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How to change my app resolution according to client display size ? For example, if someone have ultra wide or square display the app should fit perfectly according to the resolution of the display.

You need a plan for how to handle different aspect ratios. That's application-specific. Some programs can do with showing more of the map, others can do with clipping, others will need filler bands. A few applications might be OK with stretching in one of the dimensions, but I'd say that's rare.

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