[CrOS Printing] Refactor GetColorModelForMode()

The switch statment found in GetColorModelForMode() is useful for
determining whether a ColorMode is color or monochrome. Move it into a
new static function for other classes to use.

Change-Id: I834e503744c698ca82a2ef841f9b22484c49b414
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1888737
Commit-Queue: Jesse Schettler <jschettler@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#710567}

printing/printing_context_chromeos.cc

@@ -35,42 +35,16 @@ namespace printing {
 
 namespace {
 
-// convert from a ColorMode setting to a print-color-mode value from PWG 5100.13
+// 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;
-  switch (color_mode) {
-    case COLOR:
-    case CMYK:
-    case CMY:
-    case KCMY:
-    case CMY_K:
-    case RGB:
-    case RGB16:
-    case RGBA:
-    case COLORMODE_COLOR:
-    case BROTHER_CUPS_COLOR:
-    case BROTHER_BRSCRIPT3_COLOR:
-    case HP_COLOR_COLOR:
-    case PRINTOUTMODE_NORMAL:
-    case PROCESSCOLORMODEL_CMYK:
-    case PROCESSCOLORMODEL_RGB:
-      mode_string = CUPS_PRINT_COLOR_MODE_COLOR;
-      break;
-    case GRAY:
-    case BLACK:
-    case GRAYSCALE:
-    case COLORMODE_MONOCHROME:
-    case BROTHER_CUPS_MONO:
-    case BROTHER_BRSCRIPT3_BLACK:
-    case HP_COLOR_BLACK:
-    case PRINTOUTMODE_NORMAL_GRAY:
-    case PROCESSCOLORMODEL_GREYSCALE:
-      mode_string = CUPS_PRINT_COLOR_MODE_MONOCHROME;
-      break;
-    default:
-      mode_string = nullptr;
-      LOG(WARNING) << "Unrecognized color mode";
-      break;
+  base::Optional<bool> is_color =
+      PrintingContextChromeos::ColorModeIsColor(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;
@@ -245,6 +219,41 @@ PrintingContextChromeos::~PrintingContextChromeos() {
   ReleaseContext();
 }
 
+// static
+base::Optional<bool> PrintingContextChromeos::ColorModeIsColor(int color_mode) {
+  switch (color_mode) {
+    case COLOR:
+    case CMYK:
+    case CMY:
+    case KCMY:
+    case CMY_K:
+    case RGB:
+    case RGB16:
+    case RGBA:
+    case COLORMODE_COLOR:
+    case BROTHER_CUPS_COLOR:
+    case BROTHER_BRSCRIPT3_COLOR:
+    case HP_COLOR_COLOR:
+    case PRINTOUTMODE_NORMAL:
+    case PROCESSCOLORMODEL_CMYK:
+    case PROCESSCOLORMODEL_RGB:
+      return true;
+    case GRAY:
+    case BLACK:
+    case GRAYSCALE:
+    case COLORMODE_MONOCHROME:
+    case BROTHER_CUPS_MONO:
+    case BROTHER_BRSCRIPT3_BLACK:
+    case HP_COLOR_BLACK:
+    case PRINTOUTMODE_NORMAL_GRAY:
+    case PROCESSCOLORMODEL_GREYSCALE:
+      return false;
+    default:
+      LOG(WARNING) << "Unrecognized color mode.";
+      return base::nullopt;
+  }
+}
+
 void PrintingContextChromeos::AskUserForSettings(
     int max_pages,
     bool has_selection,

printing/printing_context_chromeos.h

@@ -10,6 +10,7 @@
 #include <vector>
 
 #include "base/macros.h"
+#include "base/optional.h"
 #include "printing/backend/cups_connection.h"
 #include "printing/backend/cups_deleters.h"
 #include "printing/backend/cups_printer.h"
@@ -22,6 +23,10 @@ class PRINTING_EXPORT PrintingContextChromeos : public PrintingContext {
   explicit PrintingContextChromeos(Delegate* delegate);
   ~PrintingContextChromeos() override;
 
+  // Returns true if the ColorMode setting is a color ColorMode and false if it
+  // is a monochrome ColorMode.
+  static base::Optional<bool> ColorModeIsColor(int color_mode);
+
   // PrintingContext implementation.
   void AskUserForSettings(int max_pages,
                           bool has_selection,