Where do you write the above code? Where do you write the above code? Well, that's another essay!
#Overriding text in davka software how to#
So how do you get the values of the controls while the dialog is active? Just use the control variable to access the control! For example, to determine if the OK button should be enabled, and it can only be enabled if the text value is nonblank you can write:įar easier than having to remember how to call UpdateData (is it TRUE or FALSE for the argument?) and avoids the danger of messing over the OK/ Cancel behavior. If you don't understand what a control variable is, click the hyperlink to read my essay on them. The correct way, I have found, is to use control variables. Low cost of development is also important.
To me, ease of maintenance is one of the most important concerns. Overall, I found that the three programs I wrote using UpdateData were harder to write, harder to debug, and much harder to maintain, than any program before or since in which I did not make any use of UpdateData. But if you do UpdateData, you have to deal with the fact that this flurry of events may happen in an order other than the expected order from a user, and you have to make all sorts of provisions to deal with it, such as always setting a flag that indicates if the change should be reacted to or not. Now assume that there is some issue about consistency checking, such that modifying control A affects the value in control B. This will immediately cause a set of OnChange ( WM_COMMAND/EN_CHANGE) notifications, as each edit control is returned. In addition, if you call UpdateData, it snaps values from memory into all of your edit controls. You have to make sure, every time a change is made, that you copy all the values out of the controls, via UpdateData, so that if you want to make another change and restore the values you have the correct set, not some mix of some previous values and current values. This means you have to remember to save that state! I found this the greatest problem I had in managing the use of UpdateData before I figured out that it was simply a Bad Idea. I've included it at the end.Īnother reason to avoid UpdateData is that UpdateData restores all the state. But his critique is well-taken, and you should read it. It is a flaw I never knew about because I have never used a particular feature of dialogs (well, I used it, didn't like it, and chose to deliberately avoid it). That's because if the user clicks Cancel, you've already messed over the values to represent some intermediate state that the user has just chosen to reject.ĭoug Harrison sent me a critique which points out a serious flaw in the above sequence. Nothing to it! But if you ever call UpdateData yourself, this simple paradigm won't work. This makes calling a modal dialog very simple: Therefore, the assumed behavior, or the should-be-assumed behavior, is that if you set a collection of member variables before calling DoModal, upon successful completion of the dialog the member variables will hold the new control values, and upon error completion the member variables will have the same values that you put into them. The OnCancel handler does not call UpdateData. One reason is that the OnOK handler calls UpdateData to store the control values in the associated member variables. You should never call UpdateData in a modal dialog. But a Wave of the Flounder Fin to Doug, who took the time to send me a message. I also disagree with a couple, and I'll tell you why, and you can judge for yourself what you want to do. I'm including his comments at the end, because some of them point out some potential flaws in my approach, and are valid points. It is simply the wrong way to go about it.Īfter I posted this essay, one reader, Doug Harrison, sent me a critique. Unfortunately, all of the evidence suggests that UpdateData is the correct way to handle the problem of accessing control information while working inside a dialog. It is left up to the programmer to somehow magically infer the correct way to do this. Microsoft does not adequately document the correct way to work with controls.
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