Sun Aug 13, 2023 2:17 am by bob
Indeed. If your main window is 2560x1440, and the smaller windows are displaying at 640x360, the default settings for an ISBoxer window layout will make the smaller windows internally render at 2560x1440. i.e. ALL the game windows will be rendered at 2560x1440. For the purposes of your eyes, the rendered output may be scaled, but they are still essentially 2560x1440. If you ran a "stacked full screen" layout, then they would all be displayed at 2560x1440 (one on top of the other), and this would use the exact same resources (GPU/VRAM etc) as the mini displays.
Whereas if the smaller windows were being rendered at 640x360, then
1. resources required for this is much lower (less pixels to render),
2. in game elements move around because the rendered display area is smaller and stuff needs to fit in that area,
3. relative mouse movement is annoying as the in game UI elements do not necessarily scale to the same relative size of the render area
4. if you change the render area (height/width) the game has to flush/reset the canvas and buffers the re-render the whole scene at the new size which takes a few seconds, sometimes results in a blackwindow while this happens, and depending on how the game does this, can sometimes even result in a flicker while it happens.
Hence, Instant swapping is used to have the games render at all the same resolution as it resolves quite a few issues, but, can have repercussions if you have a tool/utility which is looking at the Window size rather than the D3D canvas size to determine where to place elements.