Use DPI from Print Preview on Windows, handle non square

printing/print_settings_initializer_win.cc

Index: printing/print_settings_initializer_win.cc
diff --git a/printing/print_settings_initializer_win.cc b/printing/print_settings_initializer_win.cc
index 685c8fd6cf96dfb1ec2cf7ff08cdde161a4a9540..a9d8c3e7330b39a1405b9e48894eff4005ac8b33 100644
--- a/printing/print_settings_initializer_win.cc
+++ b/printing/print_settings_initializer_win.cc
@@ -5,6 +5,7 @@
 #include "printing/print_settings_initializer_win.h"
 
 #include <windows.h>
+#include <algorithm>
 
 #include "printing/print_settings.h"
 
@@ -104,7 +105,8 @@ void PrintSettingsInitializerWin::InitPrintSettings(
 
   print_settings->SetOrientation(dev_mode.dmOrientation == DMORIENT_LANDSCAPE);
 
-  int dpi = GetDeviceCaps(hdc, LOGPIXELSX);
+  int dpi =
+      std::min(GetDeviceCaps(hdc, LOGPIXELSX), GetDeviceCaps(hdc, LOGPIXELSY));
   print_settings->set_dpi(dpi);
 
   const int kAlphaCaps = SB_CONST_ALPHA | SB_PIXEL_ALPHA;
@@ -115,18 +117,21 @@ void PrintSettingsInitializerWin::InitPrintSettings(
   // the fax device using the 200x100 dpi setting. It's ought to break so many
   // applications that it's not even needed to care about. Blink doesn't support
   // different dpi settings in X and Y axis.
-  DCHECK_EQ(dpi, GetDeviceCaps(hdc, LOGPIXELSY));
-
   DCHECK_EQ(GetDeviceCaps(hdc, SCALINGFACTORX), 0);
   DCHECK_EQ(GetDeviceCaps(hdc, SCALINGFACTORY), 0);
 
   // Initialize |page_setup_device_units_|.
-  gfx::Size physical_size_device_units(GetDeviceCaps(hdc, PHYSICALWIDTH),
-                                       GetDeviceCaps(hdc, PHYSICALHEIGHT));
-  gfx::Rect printable_area_device_units(GetDeviceCaps(hdc, PHYSICALOFFSETX),
-                                        GetDeviceCaps(hdc, PHYSICALOFFSETY),
-                                        GetDeviceCaps(hdc, HORZRES),
-                                        GetDeviceCaps(hdc, VERTRES));
+  // DPI ratio should be an integer.

[Lei Zhang, 2017/03/31 22:21:13]

As in, we don't expect a printer to have a DPI of 450x300.

[rbpotter, 2017/04/01 00:08:02]

Actually fixed this. I have not seen any non-integer examples, but
realized I probably shouldn't assume that is the case.

+  int scale_x = GetDeviceCaps(hdc, LOGPIXELSX) / dpi;
+  int scale_y = GetDeviceCaps(hdc, LOGPIXELSY) / dpi;
+  gfx::Size physical_size_device_units(
+      GetDeviceCaps(hdc, PHYSICALWIDTH) / scale_x,
+      GetDeviceCaps(hdc, PHYSICALHEIGHT) / scale_y);
+  gfx::Rect printable_area_device_units(
+      GetDeviceCaps(hdc, PHYSICALOFFSETX) / scale_x,
+      GetDeviceCaps(hdc, PHYSICALOFFSETY) / scale_y,
+      GetDeviceCaps(hdc, HORZRES) / scale_x,
+      GetDeviceCaps(hdc, VERTRES) / scale_y);
 
   // Sanity check the printable_area: we've seen crashes caused by a printable
   // area rect of 0, 0, 0, 0, so it seems some drivers don't set it.
@@ -139,6 +144,7 @@ void PrintSettingsInitializerWin::InitPrintSettings(
   print_settings->SetPrinterPrintableArea(physical_size_device_units,
                                           printable_area_device_units,
                                           false);
+
   // Check for postscript first so that we can change the mode with the
   // first command.
   int level;