Add m_isGlyphLookupMode to UniscribeHelper class and set it to true when fill...

Add m_isGlyphLookupMode to UniscribeHelper class and set it to true when filling up glyph pages for non-BMP
codepoints. When it's set to true, UniscribeHelper does not do its own font fallback. Neither does it 
glyph placement. Font fallback will be taken care of in the simple script font path. For simple script, glyph
placement is not necessary. 


BUG=6303
TEST=http://i18nl10n.com/chrome/nonbmp2.html 
(see also http://crbug.com/6304)




Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=8483

[brettw, 2009-01-13 17:55:18]

I'm a little concerned about FillScreenOrder not doing anything, since not
having the screen order structure sized properly will violate some assumptions
in the code (even though the code that makes these assumptions "shouldn't" get
called in this case).

What do you think about a "disableFontFallback" flag instead? It seems like the
performance impact of filling the screen order is minimal, and non-BMP
characters are kind of an edge case anyway.

This flag would also be more self-explanatory about what it does, whereas I have
a hard time describing what m_isGlyphLookupMode means in practice.

[jungshik at Google, 2009-01-14 00:30:11]

On 2009/01/13 17:55:18, brettw wrote:
> I'm a little concerned about FillScreenOrder not doing anything, since not
> having the screen order structure sized properly will violate some assumptions
> in the code (even though the code that makes these assumptions "shouldn't" get
> called in this case).

Just to be safe, I'll just call it.

 
> What do you think about a "disableFontFallback" flag instead? It seems like
the
> performance impact of filling the screen order is minimal, and non-BMP
> characters are kind of an edge case anyway.
> 
> This flag would also be more self-explanatory about what it does, whereas I
have
> a hard time describing what m_isGlyphLookupMode means in practice.

That name is certainly clearer except that not doing glyph placement would not
be expected from its name. Initially, I had 'onlyLookupGlyphs', but it sounded
awkward. Hmm... it's tough. What do you think?

[jungshik at Google, 2009-01-14 08:35:50]

On 2009/01/14 00:30:11, Jungshik Shin wrote:
> On 2009/01/13 17:55:18, brettw wrote:

> > What do you think about a "disableFontFallback" flag instead? It seems like

> > This flag would also be more self-explanatory about what it does, whereas I
> have
> > a hard time describing what m_isGlyphLookupMode means in practice.
> 
> That name is certainly clearer except that not doing glyph placement would not
> be expected from its name. Initially, I had 'onlyLookupGlyphs', but it sounded
> awkward. Hmm... it's tough. What do you think?

I just changed the flag name as you suggested. For glyph placement, I added a
comment about that. As for screen ordering, patch set 2 leaves it alone
regardless of the flag value.

[brettw, 2009-01-14 21:42:56]

LGTM, thanks.