Previously, the surface damage region was being set in the same callback used for preventing render hangs in the GL backend when the surface was not visible. This was not ideal, as the callback was never fired in the case of using a different render backend or having a swap interval of 0. Use a separate frame callback for setting the surface damage region to ensure that it fires reliably, regardless of the backend being used or swap interval.
Some compositors (GNOME for example) don't set the transform flag when dealing with portrait mode displays, so the video modes won't have the width/height swapped in all cases where they should be. Check for both the 90/270 degree transform flag and if the display is taller than it is wide when determining whether to swap the width and height of the emulated video modes, and adjust the comparison logic when size testing against the native mode to account for this.
Add the hint "SDL_VIDEO_WAYLAND_MODE_EMULATION", which can be used to disable mode emulation under Wayland. When disabled, only the desktop and/or native display resolution is exposed.
Previously, scale values used by the displays and surfaces were always integers, with fractional scale values only being calculated when the backbuffer and viewport sizes were being determined. Now, if xdg-output is available, the fractional scale of output displays is calculated when the displays are enumerated and the true scale values of the output devices are used whenever possible.
This unifies the integer and fractional scaling systems, allows for the use of more accurate scale values that minimize overdraw when windows straddle multiple outputs, and lays the groundwork for the pending Wayland scaling protocols that will report the preferred scale values per-surface instead of per-output.
Compartmentalize the fullscreen mode emulation code blocks, unify the windowed/fullscreen viewport logic, consolidate all window geometry code into a central function to eliminate blocks of duplicate code and rename related variables and functions to more explicitly reflect their purpose.
Because we were sending multiple chunks of preedit strings,
`SDL_SendEditingText` was using the old `SDL_TEXTEDITING` event only.
Now if `SDL_HINT_IME_SUPPORT_EXTENDED_TEXT` is enabled, we send the full
string and correctly set the cursor position and selection size.