Stopped setting assumed screen resolution in Mozilla/XULRunner 1.8 since the browser...

Documented this problem.

diff --git a/README b/README
index df6b8f72e48e7225f5df57af1e1b41cadc2cba72..c273e4379124fa69b0882ee003b849229cc6f463 100644 (file)
--- a/README
+++ b/README
@@ -176,6 +176,34 @@ aspect ratio and sample rate.  However, each chapter will run into the
 next.  If this is a real problem, let me know, and I may be able to
 provide a better solution in a later version of VideoLink.
 
+Bugs
+----
+
+Under Mozilla 1.7, VideoLink sets the assumed screen resolution to
+40 dpi, which I reckon to be the average resolution of a standard
+definition TV display.  This should mean that text with a font size
+expressed in millimetres or points will appear around the specified
+size.  Unfortunately this setting has a different effect under
+Mozilla/XULRunner 1.8:
+
+Mozilla   Assumed    Requested     Actual size
+version  resolution    size     (pixels) (inches)
+           (dpi)
+
+  1.7    default:96    20 px       20      0.5
+  1.7    default:96    36 pt       48      1.2
+  1.7        40        20 px       20      0.5
+  1.7        40        36 pt       20      0.5
+  1.8    default:96    20 px       20      0.5
+  1.8    default:96    36 pt       48      1.2
+  1.8        40        20 px       48      1.2
+  1.8        40        36 pt       48      1.2
+
+From version 0.10, until I have a proper solution, VideoLink will not
+set the assumed screen resolution under Mozilla 1.8.  I must advise
+against using font sizes in millimetres or points since they will vary
+between browser versions.
+
 Author and copyright
 --------------------
 

diff --git a/videolink.cpp b/videolink.cpp
index 8ab52660ec2b3d347692a499af9cb4194c20d1fa..bda78ce113c51bca35894e3db3e14795eb7455b6 100644 (file)
--- a/videolink.cpp
+++ b/videolink.cpp
@@ -885,8 +885,21 @@ namespace
        // slightly different but unfortunately Mozilla doesn't
        // support non-square pixels (and neither do fontconfig or Xft
        // anyway).
-       check(pref_branch->SetIntPref("browser.display.screen_resolution",
-                                     40));
+
+       // The browser.display.screen_resolution preference sets the
+       // the nominal resolution for dimensions expressed in pixels.
+       // (They may be scaled!)  In Mozilla 1.7 it also sets the
+       // assumed resolution of the display - hence pixel sizes are
+       // respected on-screen - but this is no longer the case in
+       // 1.8.  Therefore it was renamed to layout.css.dpi in 1.8.1.
+       // In 1.8 we need to set the assumed screen resolution
+       // separately, but don't know how yet.  Setting one to 40
+       // but not the other is *bad*, so currently we set neither.
+
+#      if MOZ_VERSION_MAJOR == 1 && MOZ_VERSION_MINOR < 8
+           check(pref_branch->SetIntPref("browser.display.screen_resolution",
+                                         40));
+#      endif
     }
 
 } // namespace