emacs-27 37f9182: Fix redisplay when mode-line-format changes mode-line's height

[Eli Zaretskii]

branch: emacs-27
commit 37f9182b68c62ee1912cf28d4ea0c30b4f8d59e0
Author: Eli Zaretskii <address@hidden>
Commit: Eli Zaretskii <address@hidden>

    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)
---
 lisp/frame.el |  3 +++
 src/dispnew.c |  7 +++++++
 src/xdisp.c   | 65 ++++++++++++++++++++++++++++++++++++-----------------------
 3 files changed, 50 insertions(+), 25 deletions(-)

diff --git a/lisp/frame.el b/lisp/frame.el
index c533e5a..16ee758 100644
--- a/lisp/frame.el
+++ b/lisp/frame.el
@@ -2725,6 +2725,9 @@ See also `toggle-frame-maximized'."
         line-prefix
         wrap-prefix
         truncate-lines
+        mode-line-format
+        header-line-format
+        tab-line-format
         display-line-numbers
         display-line-numbers-width
         display-line-numbers-current-absolute
diff --git a/src/dispnew.c b/src/dispnew.c
index b2a2570..ed8c555 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 6b677b6..4856a7b 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