feat(launcher): pagination controls when item count is reached

Resolves #633

src/modules/launcher/pagination.rs

@@ -0,0 +1,140 @@
+use crate::gtk_helpers::IronbarGtkExt;
+use crate::image::new_icon_button;
+use gtk::prelude::*;
+use gtk::{Button, IconTheme, Orientation};
+use std::cell::RefCell;
+use std::ops::Deref;
+use std::rc::Rc;
+
+pub struct Pagination {
+    offset: Rc<RefCell<usize>>,
+
+    controls_container: gtk::Box,
+    btn_fwd: Button,
+}
+
+pub struct IconContext<'a> {
+    pub icon_back: &'a str,
+    pub icon_fwd: &'a str,
+    pub icon_size: i32,
+    pub icon_theme: &'a IconTheme,
+}
+
+impl Pagination {
+    pub fn new(
+        container: &gtk::Box,
+        page_size: usize,
+        orientation: Orientation,
+        icon_context: IconContext,
+    ) -> Self {
+        let scroll_box = gtk::Box::new(orientation, 0);
+
+        let scroll_back = new_icon_button(
+            icon_context.icon_back,
+            icon_context.icon_theme,
+            icon_context.icon_size,
+        );
+
+        let scroll_fwd = new_icon_button(
+            icon_context.icon_fwd,
+            icon_context.icon_theme,
+            icon_context.icon_size,
+        );
+
+        scroll_back.set_sensitive(false);
+        scroll_fwd.set_sensitive(false);
+
+        scroll_box.add_class("pagination");
+        scroll_back.add_class("btn-back");
+        scroll_fwd.add_class("btn-forward");
+
+        scroll_box.add(&scroll_back);
+        scroll_box.add(&scroll_fwd);
+        container.add(&scroll_box);
+
+        let offset = Rc::new(RefCell::new(1));
+
+        {
+            let offset = offset.clone();
+            let container = container.clone();
+            let scroll_back = scroll_back.clone();
+
+            scroll_fwd.connect_clicked(move |btn| {
+                let mut offset = offset.borrow_mut();
+                let child_count = container.children().len();
+
+                *offset = std::cmp::min(child_count - 1, *offset + page_size);
+
+                Self::update_page(&container, *offset, page_size);
+
+                if *offset + page_size >= child_count {
+                    btn.set_sensitive(false);
+                }
+
+                scroll_back.set_sensitive(true);
+            });
+        }
+
+        {
+            let offset = offset.clone();
+            let container = container.clone();
+            let scroll_fwd = scroll_fwd.clone();
+
+            scroll_back.connect_clicked(move |btn| {
+                let mut offset = offset.borrow_mut();
+                // avoid using std::cmp::max due to possible overflow
+                if page_size < *offset {
+                    *offset -= page_size;
+                } else {
+                    *offset = 1
+                };
+
+                Self::update_page(&container, *offset, page_size);
+
+                if *offset == 1 || *offset - page_size < 1 {
+                    btn.set_sensitive(false);
+                }
+
+                scroll_fwd.set_sensitive(true);
+            });
+        }
+
+        Self {
+            offset,
+
+            controls_container: scroll_box,
+            btn_fwd: scroll_fwd,
+        }
+    }
+
+    fn update_page(container: &gtk::Box, offset: usize, page_size: usize) {
+        for (i, btn) in container.children().iter().enumerate() {
+            // skip offset buttons
+            if i == 0 {
+                continue;
+            }
+
+            if i >= offset && i < offset + page_size {
+                btn.show();
+            } else {
+                btn.hide();
+            }
+        }
+    }
+
+    pub fn set_sensitive_fwd(&self, sensitive: bool) {
+        self.btn_fwd.set_sensitive(sensitive);
+    }
+
+    pub fn offset(&self) -> usize {
+        *self.offset.borrow()
+    }
+}
+
+impl Deref for Pagination {
+    type Target = gtk::Box;
+
+    fn deref(&self) -> &Self::Target {
+        &self.controls_container
+    }
+}