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Bug 2107 - SDL_RendererEventWatch doesn't always scale mouse events when SetLogicalSize is used
Summary: SDL_RendererEventWatch doesn't always scale mouse events when SetLogicalSize ...
Status: RESOLVED FIXED
Alias: None
Product: SDL
Classification: Unclassified
Component: render (show other bugs)
Version: HG 2.1
Hardware: All Android (All)
: P2 normal
Assignee: Sam Lantinga
QA Contact: Sam Lantinga
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2013-09-21 20:07 UTC by Michał Zieliński
Modified: 2019-10-14 14:44 UTC (History)
2 users (show)

See Also:

Attachments
check if logical_w_backup is set and if so, use *_backup members. (1.99 KB, patch)
2013-09-21 20:07 UTC, Michał Zieliński 		Details | Diff
test case (2.83 KB, text/x-csrc)
2017-10-20 15:27 UTC, Sylvain 		Details
View All Add an attachment (proposed patch, testcase, etc.)

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Description Michał Zieliński 2013-09-21 20:07:00 UTC 
Created attachment 1334 [details]
check if logical_w_backup is set and if so, use *_backup members.

There is a race condition when mouse events are sent from non-main thread. SDL_RendererEventWatch may end up being invoked when renderer is drawing on texture - logical_w is set to 0. Attached patch checks if logical_w_backup is set and if so, uses *_backup members.
Comment 1 Michał Zieliński 2013-09-21 20:13:15 UTC 
I just realized that this doesn't solve race condition, just makes it much harder to occur. The proper solution would need a mutex or some restructuring eliminating the need for *_backup variables.
Comment 2 Sam Lantinga 2013-09-28 06:32:54 UTC 
Out of curiosity, when are mouse events sent from non-main thread?
Comment 3 Michał Zieliński 2013-09-28 08:39:14 UTC 
On Android.
Comment 4 Sylvain 2017-10-20 13:10:19 UTC 
I haven't tested to see the issue.
But, if I understand it correctly, this happens because:

1/ android is sending Mouse event, so calling SDL_SendMouseButton(), SDL_PushEvent(), and SDL_RendererEventWatch() with logical_w/h

and, at the same time, in a different thread:

2/ SDL_SetRenderTarget() is reconfiguring internal renderer data with different logical_w/h.

If so, then this would also affect also touch events (now there handled by the EventWatch routine).


And, if I read the SDL_RendererEventWatch() code, I see that a similar issue is fixed:

https://hg.libsdl.org/SDL/rev/a8cbb653aea4
Comment 5 Sylvain 2017-10-20 15:27:20 UTC 
Created attachment 3013 [details]
test case

Here's a test-case !

It's not the usual way to do, but it shows clearly the issue without the need of threads.

Window as a size of 800x800
The renderer a logical size of 80x80
so I expect the mouse to be within [0; 80]x[0; 80]

But I use a target texture, and I poll events in the middle of using it.
I got event without the scale, e.g with [0; 800]x[0; 800].
Comment 6 Sylvain 2017-10-24 19:53:42 UTC 
similar issue with bug 2020
Comment 7 Sylvain 2019-10-14 14:42:52 UTC 
Fixed the race condition for touch event: https://hg.libsdl.org/SDL/rev/27a1bea6bdff
Comment 8 Sylvain 2019-10-14 14:44:30 UTC 
For Mouse events, this was fixed there: https://hg.libsdl.org/SDL/rev/3239c8ad2986
So I marked this as resolved