This makes it a bit easier to follow what is going on, and
allow future subdrivers to hook into a few of these functions.
Reworked the code slighly while at it, to return early where
possible.
The higher your refresh-rate, the more likely this is. Mostly you
notice this when creating a new game or when abandoning a game.
This is a bit of a hack to keep the old behaviour, as before this
patch the game was already freezing your mouse while it was changing
game-mode, and it does this too after this patch. Just now it
freezes too a few frames earlier, to prevent not drawing windows
people still expect to see.
Most modern games run on 60 fps, and for good reason. This gives
a much smoother experiences.
As some people have monitors that can do 144Hz or even 240Hz, allow
people to configure the refresh rate. Of course, the higher you
set the value, the more time the game spends on drawing pixels
instead of simulating the game, which has an effect on simulation
speed.
The simulation will still always run at 33.33 fps, and is not
influences by this setting.
Sleep for 1ms (which is always (a lot) more than 1ms) is just
randomly guessing and hoping you hit your deadline, give or take.
But given we can calculate when our next frame is happening, we
can just sleep for that exact amount. As these values are often
a bit larger, it is also more likely the OS can schedule us back
in close to our requested target. This means it is more likely we
hit our deadlines, which makes the FPS a lot more stable.
Before, every next frame was calculated from the current time.
If for some reason the current frame was drifting a bit, the
next would too, and the next more, etc etc. This meant we rarely
hit the targets we would like, like 33.33fps.
Instead, allow video-drivers to drift slightly, and schedule the
next frame based on the time the last should have happened. Only
if the drift gets too much, that deadlines are missed for longer
period of times, schedule the next frame based on the current
time.
This makes the FPS a lot smoother, as sleeps aren't as exact as
you might think.
During fast-forward, the game was drawing as fast as it could. This
means that the fast-forward was limited also by how fast we could
draw, something that people in general don't expect.
To give an extreme case, if you are fully zoomed out on a busy
map, fast-forward would be mostly limited because of the time it
takes to draw the screen.
By decoupling the draw-tick and game-tick, we can keep the pace
of the draw-tick the same while speeding up the game-tick. To use
the extreme case as example again, if you are fully zoomed out
now, the screen only redraws 33.33 times per second, fast-forwarding
or not. This means fast-forward is much more likely to go at the
same speed, no matter what you are looking at.
_realtime_tick was reset every time the diff was calculated. This
means if it would trigger, say, every N.9 milliseconds, it would
after two iterations already drift a millisecond. This adds up
pretty quick.
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.
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().
This mode doesn't wrap the mouse constantly, but requests SDL
to lock the mouse pointer. This is needed, as with Emscripten
you are not allowed to change the mouse poisition (only to lock
it into place).
Emscripten compiles to WASM, which can be loaded via
HTML / JavaScript. This allows you to play OpenTTD inside a
browser.
Co-authored-by: milek7 <me@milek7.pl>
This commit prepares for the next commit, as Emscripten needs to
have a way to trigger a single iteration of the main loop. To
keep the real changes more clear, this commit only unrolls the
loop, and makes no changes to the logic itself.
This fixes a bug that can reproduced with these steps:
* Start openttd in fullscreen mode
* Turn off fullscreen mode
* Try to resize the window. The window can't be resized.
Michael Lutz