Use DPI from Print Preview on Windows, handle non square

printing/print_settings.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef PRINTING_PRINT_SETTINGS_H_
 #define PRINTING_PRINT_SETTINGS_H_
 
 #include <string>
 
 #include "base/strings/string16.h"
@@ skipping 90 matching lines @@
 
   void set_dpi(int dpi) { dpi_ = dpi; }
   int dpi() const { return dpi_; }
 
   void set_scale_factor(double scale_factor) { scale_factor_ = scale_factor; }
   double scale_factor() const { return scale_factor_; }
 
   void set_rasterize_pdf(bool rasterize_pdf) { rasterize_pdf_ = rasterize_pdf; }
   bool rasterize_pdf() const { return rasterize_pdf_; }
 
+  void set_desired_dpi(int dpi_horizontal, int dpi_vertical) {
+#if defined(OS_WIN)
+    desired_dpi_[0] = dpi_horizontal;
+    desired_dpi_[1] = dpi_vertical;
+#endif
+  }
+
   void set_supports_alpha_blend(bool supports_alpha_blend) {
     supports_alpha_blend_ = supports_alpha_blend;
   }
   bool supports_alpha_blend() const { return supports_alpha_blend_; }
 
   int device_units_per_inch() const {
 #if defined(OS_MACOSX)
     return 72;
 #else  // defined(OS_MACOSX)
     return dpi();
@@ skipping 29 matching lines @@
 
   void set_color(ColorModel color) { color_ = color; }
   ColorModel color() const { return color_; }
 
   void set_copies(int copies) { copies_ = copies; }
   int copies() const { return copies_; }
 
   void set_duplex_mode(DuplexMode duplex_mode) { duplex_mode_ = duplex_mode; }
   DuplexMode duplex_mode() const { return duplex_mode_; }
 
-  int desired_dpi() const { return desired_dpi_; }
+  int desired_dpi_horizontal() const { return desired_dpi_[0]; }
+  int desired_dpi_vertical() const { return desired_dpi_[1]; }
 
 #if defined(OS_WIN)
   void set_print_text_with_gdi(bool use_gdi) { print_text_with_gdi_ = use_gdi; }
   bool print_text_with_gdi() const { return print_text_with_gdi_; }
 
   void set_printer_type(PrinterType type) { printer_type_ = type; }
   bool printer_is_xps() const { return printer_type_ == PrinterType::TYPE_XPS;}
   bool printer_is_ps2() const {
     return printer_type_ == PrinterType::TYPE_POSTSCRIPT_LEVEL2;
   }
   bool printer_is_ps3() const {
     return printer_type_ == PrinterType::TYPE_POSTSCRIPT_LEVEL3;
   }
 #endif
 
   // Cookie generator. It is used to initialize PrintedDocument with its
   // associated PrintSettings, to be sure that each generated PrintedPage is
   // correctly associated with its corresponding PrintedDocument.
   static int NewCookie();
 
  private:
   // Multi-page printing. Each PageRange describes a from-to page combination.
   // This permits printing selected pages only.
   PageRanges ranges_;
 
   // Desired visible dots per inch rendering for output. Printing should be

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

Observation: From what I can tell, this was only used to tell the renderer how
to scale the image in ComputeWebKitPrintParamsInDesiredDpi(), and it was hard
coded to 72.

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

Removed it.

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

Observation: Now it's being repurposed for something else, which is setting the
DPI when printing on Windows. In principle, |dpi_| below on line 236 should be
used for that, but I feel it probably gets used in many places, so this is being
used instead to avoid changing existing behavior.

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

I think just using DPI is working. I added some functions so that we
can still used dpi the way it was before (as if it is the same in
both dimensions) but it actually stores the two dimensional dpi from
print preview if the user selected one. If not, it just starts out at
zero until we fetch the default value from the printer.

   // scaled to ScreenDpi/dpix*desired_dpi.
-  int desired_dpi_;
+  int desired_dpi_[2];
 
   // Indicates if the user only wants to print the current selection.
   bool selection_only_;
 
   // Indicates what kind of margins should be applied to the printable area.
   MarginType margin_type_;
 
   // Strings to be printed as headers and footers if requested by the user.
   base::string16 title_;
   base::string16 url_;
@@ skipping 47 matching lines @@
   PrinterType printer_type_;
 #endif
 
   // If margin type is custom, this is what was requested.
   PageMargins requested_custom_margins_in_points_;
 };
 
 }  // namespace printing
 
 #endif  // PRINTING_PRINT_SETTINGS_H_