Initial revision

src/routing-drag-line.c

@@ -0,0 +1,68 @@
+// SPDX-FileCopyrightText: 2022 Geoffrey D. Bennett <g@b4.vu>
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include "routing-drag-line.h"
+#include "routing-lines.h"
+
+static void drag_enter(
+  GtkDropControllerMotion *motion,
+  gdouble                  x,
+  gdouble                  y,
+  gpointer                 data
+) {
+  struct alsa_card *card = data;
+
+  card->drag_x = x;
+  card->drag_y = y;
+  gtk_widget_queue_draw(card->drag_line);
+  gtk_widget_queue_draw(card->routing_lines);
+}
+
+static void drag_leave(
+  GtkDropControllerMotion *motion,
+  gpointer                 data
+) {
+  struct alsa_card *card = data;
+
+  card->drag_x = -1;
+  card->drag_y = -1;
+  gtk_widget_queue_draw(card->drag_line);
+  gtk_widget_queue_draw(card->routing_lines);
+}
+
+static void drag_motion(
+  GtkDropControllerMotion *motion,
+  gdouble                  x,
+  gdouble                  y,
+  gpointer                 data
+) {
+  struct alsa_card *card = data;
+
+  card->drag_x = x;
+  card->drag_y = y;
+  gtk_widget_queue_draw(card->drag_line);
+  gtk_widget_queue_draw(card->routing_lines);
+}
+
+void add_drop_controller_motion(
+  struct alsa_card *card,
+  GtkWidget *routing_overlay
+) {
+
+  // create an area to draw the drag line on
+  card->drag_line = gtk_drawing_area_new();
+  gtk_widget_set_can_target(card->drag_line, FALSE);
+  gtk_drawing_area_set_draw_func(
+    GTK_DRAWING_AREA(card->drag_line), draw_drag_line, card, NULL
+  );
+  gtk_overlay_add_overlay(
+    GTK_OVERLAY(routing_overlay), card->drag_line
+  );
+
+  // create a controller to handle the dragging
+  GtkEventController *controller = gtk_drop_controller_motion_new();
+  g_signal_connect(controller, "enter", G_CALLBACK(drag_enter), card);
+  g_signal_connect(controller, "leave", G_CALLBACK(drag_leave), card);
+  g_signal_connect(controller, "motion", G_CALLBACK(drag_motion), card);
+  gtk_widget_add_controller(card->routing_grid, controller);
+}