Yes and no. The compile-time evaluator supports short-circuiting, but it
doesn't remove neutral elements from boolean expressions.
In your example:
if ((! $mobile) && this.quirks.ie_alpha_image_loader ) {
Compiling with $mobile = `true`:
if ((! true) && this.quirks.ie_alpha_image_loader) { ... }
=> if (false && this.quirks.ie_alpha_image_loader) { ... }
=> if (false) { ... } /* short-circuiting applied */
=> /* statement removed */
Compiling with $mobile = `false`:
if ((! false) && this.quirks.ie_alpha_image_loader) { ... }
=> if (true && this.quirks.ie_alpha_image_loader) { ... }
=> /* this.quirks.ie_alpha_image_loader can't be eval'ed at compile time */
=> /* the complete statement will be emitted */
Therefore I've suggested to use the conditional operator:
if (! $mobile ? this.quirks.ie_alpha_image_loader : false) { ... }
The compile-time evaluator is applied two times for this statement:
1) for the if-clause
2) for the conditional operator
Compiling with $mobile = `true`:
if (! $mobile ? this.quirks.ie_alpha_image_loader : false) { ... }
=> if (! true ? this.quirks.ie_alpha_image_loader : false) { ... }
=> if (false ? this.quirks.ie_alpha_image_loader : false) { ... }
=> if (false) { ... }
=> /* statement removed */
Compiling with $mobile = `false`:
if (! $mobile ? this.quirks.ie_alpha_image_loader : false) { ... }
=> if (! false ? this.quirks.ie_alpha_image_loader : false) { ... }
=> if (true ? this.quirks.ie_alpha_image_loader : false) { ... }
=> /* this.quirks.ie_alpha_image_loader can't be eval'ed at compile time */
=> /* now the compiler visits the conditional expression */
=> /* this will return `this.quirks.ie_alpha_image_loader` */
=> /* if-statement is rewritten to: */
if (this.quirks.ie_alpha_image_loader) { ... }
On 1/13/2011 7:43 PM, P T Withington wrote:
Is the compile-time evaluator smart enough to short-circuit boolean expressions
even if not all the terms are compile-time constants? E.g.,
if ((! $mobile)&& this.quirks.ie_alpha_image_loader ) {
should emit no code for $mobile, and be equivalent to:
if (this.quirks.ie_alpha_image_loader) {
for non-mobile? Then you would not need the more contorted:
if (! $mobile ? this.quirks.ie_alpha_image_loader : false) {
On 2011-01-12, at 12:29, André Bargull wrote:
The conditional operator is also handled by the compile-time evaluator, so
these two alternatives actually work and only emit the minimal javascript code:
if (! $mobile ? this.quirks.ie_alpha_image_loader : false) {
i._parent.style.display = '';
} else {
i.style.display = '';
}
and:
var target = $mobile ? e.target : (e.target || e.srcElement);
On 1/12/2011 5:36 PM, Max Carlson wrote:
Change maxcarlson-20110112-6K9 by maxcarlson@friendly on 2011-01-12 08:29:25 PST
in /Users/maxcarlson/openlaszlo/trunk2
for http://svn.openlaszlo.org/openlaszlo/trunk
Summary: First pass at commenting out non-mobile code for $mobile runtime
Bugs Fixed: LPP-9645 - add if (! $mobile) {...} blocks to DHTML LFC (partial)
Technical Reviewer: hminsky
QA Reviewer: ptw
Details: Without trying too hard, I was able to reduce the total size of the
mobile LFC by ~1.6K compressed, down to 94k from 95.7k! I think this is moving
in the right direction.
I could have been more aggressive, but I'm trying to not restructure the code.
This means I have to leave some bits in, e.g.:
if (this.quirks.ie_alpha_image_loader) {
if (! $mobile) {
i._parent.style.display = '';
}
} else {
i.style.display = '';
}
I could restructure a bit and eliminate the test, but this is just a first
pass... Also, it would be nice if I could do things like:
// IE calls `target` `srcElement`
var target = e.target
if (! $mobile) {
|| e.srcElement;
}
but that freaks out the parser.
Files:
M WEB-INF/lps/lfc/kernel/dhtml/LzSprite.js
Changeset:
http://svn.openlaszlo.org/openlaszlo/patches/maxcarlson-20110112-6K9.tar
