terminal: bring back clearPromptForResize, with tests!

src/terminal/Screen.zig

@@ -677,6 +677,56 @@ pub fn clearUnprotectedCells(
     }
 }
 
+/// Clears the prompt lines if the cursor is currently at a prompt. This
+/// clears the entire line. This is used for resizing when the shell
+/// handles reflow.
+///
+/// The cleared cells are not colored with the current style background
+/// color like other clear functions, because this is a special case used
+/// for a specific purpose that does not want that behavior.
+pub fn clearPrompt(self: *Screen) void {
+    var found: ?Pin = null;
+
+    // From our cursor, move up and find all prompt lines.
+    var it = self.cursor.page_pin.rowIterator(
+        .left_up,
+        self.pages.pin(.{ .active = .{} }),
+    );
+    while (it.next()) |p| {
+        const row = p.rowAndCell().row;
+        switch (row.semantic_prompt) {
+            // We are at a prompt but we're not at the start of the prompt.
+            // We mark our found value and continue because the prompt
+            // may be multi-line.
+            .input => found = p,
+
+            // If we find the prompt then we're done. We are also done
+            // if we find any prompt continuation, because the shells
+            // that send this currently (zsh) cannot redraw every line.
+            .prompt, .prompt_continuation => {
+                found = p;
+                break;
+            },
+
+            // If we have command output, then we're most certainly not
+            // at a prompt. Break out of the loop.
+            .command => break,
+
+            // If we don't know, we keep searching.
+            .unknown => {},
+        }
+    }
+
+    // If we found a prompt, we clear it.
+    if (found) |top| {
+        var clear_it = top.rowIterator(.right_down, null);
+        while (clear_it.next()) |p| {
+            const row = p.rowAndCell().row;
+            p.page.data.clearCells(row, 0, p.page.data.size.cols);
+        }
+    }
+}
+
 /// Returns the blank cell to use when doing terminal operations that
 /// require preserving the bg color.
 fn blankCell(self: *const Screen) Cell {
@@ -2067,6 +2117,50 @@ test "Screen eraseRows history with more lines" {
     }
 }
 
+test "Screen: clearPrompt" {
+    const testing = std.testing;
+    const alloc = testing.allocator;
+
+    var s = try init(alloc, 5, 3, 0);
+    defer s.deinit();
+    const str = "1ABCD\n2EFGH\n3IJKL";
+    try s.testWriteString(str);
+
+    // Set one of the rows to be a prompt
+    {
+        s.cursorAbsolute(0, 1);
+        s.cursor.page_row.semantic_prompt = .prompt;
+        s.cursorAbsolute(0, 2);
+        s.cursor.page_row.semantic_prompt = .input;
+    }
+
+    s.clearPrompt();
+
+    {
+        const contents = try s.dumpStringAlloc(alloc, .{ .screen = .{} });
+        defer alloc.free(contents);
+        try testing.expectEqualStrings("1ABCD", contents);
+    }
+}
+
+test "Screen: clearPrompt no prompt" {
+    const testing = std.testing;
+    const alloc = testing.allocator;
+
+    var s = try init(alloc, 5, 3, 0);
+    defer s.deinit();
+    const str = "1ABCD\n2EFGH\n3IJKL";
+    try s.testWriteString(str);
+
+    s.clearPrompt();
+
+    {
+        const contents = try s.dumpStringAlloc(alloc, .{ .screen = .{} });
+        defer alloc.free(contents);
+        try testing.expectEqualStrings(str, contents);
+    }
+}
+
 test "Screen: scrolling" {
     const testing = std.testing;
     const alloc = testing.allocator;

src/terminal/Terminal.zig

@@ -2051,7 +2051,10 @@ pub fn resize(
 
     // If we're making the screen smaller, dealloc the unused items.
     if (self.active_screen == .primary) {
-        self.clearPromptForResize();
+        if (self.flags.shell_redraws_prompt) {
+            self.screen.clearPrompt();
+        }
+
         if (self.modes.get(.wraparound)) {
             try self.screen.resize(cols, rows);
         } else {
@@ -2080,14 +2083,6 @@ pub fn resize(
     };
 }
 
-/// If shell_redraws_prompt is true and we're on the primary screen,
-/// then this will clear the screen from the cursor down if the cursor is
-/// on a prompt in order to allow the shell to redraw the prompt.
-fn clearPromptForResize(self: *Terminal) void {
-    // TODO
-    _ = self;
-}
-
 /// Set the pwd for the terminal.
 pub fn setPwd(self: *Terminal, pwd: []const u8) !void {
     self.pwd.clearRetainingCapacity();