feat(core): prepare build for mobile targets (#4830)

Co-authored-by: Yu-Wei Wu <wusyong9104@gmail.com>

.changes/build-platform-alias.md

@@ -0,0 +1,5 @@
+---
+"tauri-build": patch
+---
+
+Create the `desktop` and `mobile` cfg aliases.

core/tauri-build/src/lib.rs

@@ -203,6 +203,11 @@ pub fn try_build(attributes: Attributes) -> Result<()> {
   #[cfg(feature = "config-json5")]
   println!("cargo:rerun-if-changed=tauri.conf.json5");
 
+  let target_os = std::env::var("CARGO_CFG_TARGET_OS").unwrap();
+  let mobile = target_os == "ios" || target_os == "android";
+  cfg_alias("desktop", !mobile);
+  cfg_alias("mobile", mobile);
+
   let mut config = serde_json::from_value(tauri_utils::config::parse::read_from(
     std::env::current_dir().unwrap(),
   )?)?;

core/tauri-codegen/src/context.rs

@@ -523,6 +523,7 @@ fn png_icon<P: AsRef<Path>>(
   Ok(icon)
 }
 
+#[cfg(any(windows, target_os = "macos", target_os = "linux"))]
 fn find_icon<F: Fn(&&String) -> bool>(
   config: &Config,
   config_parent: &Path,

core/tauri-runtime-wry/build.rs

@@ -0,0 +1,18 @@
+// Copyright 2019-2021 Tauri Programme within The Commons Conservancy
+// SPDX-License-Identifier: Apache-2.0
+// SPDX-License-Identifier: MIT
+
+// creates a cfg alias if `has_feature` is true.
+// `alias` must be a snake case string.
+fn alias(alias: &str, has_feature: bool) {
+  if has_feature {
+    println!("cargo:rustc-cfg={}", alias);
+  }
+}
+
+fn main() {
+  let target_os = std::env::var("CARGO_CFG_TARGET_OS").unwrap();
+  let mobile = target_os == "ios" || target_os == "android";
+  alias("desktop", !mobile);
+  alias("mobile", mobile);
+}

core/tauri-runtime-wry/src/global_shortcut.rs

@@ -16,10 +16,10 @@ use std::{
 use crate::{getter, Context, Message};
 
 use tauri_runtime::{Error, GlobalShortcutManager, Result, UserEvent};
-pub use wry::application::global_shortcut::ShortcutManager as WryShortcutManager;
-use wry::application::{
+#[cfg(desktop)]
+pub use wry::application::{
   accelerator::{Accelerator, AcceleratorId},
-  global_shortcut::GlobalShortcut,
+  global_shortcut::{GlobalShortcut, ShortcutManager as WryShortcutManager},
 };
 
 pub type GlobalShortcutListeners = Arc<Mutex<HashMap<AcceleratorId, Box<dyn Fn() + Send>>>>;