[RQt-devel] Question about subclassing QAbstractTableModel

[Michael Lawrence]

On Sun, Aug 29, 2010 at 1:58 PM, John Verzani <verzani at math.csi.cuny.edu>wrote:

> Hi, I'm trying to write an alternative to qdataFrameModel that has the same
> speed, but has a more standard treatment of roles.


I have to ask: what do you mean by a more "standard" treatment of roles?
Where does QDataFrameModel not meet your needs?


> I have the following. Two questions though:
>
> 1) The items get drawn with a checkbox next to them. I make sure the
> flags() method avoids Qt$Qt$ItemIsUserCheckable, but it is still there. Any
> idea what I'm doing wrong/missing?
>
> 2) In the data() method, the Qt docs say I should return an invalid
> QVariant instead of 0. I return NA. Is that right? I also wonder why I can't
> just call super to get the default data for the role from the parent.
>
>
Both of these questions are related. Until a few minutes ago, there was no
way to specify an invalid QVariant. It now works with NULL, for lack of a
better value. I don't like NA, since it evaluates to a logical vector. NULL
does overlap with a NULL pointer in C++, but that usage is probably uncommon
(and might work anyway).

The check marks were coming from your returning NA (which would translate to
TRUE) for the check role. Note that the IsUserCheckable flag was not set by
default but was irrelevant. It only controls whether the user can edit the
check box, not the display of the check box.

Michael

Thanks for any help, --John
>
>
> library(qtbase)
>
> n <- 10 ## or even 1e6
> Df <- data.frame(a=1:n, b= rnorm(n))
>
> qsetClass("DfModel", Qt$QAbstractTableModel, function(parent=NULL) {
>   super(parent)
>   this$dataframename <- "Df"  ## generalize after testing
> })
>
> qsetMethod("Df", DfModel, function() {
>   get(this$dataframename, envir=.GlobalEnv)
> })
>
> qsetMethod("rowCount", DfModel, function(index) nrow(this$Df()))
> qsetMethod("columnCount", DfModel, function(index) ncol(this$Df()))
>
> qsetMethod("data", DfModel, function(index, role) {
>   d <- this$Df()
>   if(index$isValid()) {
>     if(role == Qt$Qt$DisplayRole)
>       out <- as.character(d[index$row() + 1, index$column() + 1])
>     else if(role == Qt$Qt$EditRole)
>       out <- as.character(d[index$row() + 1, index$column() + 1])
>     else
>       out <- NA
>     ##    super("data", index, role) ## why does this fail?
>   }
>   return(out)
> })
>
> ## coerce value to fit into x
> fitIn <- function(x, value) UseMethod("fitIn")
> fitIn.default <- function(x, value) value
> fitIn.numeric <- function(x, value) as.numeric(value)
> fitIn.integer <- function(x, value) as.integer(value)
>
> qsetMethod("setData", DfModel, function(index, value, role) {
>
>   if(index$isValid() && role == Qt$Qt$EditRole) {
>     d <- this$Df()
>     x <- d[, index$column() + 1]
>     d[index$row() + 1, index$column() + 1] <- fitIn(x,value)
>
>     assign(this$dataframename, d, envir=.GlobalEnv)
>
>     dataChanged(index, index)
>     return(TRUE)
>   } else {
>     return(FALSE)
>   }
> })
>
> qsetMethod("flags", DfModel, function(index) {
>   if(!index$isValid()) {
>     return(Qt$Qt$ItemIsEnabled)
>   } else {
>     curFlags <- super("flags", index)
>     if(curFlags & Qt$Qt$ItemIsUserCheckable)
>       curFlags <- curFlags - Qt$Qt$ItemIsUserCheckable # try to remove
> checkable
>     return(curFlags | Qt$Qt$ItemIsEditable)
>   }
> })
>
> ## test it
> model <- DfModel()
>
> view <- Qt$QTableView()
> view$setModel(model)
>
> view$setEditTriggers(Qt$QAbstractItemView$AllEditTriggers)
>
> view$show()
> view$raise()
>
>
>
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