[demo] Add helper macros for linking to the source code on GitHub

egui/src/demos/mod.rs

@@ -43,3 +43,49 @@ pub fn warn_if_debug_build(ui: &mut crate::Ui) {
         .on_hover_text("Egui has detect that debug assertions are enabled.");
     }
 }
+
+// ----------------------------------------------------------------------------
+
+/// Create a `Hyperlink` to this file (and line) on Github
+/// Example: `ui.add(github_link_file_line!("https://github.com/YOUR/PROJECT/blob/master/", "(source code)"));`
+#[macro_export]
+macro_rules! github_link_file_line {
+    ($github_url:expr, $label:expr) => {{
+        let url = format!("{}{}#L{}", $github_url, file!(), line!());
+        Hyperlink::new(url).text($label)
+    }};
+}
+
+/// Create a `Hyperlink` to this file on github.
+/// Example: `ui.add(github_link_file!("https://github.com/YOUR/PROJECT/blob/master/", "(source code)"));`
+#[macro_export]
+macro_rules! github_link_file {
+    ($github_url:expr, $label:expr) => {{
+        let url = format!("{}{}", $github_url, file!());
+        Hyperlink::new(url).text($label)
+    }};
+}
+
+/// Create a `Hyperlink` to this egui source code file on github.
+#[doc(hidden)]
+#[macro_export]
+macro_rules! __egui_github_link_file {
+    () => {
+        __egui_github_link_file!("(source code)")
+    };
+    ($label:expr) => {
+        github_link_file!("https://github.com/emilk/egui/blob/master/", $label).small()
+    };
+}
+
+/// Create a `Hyperlink` to this egui source code file and line on github.
+#[doc(hidden)]
+#[macro_export]
+macro_rules! __egui_github_link_file_line {
+    () => {
+        __egui_github_link_file_line!("(source code)")
+    };
+    ($label:expr) => {
+        github_link_file_line!("https://github.com/emilk/egui/blob/master/", $label).small()
+    };
+}

egui/src/demos/toggle_switch.rs

@@ -90,10 +90,9 @@ fn toggle_compact(ui: &mut Ui, on: &mut bool) -> Response {
 
 pub fn demo(ui: &mut Ui, on: &mut bool) {
     ui.label("It's easy to create your own widgets!");
-    let url = format!("https://github.com/emilk/egui/blob/master/{}", file!());
     ui.horizontal(|ui| {
         ui.label("Like this toggle switch:");
         toggle(ui, on).on_hover_text("Click to toggle");
-        ui.add(Hyperlink::new(url).text("(source code)"));
+        ui.add(__egui_github_link_file!());
     });
 }

egui/src/demos/widgets.rs

@@ -46,8 +46,7 @@ impl Default for Widgets {
 
 impl Widgets {
     pub fn ui(&mut self, ui: &mut Ui) {
-        let url = format!("https://github.com/emilk/egui/blob/master/{}", file!());
-        ui.add(Hyperlink::new(url).text("Click here to read the source code for this section"));
+        ui.add(crate::__egui_github_link_file_line!());
 
         ui.horizontal(|ui| {
             ui.style_mut().spacing.item_spacing.x = 0.0;