It took me a couple of days but I found it out. So for future reference: here is my solution:
I extended the DateChooser and added an override on the function updateDisplayList(w:Number, h:Number) (In this function the SMTWTFS day names have been set).
In the updateDisplayList you can get the mx_internal::dateGrid.dayBlockArrays[column][row] Containing all the values for the CalendarLayout. In that array / array the first row on each column is the one of the SMTWTFS days. The other rows are the dayNumbers. Once I found that out it is a matter of determining what a weekend day was and adjust the colors accordingly. As I show below:
override protected function updateDisplayList(w:Number, h:Number):void
{
super.updateDisplayList(w, h);
// Now the dayBlocksArray has been filled. The Array looks as follows
// dayBlocksArray["rows"]["columns] .... therefor [i][0 (zero)] will always get the dayNames (SMTWTFS)
// Compare the dayNames with the set this.dayNames (which always start with sunday) and find the weekend days
var colIndex:uint = 0;
var rowIndex:uint = 1; // The first row (SMTWTFS) is handled seperately
var currentColumn:Array;
var dayName:UITextField;
var backgroundColor:uint = this.getStyle("dayNamesBackgroundColor");
var isWeekendCol:Boolean = false;
var currentTextFormat:TextFormat;
// When the style is not found the default of white will be used.
if (!backgroundColor)
{
backgroundColor = 0xFFFFFF;
}
for (colIndex; colIndex < 7; colIndex++)
{
// First determine if the first item in this row (SMTWTFS) is a week/weekend day
currentColumn = mx_internal::dateGrid.dayBlocksArray[colIndex];
dayName = currentColumn[0];
// Determine if this is a weekend row
// The dayNames array is fixed in the order of index 0 = sunday and index 6 = saturday.
// Therefor check of the text value of the current dayName is equal to either of
// those two. If it is we are dealing with a weekend column
isWeekendCol = dayName.text == this.dayNames[0] || dayName.text == this.dayNames[6];
if (isWeekendCol)
{
// Set the color
currentTextFormat = dayName.getTextFormat();
currentTextFormat.color = getStyle("weekendHeaderColor");
dayName.setTextFormat(currentTextFormat);
// Set the background color
dayName.background = true;
dayName.backgroundColor = backgroundColor;
}
else
{
currentTextFormat = dayName.getTextFormat();
currentTextFormat.color = getStyle("weekHeaderColor");
dayName.setTextFormat(currentTextFormat);
// Set the background color
dayName.background = true;
dayName.backgroundColor = backgroundColor;
}
// Reset the rowIndex
rowIndex = 1;
// Now go through all the other rows of this column
for (rowIndex; rowIndex < currentColumn.length; rowIndex++)
{
dayName = currentColumn[rowIndex];
if (isWeekendCol)
{
dayName.setColor(getStyle("weekendColor"));
}
else
{
dayName.setColor(getStyle("weekColor"));
}
}
}
}
In the CSS file I added the following styles:
DateChooser {
cornerRadius: 0;
headerColors: #FFFFFF, #FFFFFF;
todayColor: #00448c;
border-style:none;
dropShadowEnabled: false;
fontFamily: myGeorgia;
dayNamesBackgroundColor: #ECECEC;
weekHeaderColor:#444444;
weekendHeaderColor:#DDDDDD;
weekColor:#00317F;
weekendColor: #DDDDDD;
headerStyleName: "dateChooserHeaderStyle";
comboBoxStyleName: "comboBoxStyleName";
}
The most interesting styles here are the custom style "dayNamesBackgroundColor" (which is used to give a background color to the SMTWTFS set) and the custom styles "weekendHeaderColor", "weekHeaderColor", "weekColor", "weekendColor"
I read these colors in the method above to get full control for the difference in week/weekend colors where the SMTWTFS set could get different colors than the day number
Hope this will help other people in the future. Took me a lot of time to figure it out :)