fix: avoid unnecessary window.makeCurrent() calls

[McMurat]

This fixes the issue as discussed here

[tommyettinger]

I'm just commenting to try to bring some eyes to this; I don't personally feel like I can adequately review the code for correctness. I can review it for performance in a little while. I've had my suspicions about LWJGL3 not running as fast as it could for a while, but it's hard to compare different versions for speed. GL30 is much slower than GL20 on my machine, when using LWJGL3, which is odd, but I'm not sure if that's related to this.

[casid]

I tried this patch with my game on windows and on mac.

It worked on both and subjectively the game felt a little smoother than before.

I have vsync activated and I'm profiling how long rendering the scene takes. Before the patch, on windows the rendering took a few us, now it takes roughly 16ms. Seems like this change made vsync work properly. On mac on the other hand no changes after the patch, rendering is still a few us.

[tommyettinger]

@casid That seems odd that Mac still takes just a few microseconds -- if a frame took 1 millisecond, that would put you at about 1000 FPS, and if it's even less than 1ms/frame, the framerate would be... certainly it could be much higher than I can get with VSync off. Does it seem like your game is using more CPU or GPU time than expected on Mac?

[casid]

@tommyettinger sorry for the confusion. I'm measuring the time it takes for the SpriteBatch to complete (that's my rendered scene), not the entire render method. I did some more profiling today, and the first call to flush() seems to block until rendering is possible again. Only after this change and only on windows. Probably before this, the makeCurrent call had to block instead.