Initial commit

.gitignore

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+*.obj
+*.exp
+*.lnk
+*.lib
+*.dll
+*.gmez

LICENSE

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README.md

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+This extension backports GameMaker Studio 2.3.2's handling of the Windows
+scheduler to earlier versions of GameMaker, including Studio 1.4.
+This allows for games to run at full speed without setting the sleep margin to
+high numbers and wasting CPU.
+
+For optimal performance, import the latest version of this extension from the
+[Releases](https://github.com/skyfloogle/gmsched/releases/latest) section
+and set the sleep margin to 1ms.
+
+Note that this extension is for GMS developers. If you have a compiled game you
+want to improve the performance of, check out
+[gms_scheduler_fix (aka DBGHELP.dll)](https://github.com/omicronrex/gms_scheduler_fix).
+
+# Functions
+- **scheduler_resolution_set(res):** Sets the scheduler resolution to the given
+resolution, in milliseconds. Returns 0 on success and 1 if the resolution is
+out of range.
+- **scheduler_resolution_get():** Returns the current scheduler resolution.
+Defaults to 1ms.
+- **scheduler_resolution_get_min():** Returns the minimum possible scheduler
+resolution on the current machine.
+- **scheduler_resolution_get_max():** Returns the maximum possible scheduler
+resolution on the current machine.
+
+# Why is this a problem?
+Every 16ms (at 60fps), GameMaker will perform the necessary calculations for
+one frame, and wait for the next 16ms interval. The way this waiting happens is
+the problem here. You can call a function in Windows to
+[*Sleep*](https://docs.microsoft.com/en-us/windows/win32/api/synchapi/nf-synchapi-sleep)
+for a certain
+amount of time, in a power-efficient manner. However, this *Sleep* function is
+not very accurate. For this reason, GameMaker will take the time remaining
+until the next 16ms interval, subtract the sleep margin, and *Sleep* for that
+amount of time. For the rest of the interval, it continuously checks whether
+the time has elapsed, i.e. it busywaits. This uses 100% of one CPU core.
+
+The inaccuracy of *Sleep* gave many users bad performance issues, especially
+after its behaviour changed in certain Windows updates. As the sleep margin was
+the only known way to affect this, it became consensus that the sleep margin
+should be set to a high enough value that it would busywait for most, if not
+all, of the interval. This is a massive waste of CPU resources, and will drain
+the batteries and burn the thighs of laptop users.
+
+Fortunately, there is a better way. It is possible to improve the accuracy of
+the *Sleep* function, sometimes known as the "scheduler resolution", using the
+[*timeBeginPeriod*](https://docs.microsoft.com/en-us/windows/win32/api/timeapi/nf-timeapi-timebeginperiod)
+and
+[*timeEndPeriod*](https://docs.microsoft.com/en-us/windows/win32/api/timeapi/nf-timeapi-timeendperiod)
+functions.
+This allows you to have accurate timers without draining laptop batteries.
+Calling these functions has a slight performance cost of its own, especially on
+older versions of Windows. It doesn't compare to the cost of busywaiting all
+the time, but it is worth giving it a breather when performance isn't a
+priority (e.g. if the game is out of focus or paused).
+
+This functionality was finally added to GameMaker Studio 2 in version 2.3.2.
+Now, people no longer have to set their sleep margin to obscene numbers to get
+good performance. This extension allows Studio 1 users to take advantage of the
+same functionality.

gmsched.asm

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+; this code is public domain
+; http://creativecommons.org/publicdomain/zero/1.0/
+
+; to compile with visual studio x86 build tools in command prompt:
+; >ml /coff gmsched.asm /link /dll /nocoffgrpinfo /entry:dllmain /def:gmsched.def /out:gmsched.dll
+; this will produce a whole load of files, but you only need gmsched.dll
+
+.386
+.model flat
+
+; prototypes
+timeBeginPeriod PROTO STDCALL :DWORD
+timeEndPeriod PROTO STDCALL :DWORD
+timeGetDevCaps PROTO STDCALL :DWORD,:DWORD
+includelib winmm.lib
+
+.data?
+currentTimePeriod DWORD ?
+
+.code
+; info
+InfoText db 13,10,"=======================================",13,10," https://github.com/skyfloogle/gmsched ",13,10,"=======================================",13,10
+
+dllmain proc stdcall instance:dword,reason:dword,unused:dword
+    mov eax,1
+    ret
+dllmain endp
+
+; set period to 1 on init
+gmsched_init proc c
+	mov eax,1
+	mov currentTimePeriod,eax
+	invoke timeBeginPeriod,eax
+	ret
+gmsched_init endp
+
+; returns 0 on success, 1 on out of range (as a double)
+scheduler_resolution_set proc c FPeriod:real8
+LOCAL IPeriod:dword ; integer version of new period
+    ; convert FPeriod to dword and store in IPeriod
+    fld FPeriod
+    fistp IPeriod
+	; set new period
+	invoke timeBeginPeriod,[IPeriod]
+	; don't end old period on error
+	test eax,eax
+	jnz did_err
+	; end old period
+	invoke timeEndPeriod,[currentTimePeriod]
+	; update stored period
+	mov eax,[IPeriod]
+	mov [currentTimePeriod],eax
+	; return 0 for no error
+	fldz
+	jmp exit
+did_err:
+	; return 1 for error
+	fld1
+exit:
+	ret
+scheduler_resolution_set endp
+
+scheduler_resolution_get proc c
+    fild currentTimePeriod
+    ret
+scheduler_resolution_get endp
+
+scheduler_resolution_get_min proc c
+LOCAL timecaps[2]:dword
+	lea eax,timecaps
+	invoke timeGetDevCaps, eax, 8
+	fild timecaps[0]
+	ret
+scheduler_resolution_get_min endp
+
+scheduler_resolution_get_max proc c
+LOCAL timecaps[2]:dword
+	lea eax,timecaps
+	invoke timeGetDevCaps, eax, 8
+	fild timecaps[4]
+	ret
+scheduler_resolution_get_max endp
+
+end

gmsched.def

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+EXPORTS
+gmsched_init
+scheduler_resolution_set
+scheduler_resolution_get
+scheduler_resolution_get_min
+scheduler_resolution_get_max