Change properties of several symbols in one go

[mhugent]

One thing that I often miss in the symbology-ng dialogs is the possibility to select multiple symbols at once and change properties like color, transparency, etc. for the whole selection.
The following patch changes the symbol selector dialog to work on several symbols at once. This is then used in the categorized and graduated renderer dialog.
Martin, could you review the changes?

Regards,
Marco

[wonder-sk]

Hi Marco

I have tried the changes but I am not very happy about them (-1 to merge). The workflow for changing multiple symbols is not very intuitive. I had to look into the code to understand how to change the symbols for selected categories/ranges - to my surprise it was the button for changing the source symbol for classifcation. More usability problems followed:

• when nothing is selected then the source symbol is changed
• when symbol(s) is/are selected then both selected symbol(s) and source symbol is changed - although I only wanted to change the selected symbols
• if I choose a symbol from style with multiple symbols, the first symbol is changed, others are set to null (?)
• when one symbol is chosen, symbol properties can be opened, nothing happens with multiple symbols. This leads to inconsistency: when a symbol is double-clicked I can change its properties, but when I'm going to modify it by clicking on change button, I cannot change its properties because also source symbol is added
• when I select some symbols and double-click them, only the last one will be changed

Other minor problem is that 'delete' button does not reflect multiple selection. Also I would prefer to use ExtendedSelection instead of MutliSelection as it is more natural and easier to select ranges of items.

Given all the problems I think that symbol selector dialog is not the right way how to approach changing of multiple items at once. The symbol selector is good for choosing one symbol and I do not see a way how to elegantly alter it to support choosing several symbols at once. Additionally during the hackfest in Lisbon during the GUI brainstorming we have sketched a design for integration of symbol selector and symbol properties dialogs into one consistent (non-recursive) dialog.

I would go this way: add a context menu to the views with actions like: change color, change width, change symbol. The user would select several symbols, right-click the view and use change width action. An input dialog would pop up, showing the value of current item, the value could be modified and after clicking ok the symbols would be changed appropriately. What do you think?

[mhugent]

Hi Martin

The idea behind using the source symbol button was to have the source symbol as a sort of 'master' symbol. Like in a presentation program, if you change the master slide, it takes effect for all slides (you don't have to recreate the whole presentation).

Currently, changes to the source symbol only take effect for the next reclassify action. This is quite unintuitive, as in the gui, it only says 'symbol' and on the button 'change'. So as a user, I would expect to change symbol properties here.

That said, I don't really have a strong opinion about the GUI for changing multiple symbols. The right click approach seems ok to me, however I don't know if people find out easily enough about this possibility without reading documentation. Having a button 'change symbol properties' would be clearly visible but probably not that fast to use.

Regards,
Marco

[wonder-sk]

Hmm, in case the changing of source symbol is not intuitive then we have one more usability problem to solve. Maybe renaming the 'symbol' label to 'source symbol' or 'template' would help? Or when the user already created the classification, then GUI would ask whether to reclassify when the source symbol got changed? That may make it clear that the user changes only the source. Btw: the color ramp combo box has potentially the same problem as source symbol: it is used just for classification, then it has only informative purpose.

Another thing that comes to my mind is that the classify button could be moved above the categories view in order to give the users a better sense of context for the source symbol and source color ramp.

Regarding the changes to multiple symbols: in my view right-clicking something to get context menu with additional options is quite standard method, so the functionality should be relatively easy to discover.

[mhugent]

Sounds reasonable. Renaming 'symbol' -> 'template' and moving the 'classify' button above the view makes it more intuitive that those elements are connected.

Regarding the changes to multiple symbols: in my view right-clicking something to get context menu with additional >options is quite standard method, so the functionality should be relatively easy to discover.

Hm, but in QGIS, we have few places with right click options. The legend is the only place that comes to my mind, maybe there are others?. On the other hand, changing multiple symbols at once is often used in larger project, so it's probably not so important to discover it immediatly.

[wonder-sk]

Apart from legend I am aware of attribute table (run action, open form), identify results (various things) and now also browser dock widget.

And yes, I consider thi multiple symbols functionality as something slightly advanced, so the "discoverability" could be lower.

[mhugent]

Implemented context menu change for categorized, graduated and rule based renderer widgets