Enable hidpi on Linux, refactor a bit on Windows to share

ui/gfx/pango_util.cc

Index: ui/gfx/pango_util.cc
diff --git a/ui/gfx/pango_util.cc b/ui/gfx/pango_util.cc
index a324b7b326c373323420c8a2cfeba7a9d11c1325..3b8016a3ab12154697d4180204afbc5d04697ba4 100644
--- a/ui/gfx/pango_util.cc
+++ b/ui/gfx/pango_util.cc
@@ -85,27 +85,6 @@ cairo_font_options_t* CreateCairoFontOptions(const FontRenderParams& params) {
   return cairo_font_options;
 }
 
-// Returns the DPI that should be used by Pango.
-double GetPangoDPI() {
-  static double dpi = -1.0;
-  if (dpi < 0.0) {
-    const gfx::LinuxFontDelegate* delegate = gfx::LinuxFontDelegate::instance();
-    if (delegate)
-      dpi = delegate->GetFontDPI();
-    if (dpi <= 0.0)
-      dpi = 96.0;
-  }
-  return dpi;
-}
-
-// Returns the number of pixels in a point.
-// - multiply a point size by this to get pixels ("device units")
-// - divide a pixel size by this to get points
-double GetPixelsInPoint() {
-  static double pixels_in_point = GetPangoDPI() / 72.0;  // 72 points in an inch
-  return pixels_in_point;
-}
-
 }  // namespace
 
 void SetUpPangoLayout(
@@ -162,8 +141,7 @@ void SetUpPangoLayout(
 
   // Set the layout's resolution to match the resolution used to convert from
   // points to pixels.
-  pango_cairo_context_set_resolution(pango_layout_get_context(layout),
-                                     GetPangoDPI());
+  pango_cairo_context_set_resolution(pango_layout_get_context(layout), 96.0);

[ananta, 2014/10/17 00:49:06]

Is hardcoding to 96 here and below the right thing to do?. GetPangoDPI() would
also return the scale from the delegate.

[scottmg, 2014/10/17 23:18:42]

I'm not sure. The behaviour I'm seeing without making this 96 is that the fonts
end up scaled twice. i.e. when the desktop is 2x, the fonts are 4x.

AFAICT, this is because the device/display is 2x, so we don't also want to take
it into account here and scale the fonts a second time. (I'm a little confused
how it all fits together on Linux though.)

 
   // Set text and accelerator character if needed.
   if (flags & Canvas::SHOW_PREFIX) {
@@ -206,7 +184,7 @@ int GetPangoFontSizeInPixels(PangoFontDescription* pango_font) {
     return pango_font_description_get_size(pango_font) / PANGO_SCALE;
 
   // Otherwise, we need to convert from points.
-  return static_cast<int>(GetPixelsInPoint() *
+  return static_cast<int>((96.0 / 72.0) *

[ananta, 2014/10/17 00:49:06]

ditto

[oshima, 2014/10/22 19:48:07]

can you define const for these values with description?

       pango_font_description_get_size(pango_font) / PANGO_SCALE + 0.5);
 }