split is_mobile to is_narrow and is_oled

is_mobile doesn't really make sense for android tablets. We were
overloading this variable to mean "is_narrow". What we really want is
is_oled for mobile devices and is_narrow for if its phone-like.

Signed-off-by: William Casarin <jb55@jb55.com>

src/ui/mod.rs

@@ -72,3 +72,14 @@ pub fn is_compiled_as_mobile() -> bool {
         false
     }
 }
+
+/// Determine if the screen is narrow. This is useful for detecting mobile
+/// contexts, but with the nuance that we may also have a wide android tablet.
+pub fn is_narrow(ctx: &egui::Context) -> bool {
+    let screen_size = ctx.input(|c| c.screen_rect().size());
+    screen_size.x < 550.0
+}
+
+pub fn is_oled() -> bool {
+    is_compiled_as_mobile()
+}