to react to keyboard events, and so it's possible to make any arbitrary interactive web UI with it! It's pretty neato. This is a proof of concept! There are many minor bugs, like drag-and-drop completely breaks when trying to drag out of the overlay's clickable area, and enter/leave events jitter when sweeping the mouse along edges of the screen. That kind of thing. Related to #3 and #5, but not global; no events are duplicated here.
anko · May 3, 2021 · d40cb15 · d40cb15
1 parent 16d1a9f
commit d40cb15
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Showing 2 changed files with 65 additions and 1 deletion.
diff --git a/example/page.html b/example/page.html
@@ -26,6 +26,7 @@
 <body>
     <div id="monitor-frame-container"></div>
     <div id="explanation">
+    <input></input>
     <h1><span>Welcome to the future!</span></h1>
     <p><span>You should be able to—
         <ul>
@@ -42,6 +43,11 @@ <h1><span>Welcome to the future!</span></h1>
     </div>
     <script>
 
+        const html = document.getElementsByTagName('html')[0]
+        document.addEventListener('keydown', e => console.log(e.code))
+        window.onfocus = () => console.log("focused")
+        window.onblur = () => console.log("blurred")
+
         // Async wrapper necessary so we can use `await`
         ;(async () => {
             // Make the overlay window clickable in a 100-pixel-wide strip at

diff --git a/main.c b/main.c
@@ -392,6 +392,48 @@ void printUsage(char *programName) {
         programName);
 }
 
+// Listen for the "pointer entered window" and "pointer left window" events,
+// and in response grab or ungrab the keyboard device.
+//
+// This is necessary because our overlay window has the override_redirect flag
+// set, meaning while it can get pointer events, the desktop environment will
+// never give it keyboard events.  It can however *grab the keyboard device*
+// itself, effectively taking keyboard input focus instead of being given it.
+// So we do that.
+struct PointerEnterEventData {
+    GdkSeat *seat;
+    GdkWindow *window;
+};
+gboolean on_pointer_enter_window(
+        GtkWidget *widget, GdkEventCrossing *event, gpointer user_data) {
+    struct PointerEnterEventData *data =
+        (struct PointerEnterEventData *) user_data;
+    printf("Pointer entered window.  Grabbing.\n");
+    gdk_seat_grab(data->seat, data->window,
+            // Grab the keyboard only we already get pointer events.
+            GDK_SEAT_CAPABILITY_KEYBOARD,
+            FALSE, // owner events
+            NULL,  // cursor
+            // event that triggered the grab: Internally, gdk_seat_grab uses
+            // XIGrabDevice, which reads the event's timestamp.  The grab
+            // request is cancelled if the given event happened before the last
+            // device grab.  This makes stuff happen in the expected order when
+            // under heavy system load, where events may be handled with
+            // significant delay.
+            (GdkEvent *) event,
+            NULL,  // prepare func (don't need it; window is visible already)
+            NULL   // user_data passed to prepare func
+            );
+    return FALSE;
+}
+gboolean on_pointer_leave_window(
+        GtkWidget *widget, GdkEventCrossing *event, gpointer user_data) {
+    GdkSeat *seat = (GdkSeat *) user_data;
+    printf("Pointer left window.  Releasing grab.\n");
+    gdk_seat_ungrab(seat);
+    return FALSE;
+}
+
 int main(int argc, char **argv) {
 
     gtk_init(&argc, &argv);
@@ -661,6 +703,22 @@ int main(int argc, char **argv) {
     g_signal_connect(G_OBJECT(window), "delete-event", gtk_main_quit, NULL);
     gtk_widget_set_app_paintable(window, TRUE);
 
+    // Listen for enter and leave notify events.
+    //
+    // These are fired when the mouse pointer enters the overlay window.  They
+    // won't fire by default (because it has no input-area), but will fire if
+    // JS has called `Hudkit.setClickableAreas`, and the mouse pointer enters
+    // one of those areas.
+    GdkDisplay *display = gdk_display_get_default();
+    GdkSeat *seat = gdk_display_get_default_seat(display);
+    gtk_widget_set_events(window,
+            GDK_ENTER_NOTIFY_MASK & GDK_LEAVE_NOTIFY_MASK);
+    struct PointerEnterEventData pointer_enter_event_data = { seat };
+    g_signal_connect (window, "enter-notify-event",
+            G_CALLBACK(on_pointer_enter_window), &pointer_enter_event_data);
+    g_signal_connect (window, "leave-notify-event",
+            G_CALLBACK(on_pointer_leave_window), seat);
+
     //
     // Set up the WebKit web view widget
     //
@@ -729,7 +787,6 @@ int main(int argc, char **argv) {
     // it correctly.
     screen_changed(window, NULL, web_view);
 
-    GdkDisplay *display = gdk_display_get_default();
     GdkRectangle *rectangles = NULL;
     int nRectangles = get_monitor_rects(display, &rectangles);
 
@@ -738,6 +795,7 @@ int main(int argc, char **argv) {
     // Hide the window, so we can get our properties ready without the window
     // manager trying to mess with us.
     GdkWindow *gdk_window = gtk_widget_get_window(GTK_WIDGET(window));
+    pointer_enter_event_data.window = gdk_window;
     gdk_window_hide(GDK_WINDOW(gdk_window));
 
     // "Can't touch this!" - to the window manager