Support max-width for popup instance

Patch of pull request #29 cannot be merged now. I fix it for
current popup.el.

README.md

@@ -117,14 +117,18 @@ All of these fields can be accessed by `popup-<field>` function.
 
 ### Function: `popup-create`
 
-    popup-create point width height &key min-height around face
+    popup-create point width height &key min-height max-width around face
     selection-face scroll-bar margin-left margin-right symbol parent
     parent-offset => popup
 
 Create a popup instance at `POINT` with `WIDTH` and `HEIGHT`.
 
 `MIN-HEIGHT` is the minimal height of the popup. The default value is 0.
 
+`MAX-WIDTH` is the maximum width of the popup. The default value is
+nil (no limit). If a floating point, the value refers to the ratio of
+the window. If an integer, limit is in characters.
+
 If `AROUND` is non-nil, the popup will be displayed around the point
 but not at the point.
 
@@ -244,7 +248,7 @@ something about what cursor points to.
 
 ### Function: `popup-tip`
 
-    popup-tip string &key point around width height min-height
+    popup-tip string &key point around width height min-height max-width
     truncate margin margin-left margin-right scroll-bar parent
     parent-offset nowait nostrip prompt
 

popup.el

@@ -37,6 +37,13 @@
 
 ;;; Utilities
 
+(defun popup-calculate-max-width (max-width)
+  "Determines whether the width desired is
+character or window proportion based, And returns the result."
+  (cl-typecase max-width
+    (integer max-width)
+    (float (* (ceiling (/ (round (* max-width (window-width))) 10.0)) 10))))
+
 (defvar popup-use-optimized-column-computation t
   "Use the optimized column computation routine.
 If there is a problem, please set it nil.")
@@ -474,6 +481,7 @@ number at the point."
                         height
                         &key
                         min-height
+                        max-width
                         around
                         (face 'popup-face)
                         mouse-face
@@ -491,6 +499,10 @@ number at the point."
 MIN-HEIGHT is a minimal height of the popup. The default value is
 0.
 
+MAX-WIDTH is the maximum width of the popup. The default value is
+nil (no limit). If a floating point, the value refers to the ratio of
+the window. If an integer, limit is in characters.
+
 If AROUND is non-nil, the popup will be displayed around the
 point but not at the point.
 
@@ -521,7 +533,8 @@ KEYMAP is a keymap that will be put on the popup contents."
   (unless point
     (setq point
           (if parent (popup-child-point parent parent-offset) (point))))
-
+  (when max-width
+    (setq width (min width (popup-calculate-max-width max-width))))
   (save-excursion
     (goto-char point)
     (let* ((row (line-number-at-pos))
@@ -996,6 +1009,7 @@ HELP-DELAY is a delay of displaying helps."
                      width
                      (height 15)
                      min-height
+                     max-width
                      truncate
                      margin
                      margin-left
@@ -1036,6 +1050,7 @@ PROMPT is a prompt string when reading events during event loop."
 
   (setq tip (popup-create point width height
                           :min-height min-height
+                          :max-width max-width
                           :around around
                           :margin-left margin-left
                           :margin-right margin-right
@@ -1272,6 +1287,7 @@ PROMPT is a prompt string when reading events during event loop."
                        (around t)
                        (width (popup-preferred-width list))
                        (height 15)
+                       max-width
                        margin
                        margin-left
                        margin-right
@@ -1332,6 +1348,7 @@ isearch canceled. The arguments is whole filtered list of items."
       ;; Make scroll-bar space as margin-right
       (cl-decf margin-right))
   (setq menu (popup-create point width height
+                           :max-width max-width
                            :around around
                            :face 'popup-menu-face
                            :mouse-face 'popup-menu-mouse-face