Commit: patch 9.2.0010: Using Wayland compositor is still slow

[Christian Brabandt]

patch 9.2.0010: Using Wayland compositor is still slow

Commit: https://github.com/vim/vim/commit/ac9426bf549a5dea853ae02fa6c5dba0ef3beb95
Author: Christoffer Aasted <dez...@gmail.com>
Date: Sun Feb 15 17:21:03 2026 +0000

patch 9.2.0010: Using Wayland compositor is still slow

Problem: Using the Wayland backend in GTK, rendering remains slow due
to per-line redraws, unnecessary Cairo push/pop groups, and
scroll operations that allocate new surfaces repeatedly.
Solution: Improve rendering performance (Christoffer Aasted).

This commit does the following:
- Add gui.is_wayland to detect Wayland backend
- Avoid blocking the input loop
- Skip early redraws; let the compositor handle full-screen redraws
- Use CAIRO_OPERATOR_SOURCE to overwrite instead of blend
- Reuse scroll source region for destination scroll region
- Optimize fast scroll-up
- Remove cairo_push_group/pop_group and cairo_clip in scroll path
to reduce allocations (~50MB saved on 4K fractional scale)

Since Wayland redraws the entire screen between updates (unlike X11),
further performance gains are possible by batching drawing in other code
paths, e.g.:
- message.c: batch lines to avoid scroll
- term.c: batch terminal redraws

These could be refactored later to deferred redraw with Wayland.

closes: #19062

Signed-off-by: Christoffer Aasted <dez...@gmail.com>
Signed-off-by: Christian Brabandt <c...@256bit.org>

diff --git a/src/gui.c b/src/gui.c
index 8673ec8d8..9eef90f92 100644
--- a/src/gui.c
+++ b/src/gui.c
@@ -211,7 +211,6 @@ gui_attempt_start(void)
if (gui_get_x11_windis(&x11_window, &x11_display) == OK)
set_vim_var_nr(VV_WINDOWID, (long)x11_window);
# endif
-
// Display error messages in a dialog now.
display_errors();
}
@@ -484,6 +483,9 @@ gui_init_check(void)
result = OK;
#else
# ifdef FEAT_GUI_GTK
+# ifdef GDK_WINDOWING_WAYLAND
+ gui.is_wayland = FALSE;
+# endif
/*
* Note: Don't call gtk_init_check() before fork, it will be called after
* the fork. When calling it before fork, it make vim hang for a while.
diff --git a/src/gui.h b/src/gui.h
index da06e2ce0..2069e7486 100644
--- a/src/gui.h
+++ b/src/gui.h
@@ -389,6 +389,9 @@ typedef struct Gui
char_u *browse_fname; // file name from filedlg

guint32 event_time;
+# ifdef GDK_WINDOWING_WAYLAND
+ _Bool is_wayland; // active gdk backend in gtk is wayland
+# endif
#endif // FEAT_GUI_GTK

#if defined(FEAT_GUI_GTK) || defined(FEAT_GUI_MSWIN)
diff --git a/src/gui_gtk_x11.c b/src/gui_gtk_x11.c
index 015a2c7f6..edf6b705d 100644
--- a/src/gui_gtk_x11.c
+++ b/src/gui_gtk_x11.c
@@ -59,6 +59,9 @@ extern void bonobo_dock_item_set_behavior(BonoboDockItem *dock_item, BonoboDockI
#if defined(FEAT_GUI_GTK)
# if GTK_CHECK_VERSION(3,0,0)
# include <gdk/gdkkeysyms-compat.h>
+# ifdef GDK_WINDOWING_WAYLAND
+# include <gdk/gdkwayland.h>
+# endif
# include <gtk/gtkx.h>
# else
# include <gdk/gdkkeysyms.h>
@@ -2039,11 +2042,6 @@ scroll_event(GtkWidget *widget,
# if !GTK_CHECK_VERSION(3,22,0)
static guint32 last_smooth_event_time;
# endif
-# define DT_X11 1
-# define DT_WAYLAND 2
- static int display_type;
- if (!display_type)
- display_type = gui_mch_get_display() ? DT_X11 : DT_WAYLAND;
#endif

if (gtk_socket_id != 0 && !gtk_widget_has_focus(widget))
@@ -2101,7 +2099,7 @@ scroll_event(GtkWidget *widget,
#if GTK_CHECK_VERSION(3,4,0)
// on x11, despite not requested, when we copy into primary clipboard,
// we'll get smooth events. Unsmooth ones will also come along.
- if (event->direction == GDK_SCROLL_SMOOTH && display_type == DT_WAYLAND)
+ if (event->direction == GDK_SCROLL_SMOOTH && gui.is_wayland)
{
while (acc_x >= 1.0)
{ // right
@@ -2128,12 +2126,10 @@ scroll_event(GtkWidget *widget,
FALSE, vim_modifiers);
}
}
- else if (event->direction == GDK_SCROLL_SMOOTH && display_type == DT_X11)
+ else if (event->direction == GDK_SCROLL_SMOOTH && X_DISPLAY)
// for X11 we deal with unsmooth events, and so ignore the smooth ones
;
else
-# undef DT_X11
-# undef DT_WAYLAND
#endif
gui_send_mouse_event(button, (int)event->x, (int)event->y,
FALSE, vim_modifiers);
@@ -4004,6 +4000,12 @@ gui_mch_init(void)
gui.surface = NULL;
#endif

+#ifdef GDK_WINDOWING_WAYLAND
+ GdkDisplay *d = gdk_display_get_default();
+ if (GDK_IS_WAYLAND_DISPLAY(d))
+ gui.is_wayland = TRUE;
+#endif
+
// Determine which events we will filter.
gint event_mask =
GDK_EXPOSURE_MASK |
@@ -6619,6 +6621,11 @@ gui_mch_draw_part_cursor(int w, int h, guicolor_T color)
void
gui_mch_update(void)
{
+#ifdef GDK_WINDOWING_WAYLAND
+ // avoid early redraws; compositor does redraw
+ if (gui.is_wayland)
+ return;
+#endif
int cnt = 0; // prevent endless loop
while (g_main_context_pending(NULL) && !vim_is_input_buf_full()
&& ++cnt < 100)
@@ -6718,7 +6725,14 @@ gui_mch_wait_for_chars(long wtime)
* situations, sort of race condition).
*/
if (!input_available())
- g_main_context_iteration(NULL, TRUE);
+ {
+#ifdef GDK_WINDOWING_WAYLAND
+ if (gui.is_wayland)
+ g_main_context_iteration(NULL, FALSE);
+ else
+#endif
+ g_main_context_iteration(NULL, TRUE);
+ }

// Got char, return immediately
if (input_available())
@@ -6909,13 +6923,69 @@ gui_gtk_surface_copy_rect(int dest_x, int dest_y,
{
cairo_t * const cr = cairo_create(gui.surface);

- cairo_rectangle(cr, dest_x, dest_y, width, height);
- cairo_clip(cr);
- cairo_push_group(cr);
- cairo_set_source_surface(cr, gui.surface, dest_x - src_x, dest_y - src_y);
- cairo_paint(cr);
- cairo_pop_group_to_source(cr);
- cairo_paint(cr);
+# ifdef GDK_WINDOWING_WAYLAND
+ /*
+ Following optimizations are temporary until all callers are refactored
+ to wayland deferred redraw; .. then it could be removed.
+ */
+ static cairo_surface_t *scroll_scratch = NULL;
+ static int scratch_w = 0;
+ static int scratch_h = 0;
+ int last_row = Rows - 1;
+ int last_row_y = last_row * gui.char_height;
+ _Bool last_row_overlap = (dest_y + height) > last_row_y;
+ if (gui.is_wayland && ( !(State & MODE_CMDLINE) || !last_row_overlap) )
+ {
+ /*
+ scrolling up
+ */
+ if (dest_y < src_y)
+ {
+ cairo_set_operator(cr, CAIRO_OPERATOR_SOURCE);
+ cairo_set_source_surface(cr, gui.surface,
+ src_x - dest_x,
+ dest_y - src_y);
+ cairo_rectangle(cr, dest_x, dest_y, width, height);
+ cairo_clip(cr);
+ cairo_paint(cr);;
+ }
+ else
+ {
+ // reusing surface when scrolling, only realloc if larger
+ if (scroll_scratch == NULL || width > scratch_w || height > scratch_h)
+ {
+ cairo_surface_destroy(scroll_scratch); // safe even if NULL
+ scroll_scratch = cairo_surface_create_similar(gui.surface,
+ cairo_surface_get_content(gui.surface), width, height);
+ scratch_w = width;
+ scratch_h = height;
+ }
+
+ // capture scroll source region
+ cairo_t *tcr = cairo_create(scroll_scratch);
+ cairo_set_source_surface(tcr, gui.surface, -src_x, -src_y);
+ cairo_paint(tcr);
+ cairo_destroy(tcr);
+
+ // reuse scroll source region
+ cairo_set_operator(cr, CAIRO_OPERATOR_SOURCE);
+ cairo_rectangle(cr, dest_x, dest_y, width, height);
+ cairo_clip(cr);
+ cairo_set_source_surface(cr, scroll_scratch, dest_x, dest_y);
+ cairo_paint(cr);
+ }
+ }
+ else
+# endif
+ {
+ cairo_rectangle(cr, dest_x, dest_y, width, height);
+ cairo_clip(cr);
+ cairo_push_group(cr);
+ cairo_set_source_surface(cr, gui.surface, dest_x - src_x, dest_y - src_y);
+ cairo_paint(cr);
+ cairo_pop_group_to_source(cr);
+ cairo_paint(cr);
+ }

cairo_destroy(cr);
}
diff --git a/src/version.c b/src/version.c
index 1c7ecd3b1..ad4b50cf7 100644
--- a/src/version.c
+++ b/src/version.c
@@ -734,6 +734,8 @@ static char *(features[]) =

static int included_patches[] =
{ /* Add new patch number below this line */
+/**/
+ 10,
/**/
9,
/**/