Move window resize timeouts into the GTK frontend.

In the changes around commit 420fe75552, I made the terminal
suspend output processing while it waited for a term_size() callback
in response to a resize request. Because on X11 there are unusual
circumstances in which you never receive that callback, I also added a
last-ditch 5-second timeout, so that eventually we'll resume terminal
output processing regardless.

But the timeout lives in terminal.c, in the cross-platform code. This
is pointless on Windows (where resize processing is synchronous, so we
always finish it before the timer code next gets called anyway), but I
decided it was easier to keep the whole mechanism in terminal.c in the
absence of a good reason not to.

Now I've found that reason. We _also_ generate window resizes locally
to the GTK front end, in response to the key combinations that change
the font size, and _those_ still have an asynchrony problem.

So, to begin with, I'm refactoring the request_resize system so that
now there's an explicit callback from the frontend to the terminal to
say 'Your resize request has now been processed, whether or not you've
received a term_size() call'. On Windows, this simplifies matters
greatly because we always know exactly when to call that, and don't
have to keep a 'have we called term_size() already?' flag. On GTK, the
timing complexity previously in terminal.c has moved into window.c.

No functional change (I hope). The payoff will be in the next commit.

putty.h

@@ -1636,6 +1636,17 @@ struct TermWinVtable {
 
     void (*refresh)(TermWin *);
 
+    /* request_resize asks the front end if the terminal can please be
+     * resized to (w,h) in characters. The front end MAY call
+     * term_size() in response to tell the terminal its new size
+     * (which MAY be the requested size, or some other size if the
+     * requested one can't be achieved). The front end MAY also not
+     * call term_size() at all. But the front end MUST reply to this
+     * request by calling term_resize_request_completed(), after the
+     * responding resize event has taken place (if any).
+     *
+     * The calls to term_size and term_resize_request_completed may be
+     * synchronous callbacks from within the call to request_resize(). */
     void (*request_resize)(TermWin *, int w, int h);
 
     void (*set_title)(TermWin *, const char *title, int codepage);
@@ -2133,6 +2144,7 @@ FontSpec *platform_default_fontspec(const char *name);
 Terminal *term_init(Conf *, struct unicode_data *, TermWin *);
 void term_free(Terminal *);
 void term_size(Terminal *, int, int, int);
+void term_resize_request_completed(Terminal *);
 void term_paint(Terminal *, int, int, int, int, bool);
 void term_scroll(Terminal *, int, int);
 void term_scroll_to_selection(Terminal *, int);

terminal/terminal.c

@@ -1220,12 +1220,6 @@ static void term_timer(void *ctx, unsigned long now)
 
     if (term->window_update_pending)
         term_update_callback(term);
-
-    if (term->win_resize_pending == WIN_RESIZE_AWAIT_REPLY &&
-        now == term->win_resize_timeout) {
-        term->win_resize_pending = WIN_RESIZE_NO;
-        queue_toplevel_callback(term_out_cb, term);
-    }
 }
 
 static void term_update_callback(void *ctx)
@@ -1426,8 +1420,6 @@ void term_update(Terminal *term)
         term->win_resize_pending = WIN_RESIZE_AWAIT_REPLY;
         win_request_resize(term->win, term->win_resize_pending_w,
                            term->win_resize_pending_h);
-        term->win_resize_timeout = schedule_timer(
-            WIN_RESIZE_TIMEOUT, term_timer, term);
     }
     if (term->win_zorder_pending) {
         win_set_zorder(term->win, term->win_zorder_top);
@@ -2151,14 +2143,6 @@ void term_size(Terminal *term, int newrows, int newcols, int newsavelines)
     int sblen;
     int save_alt_which = term->alt_which;
 
-    /* If we were holding buffered terminal data because we were
-     * waiting for confirmation of a resize, queue a callback to start
-     * processing it again. */
-    if (term->win_resize_pending == WIN_RESIZE_AWAIT_REPLY) {
-        term->win_resize_pending = WIN_RESIZE_NO;
-        queue_toplevel_callback(term_out_cb, term);
-    }
-
     if (newrows == term->rows && newcols == term->cols &&
         newsavelines == term->savelines)
         return;                        /* nothing to do */
@@ -2336,6 +2320,13 @@ void term_size(Terminal *term, int newrows, int newcols, int newsavelines)
         backend_size(term->backend, term->cols, term->rows);
 }
 
+void term_resize_request_completed(Terminal *term)
+{
+    assert(term->win_resize_pending == WIN_RESIZE_AWAIT_REPLY);
+    term->win_resize_pending = WIN_RESIZE_NO;
+    queue_toplevel_callback(term_out_cb, term);
+}
+
 /*
  * Hand a backend to the terminal, so it can be notified of resizes.
  */

terminal/terminal.h

@@ -427,24 +427,6 @@ struct terminal_tag {
         WIN_RESIZE_NO, WIN_RESIZE_NEED_SEND, WIN_RESIZE_AWAIT_REPLY
     } win_resize_pending;
     int win_resize_pending_w, win_resize_pending_h;
-
-    /*
-     * Not every frontend / TermWin implementation can be relied on
-     * 100% to reply to a resize request in a timely manner. (In X11
-     * it's all asynchronous and goes via the window manager, and if
-     * your window manager is seriously unwell, you'd rather not have
-     * terminal windows start becoming unusable as a knock-on effect,
-     * since those are just the thing you might need to use for
-     * emergency WM maintenance!) So when we enter AWAIT_REPLY status,
-     * we also set a 5-second timer, after which we'll regretfully
-     * conclude that a resize is probably not going to happen after
-     * all.
-     *
-     * However, in non-emergency cases, the plan is that this
-     * shouldn't be needed, for one reason or another.
-     */
-    long win_resize_timeout;
-    #define WIN_RESIZE_TIMEOUT (TICKSPERSEC*5)
 };
 
 static inline bool in_utf(Terminal *term)

unix/window.c

@@ -189,6 +189,24 @@ struct GtkFrontend {
 #endif
     int trust_sigil_w, trust_sigil_h;
 
+    /*
+     * Not every GDK backend can be relied on 100% to reply to a
+     * resize request in a timely manner. (In X11 it's all
+     * asynchronous and goes via the window manager, and if your
+     * window manager is seriously unwell, you'd rather not have
+     * terminal windows start becoming unusable as a knock-on effect,
+     * since those are just the thing you might need to use for
+     * emergency WM maintenance!)
+     *
+     * So when we ask GTK to resize our terminal window, we also set a
+     * 5-second timer, after which we'll regretfully conclude that a
+     * resize (or ConfigureNotify telling us no resize took place) is
+     * probably not going to happen after all.
+     */
+    bool win_resize_pending, term_resize_notification_required;
+    long win_resize_timeout;
+    #define WIN_RESIZE_TIMEOUT (TICKSPERSEC*5)
+
     Seat seat;
     TermWin termwin;
     LogPolicy logpolicy;
@@ -759,6 +777,10 @@ static void drawing_area_setup(GtkFrontend *inst, int width, int height)
     inst->drawing_area_setup_called = true;
     if (inst->term)
         term_size(inst->term, h, w, conf_get_int(inst->conf, CONF_savelines));
+    if (inst->term_resize_notification_required)
+        term_resize_request_completed(inst->term);
+    if (inst->win_resize_pending)
+        inst->win_resize_pending = false;
 
     if (!inst->drawing_area_setup_needed)
         return;
@@ -2480,6 +2502,17 @@ static void gtkwin_deny_term_resize(void *vctx)
     drawing_area_setup_simple(inst);
 }
 
+static void gtkwin_timer(void *vctx, unsigned long now)
+{
+    GtkFrontend *inst = (GtkFrontend *)vctx;
+
+    if (inst->win_resize_pending && now == inst->win_resize_timeout) {
+        if (inst->term_resize_notification_required)
+            term_resize_request_completed(inst->term);
+        inst->win_resize_pending = false;        
+    }
+}
+
 static void gtkwin_request_resize(TermWin *tw, int w, int h)
 {
     GtkFrontend *inst = container_of(tw, GtkFrontend, termwin);
@@ -2525,6 +2558,7 @@ static void gtkwin_request_resize(TermWin *tw, int w, int h)
 #endif
                      0)) {
             queue_toplevel_callback(gtkwin_deny_term_resize, inst);
+            term_resize_request_completed(inst->term);
             return;
         }
     }
@@ -2613,6 +2647,10 @@ static void gtkwin_request_resize(TermWin *tw, int w, int h)
 
 #endif
 
+    inst->win_resize_pending = true;
+    inst->term_resize_notification_required = true;
+    inst->win_resize_timeout = schedule_timer(
+        WIN_RESIZE_TIMEOUT, gtkwin_timer, inst);
 }
 
 #if GTK_CHECK_VERSION(3,0,0)

windows/window.c

@@ -1667,8 +1667,6 @@ static void deinit_fonts(void)
     trust_icon = INVALID_HANDLE_VALUE;
 }
 
-static bool sent_term_size; /* only live during wintw_request_resize() */
-
 static void wintw_request_resize(TermWin *tw, int w, int h)
 {
     const struct BackendVtable *vt;
@@ -1716,28 +1714,12 @@ static void wintw_request_resize(TermWin *tw, int w, int h)
 
     if (conf_get_int(conf, CONF_resize_action) != RESIZE_FONT &&
         !IsZoomed(wgs.term_hwnd)) {
-        /*
-         * We want to send exactly one term_size() to the terminal,
-         * telling it what size it ended up after this operation.
-         *
-         * If we don't get the size we asked for in SetWindowPos, then
-         * we'll be sent a WM_SIZE message, whose handler will make
-         * that call, all before SetWindowPos even returns to here.
-         *
-         * But if that _didn't_ happen, we'll need to call term_size
-         * ourselves afterwards.
-         */
-        sent_term_size = false;
-
         width = extra_width + font_width * w;
         height = extra_height + font_height * h;
 
         SetWindowPos(wgs.term_hwnd, NULL, 0, 0, width, height,
             SWP_NOACTIVATE | SWP_NOCOPYBITS |
             SWP_NOMOVE | SWP_NOZORDER);
-
-        if (!sent_term_size)
-            term_size(term, h, w, conf_get_int(conf, CONF_savelines));
     } else {
         /*
          * If we're resizing by changing the font, we must tell the
@@ -1748,6 +1730,7 @@ static void wintw_request_resize(TermWin *tw, int w, int h)
         reset_window(0);
     }
 
+    term_resize_request_completed(term);
     InvalidateRect(wgs.term_hwnd, NULL, true);
 }
 
@@ -2188,11 +2171,6 @@ static void wm_size_resize_term(LPARAM lParam, bool border)
     } else {
         term_size(term, h, w,
                   conf_get_int(conf, CONF_savelines));
-        /* If this is happening re-entrantly during the call to
-         * SetWindowPos in wintw_request_resize, let it know that
-         * we've already done a term_size() so that it doesn't have
-         * to. */
-        sent_term_size = true;
     }
 }