fix(tray): vastly improve rendering performance

src/modules/tray/icon.rs

@@ -0,0 +1,86 @@
+use glib::ffi::g_strfreev;
+use glib::translate::ToGlibPtr;
+use gtk::ffi::gtk_icon_theme_get_search_path;
+use gtk::gdk_pixbuf::{Colorspace, InterpType};
+use gtk::prelude::IconThemeExt;
+use gtk::{gdk_pixbuf, IconLookupFlags, IconTheme, Image};
+use std::collections::HashSet;
+use std::ffi::CStr;
+use std::os::raw::{c_char, c_int};
+use std::ptr;
+use system_tray::message::tray::StatusNotifierItem;
+
+/// Gets the GTK icon theme search paths by calling the FFI function.
+/// Conveniently returns the result as a `HashSet`.
+fn get_icon_theme_search_paths(icon_theme: &IconTheme) -> HashSet<String> {
+    let mut gtk_paths: *mut *mut c_char = ptr::null_mut();
+    let mut n_elements: c_int = 0;
+    let mut paths = HashSet::new();
+    unsafe {
+        gtk_icon_theme_get_search_path(
+            icon_theme.to_glib_none().0,
+            &mut gtk_paths,
+            &mut n_elements,
+        );
+        // n_elements is never negative (that would be weird)
+        for i in 0..n_elements as usize {
+            let c_str = CStr::from_ptr(*gtk_paths.add(i));
+            if let Ok(str) = c_str.to_str() {
+                paths.insert(str.to_owned());
+            }
+        }
+
+        g_strfreev(gtk_paths);
+    }
+
+    paths
+}
+
+/// Attempts to get a GTK `Image` component
+/// for the status notifier item's icon.
+pub(crate) fn get_image_from_icon_name(
+    item: &StatusNotifierItem,
+    icon_theme: &IconTheme,
+) -> Option<Image> {
+    if let Some(path) = item.icon_theme_path.as_ref() {
+        if !path.is_empty() && !get_icon_theme_search_paths(icon_theme).contains(path) {
+            icon_theme.append_search_path(path);
+        }
+    }
+
+    item.icon_name.as_ref().and_then(|icon_name| {
+        let icon_info = icon_theme.lookup_icon(icon_name, 16, IconLookupFlags::empty());
+        icon_info.map(|icon_info| Image::from_pixbuf(icon_info.load_icon().ok().as_ref()))
+    })
+}
+
+/// Attempts to get an image from the item pixmap.
+///
+/// The pixmap is supplied in ARGB32 format,
+/// which has 8 bits per sample and a bit stride of `4*width`.
+pub(crate) fn get_image_from_pixmap(item: &StatusNotifierItem) -> Option<Image> {
+    const BITS_PER_SAMPLE: i32 = 8;
+
+    let pixmap = item
+        .icon_pixmap
+        .as_ref()
+        .and_then(|pixmap| pixmap.first())?;
+
+    let bytes = glib::Bytes::from(&pixmap.pixels);
+    let row_stride = pixmap.width * 4; //
+
+    let pixbuf = gdk_pixbuf::Pixbuf::from_bytes(
+        &bytes,
+        Colorspace::Rgb,
+        true,
+        BITS_PER_SAMPLE,
+        pixmap.width,
+        pixmap.height,
+        row_stride,
+    );
+
+    let pixbuf = pixbuf
+        .scale_simple(16, 16, InterpType::Bilinear)
+        .unwrap_or(pixbuf);
+    Some(Image::from_pixbuf(Some(&pixbuf)))
+}