On all OSes we tested the std::chrono::steady_clock is of a high
enough resolution to do millisecond measurements, which is all we
need.
By accident, this fixes a Win32 driver bug, where we would never
hit our targets, as the resolution of the clock was too low to
do accurate millisecond measurements with (it was ~16ms resolution
instead).
When there are a lot of rects to redraw, of which one of the last
ones is almost the full screen, visual tearing happens over the
vertical axis. This is most visible when scrolling the map.
This can be prevented by using less rects. To simplify the situation,
and as solutions like OpenGL need this anyway, keep a single rect
that shows the biggest size that updates everything correctly.
Although this means it needs a bit more time redrawing where it
is strictly seen not needed, it also means less commands have
to be executed in the backend. In the end, this is a trade-off,
and from experiments it seems the approach of this commit gives
a better result.
During resizing, there can still be dirty-rects ready to blit based
on the old dimensions. X11 with shared memory enabled crashes if
you try to do this. So, instead, if we resize, reset the dirty-rects.
This is fine, as moments later we mark the whole (new) screen as
dirty anyway.
The zoom level suggestion is based on the DPI scaling set in Windows.
We use 150% scaling as the threshold for 2X zoom and 300% scaling
as the threshold for 4X zoom.
We never change the real screen resolution on OSX. As such, offering a list
of resolutions is pointless. Instead of that, offer the user a list of
commonly used window sizes up to the current screen size.
In testing, I could find no reason why this statement is here.
The comment is rather unclear (it states what it does, but not
why it would be needed).
This line of code was introduced with f4f40448, which gives no
further insight on why it would be needed to have it here.
As such, let's remove it and see if anyone else reports any
problems with it. If so, this commit can be reverted and a more
clear comment should be added what this line of code is dealing
with (the WHY, not the WHAT).
This means the code depended that the caller did this for us
before MakePalette() is executed, which is neither a
requirement nor a promise the code makes.
When the wayland SDL video driver is used, an EGL context is
created in the main thread. It is not allowed to update this
context from another thread, which is exactly what our draw-thread
is trying.
The other solution would be to move all of SDL into the
draw-thread, but that would introduce a whole scala of different
problems.
The wayland SDL backend is significantly faster than the
X11 SDL backend, but there is a performance hit nevertheless.
It now follows more what the Win32 driver does, and has far less
exceptions and special casing.
MakePalette creates the Palette and prepares surface.
UpdatePalette updates the Palette.
CheckPaletteAnim checks if UpdatePalette needs to be called and
marks the whole screen dirty so DrawSurfaceToScreen will do a
full redraw.
Sometimes it returned an usererror(), sometimes Start() failed.
Now it always fails on Start(), so nothing else has to check again
what blitter is used.
AfterBlitterChange() can never change to a 0bpp, so it is sufficient
to guard this with an assert().
