From b431d8fea195b113a5bb0eb8c01b7d5d986e4450 Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Sat, 2 Nov 2013 20:30:49 -0600
Subject: [PATCH] launcher ".desktop" handling: preserve existing `Exec=`
 content

---
 .../racket-doc/scribblings/raco/launcher.scrbl   | 14 +++++++++-----
 racket/collects/launcher/launcher.rkt            | 16 ++++++++++++++--
 2 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/pkgs/racket-pkgs/racket-doc/scribblings/raco/launcher.scrbl b/pkgs/racket-pkgs/racket-doc/scribblings/raco/launcher.scrbl
index 67e67322eb..ce1500dc0d 100644
--- a/pkgs/racket-pkgs/racket-doc/scribblings/raco/launcher.scrbl
+++ b/pkgs/racket-pkgs/racket-doc/scribblings/raco/launcher.scrbl
@@ -117,11 +117,15 @@ the following additional associations apply to launchers:
 
  @item{@racket['desktop] (Unix) --- a string containing the content of
        a @filepath{.desktop} file for the launcher, where @tt{Exec}
-       and @tt{Icon} items should be omitted, because they will be
-       added automatically. The file is written to the directory
-       produced by @racket[(find-apps-dir)] or
-       @racket[(find-user-apps-dir)]. A @racket['desktop] value is
-       used only when @racket['install-mode] is also specified.}
+       and @tt{Icon} entries are added automatically. If an @tt{Exec}
+       entry exists in the string, and if its value starts with a
+       non-empty sequence of alpha-numeric ASCII characters followed
+       by a space, then the space and remainder of the value is
+       appended to the automatically generated value.
+       The @filepath{.desktop} file is written to the directory produced by
+       @racket[(find-apps-dir)] or @racket[(find-user-apps-dir)]. A
+       @racket['desktop] value is used only when
+       @racket['install-mode] is also specified.}
 
   @item{@racket['png] (Unix) : An icon file path (suffix
         @filepath{.png}) to be referenced by a @filepath{.desktop}
diff --git a/racket/collects/launcher/launcher.rkt b/racket/collects/launcher/launcher.rkt
index c08bc030fb..775e69ec4d 100644
--- a/racket/collects/launcher/launcher.rkt
+++ b/racket/collects/launcher/launcher.rkt
@@ -539,8 +539,20 @@
              file
              #:exists 'truncate
              (lambda (o)
-               (displayln (regexp-replace #rx"\n+$" (cdr m) "") o)
-               (fprintf o "Exec=~a\n" (adjust-path dest))
+               (define content (cdr m))
+               (displayln (regexp-replace #rx"\n+$"
+                                          (regexp-replace "(?m:^Exec=.*)\n*"
+                                                          content
+                                                          "")
+                                          "")
+                          o)
+               (fprintf o "Exec=~a~a\n"
+                        (adjust-path dest)
+                        ;; Keep rest of existing line, if any:
+                        (let ([m (regexp-match "(?m:^Exec=[a-zA-Z0-9]+( .*))" content)])
+                          (if m
+                              (cadr m)
+                              "")))
                (let ([m (or (assq 'png aux)
                             (assq 'ico aux))])
                  (when m