ohos: hide the app icon choice

platform/README.md

@@ -86,6 +86,7 @@ provides these crate-internal items, which shared code calls without a `cfg`:
 | `lower_current_thread_priority()` | Run the PDF worker thread at background priority. |
 | `install_preview_lifecycle()` | Register for background/memory-pressure notifications, which must call `flectar_mail::suspend_file_preview()`. |
 | `NAME` | The platform's name, which Settings uses to describe where the app icon appears. |
+| `SWITCHES_APP_ICON` | Whether apps may switch their home screen icon. Settings offers the choice only where they may. |
 | `show_app_icon(icon)` | Show the app icon chosen in Settings on the home screen. Android forwards it to the bridge its host registers with `configure_launcher_icon`; iOS switches to the alternate icon sets declared in `platform/ios/project.yml`. |
 | `email_font_dir()` | Platform font directory for the email (Blitz/Parley) renderer on hosts without Fontconfig; `None` when the fontique system backend provides the fonts. |
 

src/app_icon.rs

@@ -13,15 +13,19 @@
 //! - mobile home screens switch to icons bundled with the app, through the
 //!   platform layer.
 //!
-//! Flatpak can neither show a tray nor write to the host's icon theme, so the
-//! choice is not offered there.
+//! Flatpak can neither show a tray nor write to the host's icon theme, and
+//! some mobile platforms reserve switching the home screen icon for system
+//! apps, so the choice is not offered there.
 
 use crate::{AppIconVariant, AppWindow, tray_ui::FlectarTray};
 use flectar_mail_core::models;
 use slint::ComponentHandle;
 use std::cell::RefCell;
 
+#[cfg(desktop)]
 pub(crate) const AVAILABLE: bool = cfg!(not(feature = "flatpak"));
+#[cfg(mobile)]
+pub(crate) const AVAILABLE: bool = crate::platform::SWITCHES_APP_ICON;
 
 /// Lets Settings describe where this platform shows the icon.
 #[cfg(desktop)]

src/platform/android.rs

@@ -61,6 +61,9 @@ pub fn configure_launcher_icon(switch: impl Fn(&str) + Send + Sync + 'static) {
     let _ = LAUNCHER_ICON.set(Box::new(switch));
 }
 
+/// Android apps may switch their launcher icon, so Settings offers the choice.
+pub(crate) const SWITCHES_APP_ICON: bool = true;
+
 pub(crate) fn show_app_icon(icon: AppIcon) {
     if let Some(switch) = LAUNCHER_ICON.get() {
         switch(icon.as_str());

src/platform/ios.rs

@@ -73,6 +73,9 @@ pub(crate) fn install_preview_lifecycle() {
     unsafe { install_pdf_lifecycle_observers() }
 }
 
+/// iOS apps may switch to alternate icons, so Settings offers the choice.
+pub(crate) const SWITCHES_APP_ICON: bool = true;
+
 /// Show the alternate icon set declared in project.yml, or the primary icon.
 pub(crate) fn show_app_icon(icon: AppIcon) {
     let name: Option<&CStr> = match icon {

src/platform/ohos.rs

@@ -55,7 +55,10 @@ pub(crate) fn lower_current_thread_priority() {
 pub(crate) fn install_preview_lifecycle() {}
 
 /// Switching the home screen icon is a system API on OpenHarmony
-/// (`bundleManager.enableDynamicIcon`), so the choice applies inside the app.
+/// (`bundleManager.enableDynamicIcon`), so Settings does not offer the choice.
+pub(crate) const SWITCHES_APP_ICON: bool = false;
+
+/// Only the default icon reaches here; see [`SWITCHES_APP_ICON`].
 pub(crate) fn show_app_icon(_icon: AppIcon) {}
 
 /// Directory the email (Blitz/Parley) renderer loads fonts from. OpenHarmony