value function in GSS and math formulas

[vitrums]

I've been struggling forever with a simple task of using size properties of
an image as a constant in my ClientBundle managed .css file. Every time I
have to calculate an offset based on some image width or height, I'm forced
to involve ugly *@eval*. And with GSS things haven't become easier. My hope
is that it was just me being blind in a search for a decent TOC of either
GSS or full syntax of first generation CssResource-style .css files.

Here's a snippet:

@def POPUP_LOGGER_TOP_TAILS_HEIGHT value('popupLoggerTopTails.getHeight',
'px');
@def POPUP_LOGGER_RED_BUTTON_HEIGHT value('popupLoggerRedButton.getHeight',
'px');
@def TOP_PANEL_BUTTON_AREA_MARGIN_TOP divide(add(
POPUP_LOGGER_TOP_TAILS_HEIGHT, POPUP_LOGGER_RED_BUTTON_HEIGHT), 2);

I get this error: popup-logger.gss[line: 54 column: 42]: Size must be a
CssNumericNode with a unit or 0; was: popupLoggerTopTails().getHeight() +
"px"

Obviously I'm using *value* wrong. Here's an excerpt from CssResource.java:

- value("bundleFunction.someFunction[.other[...]]" [, "suffix"])
substitute the value of a sequence of named zero-arg function invocations.
An optional suffix will be appended to the return value of the function.
The first name is resolved relative to the bundle interface passed to
com.google.gwt.core.client.GWT.create(Class)
<eclipse-javadoc:%E2%98%82=vit-gwt-core-client/C:%5C/Users%5C/vitru%5C/.m2%5C/repository%5C/com%5C/google%5C/gwt%5C/gwt-user%5C/2.8.2%5C/gwt-user-2.8.2.jar%3Ccom.google.gwt.resources.client(CssResource.class%E2%98%83CssResource%E2%98%82com.google.gwt.core.client.GWT%E2%98%82create%E2%98%82Class>.
An example:

.bordersTheSizeOfAnImage {
border-left: value('leftBorderImageResource.getWidth', 'px') solid blue;
}


Now when it comes to GSS and the math functions:

Each of these functions can take a variable number arguments. Arguments may
be purely numeric or CSS sizes with units (though mult() and divide() only
allow the first argument to have a unit).

So technically this divide(add("15px", "10px"), 2) should work.

But instead of "15px" I get this this: *popupLoggerTopTails().getHeight() +
"px". *Looks like a waste of opportunity. Completely unusable and
counterintuitive design. It's not a *value* function. It's a *string
concatenation* function. To become a *value* function it has to be already
evaluated to "15px" at this point.

But I'm sure it's just yet another time when I got confused due to a lack
of accessible use case examples. This code snippet
at http://www.gwtproject.org:

@def SPRITE_WIDTH value('imageResource.getWidth', 'px') .selector { width:
SPRITE_WIDTH; }

is literally the best example we ever had, which ironically contains a
missing ";" after ")" syntax error.

[vitrums]

I can't get my mind around the fact that *value* function and *eval* are
always runtime substitutions for *ImageResource*, when it's clearly said in
http://www.gwtproject.org/doc/latest/DevGuideClientBundle.html for *@eval*

-

If the user-defined function can be statically evaluated by the
compiler, then the implementation of the specific CssResource should
collapse to just a string literal.

One of the major optimizations provided by ClientBundle is an image bundle
generation, and it's done at compile time. Also any ClientBundle is a
subject of GWT.create(...) call. My point is that there's no runtime
information required here. And yet for

@def MY_CONSTANT 5px;
@def TOP_PANEL_BUTTON_AREA_MARGIN_TOP eval(
"net.vit.gwt.dev.ui.popuplogger.client.PopupLoggerImpl.evalTopPanelButtonAreaMarginTop()"
);

I get only

Java expression : net.vit.gwt.dev.ui.popuplogger.client.PopupLoggerImpl.
evalTopPanelButtonAreaMarginTop()

I'm not sure at which point the call to *evalTopPanelButtonAreaMarginTop()* is
done and why so late. But it precludes from mixing *value* or *eval* in GSS
formulas. Therefore I have to either rely on CSS3 *calc()* funcion, or do
everything in static methods like *evalTopPanelButtonAreaMarginTop()*.

-----------------------------------------------------------------------------

So the task is still the same: *derive an offset, based on the information
about image(s) size and other ready-to-use constants when
CssResource.ensureInjected() is called. *

Let's say I need to declare a class *.inner* in *my.gss*, for which
*margin-top:* property would be equal to *(<height of image A> - <**height **of
image B>)/2 + constant*. I declare a static method:

*lib.MyWidgetImpl.java:*
public static String evalMarginTop() {
int val = (*resource*.imageA().getHeight() - *resource*.imageB().getHeight
()) / 2 + *css*.myConstant();
return val + "px";
}

Now where do I get *resource* and *css *from? Well, I believe I'm forced to
statically inject them. I didn't manage to find a better solution for my
GIN controlled client lib. These are the miniumum requirements:

*lib.MyWidgetImpl.java:*
@Inject static MyWidgetResources resources;
@Inject static MyWidgetCss css;

*lib/myWidget.gss*:
@def MY_CONSTANT 5px;
@def MARGIN_TOP eval("lib.MyWidgetImpl.evalMarginTop()");

.inner {
margin-top: MARGIN_TOP;
}

*lib.MyWidgetCss.java:*
@ImportedWithPrefix("myWidget")
public interface MyWidgetCss extends CssResource, SharedCss {
String DEFAULT_PATH = "lib/my.gss";
...
int myConstant();
}

*lib.MyWidgetResource.java:*
public interface MyWidgetResources extends ClientBundle {
@Source("lib/imageA.png")
ImageResource imageA();

@Source("lib/imageB.png")
ImageResource imageB();

@Source({MyWidgetCss.DEFAULT_PATH, SharedCss.DEFAULT_PATH});
MyWidgetCss myWidgetCss();
}

*Application:*

*blah.AppResource.java:*
public interface AppResource extends ClientBundle, MyWidgetResource,...other
bundles {
...
}

*blah.AppModule.java:*
@Override
protected void configure() {
bind(MyWidgetResource.class).to(AppResource.class).in(Singleton.class);
requestStaticInjection(MyWidgetImpl.class);
}

@Provides
@Singleton
public MyWidgetCss getMyWidgetCss(MyWidgetResource resources) {
return resources.MyWidgetCss();
}

I don't want to statically inject resources and request static injection
for each and every ui class in my application, for which I have a GSS file
with runtime evaluation. I want to inject resources in constructor. Why
does it have to be so ugly in order to make my GIN controlled client lib
work?