Anyone who has done serious DHTML development work knows there are many issues and quirks with the browsers out there. Of course, we had to come up with a way to deal with these cleanly for OL 4. First, I'll talk about how we deal with browser quirks. Next, I'll list the IE 7-specific issues we ran across during development of the OL4 DHTML runtime.

Capabilities-based browser quirks

1. We keep an object that lists each quirk by name, with a boolean value for whether it's active in the current browser or not. Here's a list of all the current quirks, with default values:

LzSprite.prototype.quirks = {
    fix_clickable: true
    ,fix_ie_background_height: false
    ,fix_ie_clickable: false
    ,ie_alpha_image_loader: false
    ,ie_leak_prevention: false
    ,invisible_parent_image_sizing_fix: false
    ,emulate_flash_font_metrics: true
    ,inner_html_strips_newlines: true
    ,inner_html_no_entity_apos: false
    ,css_hide_canvas_during_init: true
    ,firefox_autocomplete_bug: false
    ,hand_pointer_for_clickable: true
    ,alt_key_sends_control: false
    ,safari_textarea_subtract_scrollbar_height: false
    ,safari_avoid_clip_position_input_text: false
    ,reverse_mouse_wheel: false
    ,no_cursor_colresize: false
    ,safari_visibility_instead_of_display: false
    ,preload_images_only_once: false
    ,absolute_position_accounts_for_offset: false
}

2. Next, we use some browser detection code to turn specific quirks on or off depending on the browser we're running in:

    ...
    if (Lz.__BrowserDetect.browser == 'Opera') {
        // Fix bug in Opera where if any parent of an image is hidden the size is 0
        LzSprite.prototype.quirks['invisible_parent_image_sizing_fix'] = true;
    }
    ...

3. Finally, the sprite checks these quirks at runtime, like so:

LzSprite.prototype.__imgonload = function(i) {
    ...
    if (LzSprite.prototype.quirks.invisible_parent_image_sizing_fix) {
        Fix...
    }
...
}

This has a several benefits:
+ By conditionalizing on capabilities (instead of browser-specific version information) we can turn the quirks on or off once up front when we do the browser test.
+ It runs faster - it's quicker to test for a boolean value than test for a browser ID/version each time a given chunk of code runs.
+ We can easily and safely turn behavior on or off without touching the rest of the code.
+ Quirks can be cleanly reused when the same issue is discovered across multiple browsers. For example, when I discovered Opera had the same issue as Webkit (images with any parent div whose style.display is set to 'none' don't get valid height and width properties), all I had to do was set the 'invisible_parent_image_sizing_fix' quirk to 'true' for Opera in the browser detection phase. When this issue is fixed in future browser versions, I can easly turn the quirk back off.
+ The rest of the code is much cleaner because the quirks are 'self-documenting'. Compare these two for legibility/maintainability:

    if (this.quirks.invisible_parent_image_sizing_fix) {
        ....
    }

vs.

    if (browser.name == 'Opera' || (browser.name == 'Safari' && browser.version < 1.5)) {
        ....
    }

I encourage everyone to steal this idiom and apply it to their code! It'll make the DHTML world a better place. If only we didn't have to worry about these issues...

Then again, if you use OL 4, we'll worry about them for you! We're fond of saying 'we work hard so you don't have to.'

IE 7-specific quirks

Okay, on to the second part of the article: IE 7-specific quirks. The IE team is currently in the process of locking down features for the next version of IE. This provides an excellent opportunity for us to list the IE-specific bugs and quirks we ran across during the development of the DHTML runtime for OL 4.

I'm not trying to single out IE here - I intend to talk about quirks in other browsers (there are plenty) in the future. I just learned the IE team is soliciting feedback, and I wanted to provide some in a timely fashion! So, I'll list only issues that affect IE 7 for now:

+ Can't set opacity on any div that contains <input type="text"/> or <textarea/> without getting nasty visual artifacts in the text field.

+ Must use the AlphaImageLoader if we want opacity to apply to a div and all its children.

+ AlphaimageLoader must have its src property set to the URL of an image to prevent a red x/missing image icon from appearing

+ AlphaimageLoader does not send onload/error events - instead we have to use the img tag mentioned above

+ IE 7 still has memory leaks for apps loaded in iframes

+ Empty divs with style.backgroundColor set appear ~10px tall unless they contain an img (for less than 2px tall) or have style.fontSize = '0px' applied.

+ IE does not support &apos; when setting a div's innerHTML property

+ IE does not send onclick/onmouse* events for divs without a blank image attached

Thanks for all the hard work on IE 7 - it's miles ahead of IE 6 in almost every way. And we all love the IE developer toolbar! Of course, let me know if you need more specifics about any of these.

Best of luck, and I hope some or all of these issues can be addressed in an upcoming release!

This entry was posted on Friday, March 30th, 2007 at 2:39 am and is filed under Development, Documentation. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.