This simply toggles a flag that rejects DnD offers if false. Events were previously dropped silently, but rejecting the offer makes some desktops display a proper icon when the drop will not work.
This fixes a UBSAN warning later in this function where it calculates
(1 << SDL_BITSPERPIXEL(surface->format)). The bpp might be >= 32 and
out of range for a bit shift.
SVE/SVE2 is a new SIMD extension for AArch64. Compared to NEON, SVE/SVE2 brings the following benefits that are good for SDL projects:
- Lane prediction: we don't have to treat the tail part of a stride separately when the width is n times the hardware vector size
- Although the performance is almost no difference from NEON when the hardware vector size is 128bits, when the hardware provides a longer vector size, e.g. 256, 512, ... 2048, we can enjoy the large performance gain without modifying the source code or recompiling a library.
The functional correctness is validated in a dedicated [qemu project](https://github.com/GorgonMeducer/aarch64_qemu_mac_template/tree/SDL-SVE2-Acceleration-Validation).
The performance is tested on [Radxa Orion 6 N](https://radxa.com/products/orion/o6n/), which provides 4x A720 and 4x A520 processors. Since the vector size is 128 bits, which is the same as NEON, the performance is almost the same (or no worse than) the NEON acceleration.
Because the blend mode is explicitly set to SDL_BLENDMODE_NONE, it doesn't matter if there's a transparency channel in the texture format or not for opaque windows. This ensures that a 32-bit format is used with Metal instead of SDL_PIXELFORMAT_RGB565.
Some compositors may dispatch this too early, during the initial empty commit, when subsurfaces are attached to a toplevel window, but a buffer has yet to be committed to the parent surface. Don't set the frame callback until the initial empty commit is done, so it will be called when the actual parent surface frame is committed.
Some compositors send the frame callback as part of the initial configuration sequence, so the window may already be past the "waiting for frame" state. Ensure that the exposure event is always sent.
Under the right conditions, this extension can result is smoother resizing when rendering with OpenGL, however, it is known to cause problems in certain cases, such as when handling presentation externally.
Gate it behind a hint, and disable it by default. Developers can selectively enable it when they verify that they meet the criteria for using it, and that it behaves correctly in their apps/games.
If the cursor was created with a temporary surface that was pointing at external memory, then when the cursor is used it might be referencing memory that had already been freed.
Natural scrolling affects both axes, and the compositor may not send the vertical axis orientation if the frame has no vertical scroll motion, so purely horizontal events need to be flagged as inverted as well.
The code is using `controls.window` before checking if it isn't null.
I found this bug by accident when I tried to run `SDL_ShowSimpleMessageBox`.
It first tried using Wayland with `zenity`, but since I don't have `zenity`, it fallbacked to `X11_ShowMessageBoxImpl`.
For some reason it couldn't create a window, maybe something related to XWayland, so `controls.window` was `NULL`.
