patch 9.2.0112: popup: windows flicker when updating text

Problem:  popup: windows flicker when updating text
Solution: Only refresh the popup mask if the position or size changed,
          manually set the window redraw type instead of using
          redraw_win_later() to avoid triggering a full screen redraw.
          Handle opacity 100 correctly. Keep "firstline" sticky when
          setting options (Yasuhiro Matsumoto).

related: #19510
closes:  #19559

Signed-off-by: Yasuhiro Matsumoto <mattn.jp@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

src/popupwin.c

@@ -785,13 +785,19 @@ apply_general_options(win_T *wp, dict_T *dict)
     if (di != NULL)
     {
 	nr = dict_get_number(dict, "opacity");
-	if (nr > 0 && nr <= 100)
+	if (nr > 0 && nr < 100)
 	{
-	    // opacity: 0-100, where 0=transparent, 100=opaque
+	    // opacity: 1-99, partially transparent
 	    // Convert to blend (0=opaque, 100=transparent)
 	    wp->w_popup_flags |= POPF_OPACITY;
 	    wp->w_popup_blend = 100 - nr;
 	}
+	else if (nr == 100)
+	{
+	    // Fully opaque, same as no opacity set.
+	    wp->w_popup_flags &= ~POPF_OPACITY;
+	    wp->w_popup_blend = 0;
+	}
 	else
 	{
 	    wp->w_popup_flags &= ~POPF_OPACITY;
@@ -1098,7 +1104,8 @@ apply_options(win_T *wp, dict_T *dict, int create)
 	wp->w_valid &= ~VALID_BOTLINE;
     }
 
-    popup_mask_refresh = TRUE;
+    if (create)
+	popup_mask_refresh = TRUE;
     popup_highlight_curline(wp);
 
     return OK;
@@ -3106,7 +3113,15 @@ f_popup_settext(typval_T *argvars, typval_T *rettv UNUSED)
 	return;
 
     popup_set_buffer_text(wp->w_buffer, argvars[1]);
-    redraw_win_later(wp, UPD_NOT_VALID);
+
+    // Redraw the popup window without triggering a full screen redraw.
+    // Using redraw_win_later() with UPD_NOT_VALID would set the global
+    // must_redraw, causing may_update_popup_mask() to refresh the mask and
+    // redraw windows behind the popup, resulting in flickering.
+    wp->w_redr_type = UPD_NOT_VALID;
+    wp->w_lines_valid = 0;
+    if (must_redraw < UPD_VALID)
+	must_redraw = UPD_VALID;
     popup_adjust_position(wp);
 }
 
@@ -3391,6 +3406,7 @@ f_popup_setoptions(typval_T *argvars, typval_T *rettv UNUSED)
     char_u	*old_thumb_highlight;
     char_u	*old_border_highlight[4];
     int		need_redraw = FALSE;
+    int		need_reposition = FALSE;
     int		i;
 
     if (in_vim9script()
@@ -3419,13 +3435,25 @@ f_popup_setoptions(typval_T *argvars, typval_T *rettv UNUSED)
 
     (void)apply_options(wp, dict, FALSE);
 
+    // Keep "firstline" sticky across popup_setoptions(): when it is set, any
+    // property update should reapply it and restore the displayed top line.
+    if (wp->w_firstline > 0
+	    && wp->w_firstline <= wp->w_buffer->b_ml.ml_line_count)
+	wp->w_topline = wp->w_firstline;
+
     // Check if visual options changed and redraw if needed
     if (old_firstline != wp->w_firstline)
 	need_redraw = TRUE;
     if (old_zindex != wp->w_zindex)
+    {
 	need_redraw = TRUE;
+	need_reposition = TRUE;
+    }
     if (old_popup_flags != wp->w_popup_flags)
+    {
 	need_redraw = TRUE;
+	need_reposition = TRUE;
+    }
     if (old_scrollbar_highlight != wp->w_scrollbar_highlight)
 	need_redraw = TRUE;
     if (old_thumb_highlight != wp->w_thumb_highlight)
@@ -3437,8 +3465,23 @@ f_popup_setoptions(typval_T *argvars, typval_T *rettv UNUSED)
 	    break;
 	}
 
-    if (need_redraw)
+    if (need_reposition)
+    {
 	redraw_win_later(wp, UPD_NOT_VALID);
+	popup_mask_refresh = TRUE;
+    }
+    else if (need_redraw)
+    {
+	// Only content changed (e.g. firstline, highlight): redraw the
+	// popup window without updating the popup mask or triggering a
+	// full screen redraw.  This avoids flickering of windows behind
+	// the popup.
+	wp->w_redr_type = UPD_NOT_VALID;
+	wp->w_lines_valid = 0;
+	if (must_redraw < UPD_VALID)
+	    must_redraw = UPD_VALID;
+    }
+
 #ifdef FEAT_PROP_POPUP
     // Force redraw if opacity value changed
     if (old_blend != wp->w_popup_blend)
@@ -3446,8 +3489,14 @@ f_popup_setoptions(typval_T *argvars, typval_T *rettv UNUSED)
 	redraw_win_later(wp, UPD_NOT_VALID);
 	// Also redraw windows below the popup
 	redraw_all_later(UPD_NOT_VALID);
+	popup_mask_refresh = TRUE;
     }
 #endif
+
+    // Always recalculate popup position/size: other options like border,
+    // close, padding may have changed without affecting w_popup_flags.
+    // popup_adjust_position() only sets popup_mask_refresh when the
+    // position or size actually changed.
     popup_adjust_position(wp);
 }
 

src/screen.c

@@ -627,7 +627,7 @@ screen_line(
 		    ScreenLines[off_to + 1] = ScreenLines[off_from + 1];
 		    ScreenAttrs[off_to + 1] = ScreenAttrs[off_from];
 		}
-		if (enc_dbcs == DBCS_JPNU) // Copilot's suggestion for DBCS_JPNU
+		if (enc_dbcs == DBCS_JPNU)
 		    ScreenLines2[off_to] = ScreenLines2[off_from];
 
 		if (enc_dbcs != 0 && char_cells == 2)

src/version.c

@@ -734,6 +734,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    112,
 /**/
     111,
 /**/