Re: [Traverso-devel] Theming: fonts, colors, etc

[Nicola Döbelin]

Hi,

> Currently only colors are stored in the theming file, I'd like to improve
> that 
> situation a bit, please have a look at the 'new' format and help me figure
> out if this makes sense, if I forgot something, and so on.

That looks very flexible. Just a couple of ideas (which may already be realized 
by your suggestion):

We're asking for object->property in the source code, and if the XML parser 
finds a corresponding entry in the XML file, its value is returned. If the 
entry doesn't exist, we should suggest a default value, just as in QSettings.

In the following snipplet you classify the properties, e.g. all colors are 
grouped in a <colors></colors> block.

        <object name="VUMeter" >
            <colors>
                <color name="background" red="120" green="200" blue="255" />
            </colors>
            <gradients>
                <gradient name="background" type="linear" />
            </gradients>
            <fonts>
                <font name ="cliptitel" size="9" type="Helvetica" />
            </fonts>
        </object>

I have absolutely no experience with XML, so I may be totally wrong, but like 
this you need special functions for each class, e.g. get_color for colors, 
get_font for fonts etc. If there's a new type, the themer must be updated. E.g. 
if in future we need QPixmaps, a get_pixmap function must be added.

OTOH if the themer would have one function get_value(object, property), return 
the value as a string, and leave it to the source code to interpret it, we 
would be much more flexible. The above XML could looke like this for example:

        <object name="VUMeter" >
            <property name="color:background" value="#99aaff" />
            <property name="gradient:background" value="#ffffff;#cccccc" />
            <property name="font:cliptitle" value="(whatever QFont::toString() 
returns)" />
        </object>

At first this looks much less convenient, especially because decoding the value 
of e.g. a gradient requires some effort. Getting a font value would be:

      QString s = themer()->get_value("VUMeter", "font:cliptitle");
      QFont f;
      f.fromString(s);

But if we later decide to have more properties, e.g. by adding a background 
pixmap, the changes would be trivial:

        <object name="VUMeter" >
            <property name="color:background" value="#99aaff" />
            <property name="gradient:background" value="#ffffff;#cccccc" />
            <property name="font:cliptitle" value="(whatever QFont::toString() 
returns)" />
            <property name="pixmap:bg_tile" value="/usr/share/traverso/bg.png" 
/>
        </object>

Loading the pixmap would be:

      QString s = themer()->get_value("VUMeter", "pixmap:bg_tile");
      QPixmap p(s);

No modifications to themer required.

For very difficult cases we still could add helper functions, e.g. for gradients

      QGradient g = themer()->get_value("VUMeter", 
"gradient:background").toGradient()

which would do the decoding.

It's a bit like QSettings, which always returns QVariant and uses QVariant's 
casting functions to convert it to a different type.

I hope that's not utter nonsense... ;-)

Regards
Nic


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