library(qtbase)
library(qtutils)

wtop <- Qt $ QWidget()
ltop <- Qt $ QGridLayout()
wtop $ setLayout(ltop)
wtop$setWindowTitle("Kernel Density Estimation")

dval <- Qt$QLineEdit("set.seed(23245); rnorm(4)")
ltop $ addWidget(Qt $ QLabel("Data"), 0, 0)
ltop $ addWidget(dval, 0, 1)

hval <- Qt $ QDoubleSpinBox()
hval $ setRange(0.01, 100)
hval $ setSingleStep(0.01)
ltop $ addWidget(Qt $ QLabel("Bandwidth"), 0, 2)
ltop $ addWidget(hval, 0, 3)

kerns <- eval(formals(density.default)$kernel)
kval <- Qt$QComboBox()
for (k in kerns) kval$addItem(k)
ltop $ addWidget(Qt $ QLabel("Kernel"), 0, 4)
ltop $ addWidget(kval, 0, 5)

plotw <- QT(width = 10, height = 7)
ltop $ addWidget(plotw, 1, 0, 1, 8)

button <- Qt$QPushButton("&Update")
ltop $ addWidget(button, 0, 7)

space <- Qt$QSpacerItem(1, 1, Qt$QSizePolicy$MinimumExpanding)
ltop $ addItem(space, 0, 6)

showComp <- Qt$QCheckBox("&Show Components")
ltop $ addWidget(showComp, 1, 0, 1, 1, Qt$Qt$AlignLeft | Qt$Qt$AlignTop)

wtop


plotError <- function(msg)
{
    plot(0, 0, type="n", axes = FALSE, xlab = "", ylab = "")
    text(0, 0, msg, cex = 1)
}


plotDensity <- function(...)
{
    e <- try(parse(text = dval$text), silent = TRUE)
    if (inherits(e, "try-error"))
    {
        plotError(sprintf("Invalid expression:\n %s", dval$text))
        return()
    }
    x <- try(eval(e), silent = TRUE)
    if (inherits(x, "try-error"))
    {
        plotError(substring(as.character(x), 1, 10))
        return()
    }
    if (!is.numeric(x)) return()
    plot(density(x, bw = hval$value, kern = kval$currentText), lwd = 2)
    ## points(x, rep(0, length(x)), col = "grey", pch = 16)
    rug(x)
    if (showComp$isChecked())
    {
        for (xx in x) {
            d <- density(xx, bw = hval$value, kern = kval$currentText)
            d$y <- d$y / length(x)
            lines(d, col = "#FF000088")
        }
    }
    invisible()
}

plotDensity()

qconnect(button, signal = "clicked", handler = plotDensity)
qconnect(dval, signal = "textChanged", handler = plotDensity)
qconnect(hval, signal = "valueChanged", handler = plotDensity)
qconnect(kval, signal = "currentIndexChanged", handler = plotDensity)

1         


## wtop$setStyleSheet("font-size: 20pt")




## Alternative to QComboBox

## qsetClass("TextSpinBox", Qt$QSpinBox)

## qsetMethod("textFromValue", TextSpinBox,
##            FUN = function(i) {
##                c("gaussian",
##                  "epanechnikov",
##                  "rectangular",
##                  "triangular",
##                  "biweight", 
##                  "cosine",
##                  "optcosine")[i+1L]
##            }, access = "protected")