[ROFI] -e '-' reads from stdin

doc/rofi.1

@@ -1142,6 +1142,9 @@ cause slowdowns when set too high)
 Pops up a message dialog (used internally for showing errors) with \fImessage\fP\&.
 Message can be multi-line.
 
+.PP
+Passing \fB\fC-e -\fR reads (blocking) from standard in and displays this.
+
 .SS File browser settings
 .PP
 File browser behavior can be controlled via the following options:

doc/rofi.1.markdown

@@ -740,6 +740,8 @@ cause slowdowns when set too high)
 Pops up a message dialog (used internally for showing errors) with *message*.
 Message can be multi-line.
 
+Passing `-e -` reads (blocking) from standard in and displays this.
+
 ### File browser settings
 
 File browser behavior can be controlled via the following options:

source/rofi.c

@@ -797,8 +797,26 @@ static gboolean startup(G_GNUC_UNUSED gpointer data) {
     if (find_arg("-markup") >= 0) {
       markup = TRUE;
     }
-    if (!rofi_view_error_dialog(msg, markup)) {
+    // When we pass -, we read from stdin.
-      g_main_loop_quit(main_loop);
+    if (g_strcmp0(msg, "-") == 0) {
+      size_t index = 0, i = 0;
+      size_t length = 1024;
+      msg = malloc(length * sizeof(char));
+      while ((i = fread(&msg[index], 1, 1024, stdin))>0) {
+        index+=i;
+        length+=i;
+        msg = realloc(msg,length * sizeof(char));
+      }
+
+      if (!rofi_view_error_dialog(msg, markup)) {
+        g_main_loop_quit(main_loop);
+      }
+      g_free(msg);
+    } else {
+      // Normal version
+      if (!rofi_view_error_dialog(msg, markup)) {
+        g_main_loop_quit(main_loop);
+      }
     }
   } else if (find_arg_str("-show", &sname) == TRUE) {
     int index = mode_lookup(sname);