second brave attempt for issue #179

tabularray.sty

@@ -3676,6 +3676,7 @@
 \tl_const:Nn \c__tblr_cell_math_style_tl { \relax }
 \tl_const:Nn \c__tblr_cell_imath_style_tl { \textstyle }
 \tl_const:Nn \c__tblr_cell_dmath_style_tl { \displaystyle }
+\box_new:N \l__tblr_measured_cell_box
 
 %% Get cell text, #1: row number, #2: column number
 %% If the width of the cell is not set, split it with \\ and compute the width
@@ -3728,19 +3729,28 @@
               { \__tblr_data_item:nen { column } {#2} { width } }
           }
       }
+    \box_clear:N \l__tblr_measured_cell_box
     \dim_compare:nNnT { \l__tblr_w_tl } < { 0pt } % column width unset
       {
-        \__tblr_save_counters:n { cell }
-        \bool_if:NTF \l__tblr_cell_math_mode_bool
+        %% To keep \lTblrMeasuringBool correct we need measure=vbox from varwidth.
+        %% As an experiment, we implement it only when hook library is loaded.
+        \__tblr_lib_if_used:nTF { hook }
           {
-            %% Note that font = \boldmath will increase cell width (issue #137)
-            \hbox_set:Nn \l_tmpa_box { \l__tblr_f_tl \l__tblr_c_tl }
-            \tl_set:Nx \l__tblr_w_tl { \dim_eval:n { \box_wd:N \l_tmpa_box } }
+            \__tblr_build_vcell_with_vbox:
           }
           {
-            \__tblr_get_cell_size_with_box:
+            \__tblr_save_counters:n { cell }
+            \bool_if:NTF \l__tblr_cell_math_mode_bool
+              {
+                %% Note that font = \boldmath will increase cell width (issue #137)
+                \hbox_set:Nn \l_tmpa_box { \l__tblr_f_tl \l__tblr_c_tl }
+                \tl_set:Nx \l__tblr_w_tl { \dim_eval:n { \box_wd:N \l_tmpa_box } }
+              }
+              {
+                \__tblr_get_cell_size_with_box:
+              }
+            \__tblr_restore_counters:n { cell }
           }
-        \__tblr_restore_counters:n { cell }
       }
     \tl_put_left:NV \l__tblr_c_tl \l__tblr_f_tl
     \tl_set:Nx \l__tblr_cell_fg_tl
@@ -3751,6 +3761,23 @@
     \group_end:
   }
 
+%% Build cell vbox with varwidth and use it later when hook library is loaded
+\cs_new_protected:Npn  \__tblr_build_vcell_with_vbox:
+  {
+    \hbox_set:Nn \l__tblr_measured_cell_box
+      {
+        \begin{varwidth}{\paperwidth}
+          \TblrParboxRestore
+          \cs:w __tblr_halign_command_ \g__tblr_cell_halign_tl : \cs_end:
+          \__tblr_leave_vmode:
+           \l__tblr_f_tl
+           \l__tblr_c_tl
+        \end{varwidth}
+      }
+    \tl_set:Nx \l__tblr_w_tl { \dim_eval:n { \box_wd:N \l__tblr_measured_cell_box } }
+  }
+
+%% Measure cell width only and build it later when hook library is not loaded
 \cs_new_protected:Npn \__tblr_get_cell_size_with_box:
   {
     \tl_if_eq:NnTF \l__tblr_inner_spec_measure_tl { vbox }
@@ -3808,7 +3835,16 @@
 \cs_new_protected:Npn \__tblr_get_vcell_and_sizes:NN #1 #2
   {
     \group_begin:
-    \vbox_set:Nn \l_tmpb_box { \__tblr_make_vcell_text:NN #1 #2 }
+    \box_if_empty:NTF \l__tblr_measured_cell_box
+      { \vbox_set:Nn \l_tmpb_box { \__tblr_make_vcell_text:NN #1 #2 } }
+      {
+        \vbox_set:Nn \l_tmpb_box
+          {
+            \dim_set:Nn \tex_hsize:D { \l__tblr_w_tl }
+            \noindent
+            \hbox_unpack_drop:N \l__tblr_measured_cell_box
+          }
+      }
     \vbox_set_top:Nn \l_tmpa_box { \vbox_unpack:N \l_tmpb_box }
     \__tblr_process_stretch:
     \dim_gset:Nn \g__tblr_cell_wd_dim { \box_wd:N \l_tmpb_box }