Create constant variables kPointsPerInch and kPixelsPerInch and conversion functions.

BUG=47277
TEST=units_unittest.cc

Review URL: http://codereview.chromium.org/2877001

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@50968 0039d316-1c4b-4281-b951-d872f2087c98

8 files changed, 53 insertions, 18 deletions

diff --git a/chrome/renderer/mock_printer.cc b/chrome/renderer/mock_printer.cc
index 235e056..78b7a78 100644
--- a/chrome/renderer/mock_printer.cc
+++ b/chrome/renderer/mock_printer.cc
@@ -9,12 +9,13 @@
 #include "base/shared_memory.h"
 #include "chrome/common/render_messages.h"
 #include "ipc/ipc_message_utils.h"
+#include "printing/units.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 MockPrinter::MockPrinter()
   : printable_width_(0),
     printable_height_(0),
-    dpi_(72),
+    dpi_(printing::kPointsPerInch),
     max_shrink_(2.0),
     min_shrink_(1.25),
     desired_dpi_(72),
@@ -195,4 +196,3 @@ bool MockPrinter::SaveBitmap(
 int MockPrinter::CreateDocumentCookie() {
   return ++current_document_cookie_;
 }
-
diff --git a/chrome/renderer/print_web_view_helper.cc b/chrome/renderer/print_web_view_helper.cc
index 726ce2d..9133e38 100644
--- a/chrome/renderer/print_web_view_helper.cc
+++ b/chrome/renderer/print_web_view_helper.cc
@@ -37,7 +37,7 @@ PrepareFrameAndViewForPrint::PrepareFrameAndViewForPrint(
 #if defined(OS_MACOSX)
   // On the Mac, the printable area is in points, don't do any scaling based
   // on dpi.
-  dpi = 72;
+  dpi = printing::kPointsPerInch;
 #endif  // defined(OS_MACOSX)
   print_canvas_size_.set_width(
       printing::ConvertUnit(print_params.printable_size.width(), dpi,
diff --git a/chrome/renderer/print_web_view_helper_linux.cc b/chrome/renderer/print_web_view_helper_linux.cc
index 2a0e333..609f099 100644
--- a/chrome/renderer/print_web_view_helper_linux.cc
+++ b/chrome/renderer/print_web_view_helper_linux.cc
@@ -8,9 +8,11 @@
 #include "base/logging.h"
 #include "chrome/common/render_messages.h"
 #include "printing/native_metafile.h"
+#include "printing/units.h"
 #include "skia/ext/vector_canvas.h"
 #include "third_party/WebKit/WebKit/chromium/public/WebFrame.h"
 
+using printing::NativeMetafile;
 using WebKit::WebFrame;
 
 void PrintWebViewHelper::Print(WebFrame* frame, bool script_initiated) {
@@ -23,14 +25,11 @@ void PrintWebViewHelper::Print(WebFrame* frame, bool script_initiated) {
   // For testing purpose, we hard-coded printing parameters here.
 
   // The paper size is US Letter (8.5 in. by 11 in.).
-  // Using default margins:
-  //   Left = 0.25 in.
-  //   Right = 0.25 in.
-  //   Top = 0.25 in.
-  //   Bottom = 0.56 in.
-  const int kDPI = 72;
-  const int kWidth = static_cast<int>((8.5-0.25-0.25) * kDPI);
-  const int kHeight = static_cast<int>((11-0.25-0.56) * kDPI);
+  const int kDPI = printing::kPointsPerInch;
+  const int kWidth = static_cast<int>(
+      8.5 * kDPI - NativeMetafile::kLeftMargin - NativeMetafile::kRightMargin);
+  const int kHeight = static_cast<int>(
+      11 * kDPI - NativeMetafile::kTopMargin - NativeMetafile::kBottomMargin);
   ViewMsg_Print_Params default_settings;
   default_settings.printable_size = gfx::Size(kWidth, kHeight);
   default_settings.dpi = kDPI;
diff --git a/printing/pdf_ps_metafile_cairo.cc b/printing/pdf_ps_metafile_cairo.cc
index b87992f..96b72c5 100644
--- a/printing/pdf_ps_metafile_cairo.cc
+++ b/printing/pdf_ps_metafile_cairo.cc
@@ -14,17 +14,11 @@
 #include "base/file_descriptor_posix.h"
 #include "base/file_util.h"
 #include "base/logging.h"
+#include "printing/units.h"
 #include "skia/ext/vector_platform_device_linux.h"
 
 namespace {
 
-// The hardcoded margins, in points. These values are based on 72 dpi,
-// with approximately 0.25 margins on top, left, and right, and 0.56 on bottom.
-const double kTopMargin = 0.25 * 72.0;
-const double kBottomMargin = 0.56 * 72.0;
-const double kLeftMargin = 0.25 * 72.0;
-const double kRightMargin = 0.25 * 72.0;
-
 // Tests if |surface| is valid.
 bool IsSurfaceValid(cairo_surface_t* surface) {
   return cairo_surface_status(surface) == CAIRO_STATUS_SUCCESS;
@@ -249,4 +243,9 @@ void PdfPsMetafile::CleanUpAll() {
   skia::VectorPlatformDevice::ClearFontCache();
 }
 
+const double PdfPsMetafile::kTopMargin = 0.25 * printing::kPointsPerInch;
+const double PdfPsMetafile::kBottomMargin = 0.56 * printing::kPointsPerInch;
+const double PdfPsMetafile::kLeftMargin = 0.25 * printing::kPointsPerInch;
+const double PdfPsMetafile::kRightMargin = 0.25 * printing::kPointsPerInch;
+
 }  // namespace printing
diff --git a/printing/pdf_ps_metafile_cairo.h b/printing/pdf_ps_metafile_cairo.h
index a5ea5be..8027188 100644
--- a/printing/pdf_ps_metafile_cairo.h
+++ b/printing/pdf_ps_metafile_cairo.h
@@ -77,6 +77,13 @@ class PdfPsMetafile {
   // This function should ONLY be called after PDF/PS file is closed.
   bool SaveTo(const base::FileDescriptor& fd) const;
 
+  // The hardcoded margins, in points. These values are based on 72 dpi,
+  // with 0.25 margins on top, left, and right, and 0.56 on bottom.
+  static const double kTopMargin;
+  static const double kRightMargin;
+  static const double kBottomMargin;
+  static const double kLeftMargin;
+
  private:
   // Cleans up all resources.
   void CleanUpAll();
diff --git a/printing/units.cc b/printing/units.cc
index 5f543fe..976fa80 100644
--- a/printing/units.cc
+++ b/printing/units.cc
@@ -39,4 +39,12 @@ int ConvertHundredThousanthMeterToMilliInch(int cmm) {
   return ConvertUnit(cmm, 254, 100);
 }
 
+int ConvertPixelsToPoint(int pixels) {
+  return ConvertUnit(pixels, kPixelsPerInch, kPointsPerInch);
+}
+
+double ConvertPixelsToPointDouble(double pixels) {
+  return ConvertUnitDouble(pixels, kPixelsPerInch, kPointsPerInch);
+}
+
 }  // namespace printing
diff --git a/printing/units.h b/printing/units.h
index d23e268..cc61241 100644
--- a/printing/units.h
+++ b/printing/units.h
@@ -10,6 +10,14 @@ namespace printing {
 // Length of a thousanth of inches in 0.01mm unit.
 const int kHundrethsMMPerInch = 2540;
 
+// Length of an inch in CSS's 1pt unit.
+// http://dev.w3.org/csswg/css3-values/#absolute-length-units-cm-mm.-in-pt-pc
+const int kPointsPerInch = 72;
+
+// Length of an inch in CSS's 1px unit.
+// http://dev.w3.org/csswg/css3-values/#the-px-unit
+const int kPixelsPerInch = 96;
+
 // Converts from one unit system to another using integer arithmetics.
 int ConvertUnit(int value, int old_unit, int new_unit);
 
@@ -22,6 +30,12 @@ int ConvertMilliInchToHundredThousanthMeter(int milli_inch);
 // Converts from 0.00001 meter unit to 0.001 inch.
 int ConvertHundredThousanthMeterToMilliInch(int cmm);
 
+// Converts from 1 pixel to 1 point using integers.
+int ConvertPixelsToPoint(int pixels);
+
+// Converts from 1 pixel to 1 point using doubles.
+double ConvertPixelsToPointDouble(double pixels);
+
 }  // namespace printing
 
 #endif  // PRINTING_UNITS_H_
diff --git a/printing/units_unittest.cc b/printing/units_unittest.cc
index b2db567..82f9acb 100644
--- a/printing/units_unittest.cc
+++ b/printing/units_unittest.cc
@@ -50,4 +50,12 @@ TEST(UnitsTest, Convertions) {
   EXPECT_EQ(-1000,
             ConvertHundredThousanthMeterToMilliInch(-kHundrethsMMPerInch));
   EXPECT_EQ(0, ConvertHundredThousanthMeterToMilliInch(0));
+
+  EXPECT_EQ(8.25, ConvertPixelsToPointDouble(11.0));
+  // Round down.
+  EXPECT_EQ(8, ConvertPixelsToPoint(11));
+  EXPECT_EQ(7.5, ConvertPixelsToPointDouble(10.0));
+  // Round up.
+  EXPECT_EQ(8, ConvertPixelsToPoint(10));
+  EXPECT_EQ(0, ConvertPixelsToPoint(0));
 }