Port 'Scrolled Window' demo to Vala (#178)

Author: BharatAtbrat

src/Scrolled Window/main.vala

@@ -0,0 +1,110 @@
+#! /usr/bin/env -S vala workbench.vala --pkg libadwaita-1
+private bool auto_scrolling = false;
+
+public void main () {
+    var scrolled_window = (Gtk.ScrolledWindow) workbench.builder.get_object ("scrolled_window");
+    var container = (Gtk.Box) workbench.builder.get_object ("container");
+    var toggle_orientation = (Gtk.ToggleButton) workbench.builder.get_object ("toggle_orientation");
+    var button_start = (Gtk.Button) workbench.builder.get_object ("button_start");
+    var button_end = (Gtk.Button) workbench.builder.get_object ("button_end");
+
+    button_start.sensitive = false;
+
+    HashTable<Gtk.Orientation, Gtk.Scrollbar> scrollbars = new HashTable<Gtk.Orientation, Gtk.Scrollbar> (direct_hash, direct_equal);
+    scrollbars[Gtk.Orientation.HORIZONTAL] = (Gtk.Scrollbar) scrolled_window.get_hscrollbar ();
+    scrollbars[Gtk.Orientation.VERTICAL] = (Gtk.Scrollbar) scrolled_window.get_vscrollbar ();
+
+    toggle_orientation.toggled.connect (() => {
+        if (toggle_orientation.active) {
+            container.orientation = Gtk.Orientation.HORIZONTAL;
+        } else {
+            container.orientation = Gtk.Orientation.VERTICAL;
+        }
+    });
+
+    int num_items = 20;
+    for (int i = 0; i < num_items; i++) {
+        populate_container (container, @"Item $(i + 1)");
+    }
+
+    foreach (Gtk.Orientation orientation in scrollbars.get_keys ()) {
+        Gtk.Scrollbar scrollbar = scrollbars[orientation];
+        Gtk.Adjustment adj = scrollbar.adjustment;
+        adj.value_changed.connect (() => {
+            if (adj.value == adj.lower) {
+                button_end.sensitive = true;
+                button_start.sensitive = false;
+            } else if (adj.value == adj.upper - adj.page_size) {
+                button_end.sensitive = false;
+                button_start.sensitive = true;
+            } else {
+                // Disable buttons if scrollbar is auto-scrolling
+                button_end.sensitive = !auto_scrolling;
+                button_start.sensitive = !auto_scrolling;
+            }
+        });
+    }
+
+    scrolled_window.edge_reached.connect (() => {
+        message (@"Edge Reached");
+    });
+
+    button_start.clicked.connect (() => {
+        auto_scrolling = true;
+        Gtk.Scrollbar scrollbar = scrollbars[container.orientation];
+        Adw.Animation anim = create_scrollbar_anim (scrollbar, false);
+        anim.play ();
+    });
+
+    button_end.clicked.connect (() => {
+        auto_scrolling = true;
+        Gtk.Scrollbar scrollbar = scrollbars[container.orientation];
+        Adw.Animation anim = create_scrollbar_anim (scrollbar, true);
+        anim.play ();
+    });
+}
+
+void populate_container (Gtk.Box container, string label) {
+    Gtk.Widget item = new Adw.Bin () {
+        margin_top = 6,
+        margin_bottom = 6,
+        margin_start = 6,
+        margin_end = 6,
+        child = new Gtk.Label (label) {
+            width_request = 100,
+            height_request = 100
+        },
+        css_classes = { "card" }
+    };
+
+    container.append (item);
+}
+
+Adw.TimedAnimation create_scrollbar_anim (Gtk.Scrollbar scrollbar, bool direction) {
+    // direction = 0 -> Animates to Start
+    // direction = 1 -> Animates to End
+    Gtk.Adjustment adjustment = scrollbar.adjustment;
+    double value_to = 0;
+    if (direction) {
+        value_to = adjustment.upper - adjustment.page_size;
+    } else {
+        value_to = 0;
+    }
+
+    var target = new Adw.PropertyAnimationTarget (adjustment, "value");
+    var animation = new Adw.TimedAnimation (
+                                            scrollbar, // widget
+                                            adjustment.value, // value_from
+                                            value_to, // value_to
+                                            1000, // duration
+                                            target // target
+        ) {
+        easing = LINEAR
+    };
+
+    animation.done.connect (() => {
+        auto_scrolling = false;
+    });
+
+    return animation;
+}