Adds an optional fix for right-to-left text

Rtl text was disordering the calendar cells between columns. Added a setting to enable a fix.

The fix is made optional because it depends on a special unicode character (the "LEFT-TO-RIGHT EMBEDDING" character).

calfw.el

@@ -206,6 +206,15 @@ for example `cfw:read-date-command-simple' or `cfw:org-read-date-command'."
   :group 'cfw
   :type 'boolean)
 
+(defcustom cfw:fix-rtl-content nil
+  "If not-nil, calfw fixes right-to-left content in cells.
+When using rtl content without this enabled, the order
+of cells can be ruined e.g. the 2nd appears before the 1st.
+This fixes it by adding a \"Left-to-right Embedding\" unicode
+character to column separators."
+  :group 'cfw
+  :type 'boolean)
+
 ;;; Faces
 
 (defface cfw:face-title
@@ -1729,23 +1738,25 @@ algorithm defined at `cfw:render-line-breaker'."
          (cell-width (cfw:k 'cell-width param))
          (columns (cfw:k 'columns param))
          (num-cell-char
-          (/ cell-width (char-width cfw:fchar-horizontal-line))))
+          (/ cell-width (char-width cfw:fchar-horizontal-line)))
+         (left-to-right-enforce-char "\x202a")
+         (rtl-column-fix (if cfw:fix-rtl-content left-to-right-enforce-char "")))
     (append
      param
-     `((eol . ,EOL) (vl . ,(cfw:rt (make-string 1 cfw:fchar-vertical-line) 'cfw:face-grid))
+     `((eol . ,EOL) (vl . ,(cfw:rt (concat (make-string 1 cfw:fchar-vertical-line) rtl-column-fix ) 'cfw:face-grid))
        (hline . ,(cfw:rt
                   (concat
                    (loop for i from 0 below columns concat
                          (concat
-                          (make-string 1 (if (= i 0) cfw:fchar-top-left-corner cfw:fchar-top-junction))
+                          (make-string 1 (if (= i 0) cfw:fchar-top-left-corner cfw:fchar-top-junction)) rtl-column-fix
                           (make-string num-cell-char cfw:fchar-horizontal-line)))
                    (make-string 1 cfw:fchar-top-right-corner) EOL)
                   'cfw:face-grid))
        (cline . ,(cfw:rt
                   (concat
                    (loop for i from 0 below columns concat
                          (concat
-                          (make-string 1 (if (= i 0) cfw:fchar-left-junction cfw:fchar-junction))
+                          (make-string 1 (if (= i 0) cfw:fchar-left-junction cfw:fchar-junction)) rtl-column-fix
                           (make-string num-cell-char cfw:fchar-horizontal-line)))
                    (make-string 1 cfw:fchar-right-junction) EOL) 'cfw:face-grid))))))
 

readme.md

@@ -326,6 +326,17 @@ In the current implementation, the Calfw has 3 strategies: none, simple and word
 - `cfw:render-line-breaker-wordwrap`
     - This strategy breaks lines with the emacs function `fill-region`. Although, the line breaking algorithm of the Emacs is not so smart as more complicated ones, such as Knuth/Plass algorithm, this strategy is better than the simple one.
 
+### Right-to-left text
+
+Right-to-left events can disorder the cells' texts between columns.
+If this happens you can fix it using:
+
+```el
+(setq cfw:fix-rtl-content t)
+```
+
+(The fix adds a "Left-to-right Embedding" unicode character to column breaks)
+
 ## Calfw framework details
 
 In this section, I would explain how to add a new calendar source and how to embed the calfw component in the other applications.