Move and test CUPS IPP color model selector

The version of GetColorModelForMode() that ChromeOS uses will be used
by macOS. Rename it to GetIppColorModelForMode() and move it to
print_settings.h. Meanwhile, add some simple tests.

Bug: 1106437
Change-Id: Ic01d1cf242c6e77774d247253f6cd912c2566f5b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2303855
Commit-Queue: Daniel Hosseinian <dhoss@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#789717}

printing/print_settings.cc

@@ -10,6 +10,10 @@
 #include "printing/print_job_constants.h"
 #include "printing/units.h"
 
+#if defined(USE_CUPS) && (defined(OS_MACOSX) || defined(OS_CHROMEOS))
+#include <cups/cups.h>
+#endif
+
 namespace printing {
 
 namespace {
@@ -183,6 +187,23 @@ void GetColorModelForMode(int color_mode,
   // The default case is excluded from the above switch statement to ensure that
   // all ColorModel values are determinantly handled.
 }
+
+#if defined(OS_MACOSX) || defined(OS_CHROMEOS)
+std::string GetIppColorModelForMode(int color_mode) {
+  // Accept |UNKNOWN_COLOR_MODEL| for consistency with GetColorModelForMode().
+  if (color_mode == UNKNOWN_COLOR_MODEL)
+    return CUPS_PRINT_COLOR_MODE_MONOCHROME;
+
+  base::Optional<bool> is_color = IsColorModelSelected(color_mode);
+  if (!is_color.has_value()) {
+    NOTREACHED();
+    return std::string();
+  }
+
+  return is_color.value() ? CUPS_PRINT_COLOR_MODE_COLOR
+                          : CUPS_PRINT_COLOR_MODE_MONOCHROME;
+}
+#endif  // defined(OS_MACOSX) || defined(OS_CHROMEOS)
 #endif  // defined(USE_CUPS)
 
 base::Optional<bool> IsColorModelSelected(int color_mode) {

printing/print_settings.h

@@ -37,7 +37,12 @@ PRINTING_EXPORT base::Optional<bool> IsColorModelSelected(int color_mode);
 PRINTING_EXPORT void GetColorModelForMode(int color_mode,
                                           std::string* color_setting_name,
                                           std::string* color_value);
+
+#if defined(OS_MACOSX) || defined(OS_CHROMEOS)
+// Convert from |color_mode| to a print-color-mode value from PWG 5100.13.
+PRINTING_EXPORT std::string GetIppColorModelForMode(int color_mode);
 #endif
+#endif  // defined(USE_CUPS)
 
 // Inform the printing system that it may embed this user-agent string
 // in its output's metadata.

printing/print_settings_unittest.cc

@@ -5,6 +5,7 @@
 #include "printing/print_settings.h"
 
 #include "base/test/gtest_util.h"
+#include "build/build_config.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace printing {
@@ -43,6 +44,19 @@ TEST(PrintSettingsDeathTest, GetColorModelForModeEdges) {
   EXPECT_DCHECK_DEATH(GetColorModelForMode(COLOR_MODEL_LAST + 1,
                                            &color_setting_name, &color_value));
 }
+
+#if defined(OS_MACOSX) || defined(OS_CHROMEOS)
+TEST(PrintSettingsTest, GetIppColorModelForMode) {
+  for (int model = UNKNOWN_COLOR_MODEL; model <= COLOR_MODEL_LAST; ++model)
+    EXPECT_FALSE(GetIppColorModelForMode(model).empty());
+}
+
+TEST(PrintSettingsDeathTest, GetIppColorModelForModeEdges) {
+  ::testing::FLAGS_gtest_death_test_style = "threadsafe";
+  EXPECT_DCHECK_DEATH(GetIppColorModelForMode(UNKNOWN_COLOR_MODEL - 1));
+  EXPECT_DCHECK_DEATH(GetIppColorModelForMode(COLOR_MODEL_LAST + 1));
+}
+#endif  // defined(OS_MACOSX) || defined(OS_CHROMEOS)
 #endif  // defined(USE_CUPS)
 
 }  // namespace printing

printing/printing_context_chromeos.cc

@@ -36,20 +36,6 @@ namespace printing {
 
 namespace {
 
-// Convert from a ColorMode setting to a print-color-mode value from PWG 5100.13
-const char* GetColorModelForMode(int color_mode) {
-  const char* mode_string;
-  base::Optional<bool> is_color = IsColorModelSelected(color_mode);
-  if (is_color.has_value()) {
-    mode_string = is_color.value() ? CUPS_PRINT_COLOR_MODE_COLOR
-                                   : CUPS_PRINT_COLOR_MODE_MONOCHROME;
-  } else {
-    mode_string = nullptr;
-  }
-
-  return mode_string;
-}
-
 // Returns a new char buffer which is a null-terminated copy of |value|.  The
 // caller owns the returned string.
 char* DuplicateString(const base::StringPiece value) {
@@ -138,7 +124,7 @@ std::vector<ScopedCupsOption> SettingsToCupsOptions(
   std::vector<ScopedCupsOption> options;
   options.push_back(
       ConstructOption(kIppColor,
-                      GetColorModelForMode(settings.color())));  // color
+                      GetIppColorModelForMode(settings.color())));  // color
   options.push_back(ConstructOption(kIppDuplex, sides));         // duplexing
   options.push_back(
       ConstructOption(kIppMedia,