Partially add DECCOLM support

It's not possible with DECCOLM to temporarily set 80 or 132 column mode
since the function is a toggle between the two. Instead, only the
additional affects are run in order to get closer to passing vttest.

vttest will never be perfect due to the column mode issue.

2 files changed, 26 insertions, 0 deletions

diff --git a/src/ansi.rs b/src/ansi.rs
index 2b71e537..cf7bbea2 100644
--- a/src/ansi.rs
+++ b/src/ansi.rs
@@ -263,6 +263,18 @@ pub trait Handler {
 pub enum Mode {
     /// ?1
     CursorKeys = 1,
+    /// Select 80 or 132 columns per page
+    ///
+    /// CSI ? 3 h -> set 132 column font
+    /// CSI ? 3 l -> reset 80 column font
+    ///
+    /// Additionally,
+    ///
+    /// * set margins to default positions
+    /// * erases all data in page memory
+    /// * resets DECLRMM to unavailable
+    /// * clears data from the status line (if set to host-writable)
+    DECCOLM = 3,
     /// ?6
     Origin = 6,
     /// ?7
@@ -296,6 +308,7 @@ impl Mode {
         if private {
             Some(match num {
                 1 => Mode::CursorKeys,
+                3 => Mode::DECCOLM,
                 6 => Mode::Origin,
                 7 => Mode::LineWrap,
                 12 => Mode::BlinkingCursor,
diff --git a/src/term/mod.rs b/src/term/mod.rs
index 9993d2b3..40fb58e1 100644
--- a/src/term/mod.rs
+++ b/src/term/mod.rs
@@ -1014,6 +1014,17 @@ impl Term {
             self.grid.scroll_up(origin..end, lines);
         }
     }
+
+    fn deccolm(&mut self) {
+        // Setting 132 column font makes no sense, but run the other side effects
+        // Clear scrolling region
+        let scroll_region = Line(0)..self.grid.num_lines();
+        self.set_scrolling_region(scroll_region);
+
+        // Clear grid
+        let template = self.empty_cell;
+        self.grid.clear(|c| c.reset(&template));
+    }
 }
 
 impl ansi::TermInfo for Term {
@@ -1572,6 +1583,7 @@ impl ansi::Handler for Term {
             ansi::Mode::LineWrap => self.mode.insert(mode::LINE_WRAP),
             ansi::Mode::LineFeedNewLine => self.mode.insert(mode::LINE_FEED_NEW_LINE),
             ansi::Mode::Origin => self.mode.insert(mode::ORIGIN),
+            ansi::Mode::DECCOLM => self.deccolm(),
             _ => {
                 debug!(".. ignoring set_mode");
             }
@@ -1596,6 +1608,7 @@ impl ansi::Handler for Term {
             ansi::Mode::LineWrap => self.mode.remove(mode::LINE_WRAP),
             ansi::Mode::LineFeedNewLine => self.mode.remove(mode::LINE_FEED_NEW_LINE),
             ansi::Mode::Origin => self.mode.remove(mode::ORIGIN),
+            ansi::Mode::DECCOLM => self.deccolm(),
             _ => {
                 debug!(".. ignoring unset_mode");
             }