2 files changed, 228 insertions, 0 deletions
diff --git a/internal/notify/icons.go b/internal/notify/icons.go
new file mode 100644
index 0000000..b874581
--- /dev/null
+++ b/internal/notify/icons.go
@@ -0,0 +1,158 @@
+// Copyright (C) 2026 Danilo M. <danix@danix.xyz>
+//
+// This program is free software; you can redistribute it and/or modify
+// it under the terms of the GNU General Public License version 2 as
+// published by the Free Software Foundation.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+
+package notify
+
+import (
+	"os"
+	"path/filepath"
+	"sort"
+	"strconv"
+	"strings"
+)
+
+// IconThemeName reads the desktop's current icon theme: qt6ct is the truth on
+// this desktop, then the GTK3 setting, then hicolor. A missing or empty value
+// falls through.
+func IconThemeName() string {
+	if v := iniValue(filepath.Join(homeDir(), ".config", "qt6ct", "qt6ct.conf"), "icon_theme"); v != "" {
+		return v
+	}
+	if v := iniValue(filepath.Join(homeDir(), ".config", "gtk-3.0", "settings.ini"), "gtk-icon-theme-name"); v != "" {
+		return v
+	}
+	return "hicolor"
+}
+
+// ResolveIcon turns an app_icon or image-path value into a file path. A URI is
+// trimmed, a path is returned unchanged, and a bare name is looked up in the
+// icon theme. Nothing found is an empty string, which renders no image.
+func ResolveIcon(value string) string {
+	if value == "" {
+		return ""
+	}
+	if strings.HasPrefix(value, "file://") {
+		return strings.TrimPrefix(value, "file://")
+	}
+	if strings.Contains(value, "/") {
+		return value
+	}
+	return lookupThemeIcon(value, IconThemeName())
+}
+
+// XDGIconDirs is the icon search path: the user's dir then each data dir.
+func XDGIconDirs() []string {
+	home := os.Getenv("XDG_DATA_HOME")
+	if home == "" {
+		home = filepath.Join(homeDir(), ".local", "share")
+	}
+	dirs := []string{filepath.Join(home, "icons")}
+	for _, d := range filepath.SplitList(os.Getenv("XDG_DATA_DIRS")) {
+		if d != "" {
+			dirs = append(dirs, filepath.Join(d, "icons"))
+		}
+	}
+	if len(dirs) == 1 {
+		dirs = append(dirs, "/usr/local/share/icons", "/usr/share/icons")
+	}
+	return dirs
+}
+
+// lookupThemeIcon searches the theme, then its Inherits chain, then hicolor.
+func lookupThemeIcon(name, theme string) string {
+	seen := map[string]bool{}
+	for theme != "" && !seen[theme] {
+		seen[theme] = true
+		found, next := "", ""
+		for _, root := range XDGIconDirs() {
+			base := filepath.Join(root, theme)
+			if p := findInTheme(base, name); p != "" {
+				found = p
+				break
+			}
+			if next == "" {
+				next = inheritsOf(base)
+			}
+		}
+		if found != "" {
+			return found
+		}
+		theme = next
+	}
+	for _, root := range XDGIconDirs() {
+		if p := findInTheme(filepath.Join(root, "hicolor"), name); p != "" {
+			return p
+		}
+	}
+	return ""
+}
+
+// findInTheme prefers scalable then the largest raster under apps/.
+func findInTheme(base, name string) string {
+	sizes := []string{"scalable"}
+	matches, _ := filepath.Glob(filepath.Join(base, "apps", "[0-9]*"))
+	for _, m := range matches {
+		sizes = append(sizes, filepath.Base(m))
+	}
+	numeric := sizes[1:]
+	sort.Slice(numeric, func(i, j int) bool {
+		a, _ := strconv.Atoi(strings.TrimSuffix(numeric[i], "@2x"))
+		b, _ := strconv.Atoi(strings.TrimSuffix(numeric[j], "@2x"))
+		return a > b
+	})
+	for _, size := range sizes {
+		for _, ext := range []string{"svg", "png", "xpm"} {
+			p := filepath.Join(base, "apps", size, name+"."+ext)
+			if fileExists(p) {
+				return p
+			}
+		}
+	}
+	return ""
+}
+
+func inheritsOf(base string) string {
+	v := iniValue(filepath.Join(base, "index.theme"), "Inherits")
+	if i := strings.IndexByte(v, ','); i >= 0 {
+		v = v[:i]
+	}
+	return strings.TrimSpace(v)
+}
+
+func iniValue(path, key string) string {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return ""
+	}
+	for _, line := range strings.Split(string(data), "\n") {
+		line = strings.TrimSpace(line)
+		if strings.HasPrefix(line, "#") || !strings.Contains(line, "=") {
+			continue
+		}
+		k, v, _ := strings.Cut(line, "=")
+		if strings.TrimSpace(k) == key {
+			return strings.TrimSpace(v)
+		}
+	}
+	return ""
+}
+
+func homeDir() string {
+	if h := os.Getenv("HOME"); h != "" {
+		return h
+	}
+	return os.TempDir()
+}
+
+func fileExists(path string) bool {
+	info, err := os.Stat(path)
+	return err == nil && !info.IsDir()
+}
diff --git a/internal/notify/icons_test.go b/internal/notify/icons_test.go
new file mode 100644
index 0000000..527b330
--- /dev/null
+++ b/internal/notify/icons_test.go
@@ -0,0 +1,70 @@
+// Copyright (C) 2026 Danilo M. <danix@danix.xyz>
+//
+// This program is free software; you can redistribute it and/or modify
+// it under the terms of the GNU General Public License version 2 as
+// published by the Free Software Foundation.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+
+package notify
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestResolveIconPathAndURI(t *testing.T) {
+	if got := ResolveIcon("/usr/share/icons/x/apps/48/firefox.png"); got != "/usr/share/icons/x/apps/48/firefox.png" {
+		t.Fatalf("path passthrough: %q", got)
+	}
+	if got := ResolveIcon("file:///tmp/shot.png"); got != "/tmp/shot.png" {
+		t.Fatalf("uri: %q", got)
+	}
+	if got := ResolveIcon(""); got != "" {
+		t.Fatalf("empty: %q", got)
+	}
+}
+
+func TestResolveIconThemeName(t *testing.T) {
+	root := t.TempDir()
+	// Theme "Plum" inherits "Base"; the icon is only in Base.
+	theme := filepath.Join(root, "icons", "Plum")
+	base := filepath.Join(root, "icons", "Base")
+	plumIndex := filepath.Join(theme, "index.theme")
+	baseApp := filepath.Join(base, "apps", "48")
+	if err := os.MkdirAll(filepath.Join(theme, "apps", "scalable"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.MkdirAll(baseApp, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(plumIndex, []byte("[Icon Theme]\nInherits=Base\n"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(baseApp, "firefox.svg"), []byte("<svg/>"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+
+	t.Setenv("XDG_DATA_HOME", root)
+	t.Setenv("XDG_DATA_DIRS", "")
+	t.Setenv("HOME", filepath.Join(root, "home"))
+	if err := os.MkdirAll(filepath.Join(root, "home", ".config", "qt6ct"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(root, "home", ".config", "qt6ct", "qt6ct.conf"), []byte("icon_theme=Plum\n"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+
+	got := ResolveIcon("firefox")
+	want := filepath.Join(root, "icons", "Base", "apps", "48", "firefox.svg")
+	if got != want {
+		t.Fatalf("resolved %q, want %q", got, want)
+	}
+	if got := ResolveIcon("no-such-icon-xyz"); got != "" {
+		t.Fatalf("missing name must be empty, got %q", got)
+	}
+}