From 80a87df618af3072dbf8a0a74828a4f14d16f937 Mon Sep 17 00:00:00 2001
From: Simon Tatham <anakin@pobox.com>
Date: Thu, 12 May 2022 19:38:45 +0100
Subject: [PATCH] GTK: don't try to change font size in mid-window-resize.

If the user holds down Alt-> so that the key repeats, then a second
call to change_font_size can occur while the window resize from the
previous one has yet to complete. This leads to the new pixel size of
the window from resize #1 being interpreted in the light of the font
size from reesize #2, so that the two get out of step and the
_character_ size of the terminal changes as a result.

The simplest fix is to disallow starting a second font-size-based
window resize while the first is still in flight - which, now that the
'win_resize_pending' flag lives in window.c and not terminal.c, is
easy to achieve.
---
 unix/window.c | 29 ++++++++++++++++++-----------
 1 file changed, 18 insertions(+), 11 deletions(-)

diff --git a/unix/window.c b/unix/window.c
index 4fca971a..167020b4 100644
--- a/unix/window.c
+++ b/unix/window.c
@@ -1278,7 +1278,8 @@ gint key_event(GtkWidget *widget, GdkEventKey *event, gpointer data)
 #ifdef KEY_EVENT_DIAGNOSTICS
             debug(" - Ctrl->: increase font size\n");
 #endif
-            change_font_size(inst, +1);
+            if (!inst->win_resize_pending)
+                change_font_size(inst, +1);
             return true;
         }
         if (event->keyval == GDK_KEY_less &&
@@ -1286,7 +1287,8 @@ gint key_event(GtkWidget *widget, GdkEventKey *event, gpointer data)
 #ifdef KEY_EVENT_DIAGNOSTICS
             debug(" - Ctrl-<: increase font size\n");
 #endif
-            change_font_size(inst, -1);
+            if (!inst->win_resize_pending)
+                change_font_size(inst, -1);
             return true;
         }
 
@@ -2513,10 +2515,9 @@ static void gtkwin_timer(void *vctx, unsigned long now)
     }
 }
 
-static void gtkwin_request_resize(TermWin *tw, int w, int h)
+static void request_resize_internal(GtkFrontend *inst, bool from_terminal,
+                                    int w, int h)
 {
-    GtkFrontend *inst = container_of(tw, GtkFrontend, termwin);
-
 #if GTK_CHECK_VERSION(2,0,0)
     /*
      * Initial check: don't even try to resize a window if it's in one
@@ -2648,11 +2649,17 @@ static void gtkwin_request_resize(TermWin *tw, int w, int h)
 #endif
 
     inst->win_resize_pending = true;
-    inst->term_resize_notification_required = true;
+    inst->term_resize_notification_required = from_terminal;
     inst->win_resize_timeout = schedule_timer(
         WIN_RESIZE_TIMEOUT, gtkwin_timer, inst);
 }
 
+static void gtkwin_request_resize(TermWin *tw, int w, int h)
+{
+    GtkFrontend *inst = container_of(tw, GtkFrontend, termwin);
+    request_resize_internal(inst, true, w, h);
+}
+
 #if GTK_CHECK_VERSION(3,0,0)
 char *colour_to_css(const GdkColor *col)
 {
@@ -4834,9 +4841,9 @@ static void after_change_settings_dialog(void *vctx, int retval)
             conf_get_int(newconf, CONF_window_border) ||
             need_size) {
             set_geom_hints(inst);
-            win_request_resize(&inst->termwin,
-                               conf_get_int(newconf, CONF_width),
-                               conf_get_int(newconf, CONF_height));
+            request_resize_internal(inst, false,
+                                    conf_get_int(newconf, CONF_width),
+                                    conf_get_int(newconf, CONF_height));
         } else {
             /*
              * The above will have caused a call to term_size() for
@@ -4909,8 +4916,8 @@ static void change_font_size(GtkFrontend *inst, int increment)
     }
 
     set_geom_hints(inst);
-    win_request_resize(&inst->termwin, conf_get_int(inst->conf, CONF_width),
-                       conf_get_int(inst->conf, CONF_height));
+    request_resize_internal(inst, false, conf_get_int(inst->conf, CONF_width),
+                            conf_get_int(inst->conf, CONF_height));
     term_invalidate(inst->term);
     gtk_widget_queue_draw(inst->area);