The Release Notes for the QCharts 4.2 beta contain a write-up about Overlay Expressions, toward the end. That doc is available on the beta download page; here's the link:
quote.com
Think of an Overlay Expression as a study that charts a custom indicator, which at this time is either a symbol or arithmetic expression on symbols. In the future, when we feel there is no internal barrier to writing arbitrarily complex expressions, we will document them well and encourage people to write long ones.
To create an overlay, type <alt>SOA (which is keyboard shorthand for the right-click menu sequence "Studies | Overlay Expression | Add"). Then, in the Overlay Expression dialog, type any symbol or very short expression in the first edit area. For example, type "COMPX". Or, to give an example of an expression without claiming it is something you'd want to chart, type "SPX.X - ( VIX.X * 8 )". Spaces must separate math operators from other parts of the expression.
The "Short Nickname" field in the Overlay Expression dialog lets you assign a name to appear in the Cursor Data Window, instead of the possibly longer expression string itself. The nickname is built automatically, and should be fine. You can override it with your own string if you like. Overlays are by default 1-period moving averages of the expression you enter. If you want a real moving average, change the period, offset, or any of the other fields that define an MA. A color is automatically assigned, and is fine in most cases. Auto-color assignment creates some very unusual shades; I think you may want to see this feature in other parts of QCharts, since it: 1) saves you time; and 2) almost always creates an acceptable contrasting color.
Overlays are scaled in the vertical dimension so they fit in the same window as the chart's main symbol. There are two scaling methods. The default method, "Align Leftmost Bars," scales each overlay so that it meets the base symbol at the left chart edge. Another method, "Center Vertical Range," applies a scale factor that causes the max and min prices of each overlay to be centered on the base symbol's price range. All scaling calculations are made by examining the set of bars visible in the chart window.
When data arrives from the server for any bar visible on the chart, the y scales will be continuously recalculated. When scrolling into the past, after data required to populate the screen has been received, the y scales will NOT be recalculated. By not recalculating y scales continually for historical data, we let you scroll freely in the price dimension and expand the y scale, without interference. But when you want to "snap" the scale values back to normal, press <enter>. This does a one-time auto-scale on the base symbol's y values, and calculates y scales for any overlays. To bring the chart back to home in the x (time) axis, and also do the y scale recalculation, press <home>.
A word of caution about expression length is in order here. The ContinuumClient.dll may fail when it is asked to parse an expression that is more than a few dozen characters in length. Exercise care, and test this [undocumented, unwarranted] capability only when you are not trading, and could tolerate an access violation.
One "gotcha" in the current build is that the help button for Overlay Expressions does not bring up an RTF document about the feature, as intended. Instead, you get the main QCharts help window. This will be fixed; the doc is written and ready to drop in the next build.
New in QCharts 4.2 is the ability to select an "on-chart" study like Overlay Expression, Bollinger Band, or moving average, by clicking on it. Once clicked, the right-click menu brings up a property page for that expression. Also new is the ability to hide/unhide expressions, as an alternative to deleting them. This should save a lot of time.
In the Overlay Expressions dialog (type <alt>SO when a chart has focus), one may click on an existing overlay, then right-click to hide or unhide it. The same works for all other on-chart studies, including those I mentioned (Bollinger Band, moving average).
When selected, an overlay (or BB, or MA) is drawn one pixel thicker.
Double-clicking on a selected overlay broadcasts the symbol to linked windows, and makes it the default for the current window if its Sym button is not locked (red).
To test the drag-drop of symbols from a quote sheet to a chart, first enter a symbol or two in a quote sheet. Then, click on a row to select it (which will draw a rectangle around it or colorize it, depending on the quote sheet's format options). Then, left-click again, and with left button down, drag the mouse to a chart window. The symbol will be loaded into the chart window. Now do it again for a different quote sheet symbol, but this time hold down <ctrl> during the drop. The symbol will be added as an overlay. Both of these drag-drop operations work, whether or not the Sym button is in the locked (red) state. |
