Truncate invisible lines before storing ref-tests

Because there is no good way to store invisible lines in a backwards-
and forwards-compatible way, they buffer now gets truncated before
dumping the state of a grid when creating a ref-test.

This involved a few workaround of which a few required adding additional
methods which are only used in ref-tests, these should be minimal
though.

Since this required the creation of a truncation method anyways, some
logic has been added which automatically truncates the invisible buffer
when there are more than X (set to 100) invisible lines. This should not
impact performance because it rarely occurs, but it could save a bit of
memory when the history size is shrunk during runtime (see #1293).

This also adds an optional `config.json` file to the ref-test output
where it is possible to manually specify variables which should override
config defaults, this has been used only for history_size so far.

Creating a new ref-test does also still work, so there was no regression
here, if history size is altered, the config.json just has to be created
manually with the content `{"history_size":HIST_SIZE}`, where
`HIST_SIZE` is the desired history size.

3 files changed, 24 insertions, 10 deletions

diff --git a/tests/ref.rs b/tests/ref.rs
index 9ea0b80c..74cac6fa 100644
--- a/tests/ref.rs
+++ b/tests/ref.rs
@@ -1,5 +1,7 @@
-extern crate alacritty;
+#[macro_use]
+extern crate serde_derive;
 extern crate serde_json as json;
+extern crate alacritty;
 
 use std::fs::File;
 use std::io::{self, Read};
@@ -61,26 +63,32 @@ fn read_u8<P>(path: P) -> Vec<u8>
     res
 }
 
-fn read_string<P>(path: P) -> String
+fn read_string<P>(path: P) -> Result<String, ::std::io::Error>
     where P: AsRef<Path>
 {
     let mut res = String::new();
-    File::open(path.as_ref()).unwrap()
-        .read_to_string(&mut res).unwrap();
+    File::open(path.as_ref()).and_then(|mut f| f.read_to_string(&mut res))?;
 
-    res
+    Ok(res)
+}
+
+#[derive(Deserialize, Default)]
+struct RefConfig {
+    history_size: u32,
 }
 
 fn ref_test(dir: &Path) {
     let recording = read_u8(dir.join("alacritty.recording"));
-    let serialized_size = read_string(dir.join("size.json"));
-    let serialized_grid = read_string(dir.join("grid.json"));
+    let serialized_size = read_string(dir.join("size.json")).unwrap();
+    let serialized_grid = read_string(dir.join("grid.json")).unwrap();
+    let serialized_cfg = read_string(dir.join("config.json")).unwrap_or_default();
 
     let size: SizeInfo = json::from_str(&serialized_size).unwrap();
     let grid: Grid<Cell> = json::from_str(&serialized_grid).unwrap();
+    let ref_config: RefConfig = json::from_str(&serialized_cfg).unwrap_or_default();
 
     let mut config: Config = Default::default();
-    config.set_history((grid.len() - grid.num_lines().0) as u32);
+    config.set_history(ref_config.history_size);
 
     let mut terminal = Term::new(&config, size);
     let mut parser = ansi::Processor::new();
@@ -89,7 +97,11 @@ fn ref_test(dir: &Path) {
         parser.advance(&mut terminal, byte, &mut io::sink());
     }
 
-    if grid != *terminal.grid() {
+    // Truncate invisible lines from the grid
+    let mut term_grid = terminal.grid().clone();
+    term_grid.truncate();
+
+    if grid != term_grid {
         for i in 0..grid.len() {
             for j in 0..grid.num_cols().0 {
                 let cell = terminal.grid()[i][Column(j)];
@@ -104,5 +116,5 @@ fn ref_test(dir: &Path) {
         panic!("Ref test failed; grid doesn't match");
     }
 
-    assert_eq!(grid, *terminal.grid());
+    assert_eq!(grid, term_grid);
 }
diff --git a/tests/ref/grid_reset/config.json b/tests/ref/grid_reset/config.json
new file mode 100644
index 00000000..e794493c
--- /dev/null
+++ b/tests/ref/grid_reset/config.json
@@ -0,0 +1 @@
+{"history_size":100}
diff --git a/tests/ref/history/config.json b/tests/ref/history/config.json
new file mode 100644
index 00000000..5cca8022
--- /dev/null
+++ b/tests/ref/history/config.json
@@ -0,0 +1 @@
+{"history_size":1000}