Currently, Thunderbird 5 uses DirectWrite for font rendering when hardware acceleration is enabled. This is automatic if the user has a supported OS and non-blacklisted video drivers. On Windows, this will cause a degradation of readability for many fonts, including those used in the GUI. Firefox 4 did the same (I'd say: made the same mistake) and this led to large user outcry over "fuzzy fonts". Eventually, the core issue was understood and addressed in bug 642589 and specifically bug 661471, switching back to classic rendering for fonts which simply do not look good or correct with DirectWrite. Note that Firefox 4 and 5 have an easily user-accessible preference to disable hardware acceleration. Thunderbird 5 does not. Based on this, I would recommend that Thunderbird 5 ships with HW acceleration *disabled* by default. The benefits of HW acceleration are much more relevant to a browser, than to a email/news/calendar/etc application, whereas text readability should be paramount. This could be reversed as soon as the mention bugs land.

gfx.font_rendering.directwrite.enabled is false by default. You probably talking about gfx.direct2d.disabled which is false by default.

I'm not sure - when having HW acceleration enabled, the font rendering is fuzzy identically to FF4/5 with HW acceleration enabled. The font rendering in Firefox nightlies is OK now, in Aurora it's still broken, which suggest the mentioned bugs/patches do fix the issue. I just checked, and I see no difference in font rendering when toggling the "gfx.font_rendering.directwrite.enabled" but I do see one when toggling "gfx.direct2d.disable". Is it possible the preference is broken?

When you set gfx.direct2d.disabled to true you must restart TB.

I did that of course.

>gfx.font_rendering.directwrite.enabled is false by default. You probably talking >about gfx.direct2d.disabled which is false by default. directwrite.enabled forces DirectWrite even when HW acceleration is disabled. So that is exactly the wrong way around. DirectWrite gets enabled when HW acceleration is enabled, regardless of that setting. So I am really talking about disabling HW acceleration.

Maybe it's behaves differently on Windows Vista, because I'm on W7 and this pref works for me since introduction on nightlies. I was disabled direct2d from first day. So HW acceleration is controlled by gfx.direct2d.disabled, AFAIK, or I just forgot about another pref I changed.

(In reply to comment #6) > Maybe it's behaves differently on Windows Vista, because I'm on W7 and this > pref works for me since introduction on nightlies. I was disabled direct2d > from first day. > > So HW acceleration is controlled by gfx.direct2d.disabled, AFAIK, or I just > forgot about another pref I changed. When I turn gfx.direct2d.disabled ON, thunderbird is normally readable at startup, but as soon as there is a window refresh or somethnig like than (some 2-3seconds later) the whole window and childs become blurry. on W7 64b Core2 E6750 Radeon 5750+Catalyst 11.6 (latest)

>So HW acceleration is controlled by gfx.direct2d.disabled, AFAIK, or I just >forgot about another pref I changed. No, you are correct. I don't actually disagree with you in your comments, I just thought you suggested flipping gfx.font_rendering.directwrite.enabled to false should fix it, which it doesn't. We agree the issue is that gfx.direct2d.disabled must be true.

Since this nice bug bores me a bit, I remembered that I also got it on FF since 4.0, so I asked it for the solution (through its nice accel checkbox): So I found the hidden nasty parameter by sorting firefox about:config parameters and checking/unchecking the "use hardware acceleration if available" checkbox! B-] By doing so, if you recheck the accel & sort, then uncheck it and seek for the bold lines after those you sorted, you'll find : 1) gfx.direct2d.disabled false->true 2) layers.acceleration.disabled false->true Try it in TB and enjoy your lovely bird sharp again ;-) BTW, the profile selection window (option -p) remains blurred (parameters must not be read before it's displayed IMHO)

Best of all: I found someone that faced the same problem with MSN (http://forum.pcinpact.com/topic/156592-resolu-w7-police-decriture-et-image-floues/), he said that he solved his problem by reseting to defaults his graphics card settings (inside AMD Catalyst Control Center->Gaming->3D Application Settings Defaults Button then Apply). I just tried it and indeed it works : whether or not gfx.direct2d.disabled & layers.acceleration.disabled are true or false, the fonts remain clear B-| The effect is the same in Firefox 5 (can check/uncheck accel => no more problem). I also tried to tune some Catalyst 3D settings then => no problem also... It looks like an old gfx driver parameter messes direct2D, that gets corrected by reseting the driver settings (at least in my case).

oops, little typo mistake that stole a 't' to resetting :~)

>I found someone that faced the same problem with MSN That looks like a horrible graphics driver bug, but completely unrelated to this (MSN is not a Mozilla application). This bug is about GDI versus DirectWrite (natural) font rendering: http://www.basschouten.com/blog1.php/font-rendering-gdi-versus-directwrite >I just tried it and indeed it works : whether or not gfx.direct2d.disabled & >layers.acceleration.disabled are true or false, the fonts remain clear B-| This simply means that 2D HW acceleration on the system is disabled entirely, so you won't be able to get DirectWrite rendering for fonts where it *should* be used, nor acceleration for Canvas etc.

Does anything changed in Linux btw? Because I just checked 5.0 version in ubuntu, and while fonts doesn't look fuzzy, they become little bit thiner.

(In reply to comment #12) > That looks like a horrible graphics driver bug, but completely unrelated to > this (MSN is not a Mozilla application). > > This simply means that 2D HW acceleration on the system is disabled > entirely, so you won't be able to get DirectWrite rendering for fonts where > it *should* be used, nor acceleration for Canvas etc. I think that those are both the same bug : I met it again yesterday when upgrading to Thunderbird 5 (had also met it with FF 4) and it disappeared only when I toggled both : 1) gfx.direct2d.disabled false->true 2) layers.acceleration.disabled false->true (see comment 9) But the bug was still present on the profile selection window. When I toggled only gfx.direct2d.disabled false->true , the bug was even worse : fonts initially blurred, that became totally unreadable if anything triggered a redraw (looks like it was reblurred); the most terrible was selecting then deselecting some text => impressionism In the Catalyst Control Center 3D options, there is nothing about Direct2D, and tuning it by hand before resetting the parameters to default had no effect. That's why I think that some hidden parameter is set with defaults that fixes the problem (but I don't think it disables Direct2D)

Also see bug 668552 on general performance issues with hardware acceleration.

Reported the missing easily user-accessible preference to disable hardware acceleration in Tbird as Bug 680265

(In reply to Gian-Carlo Pascutto (:gcp) from comment #12) > >I found someone that faced the same problem with MSN > > That looks like a horrible graphics driver bug, but completely unrelated to > this (MSN is not a Mozilla application). It's not at all completely unrelated I'd say :) We use the same text drawing API's as MSN with Hardware Acceleration on.

Yes, but just enabling HW acceleration should not cause it to look that bad, unless something else is broken. Given that TB 6.0 shipped with it enabled (*sigh*), and TB 7.0 will have the fixes to revert some fonts to GDI automatically (at least I presume - does FF7 having them mean TB7 will too?), I guess this bug is useless now.

note getsatisfaction reports attached to bug 668552

I don't think this bug is useless. I recently updated Intel Mobile Series 4 graphics drivers to a version that supports HW acceleration and ever since Thunderbird was unusably slow. This should be DISABLED by default or at least simply configurable. How on earth should an average user figure that one out??

Hardware acceleration has now been disabled for TB 9 by bug 689742.

(In reply to Mathias Rufer from comment #20) > I don't think this bug is useless. I recently updated Intel Mobile Series 4 > graphics drivers to a version that supports HW acceleration and ever since > Thunderbird was unusably slow. Slow during usage or slow to start up?

Slow during usage. I should precise that this gets worse the bigger the screen resolution is. Thunderbird even stalled or crashed when displaying attached photos. One very easy way to reproduce Thunderbird (with HW acceleration) crashing is to let it run in the background and run a graphics intensive application, as example Windows 7 system assessment tool (winsat). Yes I have the most recent Intel drivers. This might still be a driver bug. I'm happy to hear that the next version will have HW acceleration disabled.