[webkit-dev] Changing minimum font size

Steve Palmer steve at opencommunity.co.uk
Mon Aug 22 17:57:41 PDT 2005

I assumed from reading the documentation that the third line was  
apparently needed because the second line merely sets a property and  
doesn't fire off any notification and hence I saw no way that the  
webview would be refreshed with the new preferences. Unfortunately my  
assumption was wrong since looking at the WebKit source shows that if  
the new preferences pointer is identical to the old one, it does  

Based on that, my next approach was this:

     if (![NSApp enableMinimumFontSize])
         [myWebView setPreferences:defaultWebPrefs];
         WebPreferences * webPrefs = [[WebPreferences alloc] init];
         [webPrefs setMinimumFontSize:[NSApp minimumFontSize]];
         [myWebView setPreferences:webPrefs];
         [webPrefs release];

to toggle setting the minimum font size on or off. This worked fine -  
except that the webview text font increased to 16pt from the original  
12pt and wouldn't budge thenafter. After some thought, I realised  
that the HTML being rendered didn't include any explicit font size in  
the stylesheet and thus it was picking up the default from the newly  
allocated WebPreference. However the default font size in webPrefs  
was different from that in defaultWebPrefs. I've no idea why but  
adding the following lines:

         [webPrefs setDefaultFontSize:[defaultWebPrefs  
         [webPrefs setDefaultFixedFontSize:[defaultWebPrefs  

after the alloc solved the problem. A better approach would appear to  
copy the entire contents of defaultWebPrefs into webPrefs after the  
alloc and before setting the minimum font size as that would ensure  
fidelity between the preferences.

Thanks for the pointer, John!

- Steve

On Aug 22, 2005, at 8:52am, John Sullivan wrote:

> On Aug 21, 2005, at 3:55 PM, Steve Palmer wrote:
>> I asked this on the cocoa-dev alias but got no response. Hopefully  
>> this is a more appropriate list?
>> I'm trying to get my head around web preferences. Based on my  
>> reading of the API documentation, this should work to change the  
>> minimum font size used by a webview that already has text:
>>         WebPreferences * webPrefs = [myWebView preferences];
>>         [webPrefs setMinimumFontSize:12];
>>         [myWebView setPreferences:webPrefs];
>> However the existing webview text isn't changed. Any suggestions  
>> what I'm missing?
>> - Steve
> The third line above isn't necessary; there's no need to set the  
> preferences back to the same WebPreferences* object.
> The other two lines seem correct. It's not clear why this wouldn't  
> be working in your case. You should be able to debug this if you  
> build WebKit from the open-source repository (see  
> webkit.opendarwin.org). Here's what should happen:
> Setting the minimum font size runs this code:
> - (void)setMinimumFontSize:(int)size
> {
>     [self _setIntegerValue: size forKey:  
> WebKitMinimumFontSizePreferenceKey];
> }
> _setIntegerValue should store the new value, and call [self  
> _postPreferencesChangesNotification]. Note that _setIntegerValue  
> will do nothing if the new value matches the old (but that  
> shouldn't be your case, since the initial value of minimumFontSize  
> should be 0, which represents no minimum.
> _postPreferencesChangedNotification should send a  
> WebPreferencesChangedNotification
> WebView should observe the _postPreferencesChangedNotification and  
> call [self _updateWebCoreSettingsFromPreferences: preferences].
> _updateWebCoreSettingsFromPreferences then calls [_private- 
> >settings setMinimumFontSize:[preferences minimumFontSize]] to make  
> the new value known to WebCore.
> -[WebCoreSettings setMinimumFontSize:] then stores the value and  
> calls [self _updateAllViews], which schedules a redraw that should  
> use the new settings.
> So one of these steps must be failing in your case for some reason.  
> You should be able to figure out which one with a little debugging.
> I hope this helps,
> John

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