[Qgis-developer] Qt 4.2 QDialogButtonBox and QMessageBox::StandardButton

[Tom Elwertowski]

Hi all,

Qt 4.2 has introduced some new features to provide better cross-platform 
button placement. For example, on a Mac, an "accept" button is placed to 
the right of a "reject" button whereas on Windows, the reverse is true.

For me (a Mac user), seeing a Cancel or reject button to the right of an 
OK or accept button is like seeing a red light on the bottom of a 
traffic signal. :)

In the coming days, I will be changing all code to use the new API. This 
message provides a brief overview. More datails can be found on the Qt 
4.2 QDialogButtonBox and QMessageBox doc pages.

When using the new StandardButtons API with QMessageBox or placing a 
QDialogButtonBox in dialog layouts, Qt will size and position buttons 
according to the platform. In some cases, even the name is adjusted; for 
example, "Discard" is "Don't Save" on a Mac.

The API uses the StandardButton enum instead of button names in 
parameters. OK, Open and Save are "accept" buttons and Cancel, Close and 
Abort are "reject" buttons. Eighteen buttons are predefined and it is 
also possible to create a custom labeled button, assign it a role and 
then add it to the dialog. The default and escape buttons are also 
selected based upon a button's role.

The old API used a zero based index and looked like this:

int ret = QMessageBox::warning(this, "Title", "Message", "Ok", "Cancel");
if (ret == 0) okAction();

The new API uses an enum and looks like this:

QMessageBox::StandardButton ret = QMessageBox:warning(this, "Title", 
"Message", QMessageBox::Ok | QMessageBox::Cancel);
if (ret == QMessageBox::Ok) okAction();

Buttons in the new API are 'or'ed together rather then listed in 
separate parameters since button order is determined by the platform 
based upon each buttons role.

Tom