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Bug 2671

Summary: Mouse Y gets 22 pixels offset after warping only if X is different to 0
Product: SDL Reporter: Javi Agenjo <javi.agenjo>
Component: eventsAssignee: Jørgen Tjernø <jorgen>
Status: RESOLVED FIXED QA Contact: Sam Lantinga <slouken>
Severity: normal    
Priority: P2 CC: amaranth72, sdlbug
Version: HG 2.1   
Hardware: x86_64   
OS: Mac OS X (All)   
Attachments: Simple testcase

Description Javi Agenjo 2014-08-05 18:53:02 UTC 
Problem related to SDL_GetMouseState and SDL_WarpMouseInWindow

I want to create a FPS game, so after computing the delta offset from previous mouse position I warp it to the center of the window. The problem is that if I dont move the mouse, the position I read using SDL_GetMouseState is right where I put it with SDL_WarpMouseInWindow, but if I move the mouse (no matter in which axis) the Y component after SDL_GetMouseState is 22 pixels offseted (plus the obvious offset from my movement), which is the height of the title bar of the window.

If I am in fullscreen (using the OSX corner icon) the offset is only 1 pixel.

It looks like that warp is in window coordinates (0,0 is on the corner of the window) but SDL_GetMouseState is in viewport coordinates (0,0 is right below the titlebar), the weird thing is that the offset only happens if the mouse moves, otherwise there is no offset in Y.

X is perfectly fine.

Tested compiling the HG SDL 2.1 version in a OSX Mavericks.
Comment 1 Javi Agenjo 2014-08-05 19:40:13 UTC 
Also note that the same code works perfectly in windows and linux, it seems more like a bug in OSX event handling.
Comment 2 Alex Szpakowski 2014-08-05 23:16:43 UTC 
Related: https://bugzilla.libsdl.org/show_bug.cgi?id=2655
Comment 3 Robotic-Brain 2014-08-08 20:54:04 UTC 
Can you provide a testcase?
Comment 4 Javi Agenjo 2014-08-08 21:02:41 UTC 
create an SDL application with a mainloop:

int x,y;

while (1)
{
	//update events
	while(SDL_PollEvent(&sdlEvent))
	{
	}
	SDL_GetMouseState(&x,&y);
	std::cout << x << "," << y << std::endl;

	SDL_WarpMouseInWindow(window, 50,50 ); 
}


This will output 50,50 unless you move the mouse, then you will see that the Y has 22 pixels offset (plus your movement)
Comment 5 Robotic-Brain 2014-08-09 00:53:33 UTC 
Created attachment 1809 [details]
Simple testcase
Comment 6 Robotic-Brain 2014-08-09 00:54:35 UTC 
Testing showed, that the SDL_MOUSEMOTION event also returns wrong coordinates

Preliminary bisect results:

first known bad build 8738:354dabd2cb58
last known good build 8721:d73e451f1dc5

all builds in between, so far suggested by "hg bisect", are completely broken in terms of window coordinates
Comment 7 Robotic-Brain 2014-08-09 01:51:25 UTC 
definite last working version 8726:9a5a5808aa14

Bug introduced in 8729:94af945dbb57 "Mac: SDL_SetWindowPosition is now relative to the menubar."

It looks like this change only exposed a bug already pressent somewhere else..
Comment 8 Robotic-Brain 2014-08-17 22:20:05 UTC 
Fixed by https://hg.libsdl.org/SDL/rev/c5e33f9a0d03