topmost

Arguments: window

Returns the value of the topmost property of a basic-pane. Applicable only to top-level windows (those windows whose parent is the screen). If true, then window will always stay in front of all non-topmost top-level windows (assuming that window is itself a top-level window; topmost has no effect for a non-top-level window).

May be specified with the :topmost initarg as usual with properties. You can setf the topmost property of a window in order to change whether it is a topmost window. One exception is that if you turn on the topmost property of a form, the form itself will not be topmost, but its running window will be.

Care should be taken when making an owned (overlapped or pop-up) window be topmost, because this can lead to the owned siblings of the window becoming non-contiguous in the occlusion order; that is, some of the sibling owned windows may come in front of another application while others stay behind it. For example, if you make a window whose parent is the development-main-window in the IDE, it will be an owned top-level window (since the development-main-window defines an is-child-allowed method to force all of its descendents to be owned windows rather than child windows). If you further make this window be a topmost window and then expose and hide the window (perhaps with pop-up-modal-dialog), then you may find that returning to Allegro from another application exposes only a single selected IDE window.

Therefore, if you make an owned (overlapped or pop-up) window (which provides modality with respect to all of its sibling owned windows) for use as a modal dialog and wish the dialog to also be topmost, then it is recommended that you turn the topmost property on just before calling pop-up-modal-dialog and turn it back off just after.

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This page was not revised from the 10.0 page.
Created 2019.8.20.