Implement tab stop manipulation

Adds implementations for TBC (tabulation clear) and HTS (set horizontal
tabstop).

src/term/mod.rs

@@ -1307,7 +1307,9 @@ impl ansi::Handler for Term {
 
     #[inline]
     fn set_horizontal_tabstop(&mut self) {
-        trace!("[unimplemented] set_horizontal_tabstop");
+        trace!("set_horizontal_tabstop");
+        let column = self.cursor.point.col;
+        self.tabs[column.0] = true;
     }
 
     #[inline]
@@ -1502,7 +1504,21 @@ impl ansi::Handler for Term {
 
     #[inline]
     fn clear_tabs(&mut self, mode: ansi::TabulationClearMode) {
-        trace!("[unimplemented] clear_tabs: {:?}", mode);
+        trace!("clear_tabs: {:?}", mode);
+        match mode {
+            ansi::TabulationClearMode::Current => {
+                let column = self.cursor.point.col;
+                self.tabs[column.0] = false;
+            },
+            ansi::TabulationClearMode::All => {
+                let len = self.tabs.len();
+                // Safe since false boolean is null, each item occupies only 1
+                // byte, and called on the length of the vec.
+                unsafe {
+                    ::std::ptr::write_bytes(self.tabs.as_mut_ptr(), 0, len);
+                }
+            }
+        }
     }
 
     #[inline]

tests/ref.rs

@@ -40,6 +40,7 @@ ref_tests! {
     vttest_origin_mode_1
     vttest_origin_mode_2
     vttest_scroll
+    vttest_tab_clear_set
     zsh_tab_completion
 }
 

tests/ref/vttest_tab_clear_set/alacritty.recording

@@ -0,0 +1,23 @@
+%                                                                               
 

jwilm@sanctuary.local ➜  ~/code/alacritty  [?1h=[?2004hvvtvttteesvttest[?1l>[?2004l
+[?1l[?3l[?4l[?5l[?6l[?7h[?8l[?40h[?45lVT100 test program, version 2.7 (20140305)Choose test type:
+
+          0. Exit
+          1. Test of cursor movements
+          2. Test of screen features
+          3. Test of character sets
+          4. Test of double-sized characters
+          5. Test of keyboard
+          6. Test of terminal reports
+          7. Test of VT52 mode
+          8. Test of VT102 features (Insert/Delete Char/Line)
+          9. Test of known bugs
+          10. Test of reset and self-test
+          11. Test non-VT100 (e.g., VT220, XTERM) terminals
+          12. Modify test-parameters
+
+          Enter choice number (0 - 12): 2
+[?7h****************************************************************************************************************************************************************[?7l****************************************************************************************************************************************************************[?7hThis should be three identical lines of *'s completely filling
+the top of the screen without any empty lines between.
+(Test of WRAP AROUND mode setting.)
+Push <RETURN>HHHHHHHHHHHHHHHHHHHHHHHHHH	*	*	*	*	*	*	*	*	*	*	*	*	*     *     *     *     *     *     *     *     *     *     *     *     *     *Test of TAB setting/resetting. These two lines
+should look the same. Push <RETURN>

tests/ref/vttest_tab_clear_set/size.json

@@ -0,0 +1 @@
+{"width":1124.0,"height":676.0,"cell_width":14.0,"cell_height":28.0}