Infralution Support

MHB · Joined: 04 Apr 2005 Posts: 69

It would be nice to be able to override the base style for a given row or cell, but CellData and RowData only have properties for the even, odd, selected and print styles separately. That makes it a bit tedious to change the appearance of an item programmatically, applying a delta to each of the properties. Is there another way?

Infralution · Joined: 28 Feb 2005 Posts: 5027

Using RowBindings makes this easy - because you can set all this stuff visually. It is worth considering using Object bindings - even if you only set up the visual stuff using them - and do every thing else programmatically.

Your OnGetCellData method can then just assign the properties from the binding eg

MHB · Joined: 04 Apr 2005 Posts: 69

I do use RowBindings, and I did override OnGetCellData because I only wanted to deviate from the default style under certain circumstances, based on runtime information.

My point was exactly what you exemplified here - I have to assign 3 different members instead of just one base style.

Actually, in my situation I just wanted to change some text to bold, and in order to do this (and nothing else), I have to code these 9 lines, a bit excessive looking to me:

Infralution · Joined: 28 Feb 2005 Posts: 5027

Maybe you missed my point. If you create an object binding using the virtual tree editor you can select the CellBinding and set the font to bold for odd, even and selected cells by setting the font in the base "Style" property. This is because row and cell bindings set up a style hierarchy similar to what you originally were asking for.

You can then programmatically determine whether or not to use the cellBinding with the bold font. This only takes the three lines of code I used before. In fact you could do it in one line of code:

MHB · Joined: 04 Apr 2005 Posts: 69

Thanks for those pieces of information, it's good to know exactly what inheritance relationships exist. However, I think you missed my point! So far, my case is rather simple, and any of these options are usable. But if I only want to change one property of the default style for one particular cell (no matter what row or column style it may derive from), instead of creating a complete new style and setting all properties, it still looks like I have to do it the complicated way, generating new styles on demand. Otherwise I may accidentally override more properties than I intended. Your suggestions require that I at coding time create a specific static style to use for each and every possible combination that may occur at runtime. This may become an issue if the application gets more complicated, with lots of different bindings and special cases. I'm not requesting multiple inheritance, just the possibility of using a style delta to override specific properties at cell level (maybe also row level). I may however also be overshooting the mark here, and trying to obtain more theoretical generality than what's actually necessary...

Infralution · Joined: 28 Feb 2005 Posts: 5027

OK I understand a little better what you are trying to do. If you really can't determine a fixed set of styles at design time then you have to fall back to creating them in the OnGetCellData method. You could still use my slightly more compact code where you apply the same Style delta to each of the three styles.

The reason there is not a parent child relationships between a base style and the styles in the CellData is performance related. In general 99% of users will use the bindings to manage styles (even if they are using programmatic data binding for everything else). The default odd, even and selected styles set in the CellData are just the VirtualTree RowOddStyle, RowEvenStyle and RowSelected style respectively. To set up a base style and parent the CellData styles from it would require creating four new styles and applying the relevant style delta(s) from the VirtualTree base styles (so that you are still able to change the base VirtualTree odd, even and selected styles and have those changes apply to rows where you may have changed the CellData.Style properties).

This is all fairly complicated and would be totally redundant if you are using row bindings - as these set up these types of style relationships. It is also a performance hit in a method which is called with a high frequency.

In summary I would reconsider whether you really do need the generality - but if you do then I'm afraid we probably can't reduce the number of lines required to write it - hopefully you only need to do it once.
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Infralution Support

MHB · Joined: 04 Apr 2005 Posts: 69

Ah, it's a performance issue. I wouldn't have thought it was, but in that case it probably isn't worth it to generalize further. I've already changed my approach to using different objects and row bindings. It's just that this is not straight forward to do without a performance hit - the data I'm displaying is transmitted over the Internet. Originally I just needed non-leaf nodes to appear bold, and network-wise that was more efficient to do at runtime during style selection, due to the implementation of the data source. Now I'm looking into changing the way the data source works accordingly.