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

5 files changed, 43 insertions, 7 deletions

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));
 }