Always query current CUPS default printer

michaelweghorn · michaelweghorn · commit 74c11fc71dbe · 2024-07-29T08:04:19.000+02:00
When asked for the default printer, always query and return the current CUPS default printer instead of whatever was the default last time this was done, to take into account that the CUPS default printer can change while the backend is running. Sample steps (without this commit in place) to reproduce an incorrect default printer being returned with cpdb-text-frontend from cpdb-libs, when the PDF printer is initially set as default: Run cpdb-text-frontend: $ cpdb-text-frontend Query for the default printer > get-default-printer PDF#CUPS Now, switch the CUPS user default printer to another one: $ lpoptions -d somedummy In the running cpdb-text-frontend instance, query the default printer again: > get-default-printer PDF#CUPS -> The outdated/previous default printer was returned. With this commit in place, the new default printer is now returned as expected: > get-default-printer somedummy#CUPS (This addresses part of issue 3) from comment [1] on the pending change to update CPDB support in LibreOffice.) [1] https://gerrit.libreoffice.org/c/core/+/169617/comments/3ef76e40_4f120b66
diff --git a/src/backend_helper.c b/src/backend_helper.c
@@ -35,12 +35,6 @@ BackendObj *get_new_BackendObj()
 /** Don't free the returned value; it is owned by BackendObj */
 char *get_default_printer(BackendObj *b)
 {
-    /** If it was  previously querie, don't query again */
-    if (b->default_printer)
-    {
-        return b->default_printer;
-    }
-
     /**first query to see if the user default printer is set**/
     int num_dests;
     cups_dest_t *dests;
@@ -51,6 +45,7 @@ char *get_default_printer(BackendObj *b)
         /** Return the user default printer */
         char *def = g_strdup(dest->name);
         cupsFreeDests(num_dests, dests);
+        g_free(b->default_printer);
         b->default_printer = def;
         return def;
     }
@@ -65,12 +60,14 @@ char *get_default_printer(BackendObj *b)
         if ((attr = ippFindAttribute(response, "printer-name",
                                      IPP_TAG_NAME)) != NULL)
         {
+            g_free(b->default_printer);
             b->default_printer = g_strdup(ippGetString(attr, 0, NULL));
             ippDelete(response);
             return b->default_printer;
         }
     }
     ippDelete(response);
+    g_free(b->default_printer);
     b->default_printer = g_strdup("NA");
     return b->default_printer;
 }

Original file line number	Diff line number	Diff line change
`@@ -35,12 +35,6 @@ BackendObj *get_new_BackendObj()`
`35`	`35`	`/** Don't free the returned value; it is owned by BackendObj */`
`36`	`36`	`char get_default_printer(BackendObj b)`
`37`	`37`	`{`
`38`		`- /** If it was previously querie, don't query again */`
`39`		`- if (b->default_printer)`
`40`		`- {`
`41`		`- return b->default_printer;`
`42`		`- }`
`43`		`-`
`44`	`38`	`/first query to see if the user default printer is set/`
`45`	`39`	`int num_dests;`
`46`	`40`	`cups_dest_t *dests;`
`@@ -51,6 +45,7 @@ char get_default_printer(BackendObj b)`
`51`	`45`	`/** Return the user default printer */`
`52`	`46`	`char *def = g_strdup(dest->name);`
`53`	`47`	`cupsFreeDests(num_dests, dests);`
	`48`	`+ g_free(b->default_printer);`
`54`	`49`	`b->default_printer = def;`
`55`	`50`	`return def;`
`56`	`51`	`}`
`@@ -65,12 +60,14 @@ char get_default_printer(BackendObj b)`
`65`	`60`	`if ((attr = ippFindAttribute(response, "printer-name",`
`66`	`61`	`IPP_TAG_NAME)) != NULL)`
`67`	`62`	`{`
	`63`	`+ g_free(b->default_printer);`
`68`	`64`	`b->default_printer = g_strdup(ippGetString(attr, 0, NULL));`
`69`	`65`	`ippDelete(response);`
`70`	`66`	`return b->default_printer;`
`71`	`67`	`}`
`72`	`68`	`}`
`73`	`69`	`ippDelete(response);`
	`70`	`+ g_free(b->default_printer);`
`74`	`71`	`b->default_printer = g_strdup("NA");`
`75`	`72`	`return b->default_printer;`
`76`	`73`	`}`