Will not pick window size, fullscreen to windowed.

**I went to start my game as usual, and expected it to flash between my desktop and a white background as it normally does before entering a fullscreen minecraft game. I expected it to play on my TV, which was screensharing my [broken] laptop screen. Instead the game kept flickering between windowed and fullscreen versions, making my screen flash black, to my default Windows 10 color, to my desktop screen, and to a fullscreen minecraft window.
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I dont know the source of the problem, and all I did was run everything on the settings previously specified. This was the first time I turned on minecraft since I started my computer. Minecraft game version does not matter, so I am unable to write steps to replicate it...
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