From e6cddcf752b335cb945bba4619b500b527cfee0a Mon Sep 17 00:00:00 2001
From: nicm <nicm>
Date: Tue, 31 Mar 2020 17:13:20 +0000
Subject: [PATCH] Add a -T flag to resize-pane to trim lines below the cursor,
 moving lines out of the history. GitHub issue 2134.

---
 cmd-resize-pane.c | 17 +++++++++++++++--
 grid.c            | 13 +++++++++++++
 tmux.1            |  5 ++++-
 3 files changed, 32 insertions(+), 3 deletions(-)

diff --git a/cmd-resize-pane.c b/cmd-resize-pane.c
index b0aa2756..fd303cc1 100644
--- a/cmd-resize-pane.c
+++ b/cmd-resize-pane.c
@@ -36,8 +36,8 @@ const struct cmd_entry cmd_resize_pane_entry = {
 	.name = "resize-pane",
 	.alias = "resizep",
 
-	.args = { "DLMRt:Ux:y:Z", 0, 1 },
-	.usage = "[-DLMRUZ] [-x width] [-y height] " CMD_TARGET_PANE_USAGE " "
+	.args = { "DLMRTt:Ux:y:Z", 0, 1 },
+	.usage = "[-DLMRTUZ] [-x width] [-y height] " CMD_TARGET_PANE_USAGE " "
 		 "[adjustment]",
 
 	.target = { 't', CMD_FIND_PANE, 0 },
@@ -60,6 +60,19 @@ cmd_resize_pane_exec(struct cmd *self, struct cmdq_item *item)
 	char			*cause;
 	u_int			 adjust;
 	int			 x, y;
+	struct grid		*gd = wp->base.grid;
+
+	if (args_has(args, 'T')) {
+		if (!TAILQ_EMPTY(&wp->modes))
+			return (CMD_RETURN_NORMAL);
+		adjust = screen_size_y(&wp->base) - 1 - wp->base.cy;
+		if (adjust > gd->hsize)
+			adjust = gd->hsize;
+		grid_remove_history(gd, adjust);
+		wp->base.cy += adjust;
+		wp->flags |= PANE_REDRAW;
+		return (CMD_RETURN_NORMAL);
+	}
 
 	if (args_has(args, 'M')) {
 		if (cmd_mouse_window(&shared->mouse, &s) == NULL)
diff --git a/grid.c b/grid.c
index 29943e6b..9678bf59 100644
--- a/grid.c
+++ b/grid.c
@@ -351,6 +351,19 @@ grid_collect_history(struct grid *gd)
 		gd->hscrolled = gd->hsize;
 }
 
+/* Remove lines from the bottom of the history. */
+void
+grid_remove_history(struct grid *gd, u_int ny)
+{
+	u_int	yy;
+
+	if (ny > gd->hsize)
+		return;
+	for (yy = 0; yy < ny; yy++)
+		grid_free_line(gd, gd->hsize + gd->sy - 1 - yy);
+	gd->hsize -= ny;
+}
+
 /*
  * Scroll the entire visible screen, moving one line into the history. Just
  * allocate a new line at the bottom and move the history size indicator.
diff --git a/tmux.1 b/tmux.1
index a3b2b0f8..b0fc5600 100644
--- a/tmux.1
+++ b/tmux.1
@@ -2261,7 +2261,7 @@ Rename the current window, or the window at
 if specified, to
 .Ar new-name .
 .It Xo Ic resize-pane
-.Op Fl DLMRUZ
+.Op Fl DLMRTUZ
 .Op Fl t Ar target-pane
 .Op Fl x Ar width
 .Op Fl y Ar height
@@ -2300,6 +2300,9 @@ and unzoomed (its normal position in the layout).
 .Fl M
 begins mouse resizing (only valid if bound to a mouse key binding, see
 .Sx MOUSE SUPPORT ) .
+.Pp T
+trims all lines below the current cursor position and moves lines out of the
+history to replace them.
 .It Xo Ic resize-window
 .Op Fl aADLRU
 .Op Fl t Ar target-window