pango 1.36.6 breaks 'Light' font styles in 0.48 and trunk

Related new warnings when building Inkscape (trunk) with pango 1.36.6 installed:

  CXX libnrtype/font-lister.o
../../src/libnrtype/font-lister.cpp:616:16: warning: enumeration value 'PANGO_WEIGHT_SEMILIGHT' not handled in switch [-Wswitch-enum]
      switch ( weight ) {
               ^
1 warning generated.

  CXX libnrtype/Layout-TNG-Output.o
../../src/libnrtype/Layout-TNG-Output.cpp:510:13: warning: enumeration value 'PANGO_WEIGHT_SEMILIGHT' not handled in switch [-Wswitch-enum]
    switch (w) {
            ^
1 warning generated.

Confirmed with trunk r13543 on Utopic

I've added 'PANGO_WEIGHT_SEMILIGHT' to both trunk and experimental branches. Does this fix the problem? (I don't have Pango 1.36.6.)

> Does this fix the problem?

No - at least not on OS X using pango 2.36.8 (tested with both backends: X11, Quartz): fonts with 'Light' styles list 'Semi-Light' in the style dropdown list (and in the Text & Font dialog), but selecting that style doesn't work. The workaround (typing 'Light' into the style entry on the text tool controls bar works as before).

I cleaned up the code a bit. Might or might not help... simplifying the conversion of Pango weight values to CSS weight values.

Some notes:

With Pango 1.36.1:

  Source Sans Pro (six weights):

    Works as expected in trunk and experimental branch.

  Source Han Sans (seven weights):

    Installed via Fedora 20 RPM (adobe-source-han-sans-cn-fonts-1.000-4.fc20.noarch):
      Pango maps both medium and regular to CSS medium weight.
Trunk specifically skips duplicate CSS weights thus only six weight shown. Experimental shows seven but only displays six (as expected since SVG stores weights using CSS).

    Installed via downloading source (http://sourceforge.net/adobe/source-han-sans/wiki/Home/):
      Pango maps

Wasn't finished with comment above...

I cleaned up the code a bit. Might or might not help... simplifying the conversion of Pango weight values to CSS weight values.

Some notes:

With Pango 1.36.1:

  Source Sans Pro (six weights):

    Works as expected in trunk and experimental branch.

  Source Han Sans (seven weights):

    Installed via Fedora 20 RPM (adobe-source-han-sans-cn-fonts-1.000-4.fc20.noarch):

      Pango maps both medium and regular to CSS medium weight.
      Trunk specifically skips duplicate CSS weights thus only six weight shown.
      Experimental shows seven but only renders six (as expected since SVG stores weights using CSS).

    Installed via downloading source (http://sourceforge.net/adobe/source-han-sans/wiki/Home/):

      Pango maps both extralight and light to light, regular and medium to medium.
      Trunks shows five weights, experimental seven.

I commented in another bug that Pango uses the PS Weight value in determining weights but this seems to not be true in the case of Source Han Sans where the PS Weight value for all faces is set to Regular (FontForge: Element->Font Info...->PS Names->Weight). The PS Weight values are "correct" in Source Sans Pro.

Looks like I'll have to install Pango 1.36.6 to make any more progress...

Pango has broken the one to one mapping between Pango weights and CSS weights by adding Semi-Light = 350 (well it was already broken with Book = 380 and Ultra-Heavy = 1000 but they are rarely used). Every font face that I have installed that previously had a Light weight now has a Semi-Light weight. Semi-Light is being mapped to CSS Normal. This is causing nasty problems with the code.

Revision 13577 in trunk seems to fix the problem. It converts any Pango Semi-Light to Light. Not the best solution. Better solutions would be:

1. Implement CSS @font-face rules.

2. Use the Font "Display Name" rather than the "CSS Name" in tracking fonts (via -inkscape-fontspec). This would work for Inkscape but fail for any other renderer since SVG relies on CSS values.

Fix confirmed with Inkscape 0.91pre2 r13577 and pango 1.36.8 on OS X 10.7.5