240021 - text zoom size increment differs between keyboard shortcut and mouse shortcut

Status: NEW

(Core :: DOM: UI Events & Focus Handling, defect)

Description

[Oakwine]

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7b) Gecko/20040404 Firefox/0.8.0+
Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7b) Gecko/20040404 Firefox/0.8.0+

There are two ways to zoom the text size; one uses the keyboard (Ctrl-+ and
Ctrl--), and the other the keyboard and mouse (Ctrl-Scrolldown and
Ctrl-Scrollup).  The zoom increments are inconsistent.  I believe that the
larger zoom increment (the numpad method) is incorrect, since my goal text size
is often between increments.  I could not locate a preference to change this
behavior.

While using the scrollwheel to zoom is a workaround, it does not allow for
"mouse-free" browsing.

Reproducible: Always
Steps to Reproduce:
1. Visit any page containing text; I like
http://www.kbuxton.com/discordia/fnord.html.
2. Hold down the CTRL key and increment the scroll wheel three times.
3. Observe what the last visible line of text is.
4. Press CTRL-0 to return to original font size.
5. Hold down the CTRL key and press the '+' on the numpad three times.
6. Observe what the last visible line of text is.

Actual Results:  
Step 3 shows more lines of text than does Step 6.

Expected Results:  
Step 6 should result in the same last line of text visible as shown in Step 3.

Prior to submitting this bug, I opened this discussion thread on Mozillazine to
get confirmation:
http://forums.mozillazine.org/viewtopic.php?p=467535

I suspect that this bug affects all platforms, but I do not know that.

Comment 1

[Asa Dotzler [:asa]]

bug 162032 suggests that this is driver dependent. 

Comment 2

[Asa Dotzler [:asa]]

bryner says it's not driver dependent.

Comment 3

[ashok baktha]

I want to report something that is related to the Text Size situation as
described in this report. 

I am using Firefox version 1.0 Release, on Windows XP Professional edition. 

I use Tabbed browsing a lot. When I am proceeding to type Ctrl-T to close a tab,
before I can get to the "T", as I am holding the Ctrl-button, the text size
starts to reduce. 

Unfortunately, this does not happen all the time.

Comment 4

[Adam Guthrie]

Per Gavin, the problem is that when you scroll your mouse, it goes the Gecko (the ESM) and when you use the keyboard it goes through viewZoomOverlay.js.

Sounds like we might be able to imitate what ZoomManager does in this function: http://lxr.mozilla.org/seamonkey/source/content/events/src/nsEventStateManager.cpp#1672, although I have a feeling things in that area might change if bug 4821 gets fixed.