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Bug 4260

Summary: Render API shouldn't check if window is hidden
Product: SDL Reporter: Ryan C. Gordon <icculus>
Component: renderAssignee: Sam Lantinga <slouken>
Status: RESOLVED WONTFIX QA Contact: Sam Lantinga <slouken>
Severity: normal    
Priority: P2    
Version: HG 2.0   
Hardware: x86   
OS: Other   

Description Ryan C. Gordon 2018-09-17 05:26:19 UTC 
I assume this change was made for iOS, seven years ago...

https://hg.libsdl.org/SDL/rev/59d398ac031e

...in recent revisions, these check if the window is "hidden" instead of minimized, but I'm wondering if these should be removed.

Apps on iOS should catch the event telling them the process went to the background and should stop drawing on their own in that case, like they would have to do if they used OpenGL directly instead of SDL's renderer, and having these checks here means that a minimized window on any platform that's rendering to a render target will end up with a blank texture that might be meant to persist for long past a single frame.

As I'm reworking the render API to batch up draw commands, there are further questions about when and if we should abort drawing like this.

The downside of removing this check is that an iOS app in the background that tries to call SDL_Render*() will crash, but I'd argue that was a bug in their app. They shouldn't be doing serious work in the background, including running their rendering loop, whether we prevent the actual rendering calls or not.

Can I remove these "/* Don't draw while we're minimized */" checks? We can definitely keep the glFinish() call on backgrounding, if that's helpful to iOS, though.

--ryan.
Comment 1 Sam Lantinga 2018-09-17 05:57:18 UTC 
The problem is that iOS enforces the "no rendering" policy immediately, but the app may not receive the notification that they should stop rendering until later. I'm fine with making that an iOS and Android only check though, if that's helpful.