New CPDB print backend for GTK Print Dialog

The Common Print Dialog Backends (CPDB) concept has GUI-toolkit-independent
backends for each print technology (CUPS, Print to File, cloud printing
services, ...) and each print dialog (GTK, Qt, Chromium, ...) is supposed
to use this backend, so that changes in print technologies can be centrally
and quickly covered by changing the backends and everything new gets available
in all print dialogs.

This commit provides a GTK print dialog backend to add support for the CPDB
concept. It communicates with all installed CPDB backends and so gives support
for all these print technologies to the GTK print dialog.

To make use of CPDB the GTK print dialog is supposed to be installed with this
backend and the 'Print To File' backend, and not any others to prevent printer
duplication.

meson_options.txt

@@ -41,6 +41,11 @@ option('media-gstreamer',
 
 # Print backends
 
+option('print-cpdb',
+       type: 'feature',
+       value: 'disabled',
+       description : 'Build the cpdb print backend')
+
 option('print-cups',
        type: 'feature',
        value: 'auto',

modules/printbackends/gtkprintbackendcpdb.h

@@ -0,0 +1,43 @@
+/* GTK - The GIMP Toolkit
+ * gtkprintbackendcpdb.h: Default implementation of GtkPrintBackend
+ * for the Common Print Dialog Backends (CPDB)
+ * Copyright (C) 2022, 2023 TinyTrebuchet <tinytrebuchet@protonmail.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+
+#ifndef __GTK_PRINT_BACKEND_CPDB_H__
+#define __GTK_PRINT_BACKEND_CPDB_H__
+
+#include <glib-object.h>
+#include <gtk/gtk.h>
+#include "gtkprintbackendprivate.h"
+
+G_BEGIN_DECLS
+
+#define GTK_TYPE_PRINT_BACKEND_CPDB             (gtk_print_backend_cpdb_get_type ())
+#define GTK_PRINT_BACKEND_CPDB(obj)             (G_TYPE_CHECK_INSTANCE_CAST ((obj), GTK_TYPE_PRINT_BACKEND_CPDB, GtkPrintBackendCpdb))
+#define GTK_IS_PRINT_BACKEND_CPDB(obj)          (G_TYPE_CHECK_INSTANCE_TYPE ((obj), GTK_TYPE_PRINT_BACKEND_CPDB))
+
+typedef struct _GtkPrintBackendCpdbClass GtkPrintBackendCpdbClass;
+typedef struct _GtkPrintBackendCpdb      GtkPrintBackendCpdb;
+
+GtkPrintBackend  *gtk_print_backend_cpdb_new        (void);
+GType             gtk_print_backend_cpdb_get_type   (void) G_GNUC_CONST;
+
+G_END_DECLS
+
+#endif /* __GTK_PRINT_BACKEND_CPDB_H__ */
+

modules/printbackends/gtkprintbackendcups.c

@@ -55,6 +55,7 @@
 
 #include "gtkcupsutils.h"
 #include "gtkcupssecretsutils.h"
+#include "gtkprintbackendutils.h"
 
 #include <gtkprintutils.h>
 #include "gtkprivate.h"
@@ -6483,87 +6484,6 @@ foreach_option_get_settings (GtkPrinterOption *option,
     gtk_print_settings_set (settings, option->name, value);
 }
 
-static gboolean
-supports_am_pm (void)
-{
-  struct tm tmp_tm = { 0 };
-  char   time[8];
-  int    length;
-
-  length = strftime (time, sizeof (time), "%p", &tmp_tm);
-
-  return length != 0;
-}
-
-/* Converts local time to UTC time. Local time has to be in one of these
- * formats:  HH:MM:SS, HH:MM, HH:MM:SS {am, pm}, HH:MM {am, pm}, HH {am, pm},
- * {am, pm} HH:MM:SS, {am, pm} HH:MM, {am, pm} HH.
- * Returns a newly allocated string holding UTC time in HH:MM:SS format
- * or NULL.
- */
-static char *
-localtime_to_utctime (const char *local_time)
-{
-  const char *formats_0[] = {" %I : %M : %S %p ", " %p %I : %M : %S ",
-                             " %H : %M : %S ",
-                             " %I : %M %p ", " %p %I : %M ",
-                             " %H : %M ",
-                             " %I %p ", " %p %I "};
-  const char *formats_1[] = {" %H : %M : %S ", " %H : %M "};
-  const char *end = NULL;
-  struct tm  *actual_local_time;
-  struct tm  *actual_utc_time;
-  struct tm   local_print_time;
-  struct tm   utc_print_time;
-  struct tm   diff_time;
-  char       *utc_time = NULL;
-  int         i, n;
-
-  if (local_time == NULL || local_time[0] == '\0')
-    return NULL;
-
-  n = supports_am_pm () ? G_N_ELEMENTS (formats_0) : G_N_ELEMENTS (formats_1);
-
-  for (i = 0; i < n; i++)
-    {
-      local_print_time.tm_hour = 0;
-      local_print_time.tm_min  = 0;
-      local_print_time.tm_sec  = 0;
-
-      if (supports_am_pm ())
-        end = strptime (local_time, formats_0[i], &local_print_time);
-      else
-        end = strptime (local_time, formats_1[i], &local_print_time);
-
-      if (end != NULL && end[0] == '\0')
-        break;
-    }
-
-  if (end != NULL && end[0] == '\0')
-    {
-      time_t rawtime;
-      time (&rawtime);
-
-      actual_utc_time = g_memdup2 (gmtime (&rawtime), sizeof (struct tm));
-      actual_local_time = g_memdup2 (localtime (&rawtime), sizeof (struct tm));
-
-      diff_time.tm_hour = actual_utc_time->tm_hour - actual_local_time->tm_hour;
-      diff_time.tm_min  = actual_utc_time->tm_min  - actual_local_time->tm_min;
-      diff_time.tm_sec  = actual_utc_time->tm_sec  - actual_local_time->tm_sec;
-
-      utc_print_time.tm_hour = ((local_print_time.tm_hour + diff_time.tm_hour) + 24) % 24;
-      utc_print_time.tm_min  = ((local_print_time.tm_min  + diff_time.tm_min)  + 60) % 60;
-      utc_print_time.tm_sec  = ((local_print_time.tm_sec  + diff_time.tm_sec)  + 60) % 60;
-
-      utc_time = g_strdup_printf ("%02d:%02d:%02d",
-                                  utc_print_time.tm_hour,
-                                  utc_print_time.tm_min,
-                                  utc_print_time.tm_sec);
-    }
-
-  return utc_time;
-}
-
 static void
 cups_printer_get_settings_from_options (GtkPrinter          *printer,
 					GtkPrinterOptionSet *options,

modules/printbackends/gtkprintbackendutils.c

@@ -0,0 +1,128 @@
+/* GTK - The GIMP Toolkit
+ * gtkprintbackendcups.h: Default implementation of GtkPrintBackend
+ * for the Common Unix Print System (CUPS)
+ * Copyright (C) 2006, 2007 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+
+#include <glib.h>
+#include <sys/random.h>
+
+#include "gtkprintbackendutils.h"
+
+/* Converts local time to UTC time. Local time has to be in one of these
+ * formats:  HH:MM:SS, HH:MM, HH:MM:SS {am, pm}, HH:MM {am, pm}, HH {am, pm},
+ * {am, pm} HH:MM:SS, {am, pm} HH:MM, {am, pm} HH.
+ * Returns a newly allocated string holding UTC time in HH:MM:SS format
+ * or NULL.
+ */
+char *
+localtime_to_utctime (const char *local_time)
+{
+  const char *formats_0[] = {" %I : %M : %S %p ", " %p %I : %M : %S ",
+                             " %H : %M : %S ",
+                             " %I : %M %p ", " %p %I : %M ",
+                             " %H : %M ",
+                             " %I %p ", " %p %I "};
+  const char *formats_1[] = {" %H : %M : %S ", " %H : %M "};
+  const char *end = NULL;
+  struct tm  *actual_local_time;
+  struct tm  *actual_utc_time;
+  struct tm   local_print_time;
+  struct tm   utc_print_time;
+  struct tm   diff_time;
+  char       *utc_time = NULL;
+  int         i, n;
+
+  if (local_time == NULL || local_time[0] == '\0')
+    return NULL;
+
+  n = supports_am_pm () ? G_N_ELEMENTS (formats_0) : G_N_ELEMENTS (formats_1);
+
+  for (i = 0; i < n; i++)
+    {
+      local_print_time.tm_hour = 0;
+      local_print_time.tm_min  = 0;
+      local_print_time.tm_sec  = 0;
+
+      if (supports_am_pm ())
+        end = strptime (local_time, formats_0[i], &local_print_time);
+      else
+        end = strptime (local_time, formats_1[i], &local_print_time);
+
+      if (end != NULL && end[0] == '\0')
+        break;
+    }
+
+  if (end != NULL && end[0] == '\0')
+    {
+      time_t rawtime;
+      time (&rawtime);
+
+      actual_utc_time = g_memdup2 (gmtime (&rawtime), sizeof (struct tm));
+      actual_local_time = g_memdup2 (localtime (&rawtime), sizeof (struct tm));
+
+      diff_time.tm_hour = actual_utc_time->tm_hour - actual_local_time->tm_hour;
+      diff_time.tm_min  = actual_utc_time->tm_min  - actual_local_time->tm_min;
+      diff_time.tm_sec  = actual_utc_time->tm_sec  - actual_local_time->tm_sec;
+
+      utc_print_time.tm_hour = ((local_print_time.tm_hour + diff_time.tm_hour) + 24) % 24;
+      utc_print_time.tm_min  = ((local_print_time.tm_min  + diff_time.tm_min)  + 60) % 60;
+      utc_print_time.tm_sec  = ((local_print_time.tm_sec  + diff_time.tm_sec)  + 60) % 60;
+
+      utc_time = g_strdup_printf ("%02d:%02d:%02d",
+                                  utc_print_time.tm_hour,
+                                  utc_print_time.tm_min,
+                                  utc_print_time.tm_sec);
+    }
+
+  return utc_time;
+}
+
+gboolean
+supports_am_pm (void)
+{
+  struct tm tmp_tm = { 0 };
+  char   time[8];
+  int    length;
+
+  length = strftime (time, sizeof (time), "%p", &tmp_tm);
+
+  return length != 0;
+}
+
+/*
+ * Generate a random string of "n" length
+ */
+char *
+random_string (int n)
+{
+  const char charset[] =  "abcdefghijklmnopqrstuvwxyz"
+                          "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+                          "0123456789";
+
+  char *str = g_new0 (char, n+1);
+  getrandom (str, n, 0);
+  for (int i=0; i<n; i++)
+    {
+      int rand = str[i] + 128;
+      int idx = rand % ((int) sizeof charset);
+      str[i] = charset[idx];
+    }
+  str[n] = '\0';
+
+  return str;
+}

modules/printbackends/gtkprintbackendutils.h

@@ -0,0 +1,27 @@
+/* GTK - The GIMP Toolkit
+ * gtkprintbackendcups.h: Default implementation of GtkPrintBackend
+ * for the Common Unix Print System (CUPS)
+ * Copyright (C) 2006, 2007 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __GTK_PRINT_BACKEND_UTILS_H__
+#define __GTK_PRINT_BACKEND_UTILS_H__
+
+char *random_string                          (int size);
+char *localtime_to_utctime                   (const char *local_time);
+gboolean supports_am_pm                      (void);
+
+#endif /* __GTK_PRINT_BACKEND_UTILS_H__ */

modules/printbackends/gtkprintercpdb.c

@@ -0,0 +1,137 @@
+/* GtkPrinterCpdb
+ * Copyright (C) 2022, 2023 TinyTrebuchet <tinytrebuchet@protonmail.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ */
+ 
+
+#include <gtkprintercpdb.h>
+
+enum {
+  PROP_0,
+  PROP_PRINTER_OBJ
+};
+
+static void gtk_printer_cpdb_init       (GtkPrinterCpdb      *printer);
+static void gtk_printer_cpdb_class_init (GtkPrinterCpdbClass *class);
+
+static GType gtk_printer_cpdb_type = 0;
+
+static void gtk_printer_cpdb_set_property (GObject      *object,
+                                           guint         prop_id,
+                                           const GValue *value,
+                                           GParamSpec   *pspec);
+static void gtk_printer_cpdb_get_property (GObject      *object,
+                                           guint         prop_id,
+                                           GValue       *value,
+                                           GParamSpec   *pspec);
+
+void 
+gtk_printer_cpdb_register_type (GTypeModule *module)
+{
+  const GTypeInfo object_info =
+  {
+    sizeof (GtkPrinterCpdbClass),
+    (GBaseInitFunc) NULL,
+    (GBaseFinalizeFunc) NULL,
+    (GClassInitFunc) gtk_printer_cpdb_class_init,
+    NULL,           /* class_finalize */
+    NULL,           /* class_data */
+    sizeof (GtkPrinterCpdb),
+    0,              /* n_preallocs */
+    (GInstanceInitFunc) gtk_printer_cpdb_init,
+  };
+
+ gtk_printer_cpdb_type = g_type_module_register_type (module,
+                                                      GTK_TYPE_PRINTER,
+                                                      "GtkPrinterCpdb",
+                                                      &object_info, 0);
+}
+
+GType
+gtk_printer_cpdb_get_type (void)
+{
+  return gtk_printer_cpdb_type;
+}
+
+static void
+gtk_printer_cpdb_class_init (GtkPrinterCpdbClass *klass)
+{
+
+  GObjectClass *object_class = G_OBJECT_CLASS (klass);
+
+  object_class->set_property = gtk_printer_cpdb_set_property;
+  object_class->get_property = gtk_printer_cpdb_get_property;
+
+  g_object_class_install_property (G_OBJECT_CLASS (klass),
+                                   PROP_PRINTER_OBJ,
+                                   g_param_spec_pointer ("printer-obj", 
+                                                         NULL, 
+                                                         NULL,
+                                                         G_PARAM_READWRITE));
+}
+
+static void
+gtk_printer_cpdb_init (GtkPrinterCpdb *self)
+{
+}
+
+static void
+gtk_printer_cpdb_set_property (GObject         *object,
+                               guint            prop_id,
+                               const GValue    *value,
+                               GParamSpec      *pspec)
+{
+  GtkPrinterCpdb *printer_cpdb = GTK_PRINTER_CPDB (object);
+  switch (prop_id)
+    {
+    case PROP_PRINTER_OBJ:
+      printer_cpdb->printer_obj = g_value_get_pointer (value);
+      break;
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+      break;
+    }
+}
+
+static void
+gtk_printer_cpdb_get_property (GObject    *object,
+                               guint       prop_id,
+                               GValue     *value,
+                               GParamSpec *pspec)
+{
+  GtkPrinterCpdb *printer_cpdb = GTK_PRINTER_CPDB (object);
+  switch (prop_id)
+    {
+    case PROP_PRINTER_OBJ:
+      g_value_set_pointer (value, printer_cpdb->printer_obj);
+      break;
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+      break;
+    }
+}
+
+cpdb_printer_obj_t *
+gtk_printer_cpdb_get_printer_obj (GtkPrinterCpdb *cpdb_printer)
+{
+  return cpdb_printer->printer_obj;
+}
+
+void
+gtk_printer_cpdb_set_printer_obj (GtkPrinterCpdb *cpdb_printer,
+                                  cpdb_printer_obj_t *printer_obj)
+{
+  cpdb_printer->printer_obj = printer_obj;
+}

modules/printbackends/gtkprintercpdb.h

@@ -0,0 +1,46 @@
+/* GtkPrinterCpdb
+ * Copyright (C) 2022, 2023 TinyTrebuchet <tinytrebuchet@protonmail.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+
+#ifndef __GTK_PRINTER_CPDB_H__
+#define __GTK_PRINTER_CPDB_H__
+
+#include <glib-object.h>
+#include <cpdb/cpdb-frontend.h>
+#include <gtk/gtkprinterprivate.h>
+
+G_BEGIN_DECLS
+
+#define GTK_TYPE_PRINTER_CPDB           (gtk_printer_cpdb_get_type ())
+G_DECLARE_FINAL_TYPE                    (GtkPrinterCpdb, gtk_printer_cpdb, GTK, PRINTER_CPDB, GtkPrinter)
+
+struct _GtkPrinterCpdb
+{
+  GtkPrinter parent_instance;
+  cpdb_printer_obj_t *printer_obj;
+};
+
+void                  gtk_printer_cpdb_register_type          (GTypeModule          *module);
+
+cpdb_printer_obj_t   *gtk_printer_cpdb_get_printer_obj        (GtkPrinterCpdb       *cpdb_printer);
+
+void                  gtk_printer_cpdb_set_printer_obj        (GtkPrinterCpdb       *cpdb_printer,
+                                                               cpdb_printer_obj_t   *printer_obj);
+
+G_END_DECLS
+
+#endif /* __GTK_PRINTER_CPDB_H__ */

modules/printbackends/meson.build

@@ -10,8 +10,27 @@ printbackends_args = [
   '-DGTK_PRINT_BACKEND_ENABLE_UNSUPPORTED',
 ] + common_cflags
 
+cpdb_dep = dependency('cpdb-frontend', version : '>=1.0', required: get_option('print-cpdb'))
 cups_dep = dependency('cups', version : '>=2.0', required: get_option('print-cups'))
-if cups_dep.found()
+
+# Use cpdb backend if present and enabled.
+# If not, use cups if present.
+# If not, use lpr.
+
+if get_option('print-cpdb').enabled() and cpdb_dep.found()
+  print_backends += 'cpdb'
+  shared_module('printbackend-cpdb',
+    sources: [
+      'gtkprintbackendcpdb.c',
+      'gtkprintercpdb.c',
+      'gtkprintbackendutils.c',
+    ],
+    c_args: printbackends_args,
+    dependencies: [libgtk_dep, cpdb_dep],
+    install_dir: printbackends_install_dir,
+    install: true,
+  )
+elif cups_dep.found()
   print_backends += 'cups'
   shared_module('printbackend-cups',
     sources: [
@@ -19,6 +38,7 @@ if cups_dep.found()
       'gtkprintercups.c',
       'gtkcupsutils.c',
       'gtkcupssecretsutils.c',
+      'gtkprintbackendutils.c',
     ],
     c_args: printbackends_args,
     dependencies: [libgtk_dep, cups_dep, colord_dep],