Lay out tabs to have integer widths.

Lay out tabs to have integer widths.

BUG=105773
TEST=no fuzzy favicons, bug 107269 does not occur

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=114273

[Robert Sesek, 2011-12-13 18:46:38]

Code lgtm, but I think it could use some commentary. This is some of the
hairiest code we have in cocoa/ :).

http://codereview.chromium.org/8921035/diff/1/chrome/browser/ui/cocoa/tabs/ta...
File chrome/browser/ui/cocoa/tabs/tab_strip_controller.mm (right):

http://codereview.chromium.org/8921035/diff/1/chrome/browser/ui/cocoa/tabs/ta...
chrome/browser/ui/cocoa/tabs/tab_strip_controller.mm:938: if
(tabWidthAccumulatedFraction >= 1.0) {
I'd maybe name and discuss the algorithm you're using.

http://codereview.chromium.org/8921035/diff/1/chrome/browser/ui/cocoa/tabs/ta...
chrome/browser/ui/cocoa/tabs/tab_strip_controller.mm:943: // In case of rounding
error, give any left over pixels to the last tab.
Why is this a "rounding error"?

[Avi (use Gerrit), 2011-12-13 19:15:01]

ptal

http://codereview.chromium.org/8921035/diff/1/chrome/browser/ui/cocoa/tabs/ta...
File chrome/browser/ui/cocoa/tabs/tab_strip_controller.mm (right):

http://codereview.chromium.org/8921035/diff/1/chrome/browser/ui/cocoa/tabs/ta...
chrome/browser/ui/cocoa/tabs/tab_strip_controller.mm:943: // In case of rounding
error, give any left over pixels to the last tab.
On 2011/12/13 18:46:38, rsesek wrote:
> Why is this a "rounding error"?

Assume that we have 181px to distribute across three tabs. Each tab will be
60.3333px.

First tab is 60px. Accumulate the .3333219 (or whatever the floating point
version of 1/3 is).
Second tab is 60px. Accumulate another .3333219.
By the third tab, we've accumulated .9999657. That's our missing pixel, but due
to rounding error it's not exactly 1. Since we're on our last tab, if we have
what's clearly "almost a pixel" we just treat it as it is.

[Robert Sesek, 2011-12-13 19:49:56]

Thanks. lgtm++

http://codereview.chromium.org/8921035/diff/1/chrome/browser/ui/cocoa/tabs/ta...
File chrome/browser/ui/cocoa/tabs/tab_strip_controller.mm (right):

http://codereview.chromium.org/8921035/diff/1/chrome/browser/ui/cocoa/tabs/ta...
chrome/browser/ui/cocoa/tabs/tab_strip_controller.mm:943: // In case of rounding
error, give any left over pixels to the last tab.
On 2011/12/13 19:15:01, Avi wrote:
> On 2011/12/13 18:46:38, rsesek wrote:
> > Why is this a "rounding error"?
> 
> Assume that we have 181px to distribute across three tabs. Each tab will be
> 60.3333px.
> 
> First tab is 60px. Accumulate the .3333219 (or whatever the floating point
> version of 1/3 is).
> Second tab is 60px. Accumulate another .3333219.
> By the third tab, we've accumulated .9999657. That's our missing pixel, but
due
> to rounding error it's not exactly 1. Since we're on our last tab, if we have
> what's clearly "almost a pixel" we just treat it as it is.

Got to love floating point math.

[Avi (use Gerrit), 2011-12-13 20:06:50]

I could use two ints to keep a rational value but I didn't think it was worth
the effort.