On my previous Windows 7 based computer (which I can no longer refer back to because it died), I used the Perforce p4v client, and changed its preferences to use Araxis Merge as the diff application. In that environment, if there was already an open Araxis Merge window, performing a diff in p4v would cause the diff result to appear in a new tab of the already open window.
In contrast, on my new Windows 10 based computer, I am using the latest version (191.183.0398) of p4v, but the same version of Araxis Merge. In this new environment, performing a diff in p4v always opens a new Araxis Merge window, even though there is a already open Araxis Merge window. That is not what I want.
Is there a way to configure p4v to use an already open window of the diff application, instead of always opening a new window?
Diffs outside of p4v
The problem does not seem to be with my diff application, Araxis Merge. As a test, I can perform a diff via the context menu in Windows Explorer. If there is already an open Araxis Merge window, performing a diff in this way causes the diff result to appear in a new tab of that existing window. That is what I want.
This test also seems to rule out the Windows 10 operating system as the culprit.
The problem was that I configured p4v to execute Merge.exe as the diff application. However, Araxis Merge has another executable named Compare.exe that I should use instead. When I configure p4v to use Compare.exe, performing a diff in p4v opens a new tab in an already open window of Araxis Merge, as desired.
The following is an example snippet of the correct p4v configuration. In the menubar, goto Edit > Preferences, then to the Diff section.
It finally dawned on me what I was doing wrong while reading the Araxis Merge command line documentation ( https://www.araxis.com/merge/documentation-windows/command-line.en ), which says in part: