fix(window-id): closes #13

 - check for window id very early
 - grab a screenshot before recording starts, to verify it works
 - present a nice error message to show what is wrong

CHANGELOG.md

@@ -6,6 +6,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## 🎯 [Unreleased]
 
+## [0.2.1] - 2020-11-17
+- improve error handling for invalid window id [issue/13] / [pull/14]
+
+[issue/13]: https://github.com/sassman/t-rec-rs/issues/13
+[pull/14]: https://github.com/sassman/t-rec-rs/pull/14
+
 ## [0.2.0] - 2020-10-12
 ### Added
 - command line parameter for natural recording `-n` or `--natural`

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "t-rec"
-version = "0.2.0"
+version = "0.2.1"
 authors = ["Sven Assmann <[email protected]>"]
 edition = "2018"
 license = "GPL-3.0-only"

README.md

@@ -28,7 +28,7 @@ Blazingly fast terminal recorder that generates animated gif images for the web
 
 ## Install
 
-**NOTE** for now `t-rec` depends on `imagemagick`, but this is going to change soon.
+**NOTE** for now `t-rec` depends on `imagemagick`.
 
 ```sh
 ❯ brew install imagemagick
@@ -53,7 +53,7 @@ or with specifying a different program to launch
 
 ```sh
 ❯ t-rec --help
-t-rec 0.2.0
+t-rec 0.2.1
 Sven Assmann <[email protected]>
 Blazingly fast terminal recorder that generates animated gif images for the web written in rust.
 
@@ -89,9 +89,11 @@ You can record not only the terminal but also every other window. There 2 ways t
 
 ```sh
 ❯ TERM_PROGRAM="google chrome" t-rec
+
 Frame cache dir: "/var/folders/m8/084p1v0x4770rpwpkrgl5b6h0000gn/T/trec-74728.rUxBx3ohGiQ2"
+Recording window: "Google Chrome 2"
 Press Ctrl+D to end recording
-Recording Window: "Google Chrome 2"
+
 ```
 
 this is how it looks then:
@@ -111,6 +113,7 @@ Code | 27600
 ❯ WINDOWID=27600 t-rec
 
 Frame cache dir: "/var/folders/m8/084p1v0x4770rpwpkrgl5b6h0000gn/T/trec-77862.BMYiHNRWqv9Y"
+Recording window id: 27600
 Press Ctrl+D to end recording
 
 ```

src/macos/screenshot.rs

@@ -17,7 +17,10 @@ pub fn capture_window_screenshot(win_id: u32) -> Result<ImageOnHeap> {
                     | kCGWindowImageShouldBeOpaque,
             )
         }
-        .context("Cannot gather screenshot")?;
+        .context(format!(
+            "Cannot grab screenshot from CGDisplay of window id {}",
+            win_id
+        ))?;
 
         let img_ref: &CGImageRef = &image;
         let (_wrong_width, h) = (img_ref.width() as u32, img_ref.height() as u32);

src/macos/window_id.rs

@@ -137,16 +137,15 @@ pub fn ls_win() -> anyhow::Result<()> {
 /// https://stackoverflow.com/questions/60117318/getting-window-owner-names-via-cgwindowlistcopywindowinfo-in-rust
 /// then some more PRs where needed:
 /// https://github.com/servo/core-foundation-rs/pulls?q=is%3Apr+author%3Asassman+
-pub fn get_window_id_for(terminal: String) -> Result<u32> {
+pub fn get_window_id_for(terminal: String) -> Result<(u32, String)> {
     for term in terminal.to_lowercase().split('.') {
         for (window_owner, window_id, _) in window_list()? {
             if let DictEntryValue::_Number(window_id) = window_id {
                 if let DictEntryValue::_String(window_owner) = window_owner {
                     let window = &window_owner.to_lowercase();
                     let terminal = &terminal.to_lowercase();
                     if window.contains(term) || terminal.contains(window) {
-                        println!("Recording Window: {:?}", window_owner);
-                        return Ok(window_id as u32);
+                        return Ok((window_id as u32, window_owner));
                     }
                 }
             }

src/main.rs

@@ -52,6 +52,9 @@ fn main() -> Result<()> {
             env::var("SHELL").unwrap_or(default)
         }
     };
+    let (win_id, window_name) =
+        current_win_id().context("Cannot retrieve the window id of the to be recorded window.")?;
+    capture_window_screenshot(win_id)?;
 
     let force_natural = args.is_present("natural-mode");
 
@@ -68,7 +71,7 @@ fn main() -> Result<()> {
         let time_codes = time_codes.clone();
         let force_natural = force_natural;
         thread::spawn(move || -> Result<()> {
-            capture_thread(&rx, time_codes, tempdir, force_natural)
+            capture_thread(&rx, win_id, time_codes, tempdir, force_natural)
         })
     };
     let interact = thread::spawn(move || -> Result<()> { sub_shell_thread(&program).map(|_| ()) });
@@ -78,6 +81,11 @@ fn main() -> Result<()> {
         "Frame cache dir: {:?}",
         tempdir.lock().expect("Cannot lock tempdir resource").path()
     );
+    if let Some(window) = window_name {
+        println!("Recording window: {:?}", window);
+    } else {
+        println!("Recording window id: {}", win_id);
+    }
     println!("Press Ctrl+D to end recording");
 
     interact
@@ -110,11 +118,11 @@ fn clear_screen() {
 /// stops once receiving something in rx
 fn capture_thread(
     rx: &Receiver<()>,
+    win_id: u32,
     time_codes: Arc<Mutex<Vec<u128>>>,
     tempdir: Arc<Mutex<TempDir>>,
     force_natural: bool,
 ) -> Result<()> {
-    let win_id = current_win_id()?;
     let duration = Duration::from_millis(250);
     let start = Instant::now();
     let mut idle_duration = Duration::from_millis(0);
@@ -192,19 +200,22 @@ fn sub_shell_thread<T: AsRef<OsStr> + Clone>(program: T) -> Result<ExitStatus> {
 /// or by the env var 'TERM_PROGRAM' and then asking the window manager for all visible windows
 /// and finding the Terminal in that list
 /// panics if WindowId was not was not there
-fn current_win_id() -> Result<u32> {
+fn current_win_id() -> Result<(u32, Option<String>)> {
     if env::var("WINDOWID").is_ok() {
-        env::var("WINDOWID")
+        let win_id = env::var("WINDOWID")
             .unwrap()
             .parse::<u32>()
-            .context("Cannot parse env variable 'WINDOWID' as number")
+            .context("Cannot parse env variable 'WINDOWID' as number")?;
+        Ok((win_id, None))
     } else {
         let terminal = env::var("TERM_PROGRAM").context(
-            "Env variable 'TERM_PROGRAM' was empty but is needed for figure out the WindowId",
+            "Env variable 'TERM_PROGRAM' was empty but it is needed for determine the window id",
+        )?;
+        let (win_id, name) = get_window_id_for(terminal.to_owned()).context(
+            format!(
+            "Cannot determine the window id of {}. Please set env variable 'WINDOWID' and try again.", terminal),
         )?;
-        get_window_id_for(terminal).context(
-            "Cannot determine the WindowId of this terminal. Please set env variable 'WINDOWID' and try again.",
-        )
+        Ok((win_id, Some(name)))
     }
 }