Fix redisplay when mode-line-format changes mode-line's height

* lisp/frame.el (top-level): Add mode-line-format,
tab-line-format, and header-line-format to the list of variables
that should trigger an immediate redisplay of the buffer's
window.  This fixes redisplay of windows when the mode line
changes its height.

* src/xdisp.c (window_box_height): Use the window's
mode_line_height, tab_line_height, and header_line_height fields
in preference to CURRENT_MODE_LINE_HEIGHT,
CURRENT_TAB_LINE_HEIGHT, and CURRENT_HEADER_LINE_HEIGHT,
respectively.  This fixes display of vertical scroll bar when the
height of the window's mode line changes.
* src/dispnew.c (adjust_glyph_matrix): When resizing a window's
matrix, reset the mode_line_p flag of the previous mode-line row,
so that the window_box_height, CURRENT_MODE_LINE_HEIGHT, and their
ilk won't use stale info.  (Bug#38828)

2 files changed, 47 insertions, 25 deletions

diff --git a/src/dispnew.c b/src/dispnew.c
index b2a257090cc..ed8c5552e75 100644
--- a/src/dispnew.c
+++ b/src/dispnew.c
@@ -534,6 +534,13 @@ adjust_glyph_matrix (struct window *w, struct glyph_matrix *matrix, int x, int y
       eassert (left >= 0 && right >= 0);
       matrix->left_margin_glyphs = left;
       matrix->right_margin_glyphs = right;
+
+      /* If we are resizing a window, make sure the previous mode-line
+         row of the window's current matrix is no longer marked as such.  */
+      if (w && matrix == w->current_matrix
+          && dim.height != matrix->nrows
+          && matrix->nrows <= matrix->rows_allocated)
+        MATRIX_MODE_LINE_ROW (matrix)->mode_line_p = false;
     }
 
   /* Number of rows to be used by MATRIX.  */
diff --git a/src/xdisp.c b/src/xdisp.c
index 6b677b63ae4..4856a7b13b6 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -1093,44 +1093,59 @@ window_box_height (struct window *w)
 
   /* Note: the code below that determines the mode-line/header-line/tab-line
      height is essentially the same as that contained in the macro
-     CURRENT_{MODE,HEADER}_LINE_HEIGHT, except that it checks whether
-     the appropriate glyph row has its `mode_line_p' flag set,
-     and if it doesn't, uses estimate_mode_line_height instead.  */
+     CURRENT_{MODE,HEADER,TAB}_LINE_HEIGHT, except that it checks whether
+     the appropriate glyph row has its `mode_line_p' flag set, and if
+     it doesn't, uses estimate_mode_line_height instead.  */
 
   if (window_wants_mode_line (w))
     {
-      struct glyph_row *ml_row
-        = (w->current_matrix && w->current_matrix->rows
-           ? MATRIX_MODE_LINE_ROW (w->current_matrix)
-           : 0);
-      if (ml_row && ml_row->mode_line_p)
-        height -= ml_row->height;
+      if (w->mode_line_height >= 0)
+        height -= w->mode_line_height;
       else
-        height -= estimate_mode_line_height (f, CURRENT_MODE_LINE_FACE_ID (w));
+        {
+          struct glyph_row *ml_row
+            = (w->current_matrix && w->current_matrix->rows
+               ? MATRIX_MODE_LINE_ROW (w->current_matrix)
+               : 0);
+          if (ml_row && ml_row->mode_line_p)
+            height -= ml_row->height;
+          else
+            height -= estimate_mode_line_height (f,
+                                                 CURRENT_MODE_LINE_FACE_ID (w));
+        }
     }
 
   if (window_wants_tab_line (w))
     {
-      struct glyph_row *tl_row
-        = (w->current_matrix && w->current_matrix->rows
-           ? MATRIX_TAB_LINE_ROW (w->current_matrix)
-           : 0);
-      if (tl_row && tl_row->mode_line_p)
-        height -= tl_row->height;
+      if (w->tab_line_height >= 0)
+        height -= w->tab_line_height;
       else
-        height -= estimate_mode_line_height (f, TAB_LINE_FACE_ID);
+        {
+          struct glyph_row *tl_row
+            = (w->current_matrix && w->current_matrix->rows
+               ? MATRIX_TAB_LINE_ROW (w->current_matrix)
+               : 0);
+          if (tl_row && tl_row->mode_line_p)
+            height -= tl_row->height;
+          else
+            height -= estimate_mode_line_height (f, TAB_LINE_FACE_ID);
+        }
     }
 
   if (window_wants_header_line (w))
     {
-      struct glyph_row *hl_row
-        = (w->current_matrix && w->current_matrix->rows
-           ? MATRIX_HEADER_LINE_ROW (w->current_matrix)
-           : 0);
-      if (hl_row && hl_row->mode_line_p)
-        height -= hl_row->height;
-      else
-        height -= estimate_mode_line_height (f, HEADER_LINE_FACE_ID);
+      if (w->header_line_height >= 0)
+        height -= w->header_line_height;
+      {
+        struct glyph_row *hl_row
+          = (w->current_matrix && w->current_matrix->rows
+             ? MATRIX_HEADER_LINE_ROW (w->current_matrix)
+             : 0);
+        if (hl_row && hl_row->mode_line_p)
+          height -= hl_row->height;
+        else
+          height -= estimate_mode_line_height (f, HEADER_LINE_FACE_ID);
+      }
     }
 
   /* With a very small font and a mode-line that's taller than