xterm audit: DECCOLM and 132COLS

src/terminal/Terminal.zig

@@ -290,40 +290,37 @@ pub fn deccolm(self: *Terminal, alloc: Allocator, mode: DeccolmMode) !void {
     const tracy = trace(@src());
     defer tracy.end();
 
-    // TODO: test
+    // If DEC mode 40 isn't enabled, then this is ignored. We also make
-
+    // sure that we don't have deccolm set because we want to fully ignore
-    // We need to support this. This corresponds to xterm's private mode 40
+    // set mode.
-    // bit. If the mode "?40" is set, then "?3" (DECCOLM) is supported. This
+    if (!self.modes.get(.enable_mode_3)) {
-    // doesn't exactly match VT100 semantics but modern terminals no longer
+        self.modes.set(.@"132_column", false);
-    // blindly accept mode 3 since its so weird in modern practice.
+        return;
-    if (!self.modes.get(.enable_mode_3)) return;
+    }
 
     // Enable it
     self.modes.set(.@"132_column", mode == .@"132_cols");
 
-    // Resize -- we can set cols to 0 because deccolm will force it
+    // Resize to the requested size
-    try self.resize(alloc, 0, self.rows);
+    try self.resize(
+        alloc,
+        switch (mode) {
+            .@"132_cols" => 132,
+            .@"80_cols" => 80,
+        },
+        self.rows,
+    );
 
-    // TODO: do not clear screen flag mode
+    // Erase our display and move our cursor.
     self.eraseDisplay(alloc, .complete, false);
     self.setCursorPos(1, 1);
-
-    // TODO: left/right margins
 }
 
 /// Resize the underlying terminal.
-pub fn resize(self: *Terminal, alloc: Allocator, cols_req: usize, rows: usize) !void {
+pub fn resize(self: *Terminal, alloc: Allocator, cols: usize, rows: usize) !void {
     const tracy = trace(@src());
     defer tracy.end();
 
-    // If we have deccolm supported then we are fixed at either 80 or 132
-    // columns depending on if mode 3 is set or not.
-    // TODO: test
-    const cols: usize = if (self.modes.get(.enable_mode_3))
-        if (self.modes.get(.@"132_column")) 132 else 80
-    else
-        cols_req;
-
     // If our cols/rows didn't change then we're done
     if (self.cols == cols and self.rows == rows) return;
 
@@ -6777,3 +6774,80 @@ test "Terminal: printRepeat no previous character" {
         try testing.expectEqualStrings("", str);
     }
 }
+
+test "Terminal: DECCOLM without DEC mode 40" {
+    const alloc = testing.allocator;
+    var t = try init(alloc, 5, 5);
+    defer t.deinit(alloc);
+
+    t.modes.set(.@"132_column", true);
+    try t.deccolm(alloc, .@"132_cols");
+    try testing.expectEqual(@as(usize, 5), t.cols);
+    try testing.expectEqual(@as(usize, 5), t.rows);
+    try testing.expect(!t.modes.get(.@"132_column"));
+}
+
+test "Terminal: DECCOLM unset" {
+    const alloc = testing.allocator;
+    var t = try init(alloc, 5, 5);
+    defer t.deinit(alloc);
+
+    t.modes.set(.enable_mode_3, true);
+    try t.deccolm(alloc, .@"80_cols");
+    try testing.expectEqual(@as(usize, 80), t.cols);
+    try testing.expectEqual(@as(usize, 5), t.rows);
+}
+
+test "Terminal: DECCOLM resets pending wrap" {
+    const alloc = testing.allocator;
+    var t = try init(alloc, 5, 5);
+    defer t.deinit(alloc);
+
+    for ("ABCDE") |c| try t.print(c);
+    try testing.expect(t.screen.cursor.pending_wrap);
+
+    t.modes.set(.enable_mode_3, true);
+    try t.deccolm(alloc, .@"80_cols");
+    try testing.expectEqual(@as(usize, 80), t.cols);
+    try testing.expectEqual(@as(usize, 5), t.rows);
+    try testing.expect(!t.screen.cursor.pending_wrap);
+}
+
+test "Terminal: DECCOLM preserves SGR bg" {
+    const alloc = testing.allocator;
+    var t = try init(alloc, 5, 5);
+    defer t.deinit(alloc);
+
+    const pen: Screen.Cell = .{
+        .bg = .{ .r = 0xFF, .g = 0x00, .b = 0x00 },
+        .attrs = .{ .has_bg = true },
+    };
+
+    t.screen.cursor.pen = pen;
+    t.modes.set(.enable_mode_3, true);
+    try t.deccolm(alloc, .@"80_cols");
+
+    {
+        const cell = t.screen.getCell(.active, 0, 0);
+        try testing.expectEqual(pen, cell);
+    }
+}
+
+test "Terminal: DECCOLM resets scroll region" {
+    const alloc = testing.allocator;
+    var t = try init(alloc, 5, 5);
+    defer t.deinit(alloc);
+
+    t.modes.set(.enable_left_and_right_margin, true);
+    t.setTopAndBottomMargin(2, 3);
+    t.setLeftAndRightMargin(3, 5);
+
+    t.modes.set(.enable_mode_3, true);
+    try t.deccolm(alloc, .@"80_cols");
+
+    try testing.expect(t.modes.get(.enable_left_and_right_margin));
+    try testing.expectEqual(@as(usize, 0), t.scrolling_region.top);
+    try testing.expectEqual(@as(usize, 4), t.scrolling_region.bottom);
+    try testing.expectEqual(@as(usize, 0), t.scrolling_region.left);
+    try testing.expectEqual(@as(usize, 79), t.scrolling_region.right);
+}

website/app/vt/modes/deccolm/page.mdx

@@ -0,0 +1,70 @@
+import VTMode from "@/components/VTMode";
+
+# Select 80 or 132 Columns per Page (DECCOLM)
+
+<VTMode value={3} />
+
+Sets the screen to 132 columns if set or 80 columns if unset.
+
+This requires [`132COLS` (DEC mode 40)](/vt/modes/132cols) to be set
+to have any effect. If `132COLS` is not set, then setting or unsetting
+this mode does nothing.
+
+When this mode changes, the screen is resized to the given column amount,
+performing reflow if necessary. If the GUI window is too narrow or too wide,
+it is typically resized to fit the explicit column count or a scrollbar is
+used. If the GUI window is manually resized (i.e. with the mouse), the column
+width of DECCOLM is not enforced.
+
+The scroll margins are reset to their default values given the new screen size.
+The cursor is moved to the top-left. The screen is erased using
+[erase display (ED) with command 2](/vt/ed).
+
+## Validation
+
+### DECCOLM V-1: Disabled
+
+```bash
+printf "ABC\n"
+printf "\033[?40l" # disable mode 3
+printf "\033[?3h"
+printf "X"
+```
+
+```
+|ABC_____|
+|Xc______|
+|________|
+```
+
+The command should be completely ignored.
+
+### DECCOLM V-2: Unset (80 Column)
+
+```bash
+printf "ABC\n"
+printf "\033[?40h" # enable mode 3
+printf "\033[?3l" # unset the mode
+printf "X"
+```
+
+```
+|X_______|
+```
+
+The screen should be 80 columns wide.
+
+### DECCOLM V-3: Set (132 Column)
+
+```bash
+printf "ABC\n"
+printf "\033[?40h" # enable mode 3
+printf "\033[?3h"
+printf "X"
+```
+
+```
+|X_______|
+```
+
+The screen should be 132 columns wide.